//! Remote Cosmian KMS Backend
//!
//! TODO: Future implementation for Cosmian KMS integration
//! Currently stubbed out as cosmian_kms_client and cosmian_kms_utils are not
//! available This will be implemented when Cosmian KMS support is added to the
//! platform

// TODO: Enable when Cosmian KMS dependencies are added to Cargo.toml
// use cosmian_kms_client::{KmsClient, ClientConf};
// use cosmian_kms_utils::crypto::wrap::unwrap_key;
use std::collections::HashMap;
use std::sync::Arc;
use std::time::Duration;

use async_trait::async_trait;
use tokio::sync::RwLock;

use crate::kms::config::RemoteConfig;
use crate::kms::error::KmsError;
use crate::kms::traits::KmsBackend;
use crate::kms::types::{HealthStatus, KeyData};

/// Remote Cosmian KMS backend implementation
/// TODO: Stubbed implementation - will be completed when Cosmian KMS is
/// integrated
#[allow(dead_code)]
pub struct RemoteKmsBackend {
    // TODO: Enable when cosmian_kms_client is available
    // client: Arc<KmsClient>,
    config: RemoteConfig,
    rate_limiter: Arc<RwLock<RateLimiter>>,
}

/// Simple token bucket rate limiter for future API rate limiting
#[allow(dead_code)]
struct RateLimiter {
    tokens: f64,
    last_refill: std::time::Instant,
    max_tokens: f64,
    refill_rate: f64,
}

impl RateLimiter {
    #[allow(dead_code)]
    fn new(max_tokens: f64, refill_rate: f64) -> Self {
        Self {
            tokens: max_tokens,
            last_refill: std::time::Instant::now(),
            max_tokens,
            refill_rate,
        }
    }

    #[allow(dead_code)]
    async fn acquire(&mut self) -> bool {
        let now = std::time::Instant::now();
        let elapsed = now.duration_since(self.last_refill).as_secs_f64();

        // Refill tokens
        self.tokens += elapsed * self.refill_rate;
        self.tokens = self.tokens.min(self.max_tokens);
        self.last_refill = now;

        // Check if we can consume a token
        if self.tokens >= 1.0 {
            self.tokens -= 1.0;
            true
        } else {
            false
        }
    }
}

impl RemoteKmsBackend {
    /// Create a new remote KMS backend
    /// TODO: Stubbed - implement when Cosmian KMS client is available
    pub async fn new(config: &RemoteConfig) -> Result<Self, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // let client_config = Self::build_client_config(config)?;
        // let client = Arc::new(KmsClient::new(client_config)
        //     .map_err(|e| KmsError::network(format!("Failed to create KMS client: {}",
        // e)))?);

        let rate_limiter = if config.rate_limit.enabled {
            Arc::new(RwLock::new(RateLimiter::new(
                config.rate_limit.burst_size as f64,
                config.rate_limit.requests_per_second as f64,
            )))
        } else {
            Arc::new(RwLock::new(RateLimiter::new(1000.0, 1000.0))) // Effectively no limit
        };

        Ok(Self {
            // TODO: Enable when cosmian_kms_client is available
            // client,
            config: config.clone(),
            rate_limiter,
        })
    }

    /// Build Cosmian KMS client configuration
    /// TODO: Stubbed - implement when Cosmian KMS client is available
    #[allow(dead_code, unused_variables)]
    fn build_client_config(config: &RemoteConfig) -> Result<(), KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // let mut client_config = ClientConf::new(&config.server_url);
        //
        // Set SSL verification
        // if !config.verify_ssl {
        // client_config = client_config.insecure();
        // }
        //
        // Set timeout
        // client_config =
        // client_config.timeout(Duration::from_secs(config.timeout_seconds));
        //
        // Configure authentication
        // match config.auth_method {
        // AuthMethod::Certificate => {
        // let cert_path = config.client_cert_path
        // .as_ref()
        // .ok_or_else(|| KmsError::config("Client certificate path required for
        // certificate auth"))?; let key_path = config.client_key_path
        // .as_ref()
        // .ok_or_else(|| KmsError::config("Client key path required for certificate
        // auth"))?;
        //
        // client_config = client_config
        // .client_cert_and_key(cert_path, key_path)
        // .map_err(|e| KmsError::auth(format!("Failed to load client certificate: {}",
        // e)))?;
        //
        // if let Some(ca_path) = &config.ca_cert_path {
        // client_config = client_config
        // .ca_cert_file(ca_path)
        // .map_err(|e| KmsError::auth(format!("Failed to load CA certificate: {}",
        // e)))?; }
        // }
        // AuthMethod::Token => {
        // let token = config.api_token
        // .as_ref()
        // .ok_or_else(|| KmsError::config("API token required for token auth"))?;
        // client_config = client_config.token(token);
        // }
        // AuthMethod::Basic => {
        // let username = config.username
        // .as_ref()
        // .ok_or_else(|| KmsError::config("Username required for basic auth"))?;
        // Password would be loaded from secure storage using password_key
        // return Err(KmsError::config("Basic auth password loading not implemented"));
        // }
        // AuthMethod::OAuth => {
        // return Err(KmsError::config("OAuth authentication not yet implemented"));
        // }
        // }
        //
        // Ok(client_config)

