// 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.

//! KMS configuration management

use crate::error::{KmsError, Result};
use rustfs_utils::{get_env_bool, get_env_opt_str, get_env_str};
use serde::{Deserialize, Serialize};
use std::path::PathBuf;
use std::time::Duration;
use url::Url;

/// KMS backend types
#[derive(Debug, Default, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub enum KmsBackend {
    /// Vault KV v2 + Transit backend (key metadata in KV, wrapping via Transit)
    #[serde(rename = "VaultKV2", alias = "Vault")]
    VaultKv2,
    /// Vault Transit backend using Vault as the cryptographic source of truth
    #[serde(rename = "VaultTransit")]
    VaultTransit,
    /// Local file-based backend for development and testing only
    #[default]
    Local,
}

/// Main KMS configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct KmsConfig {
    /// Backend type
    pub backend: KmsBackend,
    /// Default master key ID for auto-encryption
    pub default_key_id: Option<String>,
    /// Backend-specific configuration
    pub backend_config: BackendConfig,
    /// Operation timeout
    pub timeout: Duration,
    /// Number of retry attempts
    pub retry_attempts: u32,
    /// Enable caching
    pub enable_cache: bool,
    /// Cache configuration
    pub cache_config: CacheConfig,
}

impl Default for KmsConfig {
    fn default() -> Self {
        Self {
            backend: KmsBackend::default(),
            default_key_id: None,
            backend_config: BackendConfig::default(),
            timeout: Duration::from_secs(30),
            retry_attempts: 3,
            enable_cache: true,
            cache_config: CacheConfig::default(),
        }
    }
}

/// Backend-specific configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum BackendConfig {
    /// Local backend configuration
    Local(LocalConfig),
    /// Vault KV v2 + Transit backend configuration
    #[serde(rename = "VaultKV2", alias = "Vault")]
    VaultKv2(Box<VaultConfig>),
    /// Vault Transit backend configuration
    VaultTransit(Box<VaultTransitConfig>),
}

impl Default for BackendConfig {
    fn default() -> Self {
        Self::Local(LocalConfig::default())
    }
}

/// Local KMS backend configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LocalConfig {
    /// Directory to store key files
    pub key_dir: PathBuf,
    /// Master key for encrypting stored keys (if None, keys are stored in plaintext)
    pub master_key: Option<String>,
    /// File permissions for key files (octal)
    pub file_permissions: Option<u32>,
}

impl Default for LocalConfig {
    fn default() -> Self {
        Self {
            key_dir: std::env::temp_dir().join("rustfs_kms_keys"),
            master_key: None,
            file_permissions: Some(0o600), // Owner read/write only
        }
    }
}

/// Vault KV v2 + Transit backend configuration (metadata in KV, key wrapping via Transit)
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct VaultConfig {
    /// Vault server URL
    pub address: String,
    /// Authentication method
    pub auth_method: VaultAuthMethod,
    /// Vault namespace (Vault Enterprise)
    pub namespace: Option<String>,
    /// Transit engine mount path
    pub mount_path: String,
    /// KV engine mount path for storing keys
    pub kv_mount: String,
    /// Path prefix for keys in KV store
    pub key_path_prefix: String,
    /// TLS configuration
    pub tls: Option<TlsConfig>,
}

impl Default for VaultConfig {
    fn default() -> Self {
        Self {
            address: "http://localhost:8200".to_string(),
            auth_method: VaultAuthMethod::Token {
                token: "dev-token".to_string(),
            },
            namespace: None,
            mount_path: "transit".to_string(),
            kv_mount: "secret".to_string(),
            key_path_prefix: "rustfs/kms/keys".to_string(),
            tls: None,
        }
    }
}

/// Vault Transit backend configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct VaultTransitConfig {
    /// Vault server URL
    pub address: String,
    /// Authentication method
    pub auth_method: VaultAuthMethod,
    /// Vault namespace (Vault Enterprise)
    pub namespace: Option<String>,
    /// Transit engine mount path
    pub mount_path: String,
    /// TLS configuration
    pub tls: Option<TlsConfig>,
}

impl Default for VaultTransitConfig {
    fn default() -> Self {
        Self {
            address: "http://localhost:8200".to_string(),
            auth_method: VaultAuthMethod::Token {
                token: "dev-token".to_string(),
            },
            namespace: None,
            mount_path: "transit".to_string(),
            tls: None,
        }
    }
}

