rustfs/crates/filemeta/src/filemeta/version.rs

// Copyright 2024 RustFS Team
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Version meta parsing with legacy compatibility.
//!
//! **Rule**: To parse version meta bytes (from `FileMetaShallowVersion.meta` or raw `&[u8]`),
//! always use one of:
//! - `FileMetaShallowVersion::parse_version_meta()` or `into_fileinfo()`
//! - `FileMetaVersion::try_from(buf)`
//!
//! Do NOT use `FileMetaVersion::default()` + `unmarshal_msg()` directly, as that fails on
//! legacy (rmp_serde) format. `try_from` falls back to rmp_serde when hand-written decode fails.

use super::msgp_decode::{
    PrependByteReader, prealloc_hint, read_exact_vec, read_nil_or_array_len, read_nil_or_map_len, skip_msgp_value,
};
use super::*;
use crate::ChecksumInfo;
use rustfs_utils::HashAlgorithm;
use rustfs_utils::http::{
    RUSTFS_INTERNAL_PREFIX, SUFFIX_CRC, SUFFIX_FREE_VERSION, SUFFIX_INLINE_DATA, SUFFIX_PURGESTATUS, SUFFIX_TIER_FV_ID,
    SUFFIX_TIER_FV_MARKER, SUFFIX_TRANSITION_STATUS, SUFFIX_TRANSITION_TIER, SUFFIX_TRANSITION_TIER_DESTINATION_ID,
    SUFFIX_TRANSITIONED_OBJECTNAME, SUFFIX_TRANSITIONED_VERSION_ID, contains_key_bytes, get_bytes, get_consistent_bytes, get_str,
    has_internal_suffix, insert_bytes, is_internal_key, remove_bytes, strip_internal_prefix,
};

const MSGPACK_EXT8: u8 = 0xc7;
const MSGPACK_EXT16: u8 = 0xc8;
const MSGPACK_EXT32: u8 = 0xc9;
const MSGPACK_FIXEXT4: u8 = 0xd6;
const MSGPACK_FIXEXT8: u8 = 0xd7;
const MSGPACK_TIME_EXT_LEGACY: i8 = 5;
const MSGPACK_TIME_EXT_OFFICIAL: i8 = -1;
const MSGPACK_TIME_LEN: u8 = 12;

/// Sentinel signature returned when a version has no computable body (invalid /
/// missing inner object). Mirrors MinIO's `signatureErr` so such versions never
/// collide with a real all-zero legacy signature.
const SIGNATURE_ERR: [u8; 4] = [b'e', b'r', b'r', 0];

/// Order-independent hash of a `String -> String` map, mirroring MinIO's
/// `hashDeterministicString`. Msgpack map serialization order is not stable
/// across disks, so map fields must be folded in with XOR (order-independent)
/// rather than left in the marshaled body. Uses xxh64 (RustFS-internal only;
/// signatures are recomputed on write and never compared against MinIO's).
fn hash_deterministic_string(m: &HashMap<String, String>) -> u64 {
    let mut crc: u64 = 0xc2b4_0bba_c11a_7295;
    for (k, v) in m {
        crc ^= (xxhash_rust::xxh64::xxh64(k.as_bytes(), 0) ^ 0x4ee3_bbaf_7ab2_506b)
            .wrapping_add(xxhash_rust::xxh64::xxh64(v.as_bytes(), 0) ^ 0x8da4_c8da_6619_4257);
    }
    crc
}

/// Order-independent hash of a `String -> Vec<u8>` map, mirroring MinIO's
/// `hashDeterministicBytes`. See [`hash_deterministic_string`].
fn hash_deterministic_bytes(m: &HashMap<String, Vec<u8>>) -> u64 {
    let mut crc: u64 = 0x1bbc_7e1d_de65_4743;
    for (k, v) in m {
        crc ^= (xxhash_rust::xxh64::xxh64(k.as_bytes(), 0) ^ 0x4ee3_bbaf_7ab2_506b)
            .wrapping_add(xxhash_rust::xxh64::xxh64(v, 0) ^ 0x8da4_c8da_6619_4257);
    }
    crc
}

/// Fold a 64-bit crc into the 4-byte header signature, matching MinIO's
/// `binary.LittleEndian.PutUint32(tmp, uint32(crc ^ (crc>>32)))`.
fn fold_signature(crc: u64) -> [u8; 4] {
    ((crc ^ (crc >> 32)) as u32).to_le_bytes()
}

fn read_msgp_string<R: std::io::Read>(rd: &mut R) -> Result<String> {
    let len = rmp::decode::read_str_len(rd)? as usize;
    let buf = read_exact_vec(rd, len)?;
    Ok(String::from_utf8(buf)?)
}

fn read_msgp_bin<R: std::io::Read>(rd: &mut R) -> Result<Vec<u8>> {
    let len = rmp::decode::read_bin_len(rd)? as usize;
    read_exact_vec(rd, len)
}

/// Writes an `OffsetDateTime` as the ext8 / legacy (type 5, 12-byte
/// seconds+nanos) msgpack time encoding used by the V1 (Legacy) object body.
/// `read_msgp_time` decodes exactly this shape via `MSGPACK_TIME_EXT_LEGACY`.
fn write_msgp_time<W: std::io::Write>(wr: &mut W, t: OffsetDateTime) -> Result<()> {
    wr.write_all(&[MSGPACK_EXT8, MSGPACK_TIME_LEN, MSGPACK_TIME_EXT_LEGACY as u8])?;
    let mut buf = [0u8; MSGPACK_TIME_LEN as usize];
    buf[0..8].copy_from_slice(&t.unix_timestamp().to_be_bytes());
    buf[8..12].copy_from_slice(&t.nanosecond().to_be_bytes());
    wr.write_all(&buf)?;
    Ok(())
}

fn deserialize_legacy_uuid_bytes<'de, D>(deserializer: D) -> std::result::Result<Vec<u8>, D::Error>
where
    D: serde::Deserializer<'de>,
{
    struct LegacyUuidBytesVisitor;

    impl<'de> serde::de::Visitor<'de> for LegacyUuidBytesVisitor {
        type Value = Vec<u8>;

        fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
            formatter.write_str("nil or binary UUID bytes")
        }

        fn visit_none<E>(self) -> std::result::Result<Self::Value, E>
        where
            E: serde::de::Error,
        {
            Ok(Vec::new())
        }

        fn visit_unit<E>(self) -> std::result::Result<Self::Value, E>
        where
            E: serde::de::Error,
        {
            Ok(Vec::new())
        }

        fn visit_bytes<E>(self, value: &[u8]) -> std::result::Result<Self::Value, E>
        where
            E: serde::de::Error,
        {
            Ok(value.to_vec())
        }

        fn visit_byte_buf<E>(self, value: Vec<u8>) -> std::result::Result<Self::Value, E>
        where
            E: serde::de::Error,
        {
            Ok(value)
        }

        fn visit_seq<A>(self, mut seq: A) -> std::result::Result<Self::Value, A::Error>
        where
            A: serde::de::SeqAccess<'de>,
        {
            let mut value = Vec::new();
            while let Some(byte) = seq.next_element()? {
                value.push(byte);
            }
            Ok(value)
        }
    }

    deserializer.deserialize_any(LegacyUuidBytesVisitor)
}

fn decode_msgp_time_payload(ext_type: i8, payload: &[u8]) -> Result<OffsetDateTime> {
    let (secs, nanos) = match (ext_type, payload.len()) {
        (MSGPACK_TIME_EXT_LEGACY, 12) => {
            let secs = i64::from_be_bytes(payload[..8].try_into().unwrap());
            let nanos = u32::from_be_bytes(payload[8..12].try_into().unwrap());
            (secs, nanos)
        }
        (MSGPACK_TIME_EXT_OFFICIAL, 4) => (u32::from_be_bytes(payload.try_into().unwrap()) as i64, 0),
        (MSGPACK_TIME_EXT_OFFICIAL, 8) => {
            let v = u64::from_be_bytes(payload.try_into().unwrap());
            let nanos = (v >> 34) as u32;
            let secs = (v & ((1 << 34) - 1)) as i64;
            (secs, nanos)
        }
        (MSGPACK_TIME_EXT_OFFICIAL, 12) => {
            let nanos = u32::from_be_bytes(payload[..4].try_into().unwrap());
            let secs = i64::from_be_bytes(payload[4..12].try_into().unwrap());
            (secs, nanos)
        }
        _ => {
            return Err(Error::other(format!(
                "unsupported msgpack time ext type {ext_type} len {}",
                payload.len()
            )));
        }
    };

    if nanos > 999_999_999 {
        return Err(Error::other(format!("invalid msgpack time nanos: {nanos}")));
    }

    OffsetDateTime::from_unix_timestamp_nanos(secs as i128 * 1_000_000_000 + nanos as i128).map_err(Error::from)
}

fn read_msgp_time<R: std::io::Read>(rd: &mut R) -> Result<OffsetDateTime> {
    let mut tag = [0u8; 1];
    rd.read_exact(&mut tag)?;

    let (len, ext_type) = match tag[0] {
        MSGPACK_FIXEXT4 => {
            let mut typ = [0u8; 1];
            rd.read_exact(&mut typ)?;
            (4usize, typ[0] as i8)
        }
        MSGPACK_FIXEXT8 => {
            let mut typ = [0u8; 1];
            rd.read_exact(&mut typ)?;
            (8usize, typ[0] as i8)
        }
        MSGPACK_EXT8 => {
            let mut len = [0u8; 1];
            let mut typ = [0u8; 1];
            rd.read_exact(&mut len)?;
            rd.read_exact(&mut typ)?;
            (len[0] as usize, typ[0] as i8)
        }
        MSGPACK_EXT16 => {
            let mut len = [0u8; 2];
            let mut typ = [0u8; 1];
            rd.read_exact(&mut len)?;
            rd.read_exact(&mut typ)?;
            (u16::from_be_bytes(len) as usize, typ[0] as i8)
        }
        MSGPACK_EXT32 => {
            let mut len = [0u8; 4];
            let mut typ = [0u8; 1];
            rd.read_exact(&mut len)?;
            rd.read_exact(&mut typ)?;
            (u32::from_be_bytes(len) as usize, typ[0] as i8)
        }
        other => return Err(Error::other(format!("unsupported msgpack time marker: 0x{other:02x}"))),
    };

    let payload = read_exact_vec(rd, len)?;
    decode_msgp_time_payload(ext_type, &payload)
}

fn parse_legacy_uuid_bytes(bytes: &[u8], field: &str) -> Result<Option<Uuid>> {
    if bytes.is_empty() {
        return Ok(None);
    }

    if bytes.len() != 16 {
        return Err(Error::other(format!("legacy {field} must be 16 bytes, got {}", bytes.len())));
    }

    let id = Uuid::from_slice(bytes).map_err(Error::from)?;
    Ok((!id.is_nil()).then_some(id))
}

/// Decode a stored transitioned-version-id from a version's `meta_sys`.
///
/// RustFS writes it as 16 raw UUID bytes; MinIO-migrated tiered objects store
/// the remote tier's version id as a UUID *string*. Accept both, and treat any
/// absent / nil / otherwise-unparseable value as "no tier version" (matching the
/// tolerant pre-hardening behavior) rather than failing the whole object read —
/// a malformed tier id must not make an otherwise-readable object unreadable.
fn transitioned_version_id_from_meta_sys(meta_sys: &HashMap<String, Vec<u8>>) -> Option<Uuid> {
    let value = get_bytes(meta_sys, SUFFIX_TRANSITIONED_VERSION_ID)?;
    if value.is_empty() {
        return None;
    }
    if let Ok(id) = Uuid::from_slice(&value) {
        return (!id.is_nil()).then_some(id);
    }
    std::str::from_utf8(&value)
        .ok()
        .and_then(|s| Uuid::parse_str(s.trim()).ok())
        .filter(|id| !id.is_nil())
}

fn parse_legacy_erasure_algo(value: &str) -> ErasureAlgo {
    match value {
        "ReedSolomon" => ErasureAlgo::ReedSolomon,
        _ => ErasureAlgo::Invalid,
    }
}

fn parse_legacy_checksum_algo(value: &str) -> ChecksumAlgo {
    match value {
        "HighwayHash" => ChecksumAlgo::HighwayHash,
        _ => ChecksumAlgo::Invalid,
    }
}

#[derive(Debug, Deserialize)]
enum LegacyMetaV2VersionType {
    #[serde(rename = "Object")]
    Object,
    #[serde(rename = "Delete")]
    Delete,
    #[serde(rename = "DeleteMarker")]
    DeleteMarker,
}

#[derive(Debug, Deserialize)]
struct LegacyMetaV2Version {
    version_type: LegacyMetaV2VersionType,
    object: Option<LegacyMetaV2Object>,
    delete_marker: Option<LegacyMetaV2DeleteMarker>,
    write_version: u64,
}

#[derive(Debug, Deserialize)]
struct LegacyMetaV2Object {
    #[serde(default, deserialize_with = "deserialize_legacy_uuid_bytes")]
    version_id: Vec<u8>,
    #[serde(default, deserialize_with = "deserialize_legacy_uuid_bytes")]
    data_dir: Vec<u8>,
    erasure_algorithm: String,
    erasure_m: usize,
    erasure_n: usize,
    erasure_block_size: usize,
    erasure_index: usize,
    erasure_dist: Vec<u8>,
    bitrot_checksum_algo: String,
    part_numbers: Vec<usize>,
    part_etags: Vec<String>,
    part_sizes: Vec<usize>,
    part_actual_sizes: Vec<i64>,
    part_indices: Vec<Vec<u8>>,
    size: i64,
    mod_time: Option<OffsetDateTime>,
    meta_sys: HashMap<String, Vec<u8>>,
    meta_user: HashMap<String, String>,
}

#[derive(Debug, Deserialize)]
struct LegacyMetaV2DeleteMarker {
    #[serde(default, deserialize_with = "deserialize_legacy_uuid_bytes")]
    version_id: Vec<u8>,
    mod_time: Option<OffsetDateTime>,
    meta_sys: HashMap<String, Vec<u8>>,
}

#[derive(Serialize, Deserialize, Debug, Default, PartialEq, Clone, Eq, PartialOrd, Ord)]
pub struct FileMetaShallowVersion {
    pub header: FileMetaVersionHeader,
    pub meta: Vec<u8>, // FileMetaVersion.marshal_msg
}

fn write_quorum_from_erasure(data_blocks: usize, parity_blocks: usize) -> Option<usize> {
    if data_blocks == 0 {
        return None;
    }

    Some(if data_blocks == parity_blocks {
        data_blocks.saturating_add(1)
    } else {
        data_blocks
    })
}

impl FileMetaShallowVersion {
    /// Parse version meta with legacy format compatibility.
    /// Use this instead of `FileMetaVersion::default()` + `unmarshal_msg()` to handle old-version xl.meta.
    pub fn parse_version_meta(&self) -> Result<FileMetaVersion> {
        FileMetaVersion::try_from(self.meta.as_slice())
    }

    pub fn write_quorum(&self, fallback_quorum: usize) -> usize {
        let header_quorum = self.header.write_quorum(fallback_quorum);
        if self.header.has_ec() || !matches!(self.header.version_type, VersionType::Object | VersionType::Legacy) {
            return header_quorum;
        }

        self.parse_version_meta()
            .ok()
            .and_then(|version| version.erasure_write_quorum())
            .unwrap_or(header_quorum)
    }

    pub fn into_fileinfo(&self, volume: &str, path: &str, all_parts: bool) -> Result<FileInfo> {
        self.parse_version_meta()?.into_fileinfo(volume, path, all_parts)
    }
}

impl TryFrom<FileMetaVersion> for FileMetaShallowVersion {
    type Error = Error;

    fn try_from(value: FileMetaVersion) -> std::result::Result<Self, Self::Error> {
        let header = value.header();
        let meta = value.marshal_msg()?;
        Ok(Self { meta, header })
    }
}

#[derive(Serialize, Deserialize, Debug, Default, Clone, PartialEq)]
pub struct FileMetaVersion {
    #[serde(rename = "Type")]
    pub version_type: VersionType,
    #[serde(rename = "V1Obj")]
    pub legacy_object: Option<MetaObjectV1>,
    #[serde(rename = "V2Obj")]
    pub object: Option<MetaObject>,
    #[serde(rename = "DelObj")]
    pub delete_marker: Option<MetaDeleteMarker>,
    #[serde(rename = "v")]
    pub write_version: u64, // rustfs version
    /// True when parsed via rmp_serde fallback (legacy format). Used for checksum algorithm selection.
    #[serde(skip)]
    pub uses_legacy_checksum: bool,
}

impl FileMetaVersion {
    fn erasure_write_quorum(&self) -> Option<usize> {
        let (data_blocks, parity_blocks) = match self.version_type {
            VersionType::Object | VersionType::Legacy => {
                if let Some(object) = &self.object {
                    (object.erasure_m, object.erasure_n)
                } else if let Some(object) = &self.legacy_object {
                    (object.erasure.data_blocks, object.erasure.parity_blocks)
                } else {
                    return None;
                }
            }
            _ => return None,
        };

        write_quorum_from_erasure(data_blocks, parity_blocks)
    }

    fn decode_data_dir_from_v2_object(buf: &[u8]) -> Result<Option<Uuid>> {
        let mut cur = std::io::Cursor::new(buf);
        let mut fields = rmp::decode::read_map_len(&mut cur)?;
        let mut version_type = VersionType::Invalid;

        while fields > 0 {
            fields -= 1;

            let key_len = rmp::decode::read_str_len(&mut cur)? as usize;
            let key_buf = read_exact_vec(&mut cur, key_len)?;
            let key = String::from_utf8(key_buf)?;

            match key.as_str() {
                "Type" => {
                    let v: i64 = rmp::decode::read_int(&mut cur)?;
                    version_type = VersionType::from_u8(v as u8);
                }
                "V2Obj" => {
                    if version_type != VersionType::Object {
                        skip_msgp_value(&mut cur)?;
                        continue;
                    }

                    let mut first = [0u8; 1];
                    cur.read_exact(&mut first)?;
                    if first[0] == 0xc0 {
                        return Ok(None);
                    }

                    let mut prepend = PrependByteReader {
                        byte: Some(first[0]),
                        inner: &mut cur,
                    };
                    let mut obj_fields = rmp::decode::read_map_len(&mut prepend)?;
                    let mut data_dir: Option<Uuid> = None;

                    while obj_fields > 0 {
                        obj_fields -= 1;

                        let obj_key_len = rmp::decode::read_str_len(&mut prepend)? as usize;
                        let obj_key_buf = read_exact_vec(&mut prepend, obj_key_len)?;
                        let obj_key = String::from_utf8(obj_key_buf)?;

                        if obj_key == "DDir" {
                            let bin_len = rmp::decode::read_bin_len(&mut prepend)? as usize;
                            if bin_len != 16 {
                                return Err(Error::other(format!("DDir must be 16 bytes, got {bin_len}")));
                            }
                            let mut raw = [0u8; 16];
                            prepend.read_exact(&mut raw)?;
                            let id = Uuid::from_bytes(raw);
                            data_dir = if id.is_nil() { None } else { Some(id) };
                            break;
                        }

                        skip_msgp_value(&mut prepend)?;
                    }

                    return Ok(data_dir);
                }
                _ => {
                    skip_msgp_value(&mut cur)?;
                }
            }
        }

        Ok(None)
    }

    pub fn valid(&self) -> bool {
        if !self.version_type.valid() {
            return false;
        }

        match self.version_type {
            VersionType::Object => self
                .object
                .as_ref()
                .map(|v| v.erasure_algorithm.valid() && v.bitrot_checksum_algo.valid() && v.mod_time.is_some())
                .unwrap_or_default(),
            VersionType::Legacy => self.legacy_object.as_ref().map(MetaObjectV1::valid).unwrap_or_default(),
            VersionType::Delete => self
                .delete_marker
                .as_ref()
                .map(|v| v.mod_time.unwrap_or(OffsetDateTime::UNIX_EPOCH) > OffsetDateTime::UNIX_EPOCH)
                .unwrap_or_default(),
            _ => false,
        }
    }

    pub fn get_data_dir(&self) -> Option<Uuid> {
        if self.valid() {
            {
                if self.version_type == VersionType::Object {
                    self.object.as_ref().map(|v| v.data_dir).unwrap_or_default()
                } else {
                    None
                }
            }
        } else {
            Default::default()
        }
    }

    pub fn get_version_id(&self) -> Option<Uuid> {
        match self.version_type {
            VersionType::Object => self.object.as_ref().map(|v| v.version_id).unwrap_or_default(),
            VersionType::Delete => self.delete_marker.as_ref().map(|v| v.version_id).unwrap_or_default(),
            VersionType::Legacy => self.legacy_object.as_ref().and_then(MetaObjectV1::version_id),
            VersionType::Invalid => None,
        }
    }

    pub fn get_mod_time(&self) -> Option<OffsetDateTime> {
        match self.version_type {
            VersionType::Object => self.object.as_ref().map(|v| v.mod_time).unwrap_or_default(),
            VersionType::Delete => self.delete_marker.as_ref().map(|v| v.mod_time).unwrap_or_default(),
            VersionType::Legacy => self.legacy_object.as_ref().and_then(|v| v.stat.mod_time),
            VersionType::Invalid => None,
        }
    }

