fortress-api-server 1.0.0

//! # Failover Module
//!
//! This module handles automatic failover and disaster recovery,
//! ensuring high availability and data safety during node failures.

use crate::cluster::{ClusterError, ClusterResult};
use serde::{Deserialize, Serialize};
use std::collections::{HashMap, HashSet};
use std::sync::Arc;
use std::time::Duration;
use tokio::sync::{RwLock, Mutex};
use tokio::time::{interval, timeout};
use tracing::{error, info, warn};
use uuid::Uuid;

/// Failover configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FailoverConfig {
    /// Health check interval in seconds
    pub health_check_interval_secs: u64,
    /// Node timeout in seconds before considered failed
    pub node_timeout_secs: u64,
    /// Maximum number of failed nodes before triggering emergency mode
    pub max_failed_nodes: usize,
    /// Enable automatic leader election
    pub enable_auto_leader_election: bool,
    /// Leader election timeout in milliseconds
    pub leader_election_timeout_ms: u64,
    /// Enable automatic data recovery
    pub enable_auto_recovery: bool,
    /// Recovery timeout in milliseconds
    pub recovery_timeout_ms: u64,
    /// Maximum recovery attempts
    pub max_recovery_attempts: u32,
    /// Enable backup promotion
    pub enable_backup_promotion: bool,
    /// Backup promotion delay in milliseconds
    pub backup_promotion_delay_ms: u64,
}

impl Default for FailoverConfig {
    fn default() -> Self {
        Self {
            health_check_interval_secs: 10,
            node_timeout_secs: 30,
            max_failed_nodes: 2,
            enable_auto_leader_election: true,
            leader_election_timeout_ms: 5000,
            enable_auto_recovery: true,
            recovery_timeout_ms: 30000,
            max_recovery_attempts: 3,
            enable_backup_promotion: true,
            backup_promotion_delay_ms: 5000,
        }
    }
}

/// Node health status
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum NodeHealthStatus {
    /// Node is healthy
    Healthy,
    /// Node is degraded (some issues but functional)
    Degraded,
    /// Node is failed
    Failed,
    /// Node is under recovery
    Recovering,
    /// Node is in maintenance mode
    Maintenance,
}

/// Failover event
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FailoverEvent {
    /// Unique event identifier
    pub event_id: Uuid,
    /// Event type
    pub event_type: FailoverEventType,
    /// Node involved in the event
    pub node_id: Uuid,
    /// Timestamp when event occurred
    pub timestamp: chrono::DateTime<chrono::Utc>,
    /// Event description
    pub description: String,
    /// Event severity
    pub severity: FailoverSeverity,
    /// Additional event data
    pub metadata: HashMap<String, String>,
}

/// Failover event types
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum FailoverEventType {
    /// Node failure detected
    NodeFailure,
    /// Leader failure detected
    LeaderFailure,
    /// Network partition detected
    NetworkPartition,
    /// Data inconsistency detected
    DataInconsistency,
    /// Recovery initiated
    RecoveryInitiated,
    /// Recovery completed
    RecoveryCompleted,
    /// Leader election initiated
    LeaderElectionInitiated,
    /// Leader election completed
    LeaderElectionCompleted,
    /// Backup promoted
    BackupPromoted,
}

/// Failover severity levels
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum FailoverSeverity {
    /// Low severity
    Low,
    /// Medium severity
    Medium,
    /// High severity
    High,
    /// Critical severity
    Critical,
}

/// Failover message types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum FailoverMessage {
    /// Health check request
    HealthCheckRequest {
        /// ID of the node requesting health check
        requester_id: Uuid,
        /// When the request was sent
        timestamp: chrono::DateTime<chrono::Utc>,
    },
    
    /// Health check response
    HealthCheckResponse {
        /// ID of the responding node
        responder_id: Uuid,
        /// Health status of the node
        status: NodeHealthStatus,
        /// When the response was sent
        timestamp: chrono::DateTime<chrono::Utc>,
        /// Node metrics
        metrics: HashMap<String, String>,
    },
    