/// Vault authentication methods
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum VaultAuthMethod {
    /// Token authentication
    Token { token: String },
    /// AppRole authentication
    AppRole { role_id: String, secret_id: String },
}

/// TLS configuration for Vault
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TlsConfig {
    /// Path to CA certificate file
    pub ca_cert_path: Option<PathBuf>,
    /// Path to client certificate file
    pub client_cert_path: Option<PathBuf>,
    /// Path to client private key file
    pub client_key_path: Option<PathBuf>,
    /// Skip TLS verification (insecure, for development only)
    pub skip_verify: bool,
}

/// Cache configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CacheConfig {
    /// Maximum number of keys to cache
    pub max_keys: usize,
    /// TTL for cached keys
    pub ttl: Duration,
    /// Enable cache metrics
    pub enable_metrics: bool,
}

impl Default for CacheConfig {
    fn default() -> Self {
        Self {
            max_keys: 1000,
            ttl: Duration::from_secs(3600), // 1 hour
            enable_metrics: true,
        }
    }
}

impl KmsConfig {
    /// Create a new KMS configuration for local backend (for development and testing only)
    pub fn local(key_dir: PathBuf) -> Self {
        Self {
            backend: KmsBackend::Local,
            backend_config: BackendConfig::Local(LocalConfig {
                key_dir,
                ..Default::default()
            }),
            ..Default::default()
        }
    }

    /// Create a new KMS configuration for Vault backend with token authentication (recommended for production)
    pub fn vault(address: Url, token: String) -> Self {
        Self {
            backend: KmsBackend::VaultKv2,
            backend_config: BackendConfig::VaultKv2(Box::new(VaultConfig {
                address: address.to_string(),
                auth_method: VaultAuthMethod::Token { token },
                ..Default::default()
            })),
            ..Default::default()
        }
    }

    /// Create a new KMS configuration for Vault backend with AppRole authentication (recommended for production)
    pub fn vault_approle(address: Url, role_id: String, secret_id: String) -> Self {
        Self {
            backend: KmsBackend::VaultKv2,
            backend_config: BackendConfig::VaultKv2(Box::new(VaultConfig {
                address: address.to_string(),
                auth_method: VaultAuthMethod::AppRole { role_id, secret_id },
                ..Default::default()
            })),
            ..Default::default()
        }
    }

    /// Create a new KMS configuration for Vault Transit backend with token authentication
    pub fn vault_transit(address: Url, token: String) -> Self {
        Self {
            backend: KmsBackend::VaultTransit,
            backend_config: BackendConfig::VaultTransit(Box::new(VaultTransitConfig {
                address: address.to_string(),
                auth_method: VaultAuthMethod::Token { token },
                ..Default::default()
            })),
            ..Default::default()
        }
    }

    /// Get the local configuration if backend is Local
    pub fn local_config(&self) -> Option<&LocalConfig> {
        match &self.backend_config {
            BackendConfig::Local(config) => Some(config),
            _ => None,
        }
    }

    /// Get the Vault KV2 configuration if backend is VaultKv2
    pub fn vault_config(&self) -> Option<&VaultConfig> {
        match &self.backend_config {
            BackendConfig::VaultKv2(config) => Some(config),
            _ => None,
        }
    }

    /// Get the Vault Transit configuration if backend is VaultTransit
    pub fn vault_transit_config(&self) -> Option<&VaultTransitConfig> {
        match &self.backend_config {
            BackendConfig::VaultTransit(config) => Some(config),
            _ => None,
        }
    }

    /// Set default key ID
    pub fn with_default_key(mut self, key_id: String) -> Self {
        self.default_key_id = Some(key_id);
        self
    }

    /// Set operation timeout
    pub fn with_timeout(mut self, timeout: Duration) -> Self {
        self.timeout = timeout;
        self
    }

    /// Enable or disable caching
    pub fn with_cache(mut self, enable: bool) -> Self {
        self.enable_cache = enable;
        self
    }

    /// Validate the configuration
    pub fn validate(&self) -> Result<()> {
        // Validate timeout
        if self.timeout.is_zero() {
            return Err(KmsError::configuration_error("Timeout must be greater than 0"));
        }