    // decode_data_dir_from_meta reads data_dir from meta TODO: directly parse only data_dir from meta buf, msg.skip
    pub fn decode_data_dir_from_meta(buf: &[u8]) -> Result<Option<Uuid>> {
        if let Ok(data_dir) = Self::decode_data_dir_from_v2_object(buf) {
            return Ok(data_dir);
        }
        Ok(Self::try_from(buf)?.get_data_dir())
    }

    pub fn decode_from<R: std::io::Read>(&mut self, rd: &mut R) -> Result<()> {
        let mut fields = rmp::decode::read_map_len(rd)?;
        *self = FileMetaVersion::default();

        while fields > 0 {
            fields -= 1;

            let key_len = rmp::decode::read_str_len(rd)?;
            let key_buf = read_exact_vec(rd, key_len as usize)?;
            let key = String::from_utf8(key_buf)?;

            match key.as_str() {
                "Type" => {
                    let v: i64 = rmp::decode::read_int(rd)?;
                    self.version_type = VersionType::from_u8(v as u8);
                }
                "V1Obj" => {
                    let mut buf = [0u8; 1];
                    rd.read_exact(&mut buf).map_err(Error::from)?;
                    if buf[0] == 0xc0 {
                        self.legacy_object = None;
                    } else {
                        let mut prepend = PrependByteReader {
                            byte: Some(buf[0]),
                            inner: rd,
                        };
                        let mut obj = MetaObjectV1::default();
                        obj.decode_from(&mut prepend)?;
                        self.legacy_object = Some(obj);
                    }
                }
                "V2Obj" => {
                    let mut buf = [0u8; 1];
                    rd.read_exact(&mut buf).map_err(Error::from)?;
                    if buf[0] == 0xc0 {
                        self.object = None;
                    } else {
                        let mut prepend = PrependByteReader {
                            byte: Some(buf[0]),
                            inner: rd,
                        };
                        let mut obj = MetaObject::default();
                        obj.decode_from(&mut prepend)?;
                        self.object = Some(obj);
                    }
                }
                "DelObj" => {
                    let mut buf = [0u8; 1];
                    rd.read_exact(&mut buf).map_err(Error::from)?;
                    if buf[0] == 0xc0 {
                        self.delete_marker = None;
                    } else {
                        let mut prepend = PrependByteReader {
                            byte: Some(buf[0]),
                            inner: rd,
                        };
                        let mut dm = MetaDeleteMarker::default();
                        dm.decode_from(&mut prepend)?;
                        self.delete_marker = Some(dm);
                    }
                }
                "v" => {
                    let v: i64 = rmp::decode::read_int(rd)?;
                    if v < 0 {
                        return Err(Error::other("negative write_version not supported"));
                    }
                    self.write_version = v as u64;
                }
                other => {
                    tracing::debug!(field = %other, "decode_from: skipping unknown field");
                    skip_msgp_value(rd)?;
                }
            }
        }

        Ok(())
    }

    pub fn encode_to<W: std::io::Write>(&self, wr: &mut W) -> Result<()> {
        // Variable map size: omit V1Obj/V2Obj/DelObj when None
        let mut map_len: u32 = 2; // "Type" + "v"
        if self.legacy_object.is_some() {
            map_len += 1;
        }
        if self.object.is_some() {
            map_len += 1;
        }
        if self.delete_marker.is_some() {
            map_len += 1;
        }

        rmp::encode::write_map_len(wr, map_len)?;

        // Type
        rmp::encode::write_str(wr, "Type")?;
        rmp::encode::write_uint(wr, self.version_type.to_u8() as u64)?;

        // V1Obj — legacy body must round-trip; dropping it silently corrupted
        // Legacy versions on re-encode (backlog#799 B18).
        if let Some(ref legacy) = self.legacy_object {
            rmp::encode::write_str(wr, "V1Obj")?;
            legacy.encode_to(wr)?;
        }

        // V2Obj
        if let Some(ref obj) = self.object {
            rmp::encode::write_str(wr, "V2Obj")?;
            obj.encode_to(wr)?;
        }

        // DelObj
        if let Some(ref dm) = self.delete_marker {
            rmp::encode::write_str(wr, "DelObj")?;
            dm.encode_to(wr)?;
        }

        // v
        rmp::encode::write_str(wr, "v")?;
        rmp::encode::write_uint(wr, self.write_version)?;

        Ok(())
    }

    pub fn unmarshal_msg(&mut self, buf: &[u8]) -> Result<u64> {
        let mut cur = std::io::Cursor::new(buf);
        self.decode_from(&mut cur)?;
        Ok(cur.position())
    }

    pub fn marshal_msg(&self) -> Result<Vec<u8>> {
        let mut wr = Vec::new();
        self.encode_to(&mut wr)?;
        Ok(wr)
    }

    pub fn free_version(&self) -> bool {
        self.version_type == VersionType::Delete && self.delete_marker.as_ref().map(|m| m.free_version()).unwrap_or_default()
    }

    pub fn header(&self) -> FileMetaVersionHeader {
        FileMetaVersionHeader::from(self.clone())
    }

    pub fn into_fileinfo(&self, volume: &str, path: &str, all_parts: bool) -> Result<FileInfo> {
        // Only the Object arm carries part arrays and can fail the length guard; the
        // Legacy and Delete arms have no part arrays and stay infallible.
        let mut fi = match self.version_type {
            VersionType::Invalid | VersionType::Legacy => {
                if let Some(ref legacy) = self.legacy_object {
                    legacy.to_fileinfo(volume, path)
                } else {
                    FileInfo {
                        name: path.to_string(),
                        volume: volume.to_string(),
                        ..Default::default()
                    }
                }
            }
            VersionType::Object => {
                let default_object = MetaObject::default();
                self.object
                    .as_ref()
                    .unwrap_or(&default_object)
                    .into_fileinfo(volume, path, all_parts)?
            }
            VersionType::Delete => {
                let default_marker = MetaDeleteMarker::default();
                self.delete_marker
                    .as_ref()
                    .unwrap_or(&default_marker)
                    .into_fileinfo(volume, path, all_parts)
            }
        };
        fi.uses_legacy_checksum = self.uses_legacy_checksum;
        Ok(fi)
    }

    /// Support for Legacy version type
    pub fn is_legacy(&self) -> bool {
        self.version_type == VersionType::Legacy
    }

    /// Compute the header signature for this version.
    ///
    /// The signature must be identical across all disks that hold the same
    /// logical version, yet differ whenever any body field differs (tags,
    /// user/system metadata, parts, size, ...). Otherwise a partial-write
    /// divergence (e.g. `PutObjectTagging` reaching only some disks) shares the
    /// same `version_id`+`mod_time` and becomes undetectable / unhealable — the
    /// bug tracked in backlog#861 (B12), where this was hardcoded to `[0;4]`.
    ///
    /// Per-disk-varying fields (`erasure_index`) are excluded so identical
    /// content never falsely diverges. Semantics follow MinIO's
    /// `xlMetaV2Version.getSignature`.
    pub fn get_signature(&self) -> [u8; 4] {
        match self.version_type {
            VersionType::Object => self.object.as_ref().map(MetaObject::get_signature).unwrap_or(SIGNATURE_ERR),
            VersionType::Delete => self
                .delete_marker
                .as_ref()
                .map(MetaDeleteMarker::get_signature)
                .unwrap_or(SIGNATURE_ERR),
            VersionType::Legacy => self
                .legacy_object
                .as_ref()
                .map(MetaObjectV1::get_signature)
                .unwrap_or(SIGNATURE_ERR),
            _ => SIGNATURE_ERR,
        }
    }

    /// Check if this version uses data directory
    pub fn uses_data_dir(&self) -> bool {
        match self.version_type {
            VersionType::Object => self.object.as_ref().map(|obj| obj.uses_data_dir()).unwrap_or(false),
            VersionType::Legacy => false,
            _ => false,
        }
    }

    /// Check if this version uses inline data
    pub fn uses_inline_data(&self) -> bool {
        match self.version_type {
            VersionType::Object => self.object.as_ref().map(|obj| obj.inlinedata()).unwrap_or(false),
            VersionType::Legacy => false,
            _ => false,
        }
    }
}

impl TryFrom<&[u8]> for FileMetaVersion {
    type Error = Error;

    fn try_from(value: &[u8]) -> std::result::Result<Self, Self::Error> {
        let mut ver = FileMetaVersion::default();
        if ver.unmarshal_msg(value).is_ok() && ver.valid() {
            ver.uses_legacy_checksum = false;
            return Ok(ver);
        }

        if let Ok(legacy_ver) = rmp_serde::from_slice::<LegacyMetaV2Version>(value) {
            let mut ver = FileMetaVersion::try_from(legacy_ver)?;
            ver.uses_legacy_checksum = true;
            return Ok(ver);
        }

        // Fallback for legacy ver_meta: rmp_serde format
        let mut ver: Self = rmp_serde::from_slice(value).map_err(Error::other)?;
        ver.uses_legacy_checksum = true;
        Ok(ver)
    }
}

impl TryFrom<LegacyMetaV2Version> for FileMetaVersion {
    type Error = Error;

    fn try_from(value: LegacyMetaV2Version) -> std::result::Result<Self, Self::Error> {
        let (version_type, object, delete_marker) = match value.version_type {
            LegacyMetaV2VersionType::Object => (VersionType::Object, value.object.map(TryInto::try_into).transpose()?, None),
            LegacyMetaV2VersionType::Delete | LegacyMetaV2VersionType::DeleteMarker => {
                (VersionType::Delete, None, value.delete_marker.map(TryInto::try_into).transpose()?)
            }
        };

        Ok(Self {
            version_type,
            legacy_object: None,
            object,
            delete_marker,
            write_version: value.write_version,
            uses_legacy_checksum: true,
        })
    }
}

impl From<FileInfo> for FileMetaVersion {
    fn from(value: FileInfo) -> Self {
        if value.is_storage_delete_marker() {
            FileMetaVersion {
                version_type: VersionType::Delete,
                legacy_object: None,
                delete_marker: Some(MetaDeleteMarker::from(value)),
                object: None,
                write_version: 0,
                uses_legacy_checksum: false,
            }
        } else {
            // A `deleted` FileInfo that is not a canonical delete marker is only
            // legitimate as a purge-pending payload, which carries real erasure
            // geometry and is intentionally serialized as an Object. A `deleted`
            // FileInfo with neither a canonical-marker shape nor valid erasure
            // geometry would silently serialize as a zero-geometry MetaObject that
            // later fails `validate_for_metadata_read`. Write paths validate first
            // (`validate_for_erasure_write` / `validate_for_metadata_read`), so this
            // is a caller bug — surface it rather than writing malformed metadata
            // silently. (`From` is infallible, so this cannot return an error.)
            if value.deleted && !value.has_valid_erasure_geometry() {
                tracing::warn!(
                    event = "filemeta_non_canonical_deleted_fileinfo_as_object",
                    component = "filemeta",
                    "serializing a deleted FileInfo that is neither a canonical delete marker nor a valid erasure payload as an Object version; upstream validation should have rejected it"
                );
            }
            FileMetaVersion {
                version_type: VersionType::Object,
                legacy_object: None,
                delete_marker: None,
                object: Some(MetaObject::from(value)),
                write_version: 0,
                uses_legacy_checksum: false,
            }
        }
    }
}

impl TryFrom<FileMetaShallowVersion> for FileMetaVersion {
    type Error = Error;

    fn try_from(value: FileMetaShallowVersion) -> std::result::Result<Self, Self::Error> {
        FileMetaVersion::try_from(value.meta.as_slice())
    }
}

#[derive(Serialize, Deserialize, Debug, PartialEq, Default, Clone, Eq, Hash)]
pub struct FileMetaVersionHeader {
    pub version_id: Option<Uuid>,
    pub mod_time: Option<OffsetDateTime>,
    pub signature: [u8; 4],
    pub version_type: VersionType,
    pub flags: u8,
    pub ec_n: u8,
    pub ec_m: u8,
}

impl FileMetaVersionHeader {
    fn reset_for_unmarshal(&mut self) {
        self.version_id = None;
        self.mod_time = None;
        self.signature = [0; 4];
        self.version_type = VersionType::Invalid;
        self.flags = 0;
        self.ec_n = 0;
        self.ec_m = 0;
    }

    pub fn has_ec(&self) -> bool {
        self.ec_m > 0 && self.ec_n > 0
    }

    pub fn write_quorum(&self, fallback_quorum: usize) -> usize {
        if self.version_type != VersionType::Object || !self.has_ec() {
            return fallback_quorum;
        }

        write_quorum_from_erasure(usize::from(self.ec_m), usize::from(self.ec_n)).unwrap_or(fallback_quorum)
    }

    pub fn matches_not_strict(&self, o: &FileMetaVersionHeader) -> bool {
        let mut ok = self.version_id == o.version_id && self.version_type == o.version_type && self.matches_ec(o);
        // Disk-loaded headers keep the null version as Some(nil), not None: all null
        // versions share one id, so mod_time is the only thing distinguishing an
        // interrupted overwrite from the committed version.
        if self.version_id.is_none() || self.version_id == Some(Uuid::nil()) {
            ok = ok && self.mod_time == o.mod_time;
        }

        ok
    }

    pub fn matches_ec(&self, o: &FileMetaVersionHeader) -> bool {
        if self.has_ec() && o.has_ec() {
            return self.ec_n == o.ec_n && self.ec_m == o.ec_m;
        }

        true
    }

    pub fn free_version(&self) -> bool {
        self.flags & XL_FLAG_FREE_VERSION != 0
    }

    pub fn sorts_before(&self, o: &FileMetaVersionHeader) -> bool {
        if self == o {
            return false;
        }

        // Prefer newest modtime.
        if self.mod_time != o.mod_time {
            return self.mod_time > o.mod_time;
        }

        // The following doesn't make too much sense, but we want sort to be consistent nonetheless.
        // Prefer lower types
        if self.version_type != o.version_type {
            return self.version_type < o.version_type;
        }
        // Consistent sort on signature
        match self.signature.cmp(&o.signature) {
            Ordering::Greater => {
                return true;
            }
            Ordering::Less => {
                return false;
            }
            _ => {}
        }
        // Consistent sort on version_id
        match self.version_id.cmp(&o.version_id) {
            Ordering::Greater => {
                return true;
            }
            Ordering::Less => {
                return false;
            }
            _ => {}
        }

        if self.flags != o.flags {
            return self.flags > o.flags;
        }

        false
    }

    pub fn uses_data_dir(&self) -> bool {
        self.flags & Flags::UsesDataDir as u8 != 0
    }

    pub fn marshal_msg(&self) -> Result<Vec<u8>> {
        let mut wr = Vec::new();

        // array len 7
        rmp::encode::write_array_len(&mut wr, 7)?;

        // version_id
        rmp::encode::write_bin(&mut wr, self.version_id.unwrap_or_default().as_bytes())?;
        // mod_time
        rmp::encode::write_i64(&mut wr, self.mod_time.unwrap_or(OffsetDateTime::UNIX_EPOCH).unix_timestamp_nanos() as i64)?;
        // signature
        rmp::encode::write_bin(&mut wr, self.signature.as_slice())?;
        // version_type
        rmp::encode::write_uint8(&mut wr, self.version_type.to_u8())?;
        // flags
        rmp::encode::write_uint8(&mut wr, self.flags)?;
        // ec_n
        rmp::encode::write_uint8(&mut wr, self.ec_n)?;
        // ec_m
        rmp::encode::write_uint8(&mut wr, self.ec_m)?;

        Ok(wr)
    }

    pub fn unmarshal_v(&mut self, version: u8, buf: &[u8]) -> Result<u64> {
        match version {
            1 => self.unmarshal_v1(buf),
            2 => self.unmarshal_v2(buf),
            3 => self.unmarshal_msg(buf),
            _ => Err(Error::other(format!("unknown xl header version: {version}"))),
        }
    }

    pub fn unmarshal_v1(&mut self, buf: &[u8]) -> Result<u64> {
        self.reset_for_unmarshal();

        let mut cur = Cursor::new(buf);
        let alen = rmp::decode::read_array_len(&mut cur)?;
        if alen != 4 {
            return Err(Error::other(format!("version header array len err need 4 got {alen}")));
        }

        rmp::decode::read_bin_len(&mut cur)?;
        let mut version_id = [0u8; 16];
        cur.read_exact(&mut version_id)?;
        self.version_id = Some(Uuid::from_bytes(version_id));

        let unix: i128 = rmp::decode::read_int(&mut cur)?;
        let time = OffsetDateTime::from_unix_timestamp_nanos(unix)?;
        if time != OffsetDateTime::UNIX_EPOCH {
            self.mod_time = Some(time);
        }

        let typ: u8 = rmp::decode::read_int(&mut cur)?;
        self.version_type = VersionType::from_u8(typ);
        self.flags = rmp::decode::read_int(&mut cur)?;

        Ok(cur.position())
    }

    pub fn unmarshal_v2(&mut self, buf: &[u8]) -> Result<u64> {
        self.reset_for_unmarshal();

        let mut cur = Cursor::new(buf);
        let alen = rmp::decode::read_array_len(&mut cur)?;
        if alen != 5 {
            return Err(Error::other(format!("version header array len err need 5 got {alen}")));
        }

        rmp::decode::read_bin_len(&mut cur)?;
        let mut version_id = [0u8; 16];
        cur.read_exact(&mut version_id)?;
        self.version_id = Some(Uuid::from_bytes(version_id));

        let unix: i128 = rmp::decode::read_int(&mut cur)?;
        let time = OffsetDateTime::from_unix_timestamp_nanos(unix)?;
        if time != OffsetDateTime::UNIX_EPOCH {
            self.mod_time = Some(time);
        }

        rmp::decode::read_bin_len(&mut cur)?;
        cur.read_exact(&mut self.signature)?;

        let typ: u8 = rmp::decode::read_int(&mut cur)?;
        self.version_type = VersionType::from_u8(typ);
        self.flags = rmp::decode::read_int(&mut cur)?;

        Ok(cur.position())
    }

    pub fn unmarshal_msg(&mut self, buf: &[u8]) -> Result<u64> {
        self.reset_for_unmarshal();

        let mut cur = Cursor::new(buf);
        let alen = rmp::decode::read_array_len(&mut cur)?;
        if alen != 7 {
            return Err(Error::other(format!("version header array len err need 7 got {alen}")));
        }

        // version_id
        rmp::decode::read_bin_len(&mut cur)?;
        let mut buf = [0u8; 16];
        cur.read_exact(&mut buf)?;
        self.version_id = {
            let id = Uuid::from_bytes(buf);
            // if id.is_nil() { None } else { Some(id) }
            Some(id)
        };

        // mod_time
        let unix: i128 = rmp::decode::read_int(&mut cur)?;

        let time = OffsetDateTime::from_unix_timestamp_nanos(unix)?;
        if time == OffsetDateTime::UNIX_EPOCH {
            self.mod_time = None;
        } else {
            self.mod_time = Some(time);
        }

        // signature
        rmp::decode::read_bin_len(&mut cur)?;
        cur.read_exact(&mut self.signature)?;

        // version_type
        let typ: u8 = rmp::decode::read_int(&mut cur)?;
        self.version_type = VersionType::from_u8(typ);

        // flags
        self.flags = rmp::decode::read_int(&mut cur)?;
        // ec_n
        self.ec_n = rmp::decode::read_int(&mut cur)?;
        // ec_m
        self.ec_m = rmp::decode::read_int(&mut cur)?;

        Ok(cur.position())
    }

    /// Get signature for header
    pub fn get_signature(&self) -> [u8; 4] {
        self.signature
    }

    /// Check if this header represents inline data
    pub fn inline_data(&self) -> bool {
        self.flags & Flags::InlineData as u8 != 0
    }

    /// Update signature based on version content
    pub fn update_signature(&mut self, version: &FileMetaVersion) {
        self.signature = version.get_signature();
    }
}

impl PartialOrd for FileMetaVersionHeader {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for FileMetaVersionHeader {
    fn cmp(&self, other: &Self) -> Ordering {
        match self.mod_time.cmp(&other.mod_time) {
            core::cmp::Ordering::Equal => {}
            ord => return ord,
        }

        match self.version_type.cmp(&other.version_type) {
            core::cmp::Ordering::Equal => {}
            ord => return ord,
        }
        match self.signature.cmp(&other.signature) {
            core::cmp::Ordering::Equal => {}
            ord => return ord,
        }
        match self.version_id.cmp(&other.version_id) {
            core::cmp::Ordering::Equal => {}
            ord => return ord,
        }
        self.flags.cmp(&other.flags)
    }
}

impl From<FileMetaVersion> for FileMetaVersionHeader {
    fn from(value: FileMetaVersion) -> Self {
        let flags = {
            let mut f: u8 = 0;
            if value.free_version() {
                f |= Flags::FreeVersion as u8;
            }

            if value.version_type == VersionType::Object && value.object.as_ref().map(|v| v.uses_data_dir()).unwrap_or_default() {
                f |= Flags::UsesDataDir as u8;
            }

            if value.version_type == VersionType::Object && value.object.as_ref().map(|v| v.inlinedata()).unwrap_or_default() {
                f |= Flags::InlineData as u8;
            }

            f
        };

        let (ec_n, ec_m) = match (value.version_type == VersionType::Object, value.object.as_ref()) {
            (true, Some(obj)) => (obj.erasure_n as u8, obj.erasure_m as u8),
            _ => (0, 0),
        };

        Self {
            version_id: value.get_version_id(),
            mod_time: value.get_mod_time(),
            signature: value.get_signature(),
            version_type: value.version_type,
            flags,
            ec_n,
            ec_m,
        }
    }
}

#[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq)]
// Because of custom message_pack, field order must be guaranteed
pub struct MetaObject {
    #[serde(rename = "ID")]
    pub version_id: Option<Uuid>, // Version ID
    #[serde(rename = "DDir")]
    pub data_dir: Option<Uuid>, // Data dir ID
    #[serde(rename = "EcAlgo")]
    pub erasure_algorithm: ErasureAlgo, // Erasure coding algorithm
    #[serde(rename = "EcM")]
    pub erasure_m: usize, // Erasure data blocks
    #[serde(rename = "EcN")]
    pub erasure_n: usize, // Erasure parity blocks
    #[serde(rename = "EcBSize")]
    pub erasure_block_size: usize, // Erasure block size
    #[serde(rename = "EcIndex")]
    pub erasure_index: usize, // Erasure disk index
    #[serde(rename = "EcDist")]
    pub erasure_dist: Vec<u8>, // Erasure distribution
    #[serde(rename = "CSumAlgo")]
    pub bitrot_checksum_algo: ChecksumAlgo, // Bitrot checksum algo
    #[serde(rename = "PartNums")]
    pub part_numbers: Vec<usize>, // Part Numbers
    #[serde(rename = "PartETags")]
    pub part_etags: Vec<String>, // Part ETags
    #[serde(rename = "PartSizes")]
    pub part_sizes: Vec<usize>, // Part Sizes
    #[serde(rename = "PartASizes")]
    pub part_actual_sizes: Vec<i64>, // Part ActualSizes (compression)
    #[serde(rename = "PartIdx")]
    pub part_indices: Vec<Bytes>, // Part Indexes (compression)
    #[serde(rename = "Size")]
    pub size: i64, // Object version size
    #[serde(rename = "MTime")]
    pub mod_time: Option<OffsetDateTime>, // Object version modified time
    #[serde(rename = "MetaSys")]
    pub meta_sys: HashMap<String, Vec<u8>>, // Object version internal metadata
    #[serde(rename = "MetaUsr")]
    pub meta_user: HashMap<String, String>, // Object version metadata set by user
}

impl TryFrom<LegacyMetaV2Object> for MetaObject {
    type Error = Error;

    fn try_from(value: LegacyMetaV2Object) -> std::result::Result<Self, Self::Error> {
        Ok(Self {
            version_id: parse_legacy_uuid_bytes(&value.version_id, "version_id")?,
            data_dir: parse_legacy_uuid_bytes(&value.data_dir, "data_dir")?,
            erasure_algorithm: parse_legacy_erasure_algo(&value.erasure_algorithm),
            erasure_m: value.erasure_m,
            erasure_n: value.erasure_n,
            erasure_block_size: value.erasure_block_size,
            erasure_index: value.erasure_index,
            erasure_dist: value.erasure_dist,
            bitrot_checksum_algo: parse_legacy_checksum_algo(&value.bitrot_checksum_algo),
            part_numbers: value.part_numbers,
            part_etags: value.part_etags,
            part_sizes: value.part_sizes,
            part_actual_sizes: value.part_actual_sizes,
            part_indices: value.part_indices.into_iter().map(Bytes::from).collect(),
            size: value.size,
            mod_time: value.mod_time,
            meta_sys: value.meta_sys,
            meta_user: value.meta_user,
        })
    }
}