    /// Failover notification
    FailoverNotification {
        /// The failover event
        event: FailoverEvent,
    },
    
    /// Leader election request
    LeaderElectionRequest {
        /// ID of the candidate node
        candidate_id: Uuid,
        /// Current election term
        term: u64,
        /// When the request was sent
        timestamp: chrono::DateTime<chrono::Utc>,
    },
    
    /// Leader election response
    LeaderElectionResponse {
        /// ID of the voting node
        voter_id: Uuid,
        /// ID of the candidate node
        candidate_id: Uuid,
        /// Whether the vote was granted
        vote_granted: bool,
        /// Current election term
        term: u64,
        /// When the response was sent
        timestamp: chrono::DateTime<chrono::Utc>,
    },
    
    /// Recovery request
    RecoveryRequest {
        /// ID of the failed node
        failed_node_id: Uuid,
        /// Type of recovery to perform
        recovery_type: RecoveryType,
        /// When the request was sent
        timestamp: chrono::DateTime<chrono::Utc>,
    },
    
    /// Recovery response
    RecoveryResponse {
        /// Unique identifier for the request
        request_id: Uuid,
        /// Whether the recovery was successful
        success: bool,
        /// Recovery status message
        message: String,
        /// When the response was sent
        timestamp: chrono::DateTime<chrono::Utc>,
    },
}

/// Recovery types
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum RecoveryType {
    /// Full node recovery
    FullRecovery,
    /// Data recovery only
    DataRecovery,
    /// Configuration recovery
    ConfigRecovery,
    /// Service restart
    ServiceRestart,
}

/// Failover-specific errors
#[derive(Debug, thiserror::Error)]
pub enum FailoverError {
    /// Node failure detected
    #[error("Node failure detected: {0}")]
    NodeFailure(Uuid),
    
    /// Leader election process failed
    #[error("Leader election failed: {0}")]
    LeaderElectionFailed(String),
    
    /// Recovery operation failed
    #[error("Recovery failed: {0}")]
    RecoveryFailed(String),
    
    /// Network partition detected
    #[error("Network partition detected")]
    NetworkPartition,
    
    /// Not enough healthy nodes for operation
    #[error("Insufficient healthy nodes: {0}/{1}")]
    InsufficientHealthyNodes(usize, usize),
    
    /// Backup node promotion failed
    #[error("Backup promotion failed: {0}")]
    BackupPromotionFailed(String),
    
    /// Failover operation timed out
    #[error("Failover timeout")]
    FailoverTimeout,
    
    /// Invalid failover configuration
    #[error("Invalid failover configuration: {0}")]
    InvalidConfiguration(String),
}

/// Failover manager
pub struct FailoverManager {
    /// This node's ID
    node_id: Uuid,
    /// Configuration
    config: FailoverConfig,
    /// Cluster nodes
    cluster_nodes: Arc<RwLock<HashSet<Uuid>>>,
    /// Node health status
    node_health: Arc<RwLock<HashMap<Uuid, NodeHealthStatus>>>,
    /// Failover events
    failover_events: Arc<RwLock<Vec<FailoverEvent>>>,
    /// Current leader
    current_leader: Arc<RwLock<Option<Uuid>>>,
    /// Failover callbacks
    callbacks: Arc<Mutex<Vec<Box<dyn FailoverCallback + Send + Sync>>>>,
    /// Network sender
    network_sender: Arc<Mutex<dyn FailoverNetworkSender + Send + Sync>>,
    /// Recovery manager
    recovery_manager: Arc<Mutex<dyn RecoveryManager + Send + Sync>>,
}

/// Callback trait for failover events
#[async_trait::async_trait]
pub trait FailoverCallback {
    /// Called when a node failure is detected
    async fn on_node_failure(&self, node_id: Uuid, event: &FailoverEvent);
    
    /// Called when a new leader is elected
    async fn on_leader_election(&self, new_leader: Uuid, event: &FailoverEvent);
    
    /// Called when recovery is initiated for a node
    async fn on_recovery_initiated(&self, node_id: Uuid, event: &FailoverEvent);
    
