//! WebSocket proxy: bridges browser ↔ guacd TCP socket.

use crate::api::AppState;
use crate::auth::{client_ip, AuthIdentity, TrustedProxies};
use crate::db::{self, Db};
use crate::guacd::GuacdStream;
use crate::protocol::{last_instruction_boundary, Instruction};
use crate::session::{SessionManager, ShareTokenValidation};
use axum::{
    extract::{
        ws::{Message, WebSocket, WebSocketUpgrade},
        ConnectInfo, Path, Query, State,
    },
    http::StatusCode,
    response::IntoResponse,
    Extension,
};
use futures_util::{SinkExt, StreamExt};
use serde::Deserialize;
use serde_json::json;
use std::net::{IpAddr, SocketAddr};
use std::sync::Arc;
use std::time::Instant;
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio_util::sync::CancellationToken;
use uuid::Uuid;

/// Which side terminated the proxy connection.
enum ProxyResult {
    /// guacd closed the connection (with optional error).
    GuacdEnded(Option<String>),
    /// Browser/WebSocket closed the connection (with optional error).
    BrowserEnded(Option<String>),
    /// Session was cancelled externally.
    Cancelled,
}

/// Outcome of the proxy session, including whether guacd sent a disconnect instruction.
struct ProxyOutcome {
    result: ProxyResult,
    /// True if guacd sent `10.disconnect;` through the stream — indicates the
    /// remote server ended the session (user logout, crash), as opposed to the
    /// browser/network dropping the WebSocket.
    server_disconnected: bool,
}

#[derive(Deserialize)]
pub struct WsQuery {
    pub token: Option<String>,
}

/// GET /ws/:session_id — Upgrade to WebSocket and proxy to guacd.
#[allow(clippy::too_many_arguments)]
pub async fn ws_handler(
    State(manager): State<AppState>,
    ConnectInfo(addr): ConnectInfo<SocketAddr>,
    Path(session_id): Path<Uuid>,
    Query(query): Query<WsQuery>,
    headers: axum::http::HeaderMap,
    identity: Option<Extension<AuthIdentity>>,
    trusted: Option<Extension<TrustedProxies>>,
    database: Option<Extension<Db>>,
    ws: WebSocketUpgrade,
) -> impl IntoResponse {
    let proxies = trusted.map(|Extension(t)| t.0).unwrap_or_default();
    let ip = client_ip(&headers, addr.ip(), &proxies);
    let identity = identity.map(|Extension(id)| id);

    // Validate Origin header to prevent cross-site WebSocket hijacking (CSWSH).
    // Compare Origin's hostname against the request's Host header hostname.
    // Only the hostname is compared (ports stripped) to avoid false rejections
    // behind reverse proxies that may add/remove default ports.
    if let Some(origin) = headers.get("origin").and_then(|v| v.to_str().ok()) {
        let host = headers
            .get("host")
            .and_then(|v| v.to_str().ok())
            .unwrap_or("");
        if !origin_host_matches(origin, host) {
            tracing::warn!(
                session_id = %session_id,
                client_ip = %ip,
                origin = %origin,
                host = %host,
                "WebSocket upgrade rejected: Origin does not match Host (possible CSWSH)"
            );
            return (
                StatusCode::FORBIDDEN,
                axum::Json(json!({"error": "cross-origin WebSocket request rejected"})),
            )
                .into_response();
        }
    }