#[derive(Serialize, Deserialize, Debug, Default, Clone, PartialEq)]
pub struct MetaObjectV1 {
    #[serde(rename = "Version")]
    pub version: String,
    #[serde(rename = "Format")]
    pub format: String,
    #[serde(rename = "Stat")]
    pub stat: MetaObjectV1Stat,
    #[serde(rename = "Erasure")]
    pub erasure: MetaObjectV1Erasure,
    #[serde(rename = "Meta")]
    pub meta: HashMap<String, String>,
    #[serde(rename = "Parts")]
    pub parts: Vec<MetaObjectV1Part>,
    #[serde(rename = "VersionID")]
    pub version_id: String,
    #[serde(rename = "DataDir")]
    pub data_dir: String,
}

#[derive(Serialize, Deserialize, Debug, Default, Clone, PartialEq)]
pub struct MetaObjectV1Stat {
    #[serde(rename = "Size")]
    pub size: i64,
    #[serde(rename = "ModTime")]
    pub mod_time: Option<OffsetDateTime>,
    #[serde(rename = "Name")]
    pub name: String,
    #[serde(rename = "Dir")]
    pub dir: bool,
    #[serde(rename = "Mode")]
    pub mode: u32,
}

#[derive(Serialize, Deserialize, Debug, Default, Clone, PartialEq)]
pub struct MetaObjectV1ChecksumInfo {
    #[serde(rename = "PartNumber")]
    pub part_number: usize,
    #[serde(rename = "Algorithm")]
    pub algorithm: String,
    #[serde(rename = "Hash")]
    pub hash: Vec<u8>,
}

#[derive(Serialize, Deserialize, Debug, Default, Clone, PartialEq)]
pub struct MetaObjectV1Erasure {
    #[serde(rename = "Algorithm")]
    pub algorithm: String,
    #[serde(rename = "DataBlocks")]
    pub data_blocks: usize,
    #[serde(rename = "ParityBlocks")]
    pub parity_blocks: usize,
    #[serde(rename = "BlockSize")]
    pub block_size: usize,
    #[serde(rename = "Index")]
    pub index: usize,
    #[serde(rename = "Distribution")]
    pub distribution: Vec<usize>,
    #[serde(rename = "Checksums")]
    pub checksums: Vec<MetaObjectV1ChecksumInfo>,
}

#[derive(Serialize, Deserialize, Debug, Default, Clone, PartialEq)]
pub struct MetaObjectV1Part {
    #[serde(rename = "e")]
    pub etag: String,
    #[serde(rename = "n")]
    pub number: usize,
    #[serde(rename = "s")]
    pub size: usize,
    #[serde(rename = "as")]
    pub actual_size: i64,
    #[serde(rename = "mt")]
    pub mod_time: Option<OffsetDateTime>,
    #[serde(rename = "i")]
    pub index: Option<Bytes>,
    #[serde(rename = "crc")]
    pub checksums: Option<HashMap<String, String>>,
    #[serde(rename = "err")]
    pub error: Option<String>,
}

impl MetaObjectV1 {
    fn version_id(&self) -> Option<Uuid> {
        if self.version_id.is_empty() {
            None
        } else {
            Uuid::parse_str(&self.version_id).ok().filter(|id| !id.is_nil())
        }
    }

    fn valid(&self) -> bool {
        if self.format != "xl" || self.stat.mod_time.is_none() {
            return false;
        }

        let data_blocks = self.erasure.data_blocks;
        let parity_blocks = self.erasure.parity_blocks;
        data_blocks > 0
            && data_blocks >= parity_blocks
            && self.erasure.index > 0
            && self.erasure.index <= data_blocks + parity_blocks
            && crate::fileinfo::is_valid_distribution(&self.erasure.distribution, data_blocks + parity_blocks)
    }

    fn decode_from<R: std::io::Read>(&mut self, rd: &mut R) -> Result<()> {
        let mut fields = rmp::decode::read_map_len(rd)?;
        *self = Self::default();

        while fields > 0 {
            fields -= 1;
            let key = read_msgp_string(rd)?;
            match key.as_str() {
                "Version" => self.version = read_msgp_string(rd)?,
                "Format" => self.format = read_msgp_string(rd)?,
                "Stat" => self.stat.decode_from(rd)?,
                "Erasure" => self.erasure.decode_from(rd)?,
                "Meta" => {
                    let len = rmp::decode::read_map_len(rd)? as usize;
                    self.meta.clear();
                    for _ in 0..len {
                        self.meta.insert(read_msgp_string(rd)?, read_msgp_string(rd)?);
                    }
                }
                "Parts" => {
                    let len = rmp::decode::read_array_len(rd)? as usize;
                    self.parts.clear();
                    self.parts.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        let mut part = MetaObjectV1Part::default();
                        part.decode_from(rd)?;
                        self.parts.push(part);
                    }
                }
                "VersionID" => self.version_id = read_msgp_string(rd)?,
                "DataDir" => self.data_dir = read_msgp_string(rd)?,
                _ => skip_msgp_value(rd)?,
            }
        }

        Ok(())
    }

    /// Symmetric encoder for the V1 (Legacy) object body. Kept field-for-field
    /// consistent with `decode_from` so a Legacy version round-trips through
    /// `FileMetaVersion::encode_to` without losing its body (backlog#799 B18).
    fn encode_to<W: std::io::Write>(&self, wr: &mut W) -> Result<()> {
        rmp::encode::write_map_len(wr, 8)?;

        rmp::encode::write_str(wr, "Version")?;
        rmp::encode::write_str(wr, &self.version)?;

        rmp::encode::write_str(wr, "Format")?;
        rmp::encode::write_str(wr, &self.format)?;

        rmp::encode::write_str(wr, "Stat")?;
        self.stat.encode_to(wr)?;

        rmp::encode::write_str(wr, "Erasure")?;
        self.erasure.encode_to(wr)?;

        rmp::encode::write_str(wr, "Meta")?;
        rmp::encode::write_map_len(wr, self.meta.len() as u32)?;
        for (k, v) in &self.meta {
            rmp::encode::write_str(wr, k)?;
            rmp::encode::write_str(wr, v)?;
        }

        rmp::encode::write_str(wr, "Parts")?;
        rmp::encode::write_array_len(wr, self.parts.len() as u32)?;
        for part in &self.parts {
            part.encode_to(wr)?;
        }

        rmp::encode::write_str(wr, "VersionID")?;
        rmp::encode::write_str(wr, &self.version_id)?;

        rmp::encode::write_str(wr, "DataDir")?;
        rmp::encode::write_str(wr, &self.data_dir)?;

        Ok(())
    }

    fn get_signature(&self) -> [u8; 4] {
        let mut hasher = xxhash_rust::xxh64::Xxh64::new(XXHASH_SEED);
        hasher.update(self.version.as_bytes());
        hasher.update(self.format.as_bytes());
        hasher.update(&self.stat.size.to_le_bytes());
        hasher.update(&self.stat.mode.to_le_bytes());
        if let Some(mod_time) = self.stat.mod_time {
            hasher.update(&mod_time.unix_timestamp_nanos().to_le_bytes());
        }
        hasher.update(self.erasure.algorithm.as_bytes());
        hasher.update(&(self.erasure.data_blocks as u64).to_le_bytes());
        hasher.update(&(self.erasure.parity_blocks as u64).to_le_bytes());
        hasher.update(&(self.erasure.block_size as u64).to_le_bytes());
        for v in &self.erasure.distribution {
            hasher.update(&(*v as u64).to_le_bytes());
        }
        for checksum in &self.erasure.checksums {
            hasher.update(&(checksum.part_number as u64).to_le_bytes());
            hasher.update(checksum.algorithm.as_bytes());
            hasher.update(&checksum.hash);
        }
        let mut meta_keys: Vec<_> = self.meta.iter().collect();
        meta_keys.sort_by(|a, b| a.0.cmp(b.0));
        for (k, v) in meta_keys {
            hasher.update(k.as_bytes());
            hasher.update(v.as_bytes());
        }
        for part in &self.parts {
            hasher.update(&(part.number as u64).to_le_bytes());
            hasher.update(&(part.size as u64).to_le_bytes());
            hasher.update(&part.actual_size.to_le_bytes());
            hasher.update(part.etag.as_bytes());
            if let Some(mod_time) = part.mod_time {
                hasher.update(&mod_time.unix_timestamp_nanos().to_le_bytes());
            }
            if let Some(index) = &part.index {
                hasher.update(index);
            }
        }
        let hash = hasher.finish();
        let bytes = hash.to_le_bytes();
        [bytes[0], bytes[1], bytes[2], bytes[3]]
    }

    fn to_fileinfo(&self, volume: &str, path: &str) -> FileInfo {
        FileInfo {
            volume: volume.to_string(),
            name: path.to_string(),
            version_id: self.version_id(),
            mod_time: self.stat.mod_time,
            size: self.stat.size,
            mode: Some(self.stat.mode),
            metadata: self.meta.clone(),
            parts: self.parts.iter().cloned().map(Into::into).collect(),
            erasure: self.erasure.clone().into(),
            num_versions: 1,
            data_dir: Uuid::parse_str(&self.data_dir).ok().filter(|id| !id.is_nil()),
            ..Default::default()
        }
    }
}

impl MetaObjectV1Stat {
    fn decode_from<R: std::io::Read>(&mut self, rd: &mut R) -> Result<()> {
        let mut fields = rmp::decode::read_map_len(rd)?;
        *self = Self::default();

        while fields > 0 {
            fields -= 1;
            let key = read_msgp_string(rd)?;
            match key.as_str() {
                "Size" => self.size = rmp::decode::read_int(rd)?,
                "ModTime" => self.mod_time = Some(read_msgp_time(rd)?),
                "Name" => self.name = read_msgp_string(rd)?,
                "Dir" => self.dir = rmp::decode::read_bool(rd)?,
                "Mode" => self.mode = rmp::decode::read_u32(rd)?,
                _ => skip_msgp_value(rd)?,
            }
        }

        Ok(())
    }

    fn encode_to<W: std::io::Write>(&self, wr: &mut W) -> Result<()> {
        // `ModTime` is only written when present, mirroring `decode_from` (which
        // sets it only when the field exists) so a `None` mod_time stays absent
        // rather than round-tripping to `Some(UNIX_EPOCH)`.
        let map_len: u32 = if self.mod_time.is_some() { 5 } else { 4 };
        rmp::encode::write_map_len(wr, map_len)?;

        rmp::encode::write_str(wr, "Size")?;
        rmp::encode::write_sint(wr, self.size)?;

        if let Some(mod_time) = self.mod_time {
            rmp::encode::write_str(wr, "ModTime")?;
            write_msgp_time(wr, mod_time)?;
        }

        rmp::encode::write_str(wr, "Name")?;
        rmp::encode::write_str(wr, &self.name)?;

        rmp::encode::write_str(wr, "Dir")?;
        rmp::encode::write_bool(wr, self.dir)?;

        rmp::encode::write_str(wr, "Mode")?;
        // `Mode` decodes with the strict `read_u32`, which only accepts the U32
        // marker — a narrower `write_uint` marker would fail to round-trip.
        rmp::encode::write_u32(wr, self.mode)?;

        Ok(())
    }
}

impl MetaObjectV1Erasure {
    fn decode_from<R: std::io::Read>(&mut self, rd: &mut R) -> Result<()> {
        let mut fields = rmp::decode::read_map_len(rd)?;
        *self = Self::default();

        while fields > 0 {
            fields -= 1;
            let key = read_msgp_string(rd)?;
            match key.as_str() {
                "Algorithm" => self.algorithm = read_msgp_string(rd)?,
                "DataBlocks" => self.data_blocks = rmp::decode::read_int::<i64, _>(rd)? as usize,
                "ParityBlocks" => self.parity_blocks = rmp::decode::read_int::<i64, _>(rd)? as usize,
                "BlockSize" => self.block_size = rmp::decode::read_int::<i64, _>(rd)? as usize,
                "Index" => self.index = rmp::decode::read_int::<i64, _>(rd)? as usize,
                "Distribution" => {
                    let len = rmp::decode::read_array_len(rd)? as usize;
                    self.distribution.clear();
                    self.distribution.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        self.distribution.push(rmp::decode::read_int::<i64, _>(rd)? as usize);
                    }
                }
                "Checksums" => {
                    let len = rmp::decode::read_array_len(rd)? as usize;
                    self.checksums.clear();
                    self.checksums.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        let mut checksum = MetaObjectV1ChecksumInfo::default();
                        checksum.decode_from(rd)?;
                        self.checksums.push(checksum);
                    }
                }
                _ => skip_msgp_value(rd)?,
            }
        }

        Ok(())
    }

    fn encode_to<W: std::io::Write>(&self, wr: &mut W) -> Result<()> {
        rmp::encode::write_map_len(wr, 7)?;

        rmp::encode::write_str(wr, "Algorithm")?;
        rmp::encode::write_str(wr, &self.algorithm)?;

        rmp::encode::write_str(wr, "DataBlocks")?;
        rmp::encode::write_sint(wr, self.data_blocks as i64)?;

        rmp::encode::write_str(wr, "ParityBlocks")?;
        rmp::encode::write_sint(wr, self.parity_blocks as i64)?;

        rmp::encode::write_str(wr, "BlockSize")?;
        rmp::encode::write_sint(wr, self.block_size as i64)?;

        rmp::encode::write_str(wr, "Index")?;
        rmp::encode::write_sint(wr, self.index as i64)?;

        rmp::encode::write_str(wr, "Distribution")?;
        rmp::encode::write_array_len(wr, self.distribution.len() as u32)?;
        for v in &self.distribution {
            rmp::encode::write_sint(wr, *v as i64)?;
        }

        rmp::encode::write_str(wr, "Checksums")?;
        rmp::encode::write_array_len(wr, self.checksums.len() as u32)?;
        for checksum in &self.checksums {
            checksum.encode_to(wr)?;
        }

        Ok(())
    }
}

impl MetaObjectV1ChecksumInfo {
    fn decode_from<R: std::io::Read>(&mut self, rd: &mut R) -> Result<()> {
        let mut fields = rmp::decode::read_map_len(rd)?;
        *self = Self::default();

        while fields > 0 {
            fields -= 1;
            let key = read_msgp_string(rd)?;
            match key.as_str() {
                "PartNumber" => self.part_number = rmp::decode::read_int::<i64, _>(rd)? as usize,
                "Algorithm" => self.algorithm = read_msgp_string(rd)?,
                "Hash" => self.hash = read_msgp_bin(rd)?,
                _ => skip_msgp_value(rd)?,
            }
        }

        Ok(())
    }

    fn encode_to<W: std::io::Write>(&self, wr: &mut W) -> Result<()> {
        rmp::encode::write_map_len(wr, 3)?;

        rmp::encode::write_str(wr, "PartNumber")?;
        rmp::encode::write_sint(wr, self.part_number as i64)?;

        rmp::encode::write_str(wr, "Algorithm")?;
        rmp::encode::write_str(wr, &self.algorithm)?;

        rmp::encode::write_str(wr, "Hash")?;
        rmp::encode::write_bin(wr, &self.hash)?;

        Ok(())
    }
}

impl MetaObjectV1Part {
    fn decode_from<R: std::io::Read>(&mut self, rd: &mut R) -> Result<()> {
        let mut fields = rmp::decode::read_map_len(rd)?;
        *self = Self::default();

        while fields > 0 {
            fields -= 1;
            let key = read_msgp_string(rd)?;
            match key.as_str() {
                "e" => self.etag = read_msgp_string(rd)?,
                "n" => self.number = rmp::decode::read_int::<i64, _>(rd)? as usize,
                "s" => self.size = rmp::decode::read_int::<i64, _>(rd)? as usize,
                "as" => self.actual_size = rmp::decode::read_int(rd)?,
                "mt" => self.mod_time = Some(read_msgp_time(rd)?),
                "i" => self.index = Some(Bytes::from(read_msgp_bin(rd)?)),
                "crc" => {
                    let len = rmp::decode::read_map_len(rd)? as usize;
                    let mut checksums = HashMap::with_capacity(prealloc_hint(len));
                    for _ in 0..len {
                        checksums.insert(read_msgp_string(rd)?, read_msgp_string(rd)?);
                    }
                    self.checksums = Some(checksums);
                }
                "err" => self.error = Some(read_msgp_string(rd)?),
                _ => skip_msgp_value(rd)?,
            }
        }

        Ok(())
    }

    fn encode_to<W: std::io::Write>(&self, wr: &mut W) -> Result<()> {
        // Non-optional scalars are always written; optional fields only when
        // present, so a decoded part round-trips (absent stays absent).
        let mut map_len: u32 = 4; // e, n, s, as
        if self.mod_time.is_some() {
            map_len += 1;
        }
        if self.index.is_some() {
            map_len += 1;
        }
        if self.checksums.is_some() {
            map_len += 1;
        }
        if self.error.is_some() {
            map_len += 1;
        }
        rmp::encode::write_map_len(wr, map_len)?;

        rmp::encode::write_str(wr, "e")?;
        rmp::encode::write_str(wr, &self.etag)?;

        rmp::encode::write_str(wr, "n")?;
        rmp::encode::write_sint(wr, self.number as i64)?;

        rmp::encode::write_str(wr, "s")?;
        rmp::encode::write_sint(wr, self.size as i64)?;

        rmp::encode::write_str(wr, "as")?;
        rmp::encode::write_sint(wr, self.actual_size)?;

        if let Some(mt) = self.mod_time {
            rmp::encode::write_str(wr, "mt")?;
            write_msgp_time(wr, mt)?;
        }

        if let Some(ref index) = self.index {
            rmp::encode::write_str(wr, "i")?;
            rmp::encode::write_bin(wr, index)?;
        }

        if let Some(ref checksums) = self.checksums {
            rmp::encode::write_str(wr, "crc")?;
            rmp::encode::write_map_len(wr, checksums.len() as u32)?;
            for (k, v) in checksums {
                rmp::encode::write_str(wr, k)?;
                rmp::encode::write_str(wr, v)?;
            }
        }

        if let Some(ref err) = self.error {
            rmp::encode::write_str(wr, "err")?;
            rmp::encode::write_str(wr, err)?;
        }

        Ok(())
    }
}

impl From<MetaObjectV1Erasure> for ErasureInfo {
    fn from(value: MetaObjectV1Erasure) -> Self {
        ErasureInfo {
            algorithm: value.algorithm,
            data_blocks: value.data_blocks,
            parity_blocks: value.parity_blocks,
            block_size: value.block_size,
            index: value.index,
            distribution: value.distribution,
            checksums: value.checksums.into_iter().map(Into::into).collect(),
        }
    }
}

impl From<MetaObjectV1ChecksumInfo> for ChecksumInfo {
    fn from(value: MetaObjectV1ChecksumInfo) -> Self {
        ChecksumInfo {
            part_number: value.part_number,
            algorithm: match value.algorithm.as_str() {
                "sha256" => HashAlgorithm::SHA256,
                "highwayhash256" => HashAlgorithm::HighwayHash256,
                "highwayhash256S" => HashAlgorithm::HighwayHash256S,
                "blake2b" | "blake2b512" => HashAlgorithm::BLAKE2b512,
                _ => HashAlgorithm::HighwayHash256S,
            },
            hash: Bytes::from(value.hash),
        }
    }
}

impl From<MetaObjectV1Part> for ObjectPartInfo {
    fn from(value: MetaObjectV1Part) -> Self {
        ObjectPartInfo {
            etag: value.etag,
            number: value.number,
            size: value.size,
            actual_size: value.actual_size,
            mod_time: value.mod_time,
            index: value.index,
            checksums: value.checksums,
            error: value.error,
        }
    }
}

impl MetaObject {
    pub fn unmarshal_msg(&mut self, buf: &[u8]) -> Result<u64> {
        let mut cur = std::io::Cursor::new(buf);
        self.decode_from(&mut cur)?;
        Ok(cur.position())
    }

    // marshal_msg custom messagepack naming consistent with go
    pub fn marshal_msg(&self) -> Result<Vec<u8>> {
        let mut wr = Vec::new();
        self.encode_to(&mut wr)?;
        Ok(wr)
    }

    /// Compute this object version's header signature, mirroring MinIO's
    /// `xlMetaV2Object.Signature`. See [`FileMetaVersion::get_signature`] for
    /// why divergence detection requires covering every body field.
    pub fn get_signature(&self) -> [u8; 4] {
        let mut c = self.clone();

        // Zero fields that legitimately vary per disk within an erasure set.
        c.erasure_index = 0;

        // Treat an all-empty PartETags vector the same as an absent one, so two
        // disks that encode `[]` vs `["", ""]` do not falsely diverge.
        if c.part_etags.iter().all(String::is_empty) {
            c.part_etags.clear();
        }

        // Fold maps in with an order-independent hash: msgpack map order is not
        // stable across disks, so they must not be part of the marshaled body.
        let mut crc = hash_deterministic_string(&c.meta_user);
        crc ^= hash_deterministic_bytes(&c.meta_sys);
        c.meta_sys.clear();
        c.meta_user.clear();

        if let Ok(bytes) = c.marshal_msg() {
            crc ^= xxhash_rust::xxh64::xxh64(&bytes, XXHASH_SEED);
        }

        fold_signature(crc)
    }

    pub fn encode_to<W: std::io::Write>(&self, wr: &mut W) -> Result<()> {
        // Variable map size: omit PartIdx when empty
        let mut map_len = 18u32;
        if self.part_indices.is_empty() {
            map_len -= 1;
        }
        rmp::encode::write_map_len(wr, map_len)?;

        // ID
        rmp::encode::write_str(wr, "ID")?;
        rmp::encode::write_bin(wr, self.version_id.unwrap_or_default().as_bytes())?;

        // DDir
        rmp::encode::write_str(wr, "DDir")?;
        rmp::encode::write_bin(wr, self.data_dir.unwrap_or_default().as_bytes())?;