    /// Called when recovery is completed for a node
    async fn on_recovery_completed(&self, node_id: Uuid, event: &FailoverEvent);
    
    /// Called when a backup node is promoted
    async fn on_backup_promotion(&self, backup_node: Uuid, event: &FailoverEvent);
}

/// Trait for network failover operations
#[async_trait::async_trait]
pub trait FailoverNetworkSender {
    /// Send a failover message to a specific node
    async fn send_failover_message(&self, target: Uuid, message: FailoverMessage) -> ClusterResult<()>;
    
    /// Broadcast a failover message to all nodes
    async fn broadcast_failover_message(&self, message: FailoverMessage) -> ClusterResult<()>;
}

/// Trait for recovery operations
#[async_trait::async_trait]
pub trait RecoveryManager {
    /// Initiate recovery for a failed node
    async fn initiate_recovery(&self, node_id: Uuid, recovery_type: RecoveryType) -> ClusterResult<()>;
    
    /// Check the recovery status of a node
    async fn check_recovery_status(&self, node_id: Uuid) -> ClusterResult<Option<RecoveryStatus>>;
    
    /// Promote a backup node to primary
    async fn promote_backup(&self, backup_node: Uuid) -> ClusterResult<()>;
}

/// Recovery status
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RecoveryStatus {
    /// Node being recovered
    pub node_id: Uuid,
    /// Recovery type
    pub recovery_type: RecoveryType,
    /// Current recovery progress (0-100)
    pub progress: u8,
    /// Recovery status
    pub status: NodeHealthStatus,
    /// Estimated time remaining
    pub estimated_time_remaining: Option<Duration>,
    /// Recovery message
    pub message: String,
}

impl FailoverManager {
    /// Create a new failover manager
    pub fn new(
        node_id: Uuid,
        config: FailoverConfig,
        network_sender: Arc<Mutex<dyn FailoverNetworkSender + Send + Sync>>,
        recovery_manager: Arc<Mutex<dyn RecoveryManager + Send + Sync>>,
    ) -> Self {
        Self {
            node_id,
            config,
            cluster_nodes: Arc::new(RwLock::new(HashSet::new())),
            node_health: Arc::new(RwLock::new(HashMap::new())),
            failover_events: Arc::new(RwLock::new(Vec::new())),
            current_leader: Arc::new(RwLock::new(None)),
            callbacks: Arc::new(Mutex::new(Vec::new())),
            network_sender,
            recovery_manager,
        }
    }

    /// Start the failover manager
    pub async fn start(&self) -> ClusterResult<()> {
        info!("Starting failover manager for node {}", self.node_id);
        
        // Start health check loop
        let failover = self.clone();
        tokio::spawn(async move {
            failover.health_check_loop().await;
        });

        // Start event processing loop
        let failover = self.clone();
        tokio::spawn(async move {
            failover.event_processing_loop().await;
        });

        Ok(())
    }

    /// Health check loop
    async fn health_check_loop(&self) {
        let mut interval = interval(Duration::from_secs(self.config.health_check_interval_secs));
        
        loop {
            interval.tick().await;
            
            if let Err(e) = self.perform_health_checks().await {
                error!("Health check failed: {}", e);
            }
        }
    }

    /// Event processing loop
    async fn event_processing_loop(&self) {
        let mut interval = interval(Duration::from_secs(5));
        
        loop {
            interval.tick().await;
            
            if let Err(e) = self.process_failover_events().await {
                error!("Event processing failed: {}", e);
            }
        }
    }

    /// Perform health checks on all nodes
    async fn perform_health_checks(&self) -> ClusterResult<()> {
        let cluster_nodes = self.cluster_nodes.read().await;
        let nodes_to_check: Vec<Uuid> = cluster_nodes.iter().cloned().collect();
        drop(cluster_nodes);

        let mut failed_nodes = Vec::new();
        
        for node_id in nodes_to_check {
            if let Err(e) = self.check_node_health(node_id).await {
                warn!("Health check failed for node {}: {}", node_id, e);
                failed_nodes.push(node_id);
            }
        }