    // Check if this is an owner connection (session is Pending)
    let is_owner = manager.is_session_pending(session_id).await;

    if is_owner {
        // Owner path: require authenticated identity with operator+ role
        match &identity {
            Some(id) if id.has_role("operator") => {
                // Authorized — proceed
            }
            _ => {
                tracing::warn!(session_id = %session_id, client_ip = %ip, "Unauthorized owner connection attempt");
                return (
                    StatusCode::FORBIDDEN,
                    axum::Json(
                        json!({"error": "authentication required to connect as session owner"}),
                    ),
                )
                    .into_response();
            }
        }
    }

    let identity_name = identity.as_ref().map(|id| id.display_name().to_string());
    let database = database.map(|Extension(db)| db);

    ws.protocols(["guacamole"])
        .on_upgrade(move |socket| {
            handle_ws(
                manager,
                session_id,
                query.token,
                socket,
                ip,
                identity_name,
                database,
            )
        })
        .into_response()
}

async fn handle_ws(
    manager: Arc<SessionManager>,
    session_id: Uuid,
    token: Option<String>,
    ws: WebSocket,
    client_addr: IpAddr,
    identity_name: Option<String>,
    database: Option<Db>,
) {
    // Try to take the guacd stream (owner/first connection)
    let (guacd_stream, cancel) = if let Some((stream, cancel)) =
        manager.take_guacd_stream(session_id).await
    {
        let identity_str = identity_name.as_deref().unwrap_or("unknown");
        tracing::info!(session_id = %session_id, client_ip = %client_addr, identity = %identity_str, "Session owner connected");
        (stream, cancel)
    } else {
        // Not pending — try to join an active session
        // Joining requires a valid share token
        let token = match token {
            Some(t) => t,
            None => {
                tracing::warn!(session_id = %session_id, client_ip = %client_addr, "Join attempt without share token");
                return;
            }
        };

        let validation = manager.validate_share_token(session_id, &token).await;
        match &validation {
            ShareTokenValidation::Invalid => {
                tracing::warn!(session_id = %session_id, client_ip = %client_addr, "Share token rejected");
                return;
            }
            ShareTokenValidation::Owner => {}
            ShareTokenValidation::Shadow { issued_by } => {
                // Audit every shadow-token use (not just the mint). A leaked
                // token remains reusable within its TTL, but each reuse is
                // now visible in token_audit_log with the connecting IP.
                if let Some(db) = database.as_ref() {
                    let db_clone = db.clone();
                    let ip_str = client_addr.to_string();
                    let issued_by = issued_by.clone();
                    let details = format!("session_id={}, issued_by={}", session_id, issued_by);
                    let _ = tokio::task::spawn_blocking(move || {
                        if let Err(e) = db::log_token_event(
                            &db_clone,
                            None,
                            None,
                            &issued_by,
                            "shadow_used",
                            Some(&ip_str),
                            Some(&details),
                        ) {
                            tracing::warn!(error = %e, "failed to write shadow_used audit log");
                        }
                    })
                    .await;
                }
                tracing::info!(
                    session_id = %session_id,
                    client_ip = %client_addr,
                    issued_by = %issued_by,
                    "Shadow token consumed"
                );
            }
        }

        match manager.join_session(session_id).await {
            Ok((stream, cancel)) => {
                tracing::info!(session_id = %session_id, client_ip = %client_addr, "Viewer connected via share token");
                (stream, cancel)
            }
            Err(e) => {
                tracing::warn!(session_id = %session_id, client_ip = %client_addr, error = %e, "Failed to join session");
                return;
            }
        }
    };

    tracing::info!(session_id = %session_id, client_ip = %client_addr, "Starting proxy");

    // Set up recording file (only for owner connections, and only if recording is enabled)
    let is_recording_enabled = manager.is_recording_enabled(session_id).await;
    let recording_path = manager
        .recording_path()
        .join(format!("{}.guac", session_id));
    let recording_file = if is_recording_enabled && !recording_path.exists() {
        match tokio::fs::File::create(&recording_path).await {
            Ok(f) => {
                // Set restrictive permissions on recording file
                #[cfg(unix)]
                {
                    use std::os::unix::fs::PermissionsExt;
                    let _ = tokio::fs::set_permissions(
                        &recording_path,
                        std::fs::Permissions::from_mode(0o640),
                    )
                    .await;
                }