        // EcAlgo
        rmp::encode::write_str(wr, "EcAlgo")?;
        rmp::encode::write_uint(wr, self.erasure_algorithm.to_u8() as u64)?;

        // EcM
        rmp::encode::write_str(wr, "EcM")?;
        rmp::encode::write_sint(wr, self.erasure_m as i64)?;

        // EcN
        rmp::encode::write_str(wr, "EcN")?;
        rmp::encode::write_sint(wr, self.erasure_n as i64)?;

        // EcBSize
        rmp::encode::write_str(wr, "EcBSize")?;
        rmp::encode::write_sint(wr, self.erasure_block_size as i64)?;

        // EcIndex
        rmp::encode::write_str(wr, "EcIndex")?;
        rmp::encode::write_sint(wr, self.erasure_index as i64)?;

        // EcDist
        rmp::encode::write_str(wr, "EcDist")?;
        rmp::encode::write_array_len(wr, self.erasure_dist.len() as u32)?;
        for v in &self.erasure_dist {
            rmp::encode::write_uint(wr, *v as u64)?;
        }

        // CSumAlgo
        rmp::encode::write_str(wr, "CSumAlgo")?;
        rmp::encode::write_uint(wr, self.bitrot_checksum_algo.to_u8() as u64)?;

        // PartNums
        rmp::encode::write_str(wr, "PartNums")?;
        rmp::encode::write_array_len(wr, self.part_numbers.len() as u32)?;
        for n in &self.part_numbers {
            rmp::encode::write_sint(wr, *n as i64)?;
        }

        // PartETags (write nil when empty)
        rmp::encode::write_str(wr, "PartETags")?;
        if self.part_etags.is_empty() {
            rmp::encode::write_nil(wr)?;
        } else {
            rmp::encode::write_array_len(wr, self.part_etags.len() as u32)?;
            for et in &self.part_etags {
                rmp::encode::write_str(wr, et)?;
            }
        }

        // PartSizes
        rmp::encode::write_str(wr, "PartSizes")?;
        rmp::encode::write_array_len(wr, self.part_sizes.len() as u32)?;
        for s in &self.part_sizes {
            rmp::encode::write_sint(wr, *s as i64)?;
        }

        // PartASizes (write nil when empty)
        rmp::encode::write_str(wr, "PartASizes")?;
        if self.part_actual_sizes.is_empty() {
            rmp::encode::write_nil(wr)?;
        } else {
            rmp::encode::write_array_len(wr, self.part_actual_sizes.len() as u32)?;
            for s in &self.part_actual_sizes {
                rmp::encode::write_sint(wr, *s)?;
            }
        }

        // PartIdx (omit when empty)
        if !self.part_indices.is_empty() {
            rmp::encode::write_str(wr, "PartIdx")?;
            rmp::encode::write_array_len(wr, self.part_indices.len() as u32)?;
            for idx in &self.part_indices {
                rmp::encode::write_bin(wr, idx)?;
            }
        }

        // Size
        rmp::encode::write_str(wr, "Size")?;
        rmp::encode::write_sint(wr, self.size)?;

        // MTime Unix timestamp nanos
        rmp::encode::write_str(wr, "MTime")?;
        let nanos = self.mod_time.unwrap_or(OffsetDateTime::UNIX_EPOCH).unix_timestamp_nanos();
        rmp::encode::write_sint(wr, nanos as i64)?;

        // MetaSys (write nil when empty)
        rmp::encode::write_str(wr, "MetaSys")?;
        if self.meta_sys.is_empty() {
            rmp::encode::write_nil(wr)?;
        } else {
            rmp::encode::write_map_len(wr, self.meta_sys.len() as u32)?;
            for (k, v) in &self.meta_sys {
                rmp::encode::write_str(wr, k)?;
                rmp::encode::write_bin(wr, v)?;
            }
        }

        // MetaUsr (write nil when empty)
        rmp::encode::write_str(wr, "MetaUsr")?;
        if self.meta_user.is_empty() {
            rmp::encode::write_nil(wr)?;
        } else {
            rmp::encode::write_map_len(wr, self.meta_user.len() as u32)?;
            for (k, v) in &self.meta_user {
                rmp::encode::write_str(wr, k)?;
                rmp::encode::write_str(wr, v)?;
            }
        }

        Ok(())
    }

    pub fn decode_from<R: std::io::Read>(&mut self, rd: &mut R) -> Result<()> {
        let mut fields = rmp::decode::read_map_len(rd).map_err(|e| {
            tracing::error!(error = %e, "decode_from: read_map_len failed");
            e
        })?;
        *self = MetaObject::default();

        while fields > 0 {
            fields -= 1;

            let key_len = rmp::decode::read_str_len(rd).map_err(|e| {
                tracing::error!(error = %e, "decode_from: read_str_len key failed");
                e
            })?;
            let key_buf = read_exact_vec(rd, key_len as usize).map_err(|e| {
                tracing::error!(error = %e, "decode_from: read key_buf failed");
                e
            })?;
            let key = String::from_utf8(key_buf).map_err(|e| {
                tracing::error!(error = %e, "decode_from: from_utf8 key failed");
                e
            })?;

            match key.as_str() {
                "ID" => {
                    let _ = rmp::decode::read_bin_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_bin_len ID failed");
                        e
                    })?;
                    let mut buf = [0u8; 16];
                    rd.read_exact(&mut buf).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_exact ID buf failed");
                        e
                    })?;
                    let id = Uuid::from_bytes(buf);
                    self.version_id = if id.is_nil() { None } else { Some(id) };
                }
                "DDir" => {
                    let _ = rmp::decode::read_bin_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_bin_len DDir failed");
                        e
                    })?;
                    let mut buf = [0u8; 16];
                    rd.read_exact(&mut buf).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_exact DDir buf failed");
                        e
                    })?;
                    let id = Uuid::from_bytes(buf);
                    self.data_dir = if id.is_nil() { None } else { Some(id) };
                }
                "EcAlgo" => {
                    let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_int EcAlgo failed");
                        e
                    })?;
                    self.erasure_algorithm = ErasureAlgo::from_u8(v as u8);
                }
                "EcM" => {
                    let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_int EcM failed");
                        e
                    })?;
                    self.erasure_m = v as usize;
                }
                "EcN" => {
                    let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_int EcN failed");
                        e
                    })?;
                    self.erasure_n = v as usize;
                }
                "EcBSize" => {
                    let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_int EcBSize failed");
                        e
                    })?;
                    self.erasure_block_size = v as usize;
                }
                "EcIndex" => {
                    let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_int EcIndex failed");
                        e
                    })?;
                    self.erasure_index = v as usize;
                }
                "EcDist" => {
                    let len = rmp::decode::read_array_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_array_len EcDist failed");
                        e
                    })? as usize;
                    self.erasure_dist.clear();
                    self.erasure_dist.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_int EcDist item failed");
                            e
                        })?;
                        self.erasure_dist.push(v as u8);
                    }
                }
                "CSumAlgo" => {
                    let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_int CSumAlgo failed");
                        e
                    })?;
                    self.bitrot_checksum_algo = ChecksumAlgo::from_u8(v as u8);
                }
                "PartNums" => {
                    let len = rmp::decode::read_array_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_array_len PartNums failed");
                        e
                    })? as usize;
                    self.part_numbers.clear();
                    self.part_numbers.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_int PartNums item failed");
                            e
                        })?;
                        self.part_numbers.push(v as usize);
                    }
                }
                "PartETags" => {
                    let len = match read_nil_or_array_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read PartETags failed");
                        e
                    })? {
                        None => {
                            self.part_etags.clear();
                            continue;
                        }
                        Some(n) => n,
                    };
                    self.part_etags.clear();
                    self.part_etags.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        let s_len = rmp::decode::read_str_len(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_str_len PartETags item failed");
                            e
                        })?;
                        let sbuf = read_exact_vec(rd, s_len as usize).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read PartETags sbuf failed");
                            e
                        })?;
                        let s = String::from_utf8(sbuf).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: from_utf8 PartETags item failed");
                            e
                        })?;
                        self.part_etags.push(s);
                    }
                }
                "PartSizes" => {
                    let len = rmp::decode::read_array_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_array_len PartSizes failed");
                        e
                    })? as usize;
                    self.part_sizes.clear();
                    self.part_sizes.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_int PartSizes item failed");
                            e
                        })?;
                        self.part_sizes.push(v as usize);
                    }
                }
                "PartASizes" => {
                    let len = match read_nil_or_array_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read PartASizes failed");
                        e
                    })? {
                        None => {
                            self.part_actual_sizes.clear();
                            continue;
                        }
                        Some(n) => n,
                    };
                    self.part_actual_sizes.clear();
                    self.part_actual_sizes.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_int PartASizes item failed");
                            e
                        })?;
                        self.part_actual_sizes.push(v);
                    }
                }
                "PartIdx" => {
                    let len = rmp::decode::read_array_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_array_len PartIdx failed");
                        e
                    })? as usize;
                    self.part_indices.clear();
                    self.part_indices.reserve(prealloc_hint(len));
                    for _ in 0..len {
                        let blen = rmp::decode::read_bin_len(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_bin_len PartIdx item failed");
                            e
                        })? as usize;
                        let buf = read_exact_vec(rd, blen).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read PartIdx buf failed");
                            e
                        })?;
                        self.part_indices.push(Bytes::from(buf));
                    }
                }
                "Size" => {
                    let v: i64 = rmp::decode::read_int(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_int Size failed");
                        e
                    })?;
                    self.size = v;
                }
                "MTime" => {
                    let nanos: i64 = rmp::decode::read_int(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read_int MTime failed");
                        e
                    })?;
                    let time = OffsetDateTime::from_unix_timestamp_nanos(nanos as i128).inspect_err(|&e| {
                        tracing::error!(error = %e, "decode_from: from_unix_timestamp_nanos MTime failed");
                    })?;
                    self.mod_time = if time == OffsetDateTime::UNIX_EPOCH {
                        None
                    } else {
                        Some(time)
                    };
                }
                "MetaSys" => {
                    let len = match read_nil_or_map_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read MetaSys failed");
                        e
                    })? {
                        None => {
                            self.meta_sys.clear();
                            continue;
                        }
                        Some(n) => n,
                    };
                    self.meta_sys.clear();
                    for _ in 0..len {
                        let k_len = rmp::decode::read_str_len(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_str_len MetaSys key failed");
                            e
                        })?;
                        let kbuf = read_exact_vec(rd, k_len as usize).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read MetaSys kbuf failed");
                            e
                        })?;
                        let k = String::from_utf8(kbuf).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: from_utf8 MetaSys key failed");
                            e
                        })?;

                        let blen = rmp::decode::read_bin_len(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_bin_len MetaSys value failed");
                            e
                        })? as usize;
                        let v = read_exact_vec(rd, blen).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read MetaSys value failed");
                            e
                        })?;

                        self.meta_sys.insert(k, v);
                    }
                }
                "MetaUsr" => {
                    let len = match read_nil_or_map_len(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: read MetaUsr failed");
                        e
                    })? {
                        None => {
                            self.meta_user.clear();
                            continue;
                        }
                        Some(n) => n,
                    };
                    self.meta_user.clear();
                    for _ in 0..len {
                        let k_len = rmp::decode::read_str_len(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_str_len MetaUsr key failed");
                            e
                        })?;
                        let kbuf = read_exact_vec(rd, k_len as usize).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read MetaUsr kbuf failed");
                            e
                        })?;
                        let k = String::from_utf8(kbuf).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: from_utf8 MetaUsr key failed");
                            e
                        })?;

                        let v_len = rmp::decode::read_str_len(rd).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read_str_len MetaUsr value failed");
                            e
                        })?;
                        let vbuf = read_exact_vec(rd, v_len as usize).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: read MetaUsr vbuf failed");
                            e
                        })?;
                        let v = String::from_utf8(vbuf).map_err(|e| {
                            tracing::error!(error = %e, "decode_from: from_utf8 MetaUsr value failed");
                            e
                        })?;

                        self.meta_user.insert(k, v);
                    }
                }
                other => {
                    // Skip unknown fields for forward compatibility with Go (dc.Skip())
                    tracing::debug!(field = %other, "decode_from: skipping unknown field");
                    skip_msgp_value(rd).map_err(|e| {
                        tracing::error!(error = %e, "decode_from: skip unknown field failed");
                        e
                    })?;
                }
            }
        }

        Ok(())
    }

    pub fn into_fileinfo(&self, volume: &str, path: &str, all_parts: bool) -> Result<FileInfo> {
        let version_id = self.version_id.filter(|&vid| !vid.is_nil());

        let parts = if all_parts {
            let n = self.part_numbers.len();
            // Required fields: `part_sizes`/`part_actual_sizes` must match `part_numbers`
            // exactly. These arrays are decoded from independent msgpack length prefixes
            // (`decode_from`), so a truncated/half-written/bitrot xl.meta can leave them
            // shorter (or longer) than `part_numbers`. Indexing without this guard would
            // panic; silently defaulting to 0 would miscompute Content-Length / Range /
            // multipart boundaries and hand corrupt data to the client (worse than an
            // error). `n == 0` preserves the legitimate "no-part object / legacy / empty
            // array" wire (MinIO parity: empty PartNumbers is valid).
            if n != 0 && (self.part_sizes.len() != n || self.part_actual_sizes.len() != n) {
                return Err(Error::FileCorrupt);
            }
            let mut parts = vec![ObjectPartInfo::default(); n];

            for (i, part) in parts.iter_mut().enumerate() {
                part.number = self.part_numbers[i];
                part.size = self.part_sizes[i];
                part.actual_size = self.part_actual_sizes[i];

                // etag/index stay soft-guarded: they are recomputable / optional, an empty
                // PartETags is legitimate MinIO interop, and a length mismatch there does
                // not corrupt returned data.
                if self.part_etags.len() == n {
                    part.etag = self.part_etags[i].clone();
                }

                if self.part_indices.len() == n {
                    part.index = if self.part_indices[i].is_empty() {
                        None
                    } else {
                        Some(self.part_indices[i].clone())
                    };
                }
            }
            parts
        } else {
            Vec::new()
        };

        let mut metadata = HashMap::with_capacity(self.meta_user.len() + self.meta_sys.len());
        for (k, v) in &self.meta_user {
            if k == AMZ_META_UNENCRYPTED_CONTENT_LENGTH || k == AMZ_META_UNENCRYPTED_CONTENT_MD5 {
                continue;
            }

            if k == AMZ_STORAGE_CLASS && v == "STANDARD" {
                continue;
            }

            metadata.insert(k.to_owned(), v.to_owned());
        }

        for (k, v) in &self.meta_sys {
            if has_internal_suffix(k, SUFFIX_TIER_FV_ID) || has_internal_suffix(k, SUFFIX_TIER_FV_MARKER) {
                continue;
            }

            if k.eq_ignore_ascii_case(AMZ_STORAGE_CLASS) && v == b"STANDARD" {
                continue;
            }

            if is_internal_key(k) {
                metadata.insert(k.to_owned(), String::from_utf8(v.to_owned()).unwrap_or_default());
            }
        }

        let replication_state_internal = get_internal_replication_state(&metadata);

        let mut deleted = false;

        if let Some(v) = replication_state_internal.as_ref() {
            if !v.composite_version_purge_status().is_empty() {
                deleted = true;
            }

            let st = v.composite_replication_status();
            if !st.is_empty() {
                metadata.insert(AMZ_BUCKET_REPLICATION_STATUS.to_string(), st.to_string());
            }
        }

        let checksum = get_bytes(&self.meta_sys, SUFFIX_CRC).map(Bytes::from);

        let erasure = ErasureInfo {
            algorithm: self.erasure_algorithm.to_string(),
            data_blocks: self.erasure_m,
            parity_blocks: self.erasure_n,
            block_size: self.erasure_block_size,
            index: self.erasure_index,
            distribution: self.erasure_dist.iter().map(|&v| v as usize).collect(),
            ..Default::default()
        };

        let transition_status = get_bytes(&self.meta_sys, SUFFIX_TRANSITION_STATUS)
            .map(|v| String::from_utf8_lossy(&v).to_string())
            .unwrap_or_default();
        let transitioned_objname = get_bytes(&self.meta_sys, SUFFIX_TRANSITIONED_OBJECTNAME)
            .map(|v| String::from_utf8_lossy(&v).to_string())
            .unwrap_or_default();
        let transition_version_id = transitioned_version_id_from_meta_sys(&self.meta_sys);
        let transition_tier = get_bytes(&self.meta_sys, SUFFIX_TRANSITION_TIER)
            .map(|v| String::from_utf8_lossy(&v).to_string())
            .unwrap_or_default();

        Ok(FileInfo {
            version_id,
            erasure,
            data_dir: self.data_dir,
            mod_time: self.mod_time,
            size: self.size,
            name: path.to_string(),
            volume: volume.to_string(),
            parts,
            metadata,
            replication_state_internal,
            deleted,
            checksum,
            transition_status,
            transitioned_objname,
            transition_version_id,
            transition_tier,
            ..Default::default()
        })
    }

    pub fn set_transition(&mut self, fi: &FileInfo) {
        insert_bytes(&mut self.meta_sys, SUFFIX_TRANSITION_STATUS, fi.transition_status.as_bytes().to_vec());
        insert_bytes(
            &mut self.meta_sys,
            SUFFIX_TRANSITIONED_OBJECTNAME,
            fi.transitioned_objname.as_bytes().to_vec(),
        );
        if let Some(transition_version_id) = fi.transition_version_id.as_ref() {
            insert_bytes(
                &mut self.meta_sys,
                SUFFIX_TRANSITIONED_VERSION_ID,
                transition_version_id.as_bytes().to_vec(),
            );
        }
        insert_bytes(&mut self.meta_sys, SUFFIX_TRANSITION_TIER, fi.transition_tier.as_bytes().to_vec());
        if let Some(destination_id) = get_str(&fi.metadata, SUFFIX_TRANSITION_TIER_DESTINATION_ID) {
            insert_bytes(&mut self.meta_sys, SUFFIX_TRANSITION_TIER_DESTINATION_ID, destination_id.into_bytes());
        }
    }

    pub fn remove_restore_hdrs(&mut self) {
        self.meta_user.remove(X_AMZ_RESTORE.as_str());
        self.meta_user.remove(AMZ_RESTORE_EXPIRY_DAYS);
        self.meta_user.remove(AMZ_RESTORE_REQUEST_DATE);
    }

    pub fn uses_data_dir(&self) -> bool {
        if let Some(status) = get_bytes(&self.meta_sys, SUFFIX_TRANSITION_STATUS)
            && status == TRANSITION_COMPLETE.as_bytes().to_vec()
        {
            return false;
        }

        is_restored_object_on_disk(&self.meta_user)
    }

    pub fn inlinedata(&self) -> bool {
        contains_key_bytes(&self.meta_sys, SUFFIX_INLINE_DATA)
    }

    pub fn reset_inline_data(&mut self) {
        remove_bytes(&mut self.meta_sys, SUFFIX_INLINE_DATA);
    }

    /// Remove restore headers
    pub fn remove_restore_headers(&mut self) {
        // Remove any restore-related metadata
        self.meta_sys.retain(|k, _| !k.starts_with("X-Amz-Restore"));
    }

    pub fn init_free_version(&self, fi: &FileInfo) -> Result<(FileMetaVersion, bool)> {
        if fi.skip_tier_free_version() {
            return Ok((FileMetaVersion::default(), false));
        }
        if let Some(status) = get_bytes(&self.meta_sys, SUFFIX_TRANSITION_STATUS)
            && status == TRANSITION_COMPLETE.as_bytes().to_vec()
        {
            let vid = Uuid::parse_str(&fi.tier_free_version_id())?;
            let mut free_entry = FileMetaVersion {
                version_type: VersionType::Delete,
                write_version: 0,
                ..Default::default()
            };
            free_entry.delete_marker = Some(MetaDeleteMarker {
                version_id: Some(vid),
                mod_time: self.mod_time,
                meta_sys: HashMap::<String, Vec<u8>>::new(),
            });

            let delete_marker = free_entry.delete_marker.as_mut().unwrap();

            insert_bytes(&mut delete_marker.meta_sys, SUFFIX_FREE_VERSION, vec![]);

            for suffix in [
                SUFFIX_TRANSITION_TIER,
                SUFFIX_TRANSITIONED_OBJECTNAME,
                SUFFIX_TRANSITIONED_VERSION_ID,
            ] {
                if let Some(v) = get_bytes(&self.meta_sys, suffix) {
                    insert_bytes(&mut delete_marker.meta_sys, suffix, v);
                }
            }
            if contains_key_bytes(&self.meta_sys, SUFFIX_TRANSITION_TIER_DESTINATION_ID) {
                let destination_id = get_consistent_bytes(&self.meta_sys, SUFFIX_TRANSITION_TIER_DESTINATION_ID)
                    .filter(|value| value.len() == 64 && value.iter().all(u8::is_ascii_hexdigit))
                    .ok_or(Error::FileCorrupt)?;
                insert_bytes(
                    &mut delete_marker.meta_sys,
                    SUFFIX_TRANSITION_TIER_DESTINATION_ID,
                    destination_id.to_vec(),
                );
            }
            return Ok((free_entry, true));
        }
        Ok((FileMetaVersion::default(), false))
    }
}

impl From<FileInfo> for MetaObject {
    fn from(value: FileInfo) -> Self {
        let part_etags = if !value.parts.is_empty() {
            value.parts.iter().map(|v| v.etag.clone()).collect()
        } else {
            vec![]
        };

        let part_indices = if !value.parts.is_empty() {
            value.parts.iter().map(|v| v.index.clone().unwrap_or_default()).collect()
        } else {
            vec![]
        };

        let mut meta_sys = HashMap::new();
        let mut meta_user = HashMap::new();
        for (k, v) in value.metadata.iter() {
            if is_internal_key(k) {
                if is_skip_meta_key(k) {
                    continue;
                }

                meta_sys.insert(k.to_owned(), v.as_bytes().to_vec());
            } else {
                meta_user.insert(k.to_owned(), v.to_owned());
            }
        }

        if !value.transition_status.is_empty() {
            insert_bytes(&mut meta_sys, SUFFIX_TRANSITION_STATUS, value.transition_status.as_bytes().to_vec());
        }

        if !value.transitioned_objname.is_empty() {
            insert_bytes(
                &mut meta_sys,
                SUFFIX_TRANSITIONED_OBJECTNAME,
                value.transitioned_objname.as_bytes().to_vec(),
            );
        }

        if let Some(vid) = &value.transition_version_id {
            insert_bytes(&mut meta_sys, SUFFIX_TRANSITIONED_VERSION_ID, vid.as_bytes().to_vec());
        }

        if !value.transition_tier.is_empty() {
            insert_bytes(&mut meta_sys, SUFFIX_TRANSITION_TIER, value.transition_tier.as_bytes().to_vec());
        }

        if let Some(content_hash) = value.checksum {
            insert_bytes(&mut meta_sys, SUFFIX_CRC, content_hash.to_vec());
        }