        // Temporary implementation until Cosmian KMS is integrated
        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// Execute operation with rate limiting and retry logic
    /// Used by all KmsBackend trait methods when Cosmian client is available
    #[allow(dead_code)]
    async fn execute_with_retry<F, T, Fut>(&self, operation: F) -> Result<T, KmsError>
    where
        F: Fn() -> Fut + Send + Sync,
        Fut: std::future::Future<Output = Result<T, KmsError>> + Send,
        T: Send,
    {
        let mut attempts = 0;
        let mut delay = Duration::from_millis(self.config.retry.initial_delay_ms);

        loop {
            // Rate limiting
            if self.config.rate_limit.enabled {
                let mut rate_limiter = self.rate_limiter.write().await;
                while !rate_limiter.acquire().await {
                    tokio::time::sleep(Duration::from_millis(10)).await;
                }
            }

            match operation().await {
                Ok(result) => return Ok(result),
                Err(e) => {
                    attempts += 1;

                    if attempts >= self.config.retry.max_attempts || !e.is_retryable() {
                        return Err(e);
                    }

                    tokio::time::sleep(delay).await;
                    delay = Duration::from_millis(
                        (delay.as_millis() as f64 * self.config.retry.backoff_multiplier) as u64,
                    )
                    .min(Duration::from_millis(self.config.retry.max_delay_ms));
                }
            }
        }
    }

    /// Convert Cosmian KMS key to our KeyData format
    /// TODO: Stubbed - implement when cosmian_kms_client is available
    #[allow(dead_code, unused_variables)]
    fn cosmian_to_key_data(&self, _key_id: &str) -> Result<KeyData, KmsError> {
        // TODO: Implement when cosmian_kms_client::types::Key is available
        // This is a simplified conversion - actual implementation would depend on
        // Cosmian KMS SDK's key structure
        // let key_type = KeyType::Symmetric; // Default, would be determined from
        // cosmian_key let algorithm = KeyAlgorithm::Aes256Gcm; // Default,
        // would be determined from cosmian_key let key_size = 256; // Default,
        // would be determined from cosmian_key
        //
        // let usage = KeyUsage {
        // encrypt: true,
        // decrypt: true,
        // sign: false,
        // verify: false,
        // wrap: false,
        // unwrap: false,
        // derive: false,
        // export: false,
        // };
        //
        // Note: Cosmian KMS typically doesn't return key material directly
        // This would be handled through operations rather than raw key access
        // let key_material = SecretBytes::new(vec![]);
        //
        // Ok(KeyData {
        // key_id: key_id.to_string(),
        // key_type,
        // algorithm,
        // usage,
        // key_size,
        // key_material,
        // metadata: KeyMetadata::default(),
        // created_at: Utc::now(), // Would come from cosmian_key
        // last_accessed: None,
        // expires_at: None,
        // status: KeyStatus::Active,
        // tags: HashMap::new(),
        // })