        // Handle failed nodes
        for node_id in failed_nodes {
            self.handle_node_failure(node_id).await?;
        }

        Ok(())
    }

    /// Check health of a specific node
    async fn check_node_health(&self, node_id: Uuid) -> ClusterResult<()> {
        let health_request = FailoverMessage::HealthCheckRequest {
            requester_id: self.node_id,
            timestamp: chrono::Utc::now(),
        };

        let sender = self.network_sender.lock().await;
        
        // Send health check with timeout
        let timeout_duration = Duration::from_secs(self.config.node_timeout_secs);
        match timeout(timeout_duration, sender.send_failover_message(node_id, health_request)).await {
            Ok(Ok(())) => {
                // Update node health to healthy
                let mut health = self.node_health.write().await;
                health.insert(node_id, NodeHealthStatus::Healthy);
                Ok(())
            }
            Ok(Err(_e)) => {
                // Mark node as failed
                let mut health = self.node_health.write().await;
                health.insert(node_id, NodeHealthStatus::Failed);
                Err(ClusterError::Failover(FailoverError::NodeFailure(node_id)))
            }
            Err(_) => {
                // Timeout - mark node as failed
                let mut health = self.node_health.write().await;
                health.insert(node_id, NodeHealthStatus::Failed);
                Err(ClusterError::Failover(FailoverError::FailoverTimeout))
            }
        }
    }

    /// Handle node failure
    async fn handle_node_failure(&self, node_id: Uuid) -> ClusterResult<()> {
        warn!("Handling node failure for {}", node_id);
        
        // Create failover event
        let event = FailoverEvent {
            event_id: Uuid::new_v4(),
            event_type: FailoverEventType::NodeFailure,
            node_id,
            timestamp: chrono::Utc::now(),
            description: format!("Node {} has failed", node_id),
            severity: FailoverSeverity::High,
            metadata: HashMap::new(),
        };

        // Record event
        {
            let mut events = self.failover_events.write().await;
            events.push(event.clone());
        }

        // Check if this was the leader
        let is_leader = {
            let leader = self.current_leader.read().await;
            *leader == Some(node_id)
        };

        if is_leader {
            self.handle_leader_failure(node_id, &event).await?;
        }

        // Initiate recovery if enabled
        if self.config.enable_auto_recovery {
            self.initiate_recovery(node_id, RecoveryType::FullRecovery, &event).await?;
        }

        // Notify callbacks
        let callbacks = self.callbacks.lock().await;
        for callback in callbacks.iter() {
            callback.on_node_failure(node_id, &event).await;
        }

        Ok(())
    }

    /// Handle leader failure
    async fn handle_leader_failure(&self, failed_leader: Uuid, event: &FailoverEvent) -> ClusterResult<()> {
        error!("Leader {} has failed, initiating leader election", failed_leader);
        
        // Clear current leader
        {
            let mut leader = self.current_leader.write().await;
            *leader = None;
        }

        // Initiate leader election if enabled
        if self.config.enable_auto_leader_election {
            self.initiate_leader_election(event).await?;
        }

        Ok(())
    }

    /// Initiate leader election
    async fn initiate_leader_election(&self, _failure_event: &FailoverEvent) -> ClusterResult<()> {
        info!("Initiating leader election");
        
        let election_event = FailoverEvent {
            event_id: Uuid::new_v4(),
            event_type: FailoverEventType::LeaderElectionInitiated,
            node_id: self.node_id,
            timestamp: chrono::Utc::now(),
            description: "Leader election initiated due to leader failure".to_string(),
            severity: FailoverSeverity::Critical,
            metadata: HashMap::new(),
        };

        // Record election event
        {
            let mut events = self.failover_events.write().await;
            events.push(election_event.clone());
        }

        // Send election request
        let election_request = FailoverMessage::LeaderElectionRequest {
            candidate_id: self.node_id,
            term: self.get_current_term().await,
            timestamp: chrono::Utc::now(),
        };

        let sender = self.network_sender.lock().await;
        sender.broadcast_failover_message(election_request).await?;