        Self {
            version_id: value.version_id,
            data_dir: value.data_dir,
            size: value.size,
            mod_time: value.mod_time,
            erasure_algorithm: ErasureAlgo::ReedSolomon,
            erasure_m: value.erasure.data_blocks,
            erasure_n: value.erasure.parity_blocks,
            erasure_block_size: value.erasure.block_size,
            erasure_index: value.erasure.index,
            erasure_dist: value.erasure.distribution.iter().map(|x| *x as u8).collect(),
            bitrot_checksum_algo: ChecksumAlgo::HighwayHash,
            part_numbers: value.parts.iter().map(|v| v.number).collect(),
            part_etags,
            part_sizes: value.parts.iter().map(|v| v.size).collect(),
            part_actual_sizes: value.parts.iter().map(|v| v.actual_size).collect(),
            part_indices,
            meta_sys,
            meta_user,
        }
    }
}

fn get_internal_replication_state(metadata: &HashMap<String, String>) -> Option<ReplicationState> {
    let mut rs = ReplicationState::default();
    let mut has = false;

    for (k, v) in metadata.iter() {
        if has_internal_suffix(k, SUFFIX_PURGESTATUS) {
            rs.version_purge_status_internal = Some(v.clone());
            rs.purge_targets = version_purge_statuses_map(v.as_str());
            has = true;
            continue;
        }

        let sub_key_opt = strip_internal_prefix(k);
        if let Some(ref sub_key) = sub_key_opt {
            match sub_key.as_str() {
                "replica-timestamp" => {
                    has = true;
                    rs.replica_timestamp = Some(OffsetDateTime::parse(v, &Rfc3339).unwrap_or(OffsetDateTime::UNIX_EPOCH));
                }
                "replica-status" => {
                    has = true;
                    rs.replica_status = ReplicationStatusType::from(v.as_str());
                }
                "replication-timestamp" => {
                    has = true;
                    rs.replication_timestamp = Some(OffsetDateTime::parse(v, &Rfc3339).unwrap_or(OffsetDateTime::UNIX_EPOCH))
                }
                "replication-status" => {
                    has = true;
                    rs.replication_status_internal = Some(v.clone());
                    rs.targets = replication_statuses_map(v.as_str());
                }
                _ => {
                    if let Some(arn) = sub_key.strip_prefix("replication-reset-") {
                        has = true;
                        // Store the canonical full-header key so the map matches
                        // the key `target_reset_header()` produces on the
                        // write/lookup side. Storing the bare ARN keyed the map
                        // inconsistently (bare on read, full on write), which
                        // could drop reset state across merge/reflatten cycles
                        // (backlog#799 B16).
                        rs.reset_statuses_map
                            .insert(crate::replication::target_reset_header(arn), v.clone());
                    }
                }
            }
        }
    }

    if has { Some(rs) } else { None }
}

#[derive(Serialize, Deserialize, Debug, Clone, Default, PartialEq)]
pub struct MetaDeleteMarker {
    #[serde(rename = "ID")]
    pub version_id: Option<Uuid>, // Version ID for delete marker
    #[serde(rename = "MTime")]
    pub mod_time: Option<OffsetDateTime>, // Object delete marker modified time
    #[serde(rename = "MetaSys")]
    pub meta_sys: HashMap<String, Vec<u8>>, // Delete marker internal metadata
}

impl TryFrom<LegacyMetaV2DeleteMarker> for MetaDeleteMarker {
    type Error = Error;

    fn try_from(value: LegacyMetaV2DeleteMarker) -> std::result::Result<Self, Self::Error> {
        Ok(Self {
            version_id: parse_legacy_uuid_bytes(&value.version_id, "version_id")?,
            mod_time: value.mod_time,
            meta_sys: value.meta_sys,
        })
    }
}

impl MetaDeleteMarker {
    pub fn free_version(&self) -> bool {
        contains_key_bytes(&self.meta_sys, SUFFIX_FREE_VERSION)
    }

    pub fn into_fileinfo(&self, volume: &str, path: &str, _all_parts: bool) -> FileInfo {
        let metadata = self
            .meta_sys
            .clone()
            .into_iter()
            .map(|(k, v)| (k, String::from_utf8_lossy(&v).to_string()))
            .collect();
        let replication_state_internal = get_internal_replication_state(&metadata);

        let mut fi = FileInfo {
            version_id: self.version_id.filter(|&vid| !vid.is_nil()),
            name: path.to_string(),
            volume: volume.to_string(),
            deleted: true,
            mod_time: self.mod_time,
            metadata,
            replication_state_internal,
            ..Default::default()
        };

        if self.free_version() {
            fi.set_tier_free_version();
            fi.transition_tier = get_bytes(&self.meta_sys, SUFFIX_TRANSITION_TIER)
                .map(|v| String::from_utf8_lossy(&v).to_string())
                .unwrap_or_default();

            fi.transitioned_objname = get_bytes(&self.meta_sys, SUFFIX_TRANSITIONED_OBJECTNAME)
                .map(|v| String::from_utf8_lossy(&v).to_string())
                .unwrap_or_default();

            fi.transition_version_id = transitioned_version_id_from_meta_sys(&self.meta_sys);
        }

        fi
    }

    pub fn encode_to<W: std::io::Write>(&self, wr: &mut W) -> Result<()> {
        rmp::encode::write_map_len(wr, 3)?;

        // ID
        rmp::encode::write_str(wr, "ID")?;
        rmp::encode::write_bin(wr, self.version_id.unwrap_or_default().as_bytes())?;

        // MTime Unix timestamp nanos
        rmp::encode::write_str(wr, "MTime")?;
        let nanos = self.mod_time.unwrap_or(OffsetDateTime::UNIX_EPOCH).unix_timestamp_nanos();
        rmp::encode::write_sint(wr, nanos as i64)?;

        // MetaSys
        rmp::encode::write_str(wr, "MetaSys")?;
        rmp::encode::write_map_len(wr, self.meta_sys.len() as u32)?;
        for (k, v) in &self.meta_sys {
            rmp::encode::write_str(wr, k)?;
            rmp::encode::write_bin(wr, v)?;
        }

        Ok(())
    }

    pub fn decode_from<R: std::io::Read>(&mut self, rd: &mut R) -> Result<()> {
        let mut fields = rmp::decode::read_map_len(rd)?;
        *self = MetaDeleteMarker::default();

        while fields > 0 {
            fields -= 1;

            let key_len = rmp::decode::read_str_len(rd)?;
            let key_buf = read_exact_vec(rd, key_len as usize)?;
            let key = String::from_utf8(key_buf)?;

            match key.as_str() {
                "ID" => {
                    let _ = rmp::decode::read_bin_len(rd)?;
                    let mut buf = [0u8; 16];
                    rd.read_exact(&mut buf)?;
                    let id = Uuid::from_bytes(buf);
                    self.version_id = if id.is_nil() { None } else { Some(id) };
                }
                "MTime" => {
                    let nanos: i64 = rmp::decode::read_int(rd)?;
                    let time = OffsetDateTime::from_unix_timestamp_nanos(nanos as i128)?;
                    self.mod_time = if time == OffsetDateTime::UNIX_EPOCH {
                        None
                    } else {
                        Some(time)
                    };
                }
                "MetaSys" => {
                    let len = rmp::decode::read_map_len(rd)? as usize;
                    self.meta_sys.clear();
                    for _ in 0..len {
                        let k_len = rmp::decode::read_str_len(rd)?;
                        let kbuf = read_exact_vec(rd, k_len as usize)?;
                        let k = String::from_utf8(kbuf)?;

                        let blen = rmp::decode::read_bin_len(rd)? as usize;
                        let v = read_exact_vec(rd, blen)?;

                        self.meta_sys.insert(k, v);
                    }
                }
                other => {
                    // Skip unknown fields for forward compatibility, matching
                    // MetaObject::decode_from. A newer writer's extra keys must not
                    // break decoding of a delete marker (backlog#799 B17).
                    tracing::debug!(field = %other, "MetaDeleteMarker::decode_from: skipping unknown field");
                    skip_msgp_value(rd)?;
                }
            }
        }

        Ok(())
    }

    pub fn unmarshal_msg(&mut self, buf: &[u8]) -> Result<u64> {
        let mut cur = std::io::Cursor::new(buf);
        self.decode_from(&mut cur)?;
        Ok(cur.position())
    }

    pub fn marshal_msg(&self) -> Result<Vec<u8>> {
        let mut wr = Vec::new();
        self.encode_to(&mut wr)?;
        Ok(wr)
    }

    /// Compute this delete marker's header signature, mirroring MinIO's
    /// `xlMetaV2DeleteMarker.Signature`. See [`FileMetaVersion::get_signature`].
    pub fn get_signature(&self) -> [u8; 4] {
        let mut c = self.clone();

        // MetaSys is order-unstable across disks; fold it in separately.
        let mut crc = hash_deterministic_bytes(&c.meta_sys);
        c.meta_sys.clear();

        if let Ok(bytes) = c.marshal_msg() {
            crc ^= xxhash_rust::xxh64::xxh64(&bytes, XXHASH_SEED);
        }

        fold_signature(crc)
    }
}

impl From<FileInfo> for MetaDeleteMarker {
    fn from(value: FileInfo) -> Self {
        let mut meta_sys = HashMap::new();
        let mut durable_metadata: HashMap<String, (&str, bool)> = HashMap::new();
        for (key, metadata_value) in &value.metadata {
            if !is_internal_key(key) || is_skip_meta_key(key) {
                continue;
            }
            let Some(suffix) = strip_internal_prefix(key) else {
                continue;
            };
            let rustfs_preferred = key
                .get(..RUSTFS_INTERNAL_PREFIX.len())
                .is_some_and(|prefix| prefix.eq_ignore_ascii_case(RUSTFS_INTERNAL_PREFIX));
            match durable_metadata.entry(suffix) {
                std::collections::hash_map::Entry::Vacant(entry) => {
                    entry.insert((metadata_value, rustfs_preferred));
                }
                std::collections::hash_map::Entry::Occupied(mut entry) if rustfs_preferred && !entry.get().1 => {
                    entry.insert((metadata_value, true));
                }
                std::collections::hash_map::Entry::Occupied(_) => {}
            }
        }
        for (suffix, (metadata_value, _)) in durable_metadata {
            insert_bytes(&mut meta_sys, &suffix, metadata_value.as_bytes().to_vec());
        }
        if value.tier_free_version() {
            insert_bytes(&mut meta_sys, SUFFIX_FREE_VERSION, vec![]);
        }
        if !value.transition_status.is_empty() {
            insert_bytes(&mut meta_sys, SUFFIX_TRANSITION_STATUS, value.transition_status.as_bytes().to_vec());
        }
        if !value.transitioned_objname.is_empty() {
            insert_bytes(
                &mut meta_sys,
                SUFFIX_TRANSITIONED_OBJECTNAME,
                value.transitioned_objname.as_bytes().to_vec(),
            );
        }
        if let Some(version_id) = value.transition_version_id {
            insert_bytes(&mut meta_sys, SUFFIX_TRANSITIONED_VERSION_ID, version_id.as_bytes().to_vec());
        }
        if !value.transition_tier.is_empty() {
            insert_bytes(&mut meta_sys, SUFFIX_TRANSITION_TIER, value.transition_tier.as_bytes().to_vec());
        }
        Self {
            version_id: value.version_id,
            mod_time: value.mod_time,
            meta_sys,
        }
    }
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Eq, Default, Clone, PartialOrd, Ord, Hash)]
pub enum VersionType {
    #[default]
    Invalid = 0,
    Object = 1,
    Delete = 2,
    Legacy = 3,
}

impl VersionType {
    pub fn valid(&self) -> bool {
        matches!(*self, VersionType::Object | VersionType::Delete | VersionType::Legacy)
    }

    pub fn to_u8(&self) -> u8 {
        match self {
            VersionType::Invalid => 0,
            VersionType::Object => 1,
            VersionType::Delete => 2,
            VersionType::Legacy => 3,
        }
    }

    pub fn from_u8(n: u8) -> Self {
        match n {
            1 => VersionType::Object,
            2 => VersionType::Delete,
            3 => VersionType::Legacy,
            _ => VersionType::Invalid,
        }
    }
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Default, Clone)]
pub enum ChecksumAlgo {
    #[default]
    Invalid = 0,
    HighwayHash = 1,
}

impl ChecksumAlgo {
    pub fn valid(&self) -> bool {
        *self > ChecksumAlgo::Invalid
    }
    pub fn to_u8(&self) -> u8 {
        match self {
            ChecksumAlgo::Invalid => 0,
            ChecksumAlgo::HighwayHash => 1,
        }
    }
    pub fn from_u8(u: u8) -> Self {
        match u {
            1 => ChecksumAlgo::HighwayHash,
            _ => ChecksumAlgo::Invalid,
        }
    }
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Default, Clone)]
pub enum Flags {
    #[default]
    FreeVersion = 1 << 0,
    UsesDataDir = 1 << 1,
    InlineData = 1 << 2,
}

// mergeXLV2Versions
pub fn merge_file_meta_versions(
    quorum: usize,
    strict: bool,
    requested_versions: usize,
    versions: &[Vec<FileMetaShallowVersion>],
) -> Vec<FileMetaShallowVersion> {
    merge_file_meta_versions_inner(quorum, strict, requested_versions, false, versions)
}

pub(crate) fn merge_file_meta_versions_with_write_quorum(
    quorum: usize,
    strict: bool,
    requested_versions: usize,
    versions: &[Vec<FileMetaShallowVersion>],
) -> Vec<FileMetaShallowVersion> {
    merge_file_meta_versions_inner(quorum, strict, requested_versions, true, versions)
}

fn merge_file_meta_versions_inner(
    mut quorum: usize,
    mut strict: bool,
    requested_versions: usize,
    enforce_write_quorum: bool,
    versions: &[Vec<FileMetaShallowVersion>],
) -> Vec<FileMetaShallowVersion> {
    if quorum == 0 {
        quorum = 1;
    }

    if versions.len() < quorum || versions.is_empty() {
        return Vec::new();
    }

    if versions.len() == 1 {
        if !enforce_write_quorum {
            return versions[0].clone();
        }

        let required_quorum = versions[0]
            .first()
            .map(|version| version.write_quorum(quorum).max(quorum))
            .unwrap_or(quorum);
        if versions.len() >= required_quorum {
            return versions[0].clone();
        }
        return Vec::new();
    }

    if quorum == 1 {
        strict = true;
    }

    let required_quorum = |version: &FileMetaShallowVersion| {
        if enforce_write_quorum {
            version.write_quorum(quorum).max(quorum)
        } else {
            quorum
        }
    };

    let mut versions = versions.to_owned();

    let mut n_versions = 0;

    let mut merged = Vec::new();
    loop {
        let mut tops = Vec::new();
        let mut top_sig = FileMetaVersionHeader::default();
        let mut consistent = true;
        for vers in versions.iter() {
            if vers.is_empty() {
                consistent = false;
                continue;
            }
            if tops.is_empty() {
                consistent = true;
                top_sig = vers[0].header.clone();
            } else {
                consistent = consistent && vers[0].header == top_sig;
            }
            tops.push(vers[0].clone());
        }

        // check if done...
        if tops.len() < quorum {
            break;
        }

        let mut latest = FileMetaShallowVersion::default();
        if consistent {
            latest = tops[0].clone();
            if tops.len() >= required_quorum(&latest) {
                merged.push(latest.clone());
                if !latest.header.free_version() {
                    n_versions += 1;
                }
            }
        } else {
            let mut latest_count = 0;
            for (i, ver) in tops.iter().enumerate() {
                if ver.header == latest.header {
                    latest_count += 1;
                    continue;
                }

                if i == 0 || ver.header.sorts_before(&latest.header) {
                    if i == 0 || latest_count == 0 {
                        latest_count = 1;
                    } else if !strict && ver.header.matches_not_strict(&latest.header) {
                        latest_count += 1;
                    } else {
                        latest_count = 1;
                    }
                    latest = ver.clone();
                    continue;
                }

                // Mismatch, but older.
                if latest_count > 0 && !strict && ver.header.matches_not_strict(&latest.header) {
                    latest_count += 1;
                    continue;
                }

                if latest_count > 0 && ver.header.version_id == latest.header.version_id {
                    let mut x: HashMap<FileMetaVersionHeader, usize> = HashMap::new();
                    for a in tops.iter() {
                        if a.header.version_id != ver.header.version_id {
                            continue;
                        }
                        let mut a_clone = a.clone();
                        if !strict {
                            a_clone.header.signature = [0; 4];
                        }
                        *x.entry(a_clone.header).or_insert(0) += 1;
                    }
                    latest_count = 0;
                    for (k, v) in x.iter() {
                        if *v < latest_count {
                            continue;
                        }
                        if *v == latest_count && latest.header.sorts_before(k) {
                            continue;
                        }
                        tops.iter().for_each(|a| {
                            let mut hdr = a.header.clone();
                            if !strict {
                                hdr.signature = [0; 4];
                            }
                            if hdr == *k {
                                latest = a.clone();
                            }
                        });

                        latest_count = *v;
                    }
                    break;
                }
            }
            if latest_count >= required_quorum(&latest) {
                if !latest.header.free_version() {
                    n_versions += 1;
                }
                merged.push(latest.clone());
            }
        }

        // Remove from all streams up until latest modtime or if selected.
        versions.iter_mut().for_each(|vers| {
            // // Keep top entry (and remaining)...
            let mut bre = false;
            vers.retain(|ver| {
                if bre {
                    return true;
                }
                if let Ordering::Greater = ver.header.mod_time.cmp(&latest.header.mod_time) {
                    bre = true;
                    return false;
                }
                if ver.header == latest.header {
                    bre = true;
                    return false;
                }
                if let Ordering::Equal = latest.header.version_id.cmp(&ver.header.version_id) {
                    bre = true;
                    return false;
                }
                for merged_v in merged.iter() {
                    if let Ordering::Equal = ver.header.version_id.cmp(&merged_v.header.version_id) {
                        bre = true;
                        return false;
                    }
                }
                true
            });
        });
        if requested_versions > 0 && requested_versions == n_versions {
            merged.append(&mut versions[0]);
            break;
        }
    }

    // Sanity check. Enable if duplicates show up.
    // todo
    merged
}

pub fn file_info_from_raw(
    ri: RawFileInfo,
    bucket: &str,
    object: &str,
    read_data: bool,
    include_free_versions: bool,
) -> Result<FileInfo> {
    get_file_info(
        &ri.buf,
        bucket,
        object,
        "",
        FileInfoOpts {
            data: read_data,
            include_free_versions,
        },
    )
}

pub struct FileInfoOpts {
    pub data: bool,
    pub include_free_versions: bool,
}

pub fn get_file_info(buf: &[u8], volume: &str, path: &str, version_id: &str, opts: FileInfoOpts) -> Result<FileInfo> {
    let vid = {
        if version_id.is_empty() {
            None
        } else {
            Some(Uuid::parse_str(version_id)?)
        }
    };

    let meta = FileMeta::load(buf)?;
    if meta.versions.is_empty() {
        return Ok(FileInfo {
            volume: volume.to_owned(),
            name: path.to_owned(),
            version_id: vid,
            is_latest: true,
            deleted: true,
            mod_time: Some(OffsetDateTime::from_unix_timestamp(1)?),
            ..Default::default()
        });
    }

    let fi = meta.into_fileinfo(volume, path, version_id, opts.data, opts.include_free_versions, true)?;
    Ok(fi)
}

async fn read_more<R: AsyncRead + Unpin>(
    reader: &mut R,
    buf: &mut Vec<u8>,
    total_size: usize,
    read_size: usize,
    has_full: bool,
) -> Result<()> {
    use tokio::io::AsyncReadExt;
    let has = buf.len();

    if has >= read_size {
        return Ok(());
    }

    if has_full || read_size > total_size {
        return Err(Error::other(std::io::Error::new(std::io::ErrorKind::UnexpectedEof, "Unexpected EOF")));
    }

    let extra = read_size - has;
    if buf.capacity() >= read_size {
        // Extend the buffer if we have enough space.
        buf.resize(read_size, 0);
    } else {
        buf.extend(vec![0u8; extra]);
    }

    reader.read_exact(&mut buf[has..]).await?;
    Ok(())
}

pub async fn read_xl_meta_no_data<R: AsyncRead + Unpin>(reader: &mut R, size: usize) -> Result<Vec<u8>> {
    use tokio::io::AsyncReadExt;

    let mut initial = size;
    let mut has_full = true;

    if initial > META_DATA_READ_DEFAULT {
        initial = META_DATA_READ_DEFAULT;
        has_full = false;
    }

    let mut buf = vec![0u8; initial];
    reader.read_exact(&mut buf).await?;

    let (tmp_buf, major, minor) = FileMeta::check_xl2_v1(&buf)?;

    match major {
        1 => match minor {
            0 => {
                read_more(reader, &mut buf, size, size, has_full).await?;
                Ok(buf)
            }
            1..=3 => {
                let (sz, tmp_buf) = FileMeta::read_bytes_header(tmp_buf)?;
                let mut want = sz as usize + (buf.len() - tmp_buf.len());

                if minor < 2 {
                    read_more(reader, &mut buf, size, want, has_full).await?;
                    buf.truncate(want);
                    return Ok(buf);
                }

                let want_max = usize::min(want + MSGP_UINT32_SIZE, size);
                read_more(reader, &mut buf, size, want_max, has_full).await?;

                if buf.len() < want {
                    return Err(Error::FileCorrupt);
                }

                // The metadata block is followed by a 5-byte msgp uint32 CRC trailer;
                // a file truncated inside the trailer is corrupt, not a shorter meta.
                let crc_size = 5;
                if buf.len() - want < crc_size {
                    return Err(Error::FileCorrupt);
                }

                want += crc_size;

                buf.truncate(want);
                Ok(buf)
            }
            _ => Err(Error::other(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                "Unknown minor metadata version",
            ))),
        },
        _ => Err(Error::other(std::io::Error::new(
            std::io::ErrorKind::InvalidData,
            "Unknown major metadata version",
        ))),
    }
}