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// Convert our KeyData to Cosmian KMS format
    /// TODO: Stubbed - implement when cosmian_kms_client is available
    #[allow(dead_code, unused_variables)]
    fn key_data_to_cosmian(&self, _key: &KeyData) -> Result<(), KmsError> {
        // TODO: Implement when cosmian_kms_client::types::CreateKeyRequest is available
        // use cosmian_kms_client::types::{CreateKeyRequest, KeyUsageFlags};
        //
        // let mut usage_flags = KeyUsageFlags::default();
        // if key.usage.encrypt {
        // usage_flags |= KeyUsageFlags::ENCRYPT;
        // }
        // if key.usage.decrypt {
        // usage_flags |= KeyUsageFlags::DECRYPT;
        // }
        // if key.usage.sign {
        // usage_flags |= KeyUsageFlags::SIGN;
        // }
        // if key.usage.verify {
        // usage_flags |= KeyUsageFlags::VERIFY;
        // }
        //
        // Build create request based on key algorithm
        // match key.algorithm {
        // KeyAlgorithm::Aes256Gcm => {
        // Ok(CreateKeyRequest::symmetric_key(
        // 256, // key size
        // usage_flags,
        // Some(key.key_id.clone()),
        // ))
        // }
        // _ => Err(KmsError::crypto("create_key", format!("Algorithm {:?} not supported
        // by remote backend", key.algorithm))), }

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }
}

#[async_trait]
impl KmsBackend for RemoteKmsBackend {
    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn initialize(&mut self) -> Result<(), KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // Test connection to Cosmian KMS
        // self.execute_with_retry(|| async {
        // self.client.version()
        // .await
        // .map_err(|e| KmsError::network(format!("Failed to connect to KMS server: {}",
        // e)))?; Ok(())
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn store_key(&self, _key: KeyData) -> Result<String, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // let create_request = self.key_data_to_cosmian(&key)?;
        //
        // self.execute_with_retry(|| async {
        // let response = self.client.create_key(create_request.clone())
        // .await
        // .map_err(|e| KmsError::external_service("cosmian_kms", format!("Failed to
        // create key: {}", e)))?;
        //
        // Ok(response.unique_identifier)
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn get_key(&self, _key_id: &str) -> Result<Option<KeyData>, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // self.execute_with_retry(|| async {
        // match self.client.get_key(key_id).await {
        // Ok(key) => {
        // let key_data = self.cosmian_to_key_data(&key, key_id)?;
        // Ok(Some(key_data))
        // }
        // Err(e) => {
        // let error_str = e.to_string().to_lowercase();
        // if error_str.contains("not found") || error_str.contains("404") {
        // Ok(None)
        // } else {
        // Err(KmsError::external_service("cosmian_kms", format!("Failed to get key:
        // {}", e))) }
        // }
        // }
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn update_key(&self, _key_id: &str, _key: KeyData) -> Result<(), KmsError> {
        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn delete_key(&self, _key_id: &str) -> Result<bool, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // self.execute_with_retry(|| async {
        // match self.client.destroy_key(key_id).await {
        // Ok(_) => Ok(true),
        // Err(e) => {
        // let error_str = e.to_string().to_lowercase();
        // if error_str.contains("not found") || error_str.contains("404") {
        // Ok(false)
        // } else {
        // Err(KmsError::external_service("cosmian_kms", format!("Failed to delete key:
        // {}", e))) }
        // }
        // }
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn list_keys(
        &self,
        _filters: Option<HashMap<String, String>>,
    ) -> Result<Vec<String>, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // self.execute_with_retry(|| async {
        // let keys = self.client.list_keys(None, None)
        // .await
        // .map_err(|e| KmsError::external_service("cosmian_kms", format!("Failed to
        // list keys: {}", e)))?;
        //
        // Ok(keys.into_iter().map(|k| k.unique_identifier).collect())
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn key_exists(&self, _key_id: &str) -> Result<bool, KmsError> {
        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn encrypt(
        &self,
        _key_id: &str,
        _plaintext: &[u8],
        _context: Option<HashMap<String, String>>,
    ) -> Result<Vec<u8>, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // self.execute_with_retry(|| async {
        // let mut encrypt_request = cosmian_kms_client::types::EncryptRequest::new(
        // key_id,
        // plaintext.to_vec(),
        // );
        //
        // Add context as additional authenticated data if provided
        // if let Some(ctx) = &context {
        // let aad = serde_json::to_vec(ctx)
        // .map_err(|e| KmsError::serialization(format!("Failed to serialize context:
        // {}", e)))?; encrypt_request = encrypt_request.with_aad(aad);
        // }
        //
        // let response = self.client.encrypt(encrypt_request)
        // .await
        // .map_err(|e| KmsError::external_service("cosmian_kms", format!("Encryption
        // failed: {}", e)))?;
        //
        // Ok(response.data)
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn decrypt(
        &self,
        _key_id: &str,
        _ciphertext: &[u8],
        _context: Option<HashMap<String, String>>,
    ) -> Result<Vec<u8>, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // self.execute_with_retry(|| async {
        // let mut decrypt_request = cosmian_kms_client::types::DecryptRequest::new(
        // key_id,
        // ciphertext.to_vec(),
        // );
        //
        // Add context as additional authenticated data if provided
        // if let Some(ctx) = &context {
        // let aad = serde_json::to_vec(ctx)
        // .map_err(|e| KmsError::serialization(format!("Failed to serialize context:
        // {}", e)))?; decrypt_request = decrypt_request.with_aad(aad);
        // }
        //
        // let response = self.client.decrypt(decrypt_request)
        // .await
        // .map_err(|e| KmsError::external_service("cosmian_kms", format!("Decryption
        // failed: {}", e)))?;
        //
        // Ok(response.data)
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn sign(
        &self,
        _key_id: &str,
        _data: &[u8],
        _algorithm: Option<String>,
    ) -> Result<Vec<u8>, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // self.execute_with_retry(|| async {
        // let sign_request = cosmian_kms_client::types::SignRequest::new(
        // key_id,
        // data.to_vec(),
        // algorithm.as_deref(),
        // );
        //
        // let response = self.client.sign(sign_request)
        // .await
        // .map_err(|e| KmsError::external_service("cosmian_kms", format!("Signing
        // failed: {}", e)))?;
        //
        // Ok(response.signature_data)
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn verify(
        &self,
        _key_id: &str,
        _data: &[u8],
        _signature: &[u8],
        _algorithm: Option<String>,
    ) -> Result<bool, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // self.execute_with_retry(|| async {
        // let verify_request = cosmian_kms_client::types::SignatureVerifyRequest::new(
        // key_id,
        // data.to_vec(),
        // signature.to_vec(),
        // algorithm.as_deref(),
        // );
        //
        // let response = self.client.verify_signature(verify_request)
        // .await
        // .map_err(|e| KmsError::external_service("cosmian_kms", format!("Signature
        // verification failed: {}", e)))?;
        //
        // Ok(response.is_valid)
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn generate_data_key(
        &self,
        _key_id: &str,
        _key_spec: &str,
        _context: Option<HashMap<String, String>>,
    ) -> Result<(Vec<u8>, Vec<u8>), KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // self.execute_with_retry(|| async {
        // Parse key spec to determine key length
        // let key_length = match key_spec {
        // "AES_256" => 32,
        // "AES_128" => 16,
        // _ => return Err(KmsError::validation("key_spec", "Unsupported key
        // specification")), };
        //
        // Generate data key using Cosmian KMS
        // let request = cosmian_kms_client::types::GenerateDataKeyRequest::new(
        // key_id,
        // key_length,
        // context.clone(),
        // );
        //
        // let response = self.client.generate_data_key(request)
        // .await
        // .map_err(|e| KmsError::external_service("cosmian_kms", format!("Data key
        // generation failed: {}", e)))?;
        //
        // Ok((response.plaintext_data_key, response.encrypted_data_key))
        // }).await