        Ok(())
    }

    /// Get current election term
    async fn get_current_term(&self) -> u64 {
        // In a real implementation, this would be stored persistently
        // For now, return a simple counter
        1
    }

    /// Initiate recovery for a failed node
    async fn initiate_recovery(&self, node_id: Uuid, recovery_type: RecoveryType, _failure_event: &FailoverEvent) -> ClusterResult<()> {
        info!("Initiating recovery for node {}", node_id);
        
        let recovery_event = FailoverEvent {
            event_id: Uuid::new_v4(),
            event_type: FailoverEventType::RecoveryInitiated,
            node_id,
            timestamp: chrono::Utc::now(),
            description: format!("Recovery initiated for node {}", node_id),
            severity: FailoverSeverity::Medium,
            metadata: HashMap::new(),
        };

        // Record recovery event
        {
            let mut events = self.failover_events.write().await;
            events.push(recovery_event.clone());
        }

        // Update node health status
        {
            let mut health = self.node_health.write().await;
            health.insert(node_id, NodeHealthStatus::Recovering);
        }

        // Start recovery process
        let recovery_manager = self.recovery_manager.lock().await;
        recovery_manager.initiate_recovery(node_id, recovery_type).await?;

        // Notify callbacks
        let callbacks = self.callbacks.lock().await;
        for callback in callbacks.iter() {
            callback.on_recovery_initiated(node_id, &recovery_event).await;
        }

        Ok(())
    }

    /// Process failover events
    async fn process_failover_events(&self) -> ClusterResult<()> {
        let events_to_process: Vec<FailoverEvent> = {
            let mut events = self.failover_events.write().await;
            events.drain(..).collect()
        };

        for event in events_to_process {
            match event.event_type {
                FailoverEventType::NodeFailure => {
                    // Additional processing for node failures
                    self.check_cluster_health().await?;
                }
                FailoverEventType::LeaderFailure => {
                    // Additional processing for leader failures
                    self.check_cluster_health().await?;
                }
                FailoverEventType::RecoveryInitiated => {
                    // Monitor recovery progress
                    self.monitor_recovery_progress(event.node_id).await?;
                }
                _ => {
                    // Other event types
                }
            }
        }

        Ok(())
    }

    /// Check overall cluster health
    async fn check_cluster_health(&self) -> ClusterResult<()> {
        let health = self.node_health.read().await;
        let cluster_nodes = self.cluster_nodes.read().await;
        
        let healthy_nodes = health.values()
            .filter(|&status| *status == NodeHealthStatus::Healthy)
            .count();
        
        let total_nodes = cluster_nodes.len();
        drop(health);
        drop(cluster_nodes);

        if healthy_nodes < total_nodes - self.config.max_failed_nodes {
            error!("Cluster health critical: {}/{} nodes healthy", healthy_nodes, total_nodes);
            
            // Trigger emergency measures
            self.trigger_emergency_measures(healthy_nodes, total_nodes).await?;
        }

        Ok(())
    }

    /// Trigger emergency measures
    async fn trigger_emergency_measures(&self, healthy_nodes: usize, total_nodes: usize) -> ClusterResult<()> {
        warn!("Triggering emergency measures: {}/{} nodes healthy", healthy_nodes, total_nodes);
        
        // Enable backup promotion if not already enabled
        if self.config.enable_backup_promotion {
            self.promote_backup_nodes().await?;
        }

        // Notify about critical cluster state
        let emergency_event = FailoverEvent {
            event_id: Uuid::new_v4(),
            event_type: FailoverEventType::NetworkPartition,
            node_id: self.node_id,
            timestamp: chrono::Utc::now(),
            description: format!("Emergency measures triggered: {}/{} nodes healthy", healthy_nodes, total_nodes),
            severity: FailoverSeverity::Critical,
            metadata: HashMap::new(),
        };

        {
            let mut events = self.failover_events.write().await;
            events.push(emergency_event);
        }