/// Synchronous twin of [`read_more`].
///
/// Line-for-line mirror of the async version; the only difference is that
/// `reader.read_exact(&mut buf[has..]).await?` becomes the blocking
/// `std::io::Read::read_exact`. std's `read_exact` reports the same
/// `ErrorKind::UnexpectedEof` on a short read as tokio's, so the `?`
/// conversion into [`Error`] is identical. Kept in lockstep with `read_more`
/// so the two paths stay byte-for-byte equivalent (see equivalence tests).
fn read_more_sync<R: std::io::Read>(
    reader: &mut R,
    buf: &mut Vec<u8>,
    total_size: usize,
    read_size: usize,
    has_full: bool,
) -> Result<()> {
    let has = buf.len();

    if has >= read_size {
        return Ok(());
    }

    if has_full || read_size > total_size {
        return Err(Error::other(std::io::Error::new(std::io::ErrorKind::UnexpectedEof, "Unexpected EOF")));
    }

    let extra = read_size - has;
    if buf.capacity() >= read_size {
        // Extend the buffer if we have enough space.
        buf.resize(read_size, 0);
    } else {
        buf.extend(vec![0u8; extra]);
    }

    reader.read_exact(&mut buf[has..])?;
    Ok(())
}

/// Synchronous twin of [`read_xl_meta_no_data`].
///
/// Byte-for-byte equivalent to the async version for any input: the parsing
/// logic (`check_xl2_v1` / `read_bytes_header` / major-minor branches / `want`
/// computation / 5-byte CRC trailer handling / `truncate` / `FileCorrupt` /
/// `InvalidData` / `UnexpectedEof`) is copied verbatim; only the reads switch
/// from async `read_exact(...).await` to blocking `std::io::Read::read_exact`.
/// This lets a caller fold open+fstat+read into a single `spawn_blocking`
/// closure without changing any observable result.
pub fn read_xl_meta_no_data_sync<R: std::io::Read>(reader: &mut R, size: usize) -> Result<Vec<u8>> {
    let mut initial = size;
    let mut has_full = true;

    if initial > META_DATA_READ_DEFAULT {
        initial = META_DATA_READ_DEFAULT;
        has_full = false;
    }

    let mut buf = vec![0u8; initial];
    reader.read_exact(&mut buf)?;

    let (tmp_buf, major, minor) = FileMeta::check_xl2_v1(&buf)?;

    match major {
        1 => match minor {
            0 => {
                read_more_sync(reader, &mut buf, size, size, has_full)?;
                Ok(buf)
            }
            1..=3 => {
                let (sz, tmp_buf) = FileMeta::read_bytes_header(tmp_buf)?;
                let mut want = sz as usize + (buf.len() - tmp_buf.len());

                if minor < 2 {
                    read_more_sync(reader, &mut buf, size, want, has_full)?;
                    buf.truncate(want);
                    return Ok(buf);
                }

                let want_max = usize::min(want + MSGP_UINT32_SIZE, size);
                read_more_sync(reader, &mut buf, size, want_max, has_full)?;

                if buf.len() < want {
                    return Err(Error::FileCorrupt);
                }

                // The metadata block is followed by a 5-byte msgp uint32 CRC trailer;
                // a file truncated inside the trailer is corrupt, not a shorter meta.
                let crc_size = 5;
                if buf.len() - want < crc_size {
                    return Err(Error::FileCorrupt);
                }

                want += crc_size;

                buf.truncate(want);
                Ok(buf)
            }
            _ => Err(Error::other(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                "Unknown minor metadata version",
            ))),
        },
        _ => Err(Error::other(std::io::Error::new(
            std::io::ErrorKind::InvalidData,
            "Unknown major metadata version",
        ))),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde::Serialize;

    #[test]
    fn delete_marker_conversion_preserves_only_durable_internal_metadata() {
        let mut marker = FileInfo::default();
        marker
            .metadata
            .insert("x-minio-internal-purgestatus".to_string(), "pending".to_string());
        marker
            .metadata
            .insert("x-rustfs-internal-healing".to_string(), "true".to_string());
        marker.metadata.insert("content-type".to_string(), "text/plain".to_string());
        let remote_version_id = Uuid::new_v4();
        marker.transition_version_id = Some(remote_version_id);

        let converted = MetaDeleteMarker::from(marker);

        assert_eq!(converted.meta_sys.get("x-rustfs-internal-purgestatus"), Some(&b"pending".to_vec()));
        assert_eq!(converted.meta_sys.get("x-minio-internal-purgestatus"), Some(&b"pending".to_vec()));
        assert_eq!(
            get_bytes(&converted.meta_sys, SUFFIX_TRANSITIONED_VERSION_ID),
            Some(remote_version_id.as_bytes().to_vec())
        );
        assert!(!converted.meta_sys.contains_key("x-rustfs-internal-healing"));
        assert!(!converted.meta_sys.contains_key("content-type"));
    }

    #[derive(Serialize)]
    enum LegacyDeleteVersionTypeFixture {
        #[serde(rename = "DeleteMarker")]
        DeleteMarker,
    }

    #[derive(Serialize)]
    struct LegacyDeleteMarkerFixture {
        version_id: Vec<u8>,
        mod_time: Option<OffsetDateTime>,
        meta_sys: HashMap<String, Vec<u8>>,
    }

    #[derive(Serialize)]
    struct LegacyDeleteVersionFixture {
        version_type: LegacyDeleteVersionTypeFixture,
        object: Option<()>,
        delete_marker: Option<LegacyDeleteMarkerFixture>,
        write_version: u64,
    }

    #[derive(Serialize)]
    struct LegacyDeleteMarkerNilFixture {
        version_id: Option<Vec<u8>>,
        mod_time: Option<OffsetDateTime>,
        meta_sys: HashMap<String, Vec<u8>>,
    }

    #[derive(Serialize)]
    struct LegacyDeleteVersionNilFixture {
        version_type: LegacyDeleteVersionTypeFixture,
        object: Option<()>,
        delete_marker: Option<LegacyDeleteMarkerNilFixture>,
        write_version: u64,
    }

    #[derive(Serialize)]
    enum LegacyObjectVersionTypeFixture {
        #[serde(rename = "Object")]
        Object,
    }

    #[derive(Serialize)]
    struct LegacyObjectFixture {
        version_id: Option<Vec<u8>>,
        data_dir: Option<Vec<u8>>,
        erasure_algorithm: String,
        erasure_m: usize,
        erasure_n: usize,
        erasure_block_size: usize,
        erasure_index: usize,
        erasure_dist: Vec<u8>,
        bitrot_checksum_algo: String,
        part_numbers: Vec<usize>,
        part_etags: Vec<String>,
        part_sizes: Vec<usize>,
        part_actual_sizes: Vec<i64>,
        part_indices: Vec<Vec<u8>>,
        size: i64,
        mod_time: Option<OffsetDateTime>,
        meta_sys: HashMap<String, Vec<u8>>,
        meta_user: HashMap<String, String>,
    }

    #[derive(Serialize)]
    struct LegacyObjectVersionFixture {
        version_type: LegacyObjectVersionTypeFixture,
        object: Option<LegacyObjectFixture>,
        delete_marker: Option<()>,
        write_version: u64,
    }

    fn sample_version_id() -> Uuid {
        Uuid::parse_str("01234567-89ab-cdef-0123-456789abcdef").unwrap()
    }

    fn sample_mod_time() -> OffsetDateTime {
        OffsetDateTime::from_unix_timestamp_nanos(1_705_312_200_123_456_789).unwrap()
    }

    // ----------------------------------------------------------------------
    // backlog#900: MetaObject::into_fileinfo part-array length guard.
    // ----------------------------------------------------------------------

    fn object_with_parts(part_numbers: Vec<usize>, part_sizes: Vec<usize>, part_actual_sizes: Vec<i64>) -> MetaObject {
        MetaObject {
            version_id: Some(sample_version_id()),
            erasure_algorithm: ErasureAlgo::ReedSolomon,
            erasure_m: 2,
            erasure_n: 2,
            erasure_block_size: 1_048_576,
            bitrot_checksum_algo: ChecksumAlgo::HighwayHash,
            part_numbers,
            part_sizes,
            part_actual_sizes,
            mod_time: Some(sample_mod_time()),
            ..Default::default()
        }
    }

    #[test]
    fn into_fileinfo_rejects_short_part_sizes() {
        // part_numbers=2 but part_sizes=1 -> old code indexed self.part_sizes[1] and panicked.
        let obj = object_with_parts(vec![1, 2], vec![10], vec![10, 20]);
        let res = obj.into_fileinfo("bucket", "key", true);
        assert!(matches!(res, Err(Error::FileCorrupt)), "short part_sizes must map to FileCorrupt");
    }

    #[test]
    fn into_fileinfo_rejects_short_part_actual_sizes_including_empty() {
        let obj = object_with_parts(vec![1, 2], vec![10, 20], vec![]);
        let res = obj.into_fileinfo("bucket", "key", true);
        assert!(matches!(res, Err(Error::FileCorrupt)), "empty part_actual_sizes must map to FileCorrupt");
    }

    #[test]
    fn into_fileinfo_rejects_over_long_part_sizes() {
        // Strict equality: an over-long array is corrupt too (MinIO would panic on any mismatch).
        let obj = object_with_parts(vec![1], vec![10, 20], vec![10]);
        let res = obj.into_fileinfo("bucket", "key", true);
        assert!(matches!(res, Err(Error::FileCorrupt)), "over-long part_sizes must map to FileCorrupt");
    }

    #[test]
    fn into_fileinfo_all_parts_false_skips_validation() {
        // all_parts=false never enters the parts loop -> Ok, empty parts. Regression guard.
        let obj = object_with_parts(vec![1, 2], vec![10], vec![10, 20]);
        let fi = obj
            .into_fileinfo("bucket", "key", false)
            .expect("all_parts=false must not validate parts");
        assert!(fi.parts.is_empty());
    }

    #[test]
    fn into_fileinfo_healthy_parts_decode_field_by_field() {
        let mut obj = object_with_parts(vec![1, 2], vec![100, 200], vec![111, 222]);
        obj.part_etags = vec!["etag-1".to_string(), "etag-2".to_string()];
        obj.part_indices = vec![Bytes::from_static(b"idx1"), Bytes::new()];

        let fi = obj.into_fileinfo("b", "k", true).expect("healthy parts must decode");
        assert_eq!(fi.parts.len(), 2);
        assert_eq!(fi.parts[0].number, 1);
        assert_eq!(fi.parts[0].size, 100);
        assert_eq!(fi.parts[0].actual_size, 111);
        assert_eq!(fi.parts[0].etag, "etag-1");
        assert_eq!(fi.parts[0].index.as_deref(), Some(&b"idx1"[..]));
        assert_eq!(fi.parts[1].number, 2);
        assert_eq!(fi.parts[1].size, 200);
        assert_eq!(fi.parts[1].actual_size, 222);
        assert_eq!(fi.parts[1].etag, "etag-2");
        assert_eq!(fi.parts[1].index, None); // empty bytes -> None
    }

    #[test]
    fn into_fileinfo_empty_part_numbers_is_valid() {
        // No-part object (empty part_numbers) is legitimate: n==0 -> no guard -> Ok, no parts.
        let obj = object_with_parts(vec![], vec![], vec![]);
        let fi = obj.into_fileinfo("b", "k", true).expect("no-part object must be valid");
        assert!(fi.parts.is_empty());
    }

    #[test]
    fn into_fileinfo_etag_soft_guard_not_regressed() {
        // size/actual match (pass hard guard) but etag length differs -> soft guard: empty etag, not corrupt.
        let mut obj = object_with_parts(vec![1, 2], vec![10, 20], vec![10, 20]);
        obj.part_etags = vec!["only-one".to_string()];
        let fi = obj.into_fileinfo("b", "k", true).expect("etag soft guard must not fail");
        assert_eq!(fi.parts.len(), 2);
        assert_eq!(fi.parts[0].etag, ""); // soft guard: len mismatch -> default empty
    }

    fn sample_header() -> FileMetaVersionHeader {
        FileMetaVersionHeader {
            version_id: Some(sample_version_id()),
            mod_time: Some(sample_mod_time()),
            signature: [0x96, 0x33, 0x4c, 0x78],
            version_type: VersionType::Object,
            flags: 0x06,
            ec_n: 4,
            ec_m: 2,
        }
    }

    fn encode_v1_header(header: &FileMetaVersionHeader) -> Vec<u8> {
        let mut wr = Vec::new();
        rmp::encode::write_array_len(&mut wr, 4).unwrap();
        rmp::encode::write_bin(&mut wr, header.version_id.unwrap().as_bytes()).unwrap();
        rmp::encode::write_i64(&mut wr, header.mod_time.unwrap().unix_timestamp_nanos() as i64).unwrap();
        rmp::encode::write_uint8(&mut wr, header.version_type.to_u8()).unwrap();
        rmp::encode::write_uint8(&mut wr, header.flags).unwrap();
        wr
    }

    fn encode_v2_header(header: &FileMetaVersionHeader) -> Vec<u8> {
        let mut wr = Vec::new();
        rmp::encode::write_array_len(&mut wr, 5).unwrap();
        rmp::encode::write_bin(&mut wr, header.version_id.unwrap().as_bytes()).unwrap();
        rmp::encode::write_i64(&mut wr, header.mod_time.unwrap().unix_timestamp_nanos() as i64).unwrap();
        rmp::encode::write_bin(&mut wr, header.signature.as_slice()).unwrap();
        rmp::encode::write_uint8(&mut wr, header.version_type.to_u8()).unwrap();
        rmp::encode::write_uint8(&mut wr, header.flags).unwrap();
        wr
    }

    fn write_legacy_time(wr: &mut Vec<u8>, ts: OffsetDateTime) {
        wr.push(MSGPACK_EXT8);
        wr.push(12);
        wr.push(MSGPACK_TIME_EXT_LEGACY as u8);
        wr.extend_from_slice(&ts.unix_timestamp().to_be_bytes());
        wr.extend_from_slice(&ts.nanosecond().to_be_bytes());
    }

    fn encode_legacy_v1_body() -> Vec<u8> {
        let mut wr = Vec::new();
        let mod_time = sample_mod_time();

        rmp::encode::write_map_len(&mut wr, 3).unwrap();

        rmp::encode::write_str(&mut wr, "Type").unwrap();
        rmp::encode::write_uint8(&mut wr, VersionType::Legacy.to_u8()).unwrap();

        rmp::encode::write_str(&mut wr, "V1Obj").unwrap();
        rmp::encode::write_map_len(&mut wr, 8).unwrap();

        rmp::encode::write_str(&mut wr, "Version").unwrap();
        rmp::encode::write_str(&mut wr, "1.0.1").unwrap();
        rmp::encode::write_str(&mut wr, "Format").unwrap();
        rmp::encode::write_str(&mut wr, "xl").unwrap();

        rmp::encode::write_str(&mut wr, "Stat").unwrap();
        rmp::encode::write_map_len(&mut wr, 5).unwrap();
        rmp::encode::write_str(&mut wr, "Size").unwrap();
        rmp::encode::write_sint(&mut wr, 11).unwrap();
        rmp::encode::write_str(&mut wr, "ModTime").unwrap();
        write_legacy_time(&mut wr, mod_time);
        rmp::encode::write_str(&mut wr, "Name").unwrap();
        rmp::encode::write_str(&mut wr, "hello.txt").unwrap();
        rmp::encode::write_str(&mut wr, "Dir").unwrap();
        rmp::encode::write_bool(&mut wr, false).unwrap();
        rmp::encode::write_str(&mut wr, "Mode").unwrap();
        rmp::encode::write_u32(&mut wr, 0o644).unwrap();

        rmp::encode::write_str(&mut wr, "Erasure").unwrap();
        rmp::encode::write_map_len(&mut wr, 7).unwrap();
        rmp::encode::write_str(&mut wr, "Algorithm").unwrap();
        rmp::encode::write_str(&mut wr, "ReedSolomon").unwrap();
        rmp::encode::write_str(&mut wr, "DataBlocks").unwrap();
        rmp::encode::write_sint(&mut wr, 4).unwrap();
        rmp::encode::write_str(&mut wr, "ParityBlocks").unwrap();
        rmp::encode::write_sint(&mut wr, 2).unwrap();
        rmp::encode::write_str(&mut wr, "BlockSize").unwrap();
        rmp::encode::write_sint(&mut wr, 1_048_576).unwrap();
        rmp::encode::write_str(&mut wr, "Index").unwrap();
        rmp::encode::write_sint(&mut wr, 1).unwrap();
        rmp::encode::write_str(&mut wr, "Distribution").unwrap();
        rmp::encode::write_array_len(&mut wr, 6).unwrap();
        for value in 1..=6 {
            rmp::encode::write_sint(&mut wr, value).unwrap();
        }
        rmp::encode::write_str(&mut wr, "Checksums").unwrap();
        rmp::encode::write_array_len(&mut wr, 0).unwrap();

        rmp::encode::write_str(&mut wr, "Meta").unwrap();
        rmp::encode::write_map_len(&mut wr, 1).unwrap();
        rmp::encode::write_str(&mut wr, "content-type").unwrap();
        rmp::encode::write_str(&mut wr, "text/plain").unwrap();

        rmp::encode::write_str(&mut wr, "Parts").unwrap();
        rmp::encode::write_array_len(&mut wr, 1).unwrap();
        rmp::encode::write_map_len(&mut wr, 5).unwrap();
        rmp::encode::write_str(&mut wr, "e").unwrap();
        rmp::encode::write_str(&mut wr, "etag-1").unwrap();
        rmp::encode::write_str(&mut wr, "n").unwrap();
        rmp::encode::write_sint(&mut wr, 1).unwrap();
        rmp::encode::write_str(&mut wr, "s").unwrap();
        rmp::encode::write_sint(&mut wr, 11).unwrap();
        rmp::encode::write_str(&mut wr, "as").unwrap();
        rmp::encode::write_sint(&mut wr, 11).unwrap();
        rmp::encode::write_str(&mut wr, "mt").unwrap();
        write_legacy_time(&mut wr, mod_time);

        rmp::encode::write_str(&mut wr, "VersionID").unwrap();
        rmp::encode::write_str(&mut wr, "").unwrap();
        rmp::encode::write_str(&mut wr, "DataDir").unwrap();
        rmp::encode::write_str(&mut wr, "legacy").unwrap();

        rmp::encode::write_str(&mut wr, "v").unwrap();
        rmp::encode::write_uint(&mut wr, 1).unwrap();

        wr
    }

    fn encode_legacy_v2_object_body(data_blocks: usize, parity_blocks: usize) -> Vec<u8> {
        let drive_count = data_blocks + parity_blocks;
        let payload = LegacyObjectVersionFixture {
            version_type: LegacyObjectVersionTypeFixture::Object,
            object: Some(LegacyObjectFixture {
                version_id: Some(sample_version_id().as_bytes().to_vec()),
                data_dir: Some(Uuid::from_u128(42).as_bytes().to_vec()),
                erasure_algorithm: "ReedSolomon".to_string(),
                erasure_m: data_blocks,
                erasure_n: parity_blocks,
                erasure_block_size: 1_048_576,
                erasure_index: 1,
                erasure_dist: (1..=drive_count)
                    .map(|idx| u8::try_from(idx).expect("test drive index should fit u8"))
                    .collect(),
                bitrot_checksum_algo: "HighwayHash".to_string(),
                part_numbers: vec![1],
                part_etags: vec!["etag-1".to_string()],
                part_sizes: vec![11],
                part_actual_sizes: vec![11],
                part_indices: vec![Vec::new()],
                size: 11,
                mod_time: Some(sample_mod_time()),
                meta_sys: HashMap::new(),
                meta_user: HashMap::from([("content-type".to_string(), "text/plain".to_string())]),
            }),
            delete_marker: None,
            write_version: 3,
        };

        rmp_serde::to_vec_named(&payload).expect("legacy object payload should marshal")
    }

    #[test]
    fn version_header_unmarshal_v1_uses_legacy_layout_defaults() {
        let expected = sample_header();
        let encoded = encode_v1_header(&expected);

        let mut decoded = FileMetaVersionHeader::default();
        decoded.unmarshal_v(1, &encoded).unwrap();

        assert_eq!(decoded.version_id, expected.version_id);
        assert_eq!(decoded.mod_time, expected.mod_time);
        assert_eq!(decoded.version_type, expected.version_type);
        assert_eq!(decoded.flags, expected.flags);
        assert_eq!(decoded.signature, [0; 4]);
        assert_eq!(decoded.ec_n, 0);
        assert_eq!(decoded.ec_m, 0);
    }

    #[test]
    fn version_header_unmarshal_v2_keeps_signature_and_zeroes_ec() {
        let expected = sample_header();
        let encoded = encode_v2_header(&expected);

        let mut decoded = FileMetaVersionHeader::default();
        decoded.unmarshal_v(2, &encoded).unwrap();

        assert_eq!(decoded.version_id, expected.version_id);
        assert_eq!(decoded.mod_time, expected.mod_time);
        assert_eq!(decoded.signature, expected.signature);
        assert_eq!(decoded.version_type, expected.version_type);
        assert_eq!(decoded.flags, expected.flags);
        assert_eq!(decoded.ec_n, 0);
        assert_eq!(decoded.ec_m, 0);
    }

    #[test]
    fn shallow_version_write_quorum_uses_legacy_object_payload_when_header_lacks_ec() {
        let expected = sample_header();
        let encoded = encode_v2_header(&expected);
        let mut header = FileMetaVersionHeader::default();
        header.unmarshal_v(2, &encoded).expect("legacy v2 header should decode");

        let version = FileMetaShallowVersion {
            header,
            meta: encode_legacy_v2_object_body(7, 1),
        };

        assert_eq!(version.header.write_quorum(5), 5);
        assert_eq!(version.write_quorum(5), 7);
    }

    #[test]
    fn shallow_version_write_quorum_uses_zero_parity_object_payload() {
        let expected = sample_header();
        let encoded = encode_v2_header(&expected);
        let mut header = FileMetaVersionHeader::default();
        header.unmarshal_v(2, &encoded).expect("legacy v2 header should decode");

        let version = FileMetaShallowVersion {
            header,
            meta: encode_legacy_v2_object_body(4, 0),
        };

        assert_eq!(version.header.write_quorum(2), 2);
        assert_eq!(version.write_quorum(2), 4);
    }