        // Validate retry attempts
        if self.retry_attempts == 0 {
            return Err(KmsError::configuration_error("Retry attempts must be greater than 0"));
        }

        // Validate backend-specific configuration
        match &self.backend_config {
            BackendConfig::Local(config) => {
                if !config.key_dir.is_absolute() {
                    return Err(KmsError::configuration_error("Local key directory must be an absolute path"));
                }
            }
            BackendConfig::VaultKv2(config) => {
                if !config.address.starts_with("http://") && !config.address.starts_with("https://") {
                    return Err(KmsError::configuration_error("Vault KV2 address must use http or https scheme"));
                }

                if config.mount_path.is_empty() {
                    return Err(KmsError::configuration_error("Vault KV2 mount path cannot be empty"));
                }

                // Validate TLS configuration if using HTTPS
                if config.address.starts_with("https://")
                    && let Some(ref tls) = config.tls
                    && !tls.skip_verify
                {
                    // In production, we should have proper TLS configuration
                    if tls.ca_cert_path.is_none() && tls.client_cert_path.is_none() {
                        tracing::warn!("Using HTTPS without custom TLS configuration - relying on system CA");
                    }
                }
            }
            BackendConfig::VaultTransit(config) => {
                if !config.address.starts_with("http://") && !config.address.starts_with("https://") {
                    return Err(KmsError::configuration_error("Vault Transit address must use http or https scheme"));
                }

                if config.mount_path.is_empty() {
                    return Err(KmsError::configuration_error("Vault Transit mount path cannot be empty"));
                }

                if config.address.starts_with("https://")
                    && let Some(ref tls) = config.tls
                    && !tls.skip_verify
                    && tls.ca_cert_path.is_none()
                    && tls.client_cert_path.is_none()
                {
                    tracing::warn!("Using HTTPS without custom TLS configuration - relying on system CA");
                }
            }
        }

        // Validate cache configuration
        if self.enable_cache && self.cache_config.max_keys == 0 {
            return Err(KmsError::configuration_error("Cache max_keys must be greater than 0"));
        }

        Ok(())
    }

    /// Load configuration from environment variables
    pub fn from_env() -> Result<Self> {
        let mut config = Self::default();

        // Backend type
        if let Some(backend_type) = get_env_opt_str("RUSTFS_KMS_BACKEND") {
            config.backend = match backend_type.to_lowercase().as_str() {
                "local" => KmsBackend::Local,
                "vault" | "vault-kv2" | "vault_kv2" => KmsBackend::VaultKv2,
                "vault-transit" | "vault_transit" => KmsBackend::VaultTransit,
                _ => return Err(KmsError::configuration_error(format!("Unknown KMS backend: {backend_type}"))),
            };
        }

        // Default key ID
        if let Some(key_id) = get_env_opt_str("RUSTFS_KMS_DEFAULT_KEY_ID") {
            config.default_key_id = Some(key_id);
        }

        // Timeout
        if let Some(timeout_str) = get_env_opt_str("RUSTFS_KMS_TIMEOUT_SECS") {
            let timeout_secs = timeout_str
                .parse::<u64>()
                .map_err(|_| KmsError::configuration_error("Invalid timeout value"))?;
            config.timeout = Duration::from_secs(timeout_secs);
        }

        // Retry attempts
        if let Some(retries_str) = get_env_opt_str("RUSTFS_KMS_RETRY_ATTEMPTS") {
            config.retry_attempts = retries_str
                .parse()
                .map_err(|_| KmsError::configuration_error("Invalid retry attempts value"))?;
        }

        // Enable cache
        config.enable_cache = get_env_bool("RUSTFS_KMS_ENABLE_CACHE", config.enable_cache);