        Ok(())
    }

    /// Promote backup nodes
    async fn promote_backup_nodes(&self) -> ClusterResult<()> {
        info!("Promoting backup nodes");
        
        // In a real implementation, this would identify backup nodes
        // and promote them to active status
        
        let health = self.node_health.read().await;
        let cluster_nodes = self.cluster_nodes.read().await;
        
        for node_id in cluster_nodes.iter() {
            if let Some(status) = health.get(node_id) {
                if *status == NodeHealthStatus::Healthy {
                    // This node could be promoted
                    let promotion_event = FailoverEvent {
                        event_id: Uuid::new_v4(),
                        event_type: FailoverEventType::BackupPromoted,
                        node_id: *node_id,
                        timestamp: chrono::Utc::now(),
                        description: format!("Backup node {} promoted", node_id),
                        severity: FailoverSeverity::Medium,
                        metadata: HashMap::new(),
                    };

                    // Record promotion event
                    {
                        let mut events = self.failover_events.write().await;
                        events.push(promotion_event.clone());
                    }

                    // Notify callbacks
                    let callbacks = self.callbacks.lock().await;
                    for callback in callbacks.iter() {
                        callback.on_backup_promotion(*node_id, &promotion_event).await;
                    }
                }
            }
        }

        Ok(())
    }

    /// Monitor recovery progress
    async fn monitor_recovery_progress(&self, node_id: Uuid) -> ClusterResult<()> {
        let recovery_manager = self.recovery_manager.lock().await;
        
        match recovery_manager.check_recovery_status(node_id).await {
            Ok(Some(status)) => {
                if status.status == NodeHealthStatus::Healthy {
                    // Recovery completed
                    let completion_event = FailoverEvent {
                        event_id: Uuid::new_v4(),
                        event_type: FailoverEventType::RecoveryCompleted,
                        node_id,
                        timestamp: chrono::Utc::now(),
                        description: format!("Recovery completed for node {}", node_id),
                        severity: FailoverSeverity::Low,
                        metadata: HashMap::new(),
                    };

                    // Update node health
                    {
                        let mut health = self.node_health.write().await;
                        health.insert(node_id, NodeHealthStatus::Healthy);
                    }

                    // Record completion event
                    {
                        let mut events = self.failover_events.write().await;
                        events.push(completion_event.clone());
                    }

                    // Notify callbacks
                    let callbacks = self.callbacks.lock().await;
                    for callback in callbacks.iter() {
                        callback.on_recovery_completed(node_id, &completion_event).await;
                    }
                }
            }
            Ok(None) => {
                // Recovery still in progress
            }
            Err(e) => {
                error!("Failed to check recovery status for node {}: {}", node_id, e);
            }
        }

        Ok(())
    }

    /// Handle incoming failover message
    pub async fn handle_message(&self, _source: Uuid, message: FailoverMessage) -> ClusterResult<Option<FailoverMessage>> {
        match message {
            FailoverMessage::HealthCheckRequest { requester_id, timestamp } => {
                self.handle_health_check_request(requester_id, timestamp).await
            }
            FailoverMessage::HealthCheckResponse { responder_id, status, timestamp, metrics } => {
                self.handle_health_check_response(responder_id, status, timestamp, metrics).await?;
                Ok(None)
            }
            FailoverMessage::FailoverNotification { event } => {
                self.handle_failover_notification(event).await?;
                Ok(None)
            }
            FailoverMessage::LeaderElectionRequest { candidate_id, term, timestamp } => {
                self.handle_leader_election_request(candidate_id, term, timestamp).await
            }
            FailoverMessage::LeaderElectionResponse { voter_id, candidate_id, vote_granted, term, timestamp } => {
                self.handle_leader_election_response(voter_id, candidate_id, vote_granted, term, timestamp).await?;
                Ok(None)
            }
            FailoverMessage::RecoveryRequest { failed_node_id, recovery_type, timestamp } => {
                self.handle_recovery_request(failed_node_id, recovery_type, timestamp).await
            }
            FailoverMessage::RecoveryResponse { request_id, success, message, timestamp } => {
                self.handle_recovery_response(request_id, success, message, timestamp).await?;
                Ok(None)
            }
        }
    }