    #[test]
    fn version_header_unmarshal_v3_round_trips_current_layout() {
        let expected = sample_header();
        let encoded = expected.marshal_msg().unwrap();

        let mut decoded = FileMetaVersionHeader::default();
        decoded.unmarshal_v(3, &encoded).unwrap();

        assert_eq!(decoded, expected);
    }

    #[test]
    fn legacy_v1_object_body_decodes_into_fileinfo() {
        let encoded = encode_legacy_v1_body();
        let decoded = FileMetaVersion::try_from(encoded.as_slice()).unwrap();

        assert_eq!(decoded.version_type, VersionType::Legacy);
        assert!(decoded.valid());
        assert!(decoded.legacy_object.is_some());

        let fi = decoded.into_fileinfo("bucket", "hello.txt", true).expect("into_fileinfo");
        assert_eq!(fi.volume, "bucket");
        assert_eq!(fi.name, "hello.txt");
        assert_eq!(fi.size, 11);
        assert_eq!(fi.mod_time, Some(sample_mod_time()));
        assert_eq!(fi.mode, Some(0o644));
        assert_eq!(fi.parts.len(), 1);
        assert_eq!(fi.parts[0].etag, "etag-1");
        assert_eq!(fi.parts[0].size, 11);
        assert_eq!(fi.erasure.data_blocks, 4);
        assert_eq!(fi.erasure.parity_blocks, 2);
        assert_eq!(fi.metadata.get("content-type").map(String::as_str), Some("text/plain"));
    }

    #[test]
    fn legacy_meta_v2_delete_marker_decodes_into_delete_fileinfo() {
        let payload = LegacyDeleteVersionFixture {
            version_type: LegacyDeleteVersionTypeFixture::DeleteMarker,
            object: None,
            delete_marker: Some(LegacyDeleteMarkerFixture {
                version_id: sample_version_id().as_bytes().to_vec(),
                mod_time: Some(sample_mod_time()),
                meta_sys: HashMap::from([("x-rustfs-test".to_string(), b"gone".to_vec())]),
            }),
            write_version: 9,
        };
        let encoded = rmp_serde::to_vec_named(&payload).unwrap();

        let decoded = FileMetaVersion::try_from(encoded.as_slice()).unwrap();

        assert_eq!(decoded.version_type, VersionType::Delete);
        assert!(decoded.object.is_none());
        assert!(decoded.delete_marker.is_some());
        assert!(decoded.uses_legacy_checksum);

        let fi = decoded.into_fileinfo("bucket", "gone.txt", true).expect("into_fileinfo");
        assert!(fi.deleted);
        assert_eq!(fi.volume, "bucket");
        assert_eq!(fi.name, "gone.txt");
        assert_eq!(fi.version_id, Some(sample_version_id()));
        assert_eq!(fi.mod_time, Some(sample_mod_time()));
        assert_eq!(fi.metadata.get("x-rustfs-test").map(String::as_str), Some("gone"));
        assert!(fi.uses_legacy_checksum);
    }

    #[test]
    fn legacy_meta_v2_delete_marker_decodes_into_delete_fileinfo_via_struct() {
        let version_id = sample_version_id();
        let mod_time = sample_mod_time();
        let version = LegacyMetaV2Version {
            version_type: LegacyMetaV2VersionType::DeleteMarker,
            object: None,
            delete_marker: Some(LegacyMetaV2DeleteMarker {
                version_id: version_id.as_bytes().to_vec(),
                mod_time: Some(mod_time),
                meta_sys: HashMap::from([("x-minio-internal".to_string(), b"present".to_vec())]),
            }),
            write_version: 7,
        };

        let decoded = FileMetaVersion::try_from(version).unwrap();

        assert_eq!(decoded.version_type, VersionType::Delete);
        assert!(decoded.uses_legacy_checksum);
        assert!(decoded.object.is_none());

        let delete_marker = decoded.delete_marker.as_ref().expect("delete marker should be decoded");
        assert_eq!(delete_marker.version_id, Some(version_id));
        assert_eq!(delete_marker.mod_time, Some(mod_time));

        let fi = decoded.into_fileinfo("bucket", "deleted.txt", true).expect("into_fileinfo");
        assert!(fi.deleted);
        assert_eq!(fi.version_id, Some(version_id));
        assert_eq!(fi.mod_time, Some(mod_time));
        assert_eq!(fi.metadata.get("x-minio-internal").map(String::as_str), Some("present"));
    }

    #[test]
    fn legacy_meta_v2_delete_marker_rejects_invalid_uuid_bytes() {
        let payload = LegacyDeleteVersionFixture {
            version_type: LegacyDeleteVersionTypeFixture::DeleteMarker,
            object: None,
            delete_marker: Some(LegacyDeleteMarkerFixture {
                version_id: vec![7; 15],
                mod_time: Some(sample_mod_time()),
                meta_sys: HashMap::new(),
            }),
            write_version: 10,
        };
        let encoded = rmp_serde::to_vec_named(&payload).unwrap();

        let err = FileMetaVersion::try_from(encoded.as_slice()).expect_err("invalid legacy delete marker UUID must fail");
        assert!(err.to_string().contains("legacy version_id must be 16 bytes"));
    }

    #[test]
    fn legacy_meta_v2_delete_marker_rejects_invalid_uuid_bytes_via_struct() {
        let err = MetaDeleteMarker::try_from(LegacyMetaV2DeleteMarker {
            version_id: vec![1, 2, 3],
            mod_time: Some(sample_mod_time()),
            meta_sys: HashMap::new(),
        })
        .expect_err("invalid legacy delete-marker version ids should be rejected");

        assert!(err.to_string().contains("legacy version_id must be 16 bytes"));
    }

    #[test]
    fn legacy_meta_v2_object_accepts_nil_uuid_fields() {
        let payload = LegacyObjectVersionFixture {
            version_type: LegacyObjectVersionTypeFixture::Object,
            object: Some(LegacyObjectFixture {
                version_id: None,
                data_dir: None,
                erasure_algorithm: "ReedSolomon".to_string(),
                erasure_m: 2,
                erasure_n: 4,
                erasure_block_size: 1_048_576,
                erasure_index: 1,
                erasure_dist: vec![1, 2, 3, 4, 5, 6],
                bitrot_checksum_algo: "HighwayHash".to_string(),
                part_numbers: vec![1],
                part_etags: vec!["etag-1".to_string()],
                part_sizes: vec![11],
                part_actual_sizes: vec![11],
                part_indices: vec![Vec::new()],
                size: 11,
                mod_time: Some(sample_mod_time()),
                meta_sys: HashMap::new(),
                meta_user: HashMap::from([("content-type".to_string(), "text/plain".to_string())]),
            }),
            delete_marker: None,
            write_version: 3,
        };
        let encoded = rmp_serde::to_vec_named(&payload).unwrap();

        let decoded = FileMetaVersion::try_from(encoded.as_slice()).unwrap();
        let object = decoded.object.as_ref().expect("object should be decoded");

        assert_eq!(decoded.version_type, VersionType::Object);
        assert!(decoded.uses_legacy_checksum);
        assert_eq!(object.version_id, None);
        assert_eq!(object.data_dir, None);

        let fi = decoded
            .into_fileinfo("bucket", "legacy-nil.txt", true)
            .expect("into_fileinfo");
        assert_eq!(fi.version_id, None);
        assert_eq!(fi.data_dir, None);
        assert_eq!(fi.metadata.get("content-type").map(String::as_str), Some("text/plain"));
    }

    #[test]
    fn legacy_meta_v2_delete_marker_accepts_nil_version_id() {
        let payload = LegacyDeleteVersionNilFixture {
            version_type: LegacyDeleteVersionTypeFixture::DeleteMarker,
            object: None,
            delete_marker: Some(LegacyDeleteMarkerNilFixture {
                version_id: None,
                mod_time: Some(sample_mod_time()),
                meta_sys: HashMap::from([("x-rustfs-test".to_string(), b"gone".to_vec())]),
            }),
            write_version: 11,
        };
        let encoded = rmp_serde::to_vec_named(&payload).unwrap();

        let decoded = FileMetaVersion::try_from(encoded.as_slice()).unwrap();
        let delete_marker = decoded.delete_marker.as_ref().expect("delete marker should be decoded");

        assert_eq!(decoded.version_type, VersionType::Delete);
        assert!(decoded.uses_legacy_checksum);
        assert_eq!(delete_marker.version_id, None);
        assert_eq!(delete_marker.mod_time, Some(sample_mod_time()));

        let fi = decoded.into_fileinfo("bucket", "deleted.txt", true).expect("into_fileinfo");
        assert!(fi.deleted);
        assert_eq!(fi.version_id, None);
        assert_eq!(fi.mod_time, Some(sample_mod_time()));
        assert_eq!(fi.metadata.get("x-rustfs-test").map(String::as_str), Some("gone"));
    }

    #[test]
    fn decode_data_dir_from_meta_extracts_v2_object_fast_path() {
        let data_dir = Uuid::new_v4();
        let version = FileMetaVersion {
            version_type: VersionType::Object,
            object: Some(MetaObject {
                version_id: Some(Uuid::new_v4()),
                data_dir: Some(data_dir),
                erasure_algorithm: ErasureAlgo::ReedSolomon,
                erasure_m: 2,
                erasure_n: 4,
                erasure_block_size: 1024 * 1024,
                erasure_index: 1,
                erasure_dist: vec![1, 2, 3, 4, 5, 6],
                bitrot_checksum_algo: ChecksumAlgo::HighwayHash,
                size: 64 * 1024,
                mod_time: Some(OffsetDateTime::now_utc()),
                ..Default::default()
            }),
            ..Default::default()
        };

        let encoded = version.marshal_msg().expect("marshal");
        let decoded = FileMetaVersion::decode_data_dir_from_meta(&encoded).expect("decode data_dir");
        assert_eq!(decoded, Some(data_dir));
    }

    fn make_meta_object_with_sys(meta_sys: HashMap<String, Vec<u8>>) -> MetaObject {
        MetaObject {
            erasure_algorithm: ErasureAlgo::ReedSolomon,
            erasure_m: 2,
            erasure_n: 4,
            erasure_block_size: 1_048_576,
            erasure_index: 1,
            erasure_dist: vec![1, 2, 3, 4, 5, 6],
            bitrot_checksum_algo: ChecksumAlgo::HighwayHash,
            meta_sys,
            ..Default::default()
        }
    }

    #[test]
    fn meta_object_transition_version_id_absent_yields_none() {
        let fi = make_meta_object_with_sys(HashMap::new())
            .into_fileinfo("b", "k", false)
            .expect("into_fileinfo");
        assert_eq!(fi.transition_version_id, None);
    }

    #[test]
    fn meta_object_transition_version_id_empty_bytes_yields_none() {
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, vec![]);
        let fi = make_meta_object_with_sys(sys)
            .into_fileinfo("b", "k", false)
            .expect("into_fileinfo");
        assert_eq!(fi.transition_version_id, None);
    }

    #[test]
    fn meta_object_transition_version_id_nil_uuid_yields_none() {
        // Regression: old code used unwrap_or_default() which turned nil bytes into Some(Uuid::nil())
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, Uuid::nil().as_bytes().to_vec());
        let fi = make_meta_object_with_sys(sys)
            .into_fileinfo("b", "k", false)
            .expect("into_fileinfo");
        assert_eq!(fi.transition_version_id, None);
    }

    #[test]
    fn meta_object_transition_version_id_valid_uuid_round_trips() {
        let id = sample_version_id();
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, id.as_bytes().to_vec());
        let fi = make_meta_object_with_sys(sys)
            .into_fileinfo("b", "k", false)
            .expect("into_fileinfo");
        assert_eq!(fi.transition_version_id, Some(id));
    }

    #[test]
    fn meta_object_transition_version_id_unparseable_stays_readable_as_none() {
        // A non-UUID / non-16-byte tier version id must NOT make the object
        // unreadable; it is tolerated as "no tier version" (compat with
        // pre-hardening behavior and foreign/edge metadata).
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, b"not-a-uuid".to_vec());
        let fi = make_meta_object_with_sys(sys)
            .into_fileinfo("b", "k", false)
            .expect("unparseable transition version id must not fail the object read");
        assert_eq!(fi.transition_version_id, None);
    }

    #[test]
    fn meta_object_transition_version_id_minio_string_form_is_recovered() {
        // MinIO-migrated tiered objects store the remote tier's version id as a
        // UUID string, not 16 raw bytes; recover it instead of dropping it.
        let id = sample_version_id();
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, id.to_string().into_bytes());
        let fi = make_meta_object_with_sys(sys)
            .into_fileinfo("b", "k", false)
            .expect("string-form transition version id must decode");
        assert_eq!(fi.transition_version_id, Some(id));
    }

    #[test]
    fn delete_marker_free_version_transition_version_id_nil_uuid_yields_none() {
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_FREE_VERSION, vec![]);
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, Uuid::nil().as_bytes().to_vec());
        let fi = MetaDeleteMarker {
            version_id: None,
            mod_time: None,
            meta_sys: sys,
        }
        .into_fileinfo("b", "k", false);
        assert_eq!(fi.transition_version_id, None);
    }

    #[test]
    fn delete_marker_free_version_transition_version_id_valid_uuid_round_trips() {
        let id = sample_version_id();
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_FREE_VERSION, vec![]);
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, id.as_bytes().to_vec());
        let fi = MetaDeleteMarker {
            version_id: None,
            mod_time: None,
            meta_sys: sys,
        }
        .into_fileinfo("b", "k", false);
        assert_eq!(fi.transition_version_id, Some(id));
    }

    #[test]
    fn delete_marker_free_version_transition_version_id_unparseable_stays_readable() {
        // A malformed tier version id must not make a free-version record corrupt:
        // it decodes to None and stays readable. Otherwise free-version expiry
        // fails and the remote-tier object leaks.
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_FREE_VERSION, vec![]);
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, b"not-a-uuid".to_vec());
        insert_bytes(&mut sys, SUFFIX_TRANSITION_TIER, b"WARM".to_vec());
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_OBJECTNAME, b"remote-object".to_vec());
        let fi = MetaDeleteMarker {
            version_id: Some(sample_version_id()),
            mod_time: Some(sample_mod_time()),
            meta_sys: sys,
        }
        .into_fileinfo("b", "k", false);

        assert_eq!(fi.transition_version_id, None);
        fi.validate_for_metadata_read()
            .expect("free-version record with an unparseable tier id must remain readable");
    }

    #[test]
    fn delete_marker_free_version_transition_version_id_minio_string_form_is_recovered() {
        // MinIO stores the tier version id as a UUID string; recover it.
        let id = sample_version_id();
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_FREE_VERSION, vec![]);
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_VERSION_ID, id.to_string().into_bytes());
        insert_bytes(&mut sys, SUFFIX_TRANSITION_TIER, b"WARM".to_vec());
        insert_bytes(&mut sys, SUFFIX_TRANSITIONED_OBJECTNAME, b"remote-object".to_vec());
        let fi = MetaDeleteMarker {
            version_id: Some(sample_version_id()),
            mod_time: Some(sample_mod_time()),
            meta_sys: sys,
        }
        .into_fileinfo("b", "k", false);

        assert_eq!(fi.transition_version_id, Some(id));
    }

    #[test]
    fn version_header_sorts_before_prefers_object_over_delete_marker_on_equal_mod_time() {
        let object = FileMetaVersionHeader {
            version_id: Some(Uuid::from_u128(1)),
            mod_time: Some(sample_mod_time()),
            version_type: VersionType::Object,
            ..Default::default()
        };
        let delete_marker = FileMetaVersionHeader {
            version_id: Some(Uuid::from_u128(2)),
            version_type: VersionType::Delete,
            ..object
        };

        // With equal mod_time the tie is broken by "prefer lower types":
        // Object (1) sorts before Delete (2), regardless of version_id.
        assert!(object.sorts_before(&delete_marker));
        assert!(!delete_marker.sorts_before(&object));
    }

    #[test]
    fn version_header_sorts_before_equal_mod_time_is_deterministic_and_antisymmetric() {
        let a = FileMetaVersionHeader {
            version_id: Some(Uuid::from_u128(1)),
            mod_time: Some(sample_mod_time()),
            version_type: VersionType::Object,
            ..Default::default()
        };
        let b = FileMetaVersionHeader {
            version_id: Some(Uuid::from_u128(2)),
            ..a.clone()
        };

        // Equal mod_time and version_type: the higher version_id sorts first,
        // and exactly one of the two orderings holds so merge sees a stable
        // total order for distinct headers.
        assert!(b.sorts_before(&a));
        assert!(!a.sorts_before(&b));
        assert_ne!(a.sorts_before(&b), b.sorts_before(&a));

        // A header never sorts before an identical header.
        assert!(!a.sorts_before(&a.clone()));
    }

    #[test]
    fn version_header_sorts_before_breaks_signature_tie_before_version_id() {
        // Two same-type Object headers with equal mod_time but differing
        // signature and version_id. Matching MinIO's sortsBefore, the higher
        // signature wins the tie ahead of the version_id comparison, even when
        // version_id would order the two the other way.
        let lower_sig_higher_id = FileMetaVersionHeader {
            version_id: Some(Uuid::from_u128(2)),
            mod_time: Some(sample_mod_time()),
            version_type: VersionType::Object,
            signature: [0x00, 0x00, 0x00, 0x01],
            ..Default::default()
        };
        let higher_sig_lower_id = FileMetaVersionHeader {
            version_id: Some(Uuid::from_u128(1)),
            signature: [0x00, 0x00, 0x00, 0x02],
            ..lower_sig_higher_id.clone()
        };

        assert!(higher_sig_lower_id.sorts_before(&lower_sig_higher_id));
        assert!(!lower_sig_higher_id.sorts_before(&higher_sig_lower_id));
    }

    #[test]
    fn version_header_sorts_before_version_id_only_breaks_signature_tie() {
        // Equal mod_time, version_type, and signature: only then does version_id
        // decide, and the higher version_id sorts first.
        let a = FileMetaVersionHeader {
            version_id: Some(Uuid::from_u128(1)),
            mod_time: Some(sample_mod_time()),
            version_type: VersionType::Object,
            signature: [0x0a, 0x0b, 0x0c, 0x0d],
            ..Default::default()
        };
        let b = FileMetaVersionHeader {
            version_id: Some(Uuid::from_u128(2)),
            ..a.clone()
        };

        assert!(b.sorts_before(&a));
        assert!(!a.sorts_before(&b));
    }

    #[test]
    fn merge_file_meta_versions_survives_garbage_header_stream() {
        let valid = FileMetaShallowVersion {
            header: sample_header(),
            meta: Vec::new(),
        };
        let garbage = FileMetaShallowVersion {
            header: FileMetaVersionHeader {
                version_id: None,
                mod_time: None,
                signature: [0xde, 0xad, 0xbe, 0xef],
                version_type: VersionType::Invalid,
                flags: 0xff,
                ec_n: 0,
                ec_m: 0,
            },
            meta: b"not-a-valid-msgpack-version".to_vec(),
        };

        // One disk returns a garbage header alongside two healthy streams:
        // merge must not panic and must still return the quorum version.
        let merged = merge_file_meta_versions(2, true, 0, &[vec![valid.clone()], vec![valid.clone()], vec![garbage]]);

        assert_eq!(merged, vec![valid]);
    }

    /// Build a single distinct Object version header for the union tests.
    fn union_version(version_u128: u128, mod_unix: i64) -> FileMetaShallowVersion {
        FileMetaShallowVersion {
            header: FileMetaVersionHeader {
                version_id: Some(Uuid::from_u128(version_u128)),
                mod_time: Some(OffsetDateTime::from_unix_timestamp(mod_unix).expect("valid timestamp")),
                signature: [0x11, 0x22, 0x33, 0x44],
                version_type: VersionType::Object,
                flags: 0,
                ec_n: 4,
                ec_m: 2,
            },
            meta: Vec::new(),
        }
    }

    /// backlog#920: quorum==1 (union) must surface EVERY version present on ANY
    /// per-disk stream, even when the per-disk version sets are fully DISJOINT
    /// (a version living on a single disk). This is the enumeration guarantee the
    /// sub-quorum disk-walk depends on.
    #[test]
    fn merge_union_quorum1_yields_full_union_over_disjoint_disks() {
        let a = union_version(0xA, 1_705_312_300);
        let b = union_version(0xB, 1_705_312_200);
        let c = union_version(0xC, 1_705_312_100);

        // Three disks, each holding exactly ONE distinct version (disjoint sets).
        let disks = [vec![a], vec![b], vec![c]];
        let merged = merge_file_meta_versions(1, true, 0, &disks);

        let ids: std::collections::HashSet<Option<Uuid>> = merged.iter().map(|v| v.header.version_id).collect();
        assert_eq!(merged.len(), 3, "union must retain all three disjoint versions: {merged:?}");
        assert!(ids.contains(&Some(Uuid::from_u128(0xA))));
        assert!(ids.contains(&Some(Uuid::from_u128(0xB))));
        assert!(ids.contains(&Some(Uuid::from_u128(0xC))));

        // Contrast: read-quorum (2) over the same disjoint streams surfaces NONE,
        // because no version reaches two agreeing disks. This is the exact gap.
        let read_quorum = merge_file_meta_versions(2, true, 0, &disks);
        assert!(
            read_quorum.is_empty(),
            "read-quorum merge must drop every sub-quorum version, got {read_quorum:?}"
        );
    }

    /// The equal-modTime / distinct-versionId retain-and-advance branch: two
    /// versions sharing a mod_time but with different ids must BOTH survive the
    /// union merge (they are not collapsed as duplicates).
    #[test]
    fn merge_union_quorum1_retains_equal_modtime_distinct_version_ids() {
        let same_time = 1_705_312_300;
        let a = union_version(0xAA, same_time);
        let b = union_version(0xBB, same_time);

        let disks = [vec![a], vec![b]];
        let merged = merge_file_meta_versions(1, true, 0, &disks);

        let ids: std::collections::HashSet<Option<Uuid>> = merged.iter().map(|v| v.header.version_id).collect();
        assert_eq!(merged.len(), 2, "equal-modTime distinct-id versions must both survive: {merged:?}");
        assert!(ids.contains(&Some(Uuid::from_u128(0xAA))));
        assert!(ids.contains(&Some(Uuid::from_u128(0xBB))));
    }

    #[test]
    fn meta_object_init_free_version_rejects_invalid_tier_free_version_id() {
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_TRANSITION_STATUS, TRANSITION_COMPLETE.as_bytes().to_vec());

        let obj = make_meta_object_with_sys(sys);
        let mut fi = FileInfo::new("object", 2, 2);
        fi.set_tier_free_version_id("not-a-uuid");

        let err = obj
            .init_free_version(&fi)
            .expect_err("invalid free-version UUID should return an error instead of panicking");

        assert!(matches!(err, Error::UuidParse(_)));
    }

    #[test]
    fn meta_object_init_free_version_preserves_transition_destination_identity() {
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_TRANSITION_STATUS, TRANSITION_COMPLETE.as_bytes().to_vec());
        let identity = b"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef".to_vec();
        insert_bytes(&mut sys, SUFFIX_TRANSITION_TIER_DESTINATION_ID, identity.clone());
        let obj = make_meta_object_with_sys(sys);
        let mut fi = FileInfo::new("object", 2, 2);
        fi.set_tier_free_version_id(&Uuid::new_v4().to_string());

        let (free_version, created) = obj
            .init_free_version(&fi)
            .expect("free-version initialization should succeed");
        let meta_sys = &free_version
            .delete_marker
            .expect("free-version should be a delete marker")
            .meta_sys;

        assert!(created);
        assert_eq!(get_bytes(meta_sys, SUFFIX_TRANSITION_TIER_DESTINATION_ID), Some(identity));
        assert!(meta_sys.contains_key(&format!(
            "{}{}",
            rustfs_utils::http::metadata_compat::RUSTFS_INTERNAL_PREFIX,
            SUFFIX_TRANSITION_TIER_DESTINATION_ID
        )));
        assert!(meta_sys.contains_key(&format!(
            "{}{}",
            rustfs_utils::http::metadata_compat::MINIO_INTERNAL_PREFIX,
            SUFFIX_TRANSITION_TIER_DESTINATION_ID
        )));
    }