        // Backend-specific configuration
        match config.backend {
            KmsBackend::Local => {
                let key_dir = get_env_str("RUSTFS_KMS_LOCAL_KEY_DIR", "./kms_keys");
                let master_key = get_env_opt_str("RUSTFS_KMS_LOCAL_MASTER_KEY");

                config.backend_config = BackendConfig::Local(LocalConfig {
                    key_dir: PathBuf::from(key_dir),
                    master_key,
                    file_permissions: Some(0o600),
                });
            }
            KmsBackend::VaultKv2 => {
                let address = get_env_str("RUSTFS_KMS_VAULT_ADDRESS", "http://localhost:8200");
                let token = get_env_str("RUSTFS_KMS_VAULT_TOKEN", "dev-token");

                config.backend_config = BackendConfig::VaultKv2(Box::new(VaultConfig {
                    address,
                    auth_method: VaultAuthMethod::Token { token },
                    namespace: get_env_opt_str("RUSTFS_KMS_VAULT_NAMESPACE"),
                    mount_path: get_env_str("RUSTFS_KMS_VAULT_MOUNT_PATH", "transit"),
                    kv_mount: get_env_str("RUSTFS_KMS_VAULT_KV_MOUNT", "secret"),
                    key_path_prefix: get_env_str("RUSTFS_KMS_VAULT_KEY_PREFIX", "rustfs/kms/keys"),
                    tls: None,
                }));
            }
            KmsBackend::VaultTransit => {
                let address = get_env_str("RUSTFS_KMS_VAULT_ADDRESS", "http://localhost:8200");
                let token = get_env_str("RUSTFS_KMS_VAULT_TOKEN", "dev-token");

                config.backend_config = BackendConfig::VaultTransit(Box::new(VaultTransitConfig {
                    address,
                    auth_method: VaultAuthMethod::Token { token },
                    namespace: get_env_opt_str("RUSTFS_KMS_VAULT_NAMESPACE"),
                    mount_path: get_env_str("RUSTFS_KMS_VAULT_MOUNT_PATH", "transit"),
                    tls: None,
                }));
            }
        }

        config.validate()?;
        Ok(config)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use temp_env::with_vars;
    use tempfile::TempDir;

    #[test]
    fn test_default_config() {
        let config = KmsConfig::default();
        assert_eq!(config.backend, KmsBackend::Local);
        assert!(config.validate().is_ok());
    }

    #[test]
    fn test_local_config() {
        let temp_dir = TempDir::new().expect("Failed to create temp dir");
        let config = KmsConfig::local(temp_dir.path().to_path_buf());

        assert_eq!(config.backend, KmsBackend::Local);
        assert!(config.validate().is_ok());

        let local_config = config.local_config().expect("Should have local config");
        assert_eq!(local_config.key_dir, temp_dir.path());
    }

    #[test]
    fn test_vault_config() {
        let address = Url::parse("https://vault.example.com:8200").expect("Valid URL");
        let config = KmsConfig::vault(address.clone(), "test-token".to_string());

        assert_eq!(config.backend, KmsBackend::VaultKv2);
        assert!(config.validate().is_ok());

        let vault_config = config.vault_config().expect("Should have vault config");
        assert_eq!(vault_config.address, address.as_str());
    }

    #[test]
    fn test_vault_transit_config() {
        let address = Url::parse("https://vault.example.com:8200").expect("Valid URL");
        let config = KmsConfig::vault_transit(address.clone(), "test-token".to_string());

        assert_eq!(config.backend, KmsBackend::VaultTransit);
        assert!(config.validate().is_ok());

        let vault_config = config.vault_transit_config().expect("Should have vault transit config");
        assert_eq!(vault_config.address, address.as_str());
        assert_eq!(vault_config.mount_path, "transit");
    }

    #[test]
    fn test_vault_kv2_backend_serialization_uses_pascal_case() {
        let serialized = serde_json::to_string(&KmsBackend::VaultKv2).expect("backend should serialize");
        assert_eq!(serialized, "\"VaultKV2\"");
        let legacy: KmsBackend = serde_json::from_str("\"Vault\"").expect("legacy Vault label should deserialize");
        assert_eq!(legacy, KmsBackend::VaultKv2);
    }

    #[test]
    fn test_legacy_persisted_backend_config_vault_key_deserializes() {
        let raw = r#"{
            "backend": "Vault",
            "backend_config": {
                "Vault": {
                    "address": "http://127.0.0.1:8200",
                    "auth_method": { "Token": { "token": "t" } },
                    "namespace": null,
                    "mount_path": "transit",
                    "kv_mount": "secret",
                    "key_path_prefix": "rustfs/kms/keys",
                    "tls": null
                }
            },
            "default_key_id": null,
            "timeout": {"secs": 30, "nanos": 0},
            "retry_attempts": 3,
            "enable_cache": true,
            "cache_config": {
                "max_keys": 1000,
                "ttl": {"secs": 3600, "nanos": 0},
                "enable_metrics": true
            }
        }"#;
        let config: KmsConfig = serde_json::from_str(raw).expect("legacy persisted kms config");
        assert_eq!(config.backend, KmsBackend::VaultKv2);
        assert!(config.vault_config().is_some());
    }