                // Write sidecar .meta file with session context
                {
                    let session_info = manager.get_session(session_id).await;
                    let ab_entry = session_info
                        .as_ref()
                        .and_then(|s| s.address_book_entry.clone());
                    let meta = crate::recording::RecordingMeta {
                        address_book_entry: ab_entry,
                        created_at: chrono::Utc::now().to_rfc3339(),
                        user: session_info.as_ref().map(|s| s.created_by.clone()),
                        folder: session_info
                            .as_ref()
                            .and_then(|s| s.address_book_folder.clone()),
                        entry_display_name: session_info
                            .as_ref()
                            .and_then(|s| s.entry_display_name.clone()),
                        session_type: session_info
                            .as_ref()
                            .map(|s| format!("{:?}", s.session_type).to_lowercase()),
                    };
                    if let Err(e) = crate::recording::write_meta(&recording_path, &meta) {
                        tracing::warn!(session_id = %session_id, error = %e, "Failed to write recording .meta");
                    }
                }

                Some(f)
            }
            Err(e) => {
                tracing::error!(session_id = %session_id, error = %e, "Failed to create recording file");
                None
            }
        }
    } else {
        None // Viewer connections don't record, or recording is disabled
    };

    // Run the bidirectional proxy
    let start = Instant::now();
    let proxy_outcome = proxy_ws_guacd(ws, guacd_stream, recording_file, cancel).await;
    let elapsed = start.elapsed();
    let server_disconnected = proxy_outcome.server_disconnected;
    let proxy_result = proxy_outcome.result;

    manager.disconnect_viewer(session_id).await;

    // Log termination direction and timing
    let mark_error = match &proxy_result {
        ProxyResult::GuacdEnded(err) => {
            if elapsed.as_secs() < 5 {
                tracing::warn!(
                    session_id = %session_id, client_ip = %client_addr,
                    elapsed_ms = elapsed.as_millis() as u64,
                    error = ?err,
                    "guacd closed connection quickly (possible connection failure)"
                );
                true // mark as error
            } else {
                tracing::info!(
                    session_id = %session_id, client_ip = %client_addr,
                    elapsed_secs = elapsed.as_secs(),
                    "Proxy ended: guacd closed connection"
                );
                false
            }
        }
        ProxyResult::BrowserEnded(err) => {
            tracing::info!(
                session_id = %session_id, client_ip = %client_addr,
                elapsed_secs = elapsed.as_secs(),
                error = ?err,
                "Proxy ended: browser disconnected"
            );
            false
        }
        ProxyResult::Cancelled => {
            tracing::info!(
                session_id = %session_id, client_ip = %client_addr,
                elapsed_secs = elapsed.as_secs(),
                "Proxy ended: session cancelled"
            );
            false
        }
    };

    let status_str;
    if mark_error {
        manager.error_session(session_id).await;
        status_str = "error";
    } else {
        // Only mark completed if no more active connections
        let info = manager.get_session(session_id).await;
        if let Some(info) = info {
            if info.active_connections == 0 {
                manager.complete_session(session_id).await;
                status_str = "completed";
            } else {
                status_str = "active";
            }
        } else {
            status_str = "completed";
        }
    }

    // VDI container lifecycle on session end
    if let Some((crate::session::SessionType::Vdi, Some(ref _cid))) =
        manager.get_vdi_info(session_id).await
    {
        if server_disconnected {
            // User logged out / session crashed → stop container immediately
            manager.stop_vdi_container(session_id).await;
            // Clean up session thumbnail
            let _ = tokio::fs::remove_file(manager.thumbnail_path(session_id)).await;
        } else {
            // Browser disconnect / network drop → container persists.
            // Copy session thumbnail to container-keyed file for the active desktops UI.
            let session_thumb = manager.thumbnail_path(session_id);
            // Derive container name from session username
            if let Some(info) = manager.get_session(session_id).await {
                let container_name = format!("rustguac-vdi-{}", info.username);
                let vdi_thumb = manager.vdi_thumbnail_path(&container_name);
                if session_thumb.exists() {
                    let _ = tokio::fs::copy(&session_thumb, &vdi_thumb).await;
                }
            }
        }
    }