        Err(KmsError::config(
            "Cosmian KMS client not available - use KMS Service instead",
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn health_check(&self) -> Result<HealthStatus, KmsError> {
        // TODO: Uncomment when cosmian_kms_client is available
        // let start = std::time::Instant::now();
        //
        // let result = self.execute_with_retry(|| async {
        // self.client.version()
        // .await
        // .map_err(|e| KmsError::network(format!("Health check failed: {}", e)))
        // }).await;
        //
        // let elapsed = start.elapsed();
        // let mut metrics = HashMap::new();
        // metrics.insert("response_time_ms".to_string(), elapsed.as_millis() as f64);
        //
        // match result {
        // Ok(version) => {
        // Ok(HealthStatus {
        // healthy: true,
        // message: format!("Remote KMS backend healthy - server version: {}", version),
        // last_check: Utc::now(),
        // metrics,
        // })
        // }
        // Err(e) => {
        // Ok(HealthStatus::unhealthy(format!("Remote KMS backend unhealthy: {}", e)))
        // }
        // }

        Ok(HealthStatus::unhealthy(
            "Cosmian KMS client not available - use KMS Service instead".to_string(),
        ))
    }

    /// TODO: Stubbed - Cosmian KMS integration not yet available
    async fn shutdown(&mut self) -> Result<(), KmsError> {
        // No cleanup needed for stubbed implementation
        Ok(())
    }
}