    #[test]
    fn meta_object_init_free_version_accepts_single_prefix_transition_destination_identity() {
        let mut sys = HashMap::new();
        insert_bytes(&mut sys, SUFFIX_TRANSITION_STATUS, TRANSITION_COMPLETE.as_bytes().to_vec());
        let identity = b"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef".to_vec();
        sys.insert(
            format!(
                "{}{}",
                rustfs_utils::http::metadata_compat::MINIO_INTERNAL_PREFIX,
                SUFFIX_TRANSITION_TIER_DESTINATION_ID
            ),
            identity.clone(),
        );
        let obj = make_meta_object_with_sys(sys);
        let mut fi = FileInfo::new("object", 2, 2);
        fi.set_tier_free_version_id(&Uuid::new_v4().to_string());

        let (free_version, created) = obj
            .init_free_version(&fi)
            .expect("single-prefix legacy destination identity should remain compatible");
        let meta_sys = &free_version
            .delete_marker
            .expect("free-version should be a delete marker")
            .meta_sys;

        assert!(created);
        assert_eq!(
            get_consistent_bytes(meta_sys, SUFFIX_TRANSITION_TIER_DESTINATION_ID),
            Some(identity.as_slice())
        );
    }

    #[test]
    fn meta_object_init_free_version_rejects_conflicting_or_invalid_transition_destination_identity() {
        let valid_identity = b"0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef".to_vec();
        for (rustfs_identity, minio_identity) in [
            (
                valid_identity,
                b"abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789".to_vec(),
            ),
            (b"not-hex".to_vec(), b"not-hex".to_vec()),
            (Vec::new(), Vec::new()),
        ] {
            let mut sys = HashMap::new();
            insert_bytes(&mut sys, SUFFIX_TRANSITION_STATUS, TRANSITION_COMPLETE.as_bytes().to_vec());
            sys.insert(
                format!(
                    "{}{}",
                    rustfs_utils::http::metadata_compat::RUSTFS_INTERNAL_PREFIX,
                    SUFFIX_TRANSITION_TIER_DESTINATION_ID
                ),
                rustfs_identity,
            );
            sys.insert(
                format!(
                    "{}{}",
                    rustfs_utils::http::metadata_compat::MINIO_INTERNAL_PREFIX,
                    SUFFIX_TRANSITION_TIER_DESTINATION_ID
                ),
                minio_identity,
            );
            let obj = make_meta_object_with_sys(sys);
            let mut fi = FileInfo::new("object", 2, 2);
            fi.set_tier_free_version_id(&Uuid::new_v4().to_string());

            assert_eq!(
                obj.init_free_version(&fi)
                    .expect_err("unsafe destination identity must fail closed"),
                Error::FileCorrupt
            );
        }
    }

    #[test]
    fn delete_marker_decode_skips_unknown_fields_for_forward_compat() {
        // A newer writer emits the three known fields plus an extra one. Decoding
        // must skip the unknown field instead of erroring (backlog#799 B17).
        let vid = Uuid::from_u128(0x1234);
        let mut buf = Vec::new();
        rmp::encode::write_map_len(&mut buf, 4).unwrap();
        rmp::encode::write_str(&mut buf, "ID").unwrap();
        rmp::encode::write_bin(&mut buf, vid.as_bytes()).unwrap();
        rmp::encode::write_str(&mut buf, "MTime").unwrap();
        rmp::encode::write_sint(&mut buf, 1_700_000_000_000_000_000i64).unwrap();
        rmp::encode::write_str(&mut buf, "MetaSys").unwrap();
        rmp::encode::write_map_len(&mut buf, 0).unwrap();
        // Unknown field a future version added.
        rmp::encode::write_str(&mut buf, "FutureField").unwrap();
        rmp::encode::write_str(&mut buf, "ignored").unwrap();

        let mut dm = MetaDeleteMarker::default();
        dm.decode_from(&mut std::io::Cursor::new(buf))
            .expect("unknown fields must be skipped, not rejected");
        assert_eq!(dm.version_id, Some(vid));
        assert!(dm.mod_time.is_some());
    }

    #[test]
    fn get_internal_replication_state_keeps_canonical_reset_key() {
        // The reset status is stored on disk under the full internal key; parsing
        // must keep it keyed by `target_reset_header(arn)` (not the bare ARN) so
        // `ReplicationState::target_state` finds it after a round trip
        // (backlog#799 B16).
        let arn = "arn:rustfs:replication:us-east-1:target:bucket";
        let ts = "2026-06-30T00:00:00Z;reset-1".to_string();
        let key = crate::replication::target_reset_header(arn);
        let mut metadata = HashMap::new();
        metadata.insert(key.clone(), ts.clone());

        let rs = get_internal_replication_state(&metadata).expect("reset state should parse");
        assert_eq!(
            rs.reset_statuses_map.get(&key),
            Some(&ts),
            "map must be keyed by target_reset_header, not the bare ARN"
        );
        assert_eq!(
            rs.target_state(arn).resync_timestamp,
            ts,
            "lookup must find the round-tripped reset status"
        );
    }

    // ---- Header signature (backlog#861 / B12) ----

    fn signed_object() -> MetaObject {
        MetaObject {
            version_id: Some(sample_version_id()),
            data_dir: Some(sample_version_id()),
            erasure_algorithm: ErasureAlgo::ReedSolomon,
            erasure_m: 2,
            erasure_n: 4,
            erasure_block_size: 1_048_576,
            erasure_index: 3,
            erasure_dist: vec![1, 2, 3, 4, 5, 6],
            bitrot_checksum_algo: ChecksumAlgo::HighwayHash,
            part_numbers: vec![1],
            part_etags: vec!["etag-1".to_string()],
            part_sizes: vec![11],
            part_actual_sizes: vec![11],
            size: 11,
            mod_time: Some(sample_mod_time()),
            meta_user: HashMap::from([("content-type".to_string(), "text/plain".to_string())]),
            ..Default::default()
        }
    }

    #[test]
    fn signature_is_no_longer_hardcoded_zero() {
        // Regression for B12: the write-path header must carry a real signature.
        let version = FileMetaVersion {
            version_type: VersionType::Object,
            object: Some(signed_object()),
            ..Default::default()
        };
        let header = version.header();
        assert_ne!(header.signature, [0, 0, 0, 0], "object header signature must be computed, not zeroed");
        assert_eq!(header.signature, version.get_signature(), "header must use the computed signature");
    }

    #[test]
    fn signature_ignores_per_disk_erasure_index() {
        // Two disks in the same set hold the same version but differ only in the
        // per-disk EcIndex; their signatures must match so heal does not see a
        // false divergence.
        let mut disk_a = signed_object();
        disk_a.erasure_index = 1;
        let mut disk_b = signed_object();
        disk_b.erasure_index = 5;
        assert_eq!(disk_a.get_signature(), disk_b.get_signature());
    }

    #[test]
    fn signature_detects_tag_and_metadata_divergence() {
        // The exact bug: same version_id + same mod_time, but a PutObjectTagging
        // that only reached some disks. Signatures must differ so the divergence
        // is detectable / healable.
        let base = signed_object();

        let mut tagged = base.clone();
        tagged
            .meta_sys
            .insert("x-rustfs-internal-tags".to_string(), b"env=prod".to_vec());
        assert_ne!(base.get_signature(), tagged.get_signature(), "meta_sys change must move the signature");

        let mut user_changed = base.clone();
        user_changed
            .meta_user
            .insert("x-amz-meta-owner".to_string(), "alice".to_string());
        assert_ne!(
            base.get_signature(),
            user_changed.get_signature(),
            "meta_user change must move the signature"
        );

        let mut resized = base.clone();
        resized.size += 1;
        resized.part_sizes = vec![12];
        assert_ne!(base.get_signature(), resized.get_signature(), "body change must move the signature");
    }

    #[test]
    fn signature_is_map_order_independent() {
        // HashMap iteration order is not stable across disks; folding maps in
        // order-independently must produce the same signature regardless.
        let mut a = signed_object();
        let mut b = signed_object();
        for obj in [&mut a, &mut b] {
            obj.meta_user.clear();
        }
        a.meta_user.insert("k1".into(), "v1".into());
        a.meta_user.insert("k2".into(), "v2".into());
        a.meta_user.insert("k3".into(), "v3".into());
        // Insert in a different order into b.
        b.meta_user.insert("k3".into(), "v3".into());
        b.meta_user.insert("k1".into(), "v1".into());
        b.meta_user.insert("k2".into(), "v2".into());
        assert_eq!(a.get_signature(), b.get_signature());

        // But a different value for the same key must still diverge.
        let mut c = a.clone();
        c.meta_user.insert("k2".into(), "changed".into());
        assert_ne!(a.get_signature(), c.get_signature());
    }

    #[test]
    fn signature_treats_empty_and_all_empty_part_etags_alike() {
        let mut none = signed_object();
        none.part_etags.clear();
        let mut all_empty = signed_object();
        all_empty.part_etags = vec![String::new(), String::new()];
        assert_eq!(none.get_signature(), all_empty.get_signature());
    }

    #[test]
    fn delete_marker_signature_detects_meta_sys_divergence() {
        let base = MetaDeleteMarker {
            version_id: Some(sample_version_id()),
            mod_time: Some(sample_mod_time()),
            meta_sys: HashMap::new(),
        };
        let mut diverged = base.clone();
        diverged
            .meta_sys
            .insert("x-rustfs-internal-purgestatus".to_string(), b"pending".to_vec());
        assert_ne!(base.get_signature(), diverged.get_signature());

        // Same content is stable across recomputation.
        assert_eq!(base.get_signature(), base.get_signature());
    }

    #[test]
    fn invalid_version_uses_error_sentinel_not_zero() {
        // A version whose inner body is missing must not masquerade as an
        // all-zero legacy signature.
        let version = FileMetaVersion {
            version_type: VersionType::Object,
            object: None,
            ..Default::default()
        };
        assert_eq!(version.get_signature(), SIGNATURE_ERR);
        assert_ne!(version.get_signature(), [0, 0, 0, 0]);
    }

    /// Regression for backlog#799 B18: a Legacy (V1Obj) version must survive an
    /// encode/decode round trip. `encode_to` used to omit the `V1Obj` field
    /// entirely, silently dropping the whole legacy body on re-marshal.
    #[test]
    fn legacy_version_body_round_trips_through_encode() {
        let mut meta = HashMap::new();
        meta.insert("content-type".to_string(), "application/octet-stream".to_string());

        let mut crc = HashMap::new();
        crc.insert("crc32c".to_string(), "deadbeef".to_string());

        let legacy = MetaObjectV1 {
            version: "1.0.1".to_string(),
            format: "xl".to_string(),
            stat: MetaObjectV1Stat {
                size: 4096,
                mod_time: Some(
                    OffsetDateTime::from_unix_timestamp(1_700_000_123)
                        .unwrap()
                        .replace_nanosecond(456)
                        .unwrap(),
                ),
                name: "obj".to_string(),
                dir: false,
                mode: 0o644,
            },
            erasure: MetaObjectV1Erasure {
                algorithm: "klauspost/reedsolomon/vandermonde".to_string(),
                data_blocks: 4,
                parity_blocks: 2,
                block_size: 10 << 20,
                index: 1,
                distribution: vec![1, 2, 3, 4, 5, 6],
                checksums: vec![MetaObjectV1ChecksumInfo {
                    part_number: 1,
                    algorithm: "highwayhash256S".to_string(),
                    hash: vec![0xaa, 0xbb, 0xcc, 0xdd],
                }],
            },
            meta,
            parts: vec![MetaObjectV1Part {
                etag: "etag-1".to_string(),
                number: 1,
                size: 4096,
                actual_size: 4096,
                mod_time: Some(OffsetDateTime::from_unix_timestamp(1_700_000_100).unwrap()),
                index: Some(Bytes::from_static(&[1, 2, 3])),
                checksums: Some(crc),
                error: None,
            }],
            version_id: "00000000-0000-0000-0000-000000000001".to_string(),
            data_dir: "11111111-1111-1111-1111-111111111111".to_string(),
        };

        let version = FileMetaVersion {
            version_type: VersionType::Legacy,
            legacy_object: Some(legacy.clone()),
            ..Default::default()
        };

        let buf = version.marshal_msg().expect("marshal must succeed");
        let mut decoded = FileMetaVersion::default();
        decoded.unmarshal_msg(&buf).expect("unmarshal must succeed");

        assert_eq!(decoded.version_type, VersionType::Legacy);
        let decoded_legacy = decoded.legacy_object.expect("legacy body must survive round trip");
        assert_eq!(decoded_legacy, legacy, "legacy body must be byte-for-byte preserved");
    }

    /// A `None` `Stat.ModTime` must stay `None` across encode/decode — the
    /// encoder writes the field only when present, mirroring the decoder, so it
    /// never silently becomes `Some(UNIX_EPOCH)` (backlog#799 B18 hardening).
    #[test]
    fn legacy_stat_none_mod_time_round_trips_as_none() {
        let stat = MetaObjectV1Stat {
            size: 10,
            mod_time: None,
            name: "n".to_string(),
            dir: true,
            mode: 0o755,
        };

        let mut buf = Vec::new();
        stat.encode_to(&mut buf).expect("encode must succeed");
        let mut decoded = MetaObjectV1Stat::default();
        decoded
            .decode_from(&mut std::io::Cursor::new(&buf))
            .expect("decode must succeed");

        assert_eq!(decoded, stat);
        assert!(decoded.mod_time.is_none(), "absent mod_time must not become Some(UNIX_EPOCH)");
    }
}

/// Equivalence tests proving `read_xl_meta_no_data_sync` returns byte-for-byte
/// identical `Result`s to the async `read_xl_meta_no_data` for every code path.
///
/// This is the critical guard for HP-12 item 1: the ecstore metadata read path
/// folds open+fstat+read into one `spawn_blocking` closure that calls the sync
/// twin, and it MUST NOT drift from the async version in either the Ok bytes or
/// the Err variant.
#[cfg(test)]
mod read_xl_meta_sync_equivalence_tests {
    use super::*;
    use std::io::Cursor as StdCursor;
    // tokio implements `AsyncRead` for `std::io::Cursor`, so the same type
    // drives both the async and the sync readers.
    use std::io::Cursor as TokioCursor;

    /// 8-byte xl.meta header: "XL2 " magic + LE major + LE minor.
    fn header(major: u16, minor: u16) -> Vec<u8> {
        let mut v = Vec::with_capacity(8);
        v.extend_from_slice(&XL_FILE_HEADER);
        v.extend_from_slice(&major.to_le_bytes());
        v.extend_from_slice(&minor.to_le_bytes());
        v
    }

    /// 5-byte msgpack `bin32` length prefix (marker 0xc6 + 4-byte BE length),
    /// matching what `read_bytes_header` decodes via `read_bin_len`.
    fn bin32_prefix(len: u32) -> [u8; 5] {
        let mut p = [0u8; 5];
        p[0] = 0xc6;
        p[1..].copy_from_slice(&len.to_be_bytes());
        p
    }

    /// Build a v1.x xl.meta buffer: header + bin32(meta_len) + meta payload +
    /// `crc_bytes` trailer bytes + `inline` trailing inline-data bytes. The meta
    /// payload content is irrelevant: `read_xl_meta_no_data` never parses it.
    fn build_v1x(minor: u16, meta_len: usize, crc_bytes: usize, inline: usize) -> Vec<u8> {
        let mut v = header(1, minor);
        v.extend_from_slice(&bin32_prefix(meta_len as u32));
        v.extend(std::iter::repeat_n(0xABu8, meta_len));
        v.extend(std::iter::repeat_n(0xC1u8, crc_bytes));
        v.extend(std::iter::repeat_n(0xCDu8, inline));
        v
    }

    async fn run_async(buf: &[u8], size: usize) -> Result<Vec<u8>> {
        let mut r = TokioCursor::new(buf.to_vec());
        read_xl_meta_no_data(&mut r, size).await
    }

    fn run_sync(buf: &[u8], size: usize) -> Result<Vec<u8>> {
        let mut r = StdCursor::new(buf.to_vec());
        read_xl_meta_no_data_sync(&mut r, size)
    }

    /// Drive both implementations with the same input and assert the results
    /// are equivalent (Ok bytes equal, or Err variant equal per `Error`'s
    /// `PartialEq`, which compares io kind + message for `Error::Io`).
    async fn assert_equivalent(label: &str, buf: &[u8], size: usize) -> Result<Vec<u8>> {
        let a = run_async(buf, size).await;
        let s = run_sync(buf, size);
        match (&a, &s) {
            (Ok(ab), Ok(sb)) => assert_eq!(ab, sb, "[{label}] Ok bytes must match"),
            (Err(ae), Err(se)) => assert_eq!(ae, se, "[{label}] Err variant must match"),
            _ => panic!("[{label}] async/sync disagree on Ok vs Err: async={a:?} sync={s:?}"),
        }
        a
    }

    #[tokio::test]
    async fn equivalence_across_all_paths() {
        // (a) v1.0: whole-file read path.
        {
            let mut buf = header(1, 0);
            buf.extend(std::iter::repeat_n(0x11u8, 24));
            let len = buf.len();
            let out = assert_equivalent("v1.0", &buf, len).await.unwrap();
            assert_eq!(out, buf, "v1.0 returns the whole file");
        }

        // (b) v1.1 / v1.2 / v1.3, each a clean well-formed buffer.
        // v1.1: minor < 2, no CRC trailer; returns header+prefix+meta.
        {
            let buf = build_v1x(1, 10, 0, 0);
            let len = buf.len();
            let out = assert_equivalent("v1.1", &buf, len).await.unwrap();
            assert_eq!(out.len(), 8 + 5 + 10, "v1.1 -> header+prefix+meta");
        }
        // v1.2: minor >= 2, 5-byte CRC trailer retained.
        {
            let buf = build_v1x(2, 15, 5, 0);
            let len = buf.len();
            let out = assert_equivalent("v1.2", &buf, len).await.unwrap();
            assert_eq!(out.len(), 8 + 5 + 15 + 5, "v1.2 -> header+prefix+meta+crc");
        }
        // v1.3: minor >= 2, 5-byte CRC trailer retained.
        {
            let buf = build_v1x(3, 20, 5, 0);
            let len = buf.len();
            let out = assert_equivalent("v1.3", &buf, len).await.unwrap();
            assert_eq!(out.len(), 8 + 5 + 20 + 5, "v1.3 -> header+prefix+meta+crc");
        }

        // (c) size > META_DATA_READ_DEFAULT: initial 4KiB read then read_more.
        {
            let meta_len = 5000; // total = 8 + 5 + 5000 + 5 = 5018 > 4096
            let buf = build_v1x(3, meta_len, 5, 0);
            assert!(buf.len() > META_DATA_READ_DEFAULT);
            let len = buf.len();
            let out = assert_equivalent("v1.3-large", &buf, len).await.unwrap();
            assert_eq!(out.len(), 8 + 5 + meta_len + 5);
        }

        // (d) truncated inside the header -> UnexpectedEof (initial read_exact
        // fails because the reader holds fewer bytes than the claimed size).
        {
            let buf = XL_FILE_HEADER.to_vec(); // only 4 bytes present
            assert_equivalent("truncated-header", &buf, 8).await.unwrap_err();
        }

        // (e) truncated inside the CRC trailer -> FileCorrupt (v1.3 with only
        // 2 of the 5 trailer bytes present; size matches the buffer).
        {
            let buf = build_v1x(3, 10, 2, 0); // want=23, buf.len()=25, 25-23=2 < 5
            let len = buf.len();
            let e = assert_equivalent("truncated-crc", &buf, len).await.unwrap_err();
            assert_eq!(e, Error::FileCorrupt);
        }

        // (f) unknown major / unknown minor -> InvalidData.
        // Unknown major: major=0 passes check_xl2_v1 (0 <= MAJOR) but misses the
        // `1 =>` arm.
        {
            let buf = header(0, 0);
            let e = assert_equivalent("unknown-major", &buf, buf.len()).await.unwrap_err();
            assert_eq!(
                e,
                Error::other(std::io::Error::new(std::io::ErrorKind::InvalidData, "Unknown major metadata version"))
            );
        }
        // Unknown minor: major=1, minor=4 misses the `0` and `1..=3` arms.
        {
            let buf = header(1, 4);
            let e = assert_equivalent("unknown-minor", &buf, buf.len()).await.unwrap_err();
            assert_eq!(
                e,
                Error::other(std::io::Error::new(std::io::ErrorKind::InvalidData, "Unknown minor metadata version"))
            );
        }

        // (g) want boundaries.
        // Exact fit: size == want + crc, no inline data.
        {
            let buf = build_v1x(3, 20, 5, 0); // size == want+5 exactly
            let len = buf.len();
            let out = assert_equivalent("want-exact-fit", &buf, len).await.unwrap();
            assert_eq!(out, buf);
        }
        // Inline data past the trailer: truncate drops it, want_max clamps below size.
        {
            let buf = build_v1x(3, 20, 5, 100); // size = want+5+100
            let len = buf.len();
            let out = assert_equivalent("want-with-inline", &buf, len).await.unwrap();
            assert_eq!(out.len(), 8 + 5 + 20 + 5, "inline data is dropped by truncate");
        }

        // (h) read_more's own read_exact hits EOF (has_full=false, read_size
        // within claimed size but the reader is physically shorter).
        {
            // prefix claims a 5000-byte meta so size=5018, but only 4100 bytes exist.
            let mut buf = header(1, 3);
            buf.extend_from_slice(&bin32_prefix(5000));
            buf.extend(std::iter::repeat_n(0xABu8, 4100 - buf.len()));
            assert_eq!(buf.len(), 4100);
            let e = assert_equivalent("read_more-eof", &buf, 5018).await.unwrap_err();
            assert_eq!(e, Error::Unexpected, "short read surfaces as Unexpected");
        }
    }
}