    // Record session end in history
    manager.end_session_history(
        session_id,
        status_str,
        elapsed.as_secs(),
        is_recording_enabled,
    );

    // Per-entry recording rotation (after session ends, recording file is complete)
    if is_recording_enabled {
        if let Some((Some(entry_key), Some(max_recs))) =
            manager.get_recording_meta(session_id).await
        {
            if max_recs > 0 {
                let rec_dir = manager.recording_path().to_path_buf();
                tokio::task::spawn_blocking(move || {
                    crate::recording::rotate_per_entry(&rec_dir, &entry_key, max_recs);
                });
            }
        }
    }

    tracing::info!(session_id = %session_id, client_ip = %client_addr, "Session disconnected");
}

/// Bidirectional proxy between WebSocket and guacd stream (TCP or TLS).
async fn proxy_ws_guacd(
    ws: WebSocket,
    guacd: GuacdStream,
    recording_file: Option<tokio::fs::File>,
    cancel: CancellationToken,
) -> ProxyOutcome {
    let (guacd_read, guacd_write) = tokio::io::split(guacd);
    let (ws_write, ws_read) = ws.split();

    let recording = recording_file.map(|f| Arc::new(tokio::sync::Mutex::new(f)));

    // Shared flag: set by guacd_to_ws when it sees `10.disconnect;` in the stream
    let server_disconnected = Arc::new(std::sync::atomic::AtomicBool::new(false));

    // The WebSocket sink is shared so both halves can write to it. The browser →
    // guacd side needs to echo `0.,4.ping,...` instructions back to the client
    // (Apache webapp parity), without ever forwarding them to guacd.
    let ws_sink = Arc::new(tokio::sync::Mutex::new(ws_write));

    // guacd → browser (also tee to recording)
    let recording_clone = recording.clone();
    let sd_flag = server_disconnected.clone();
    let ws_sink_g = ws_sink.clone();
    let guacd_to_browser =
        tokio::spawn(
            async move { guacd_to_ws(guacd_read, ws_sink_g, recording_clone, sd_flag).await },
        );

    // browser → guacd
    let ws_sink_b = ws_sink.clone();
    let browser_to_guacd =
        tokio::spawn(async move { ws_to_guacd(ws_read, guacd_write, ws_sink_b).await });

    // Wait for either direction to finish, or cancellation
    let result = tokio::select! {
        result = guacd_to_browser => {
            let err = match result {
                Ok(Err(e)) => Some(e.to_string()),
                Err(e) => Some(e.to_string()),
                _ => None,
            };
            ProxyResult::GuacdEnded(err)
        }
        result = browser_to_guacd => {
            let err = match result {
                Ok(Err(e)) => Some(e.to_string()),
                Err(e) => Some(e.to_string()),
                _ => None,
            };
            ProxyResult::BrowserEnded(err)
        }
        _ = cancel.cancelled() => {
            ProxyResult::Cancelled
        }
    };

    ProxyOutcome {
        result,
        server_disconnected: server_disconnected.load(std::sync::atomic::Ordering::Relaxed),
    }
}

type WsSink = Arc<tokio::sync::Mutex<futures_util::stream::SplitSink<WebSocket, Message>>>;

/// Maximum bytes the guacd-side carry buffer is allowed to grow to before
/// force-flushing without a clean instruction boundary. In practice guacd
/// instructions are tiny; this exists to bound memory if upstream sends
/// something pathological. 16 MiB is well above any real instruction.
const MAX_GUACD_CARRY: usize = 16 * 1024 * 1024;