    #[test]
    fn test_vault_transit_backend_serialization_uses_pascal_case() {
        let serialized = serde_json::to_string(&KmsBackend::VaultTransit).expect("backend should serialize");
        assert_eq!(serialized, "\"VaultTransit\"");
    }

    #[test]
    fn test_config_validation() {
        let mut config = KmsConfig::default();

        // Valid config
        assert!(config.validate().is_ok());

        // Invalid timeout
        config.timeout = Duration::from_secs(0);
        assert!(config.validate().is_err());

        // Reset timeout and test invalid retry attempts
        config.timeout = Duration::from_secs(30);
        config.retry_attempts = 0;
        assert!(config.validate().is_err());
    }

    #[test]
    fn test_from_env_reads_vault_settings() {
        with_vars(
            vec![
                ("RUSTFS_KMS_BACKEND", Some("vault")),
                ("RUSTFS_KMS_DEFAULT_KEY_ID", Some("tenant-key")),
                ("RUSTFS_KMS_TIMEOUT_SECS", Some("42")),
                ("RUSTFS_KMS_RETRY_ATTEMPTS", Some("7")),
                ("RUSTFS_KMS_ENABLE_CACHE", Some("false")),
                ("RUSTFS_KMS_VAULT_ADDRESS", Some("https://vault.example.com")),
                ("RUSTFS_KMS_VAULT_TOKEN", Some("vault-token")),
                ("RUSTFS_KMS_VAULT_NAMESPACE", Some("tenant-a")),
                ("RUSTFS_KMS_VAULT_MOUNT_PATH", Some("transit-alt")),
                ("RUSTFS_KMS_VAULT_KV_MOUNT", Some("secret-alt")),
                ("RUSTFS_KMS_VAULT_KEY_PREFIX", Some("tenant/keys")),
            ],
            || {
                let config = KmsConfig::from_env().expect("kms config should load from env");

                assert_eq!(config.backend, KmsBackend::VaultKv2);
                assert_eq!(config.default_key_id.as_deref(), Some("tenant-key"));
                assert_eq!(config.timeout, Duration::from_secs(42));
                assert_eq!(config.retry_attempts, 7);
                assert!(!config.enable_cache);

                let vault = config.vault_config().expect("vault backend config");
                assert_eq!(vault.address, "https://vault.example.com");
                assert_eq!(vault.namespace.as_deref(), Some("tenant-a"));
                assert_eq!(vault.mount_path, "transit-alt");
                assert_eq!(vault.kv_mount, "secret-alt");
                assert_eq!(vault.key_path_prefix, "tenant/keys");
            },
        );
    }

    #[test]
    fn test_from_env_reads_vault_transit_settings() {
        with_vars(
            vec![
                ("RUSTFS_KMS_BACKEND", Some("vault-transit")),
                ("RUSTFS_KMS_DEFAULT_KEY_ID", Some("tenant-key")),
                ("RUSTFS_KMS_VAULT_ADDRESS", Some("https://vault.example.com")),
                ("RUSTFS_KMS_VAULT_TOKEN", Some("vault-token")),
                ("RUSTFS_KMS_VAULT_NAMESPACE", Some("tenant-a")),
                ("RUSTFS_KMS_VAULT_MOUNT_PATH", Some("transit-alt")),
            ],
            || {
                let config = KmsConfig::from_env().expect("kms config should load from env");

                assert_eq!(config.backend, KmsBackend::VaultTransit);
                assert_eq!(config.default_key_id.as_deref(), Some("tenant-key"));

                let vault = config.vault_transit_config().expect("vault transit backend config");
                assert_eq!(vault.address, "https://vault.example.com");
                assert_eq!(vault.namespace.as_deref(), Some("tenant-a"));
                assert_eq!(vault.mount_path, "transit-alt");
            },
        );
    }
}