/// Forward data from guacd to WebSocket, recording along the way.
///
/// The browser's Tunnel.js parser concatenates every Message::Text into a
/// single rolling buffer with no message-boundary semantics. If we send a
/// chunk that ends mid-instruction and `ws_to_guacd` then echoes a tunnel
/// ping over the shared sink, the ping bytes splice into the middle of the
/// in-flight instruction and the parser blows up with "Element terminator
/// of instruction was not ';' nor ','". To prevent that, every Message::Text
/// we emit ends at a true Guacamole instruction boundary; partial tail data
/// is held in `carry` until the next read completes it.
async fn guacd_to_ws(
    mut guacd: tokio::io::ReadHalf<GuacdStream>,
    ws: WsSink,
    recording: Option<Arc<tokio::sync::Mutex<tokio::fs::File>>>,
    server_disconnected: Arc<std::sync::atomic::AtomicBool>,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    let mut buf = vec![0u8; 65536];
    let mut carry: Vec<u8> = Vec::new();

    loop {
        let n = guacd.read(&mut buf).await?;
        if n == 0 {
            break;
        }

        let data = &buf[..n];

        // Recording captures the raw guacd stream regardless of buffering.
        if let Some(ref recording) = recording {
            let mut file = recording.lock().await;
            let _ = file.write_all(data).await;
        }

        carry.extend_from_slice(data);

        // Flush up to the last complete instruction boundary in the carry.
        // Anything past that is held over for the next read.
        let to_send_bytes: Vec<u8> = match last_instruction_boundary(&carry) {
            Some(end) => carry.drain(..end).collect(),
            None if carry.len() > MAX_GUACD_CARRY => {
                tracing::warn!(
                    len = carry.len(),
                    cap = MAX_GUACD_CARRY,
                    "guacd carry exceeded cap; force-flushing without instruction boundary"
                );
                std::mem::take(&mut carry)
            }
            None => continue,
        };

        // The boundary scanner only advances over valid UTF-8, so this
        // String::from_utf8 should never fail in practice; defensive in
        // case a force-flush above happened mid-multibyte char.
        let text = String::from_utf8(to_send_bytes).map_err(
            |e| -> Box<dyn std::error::Error + Send + Sync> {
                format!("invalid UTF-8 from guacd: {}", e).into()
            },
        )?;

        // Detect guacd-initiated disconnect (server-side logout/crash).
        // guacd sends "10.disconnect;" as the final instruction when the
        // remote server ends the session. Buffering at instruction boundary
        // means the disconnect appears intact in the flushed text, either
        // at the start or after a previous ";".
        if text.starts_with("10.disconnect;") || text.contains(";10.disconnect;") {
            server_disconnected.store(true, std::sync::atomic::Ordering::Relaxed);
        }

        let mut sink = ws.lock().await;
        sink.send(Message::Text(text.into())).await?;
    }

    Ok(())
}

/// Forward data from WebSocket to guacd, intercepting empty-opcode tunnel
/// pings. The Guacamole client sends `0.,4.ping,<ts>;` every 500ms over the
/// "internal data" opcode (the empty string) to keep the tunnel from going
/// UNSTABLE. Apache's webapp echoes these back without ever forwarding them
/// to guacd; guacd silently drops unknown opcodes (libguac/user-handlers.c
/// `__guac_user_call_opcode_handler`), so without echoing here the client
/// would mark the tunnel UNSTABLE after 1.5s of guacd quiet time and close
/// it after 15s. We mirror Apache's filter behaviour.
async fn ws_to_guacd(
    mut ws_read: futures_util::stream::SplitStream<WebSocket>,
    mut guacd: tokio::io::WriteHalf<GuacdStream>,
    ws_sink: WsSink,
) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    while let Some(msg) = ws_read.next().await {
        let msg = msg?;
        match msg {
            Message::Text(text) => {
                // Empty-opcode instructions always start with "0.," — fast
                // path skips the parse for normal traffic.
                if text.starts_with("0.,") {
                    if let Ok(instr) = Instruction::parse(text.trim_end_matches(';')) {
                        if instr.opcode.is_empty() {
                            // Echo ping requests; drop everything else on the
                            // internal channel.
                            if instr.args.first().map(|s| s.as_str()) == Some("ping") {
                                let echo = Instruction::new("", instr.args).encode();
                                let mut sink = ws_sink.lock().await;
                                sink.send(Message::Text(echo.into())).await?;
                            }
                            continue;
                        }
                    }
                }

                // Log clipboard instructions from browser → guacd
                if text.contains(".clipboard,") {
                    tracing::info!("browser sent clipboard instruction to guacd");
                }
                guacd.write_all(text.as_bytes()).await?;
            }
            Message::Binary(_) => {
                continue;
            }
            Message::Close(_) => break,
            _ => {}
        }
    }

    Ok(())
}

/// Return true if the browser-supplied Origin and the request Host header
/// refer to the same hostname (ports stripped). Extracted for test.
///
/// If either value is missing or empty, the request is allowed — matches
/// the prior `unwrap_or("")` behaviour where axum had no header and no
/// CSWSH signal. The caller must still ensure auth is enforced separately.
pub(crate) fn origin_host_matches(origin: &str, host: &str) -> bool {
    let origin_host = origin
        .trim_start_matches("https://")
        .trim_start_matches("http://")
        .trim_end_matches('/')
        .split(':')
        .next()
        .unwrap_or("");
    let host_name = host.split(':').next().unwrap_or("");
    if host_name.is_empty() || origin_host.is_empty() {
        return true;
    }
    origin_host.eq_ignore_ascii_case(host_name)
}

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

    #[test]
    fn origin_match_same_hostname_no_ports() {
        assert!(origin_host_matches(
            "https://console.example.com",
            "console.example.com"
        ));
    }

    #[test]
    fn origin_match_ports_stripped() {
        assert!(origin_host_matches(
            "https://console.example.com:8443",
            "console.example.com:80"
        ));
        assert!(origin_host_matches("http://host.local:8080", "host.local"));
    }

    #[test]
    fn origin_match_trailing_slash_tolerated() {
        assert!(origin_host_matches(
            "https://console.example.com/",
            "console.example.com"
        ));
    }

    #[test]
    fn origin_match_case_insensitive_hostname() {
        // DNS is case-insensitive; browsers can vary casing.
        assert!(origin_host_matches(
            "https://Console.Example.COM",
            "console.example.com"
        ));
    }

    #[test]
    fn origin_mismatch_different_subdomain_rejected() {
        assert!(!origin_host_matches(
            "https://evil.example.com",
            "console.example.com"
        ));
    }

    #[test]
    fn origin_mismatch_unrelated_host_rejected() {
        assert!(!origin_host_matches(
            "https://evil.attacker.io",
            "console.example.com"
        ));
    }

    #[test]
    fn origin_empty_allowed_preserves_prior_behaviour() {
        // No Origin header (rare — server-side fetches / Firefox in some
        // contexts) must be allowed by this check; caller still enforces
        // auth. Same for empty Host (shouldn't happen, but belt + braces).
        assert!(origin_host_matches("", "console.example.com"));
        assert!(origin_host_matches("https://console.example.com", ""));
    }

    #[test]
    fn origin_mismatch_path_in_origin_ignored_by_host() {
        // An Origin with a path should never happen (spec forbids it) but
        // if it slips through, the split should not cause a match by
        // accident.
        assert!(!origin_host_matches(
            "https://evil.example.com/path",
            "console.example.com"
        ));
    }

    #[test]
    fn origin_mismatch_prefix_attack_rejected() {
        // `console.example.com.attacker.io` must NOT match
        // `console.example.com`. Split-on-`:` + exact compare handles this.
        assert!(!origin_host_matches(
            "https://console.example.com.attacker.io",
            "console.example.com"
        ));
    }
}