    /// Handle health check request
    async fn handle_health_check_request(&self, _requester_id: Uuid, _timestamp: chrono::DateTime<chrono::Utc>) -> ClusterResult<Option<FailoverMessage>> {
        let response = FailoverMessage::HealthCheckResponse {
            responder_id: self.node_id,
            status: NodeHealthStatus::Healthy,
            timestamp: chrono::Utc::now(),
            metrics: HashMap::new(),
        };

        Ok(Some(response))
    }

    /// Handle health check response
    async fn handle_health_check_response(&self, responder_id: Uuid, status: NodeHealthStatus, _timestamp: chrono::DateTime<chrono::Utc>, _metrics: HashMap<String, String>) -> ClusterResult<()> {
        // Update node health status
        let mut health = self.node_health.write().await;
        health.insert(responder_id, status);
        
        Ok(())
    }

    /// Handle failover notification
    async fn handle_failover_notification(&self, event: FailoverEvent) -> ClusterResult<()> {
        // Record the event
        {
            let mut events = self.failover_events.write().await;
            events.push(event.clone());
        }

        // Process based on event type
        match event.event_type {
            FailoverEventType::LeaderElectionCompleted => {
                if let Some(leader_id) = event.metadata.get("new_leader") {
                    if let Ok(uuid) = Uuid::parse_str(leader_id) {
                        let mut leader = self.current_leader.write().await;
                        *leader = Some(uuid);
                        
                        // Notify callbacks
                        let callbacks = self.callbacks.lock().await;
                        for callback in callbacks.iter() {
                            callback.on_leader_election(uuid, &event).await;
                        }
                    }
                }
            }
            _ => {
                // Other event types
            }
        }

        Ok(())
    }

    /// Handle leader election request
    async fn handle_leader_election_request(&self, candidate_id: Uuid, term: u64, _timestamp: chrono::DateTime<chrono::Utc>) -> ClusterResult<Option<FailoverMessage>> {
        // Simple voting logic - in a real implementation, this would be more sophisticated
        let vote_granted = true; // For now, always grant vote
        
        let response = FailoverMessage::LeaderElectionResponse {
            voter_id: self.node_id,
            candidate_id,
            vote_granted,
            term,
            timestamp: chrono::Utc::now(),
        };

        Ok(Some(response))
    }

    /// Handle leader election response
    async fn handle_leader_election_response(&self, voter_id: Uuid, candidate_id: Uuid, vote_granted: bool, term: u64, _timestamp: chrono::DateTime<chrono::Utc>) -> ClusterResult<()> {
        // In a real implementation, this would count votes and determine election outcome
        if vote_granted && candidate_id == self.node_id {
            info!("Received vote from {} for term {}", voter_id, term);
        }

        Ok(())
    }

    /// Handle recovery request
    async fn handle_recovery_request(&self, failed_node_id: Uuid, recovery_type: RecoveryType, _timestamp: chrono::DateTime<chrono::Utc>) -> ClusterResult<Option<FailoverMessage>> {
        let recovery_manager = self.recovery_manager.lock().await;
        
        match recovery_manager.initiate_recovery(failed_node_id, recovery_type).await {
            Ok(()) => {
                let response = FailoverMessage::RecoveryResponse {
                    request_id: Uuid::new_v4(),
                    success: true,
                    message: "Recovery initiated successfully".to_string(),
                    timestamp: chrono::Utc::now(),
                };
                Ok(Some(response))
            }
            Err(e) => {
                let response = FailoverMessage::RecoveryResponse {
                    request_id: Uuid::new_v4(),
                    success: false,
                    message: format!("Recovery failed: {}", e),
                    timestamp: chrono::Utc::now(),
                };
                Ok(Some(response))
            }
        }
    }

    /// Handle recovery response
    async fn handle_recovery_response(&self, request_id: Uuid, success: bool, message: String, _timestamp: chrono::DateTime<chrono::Utc>) -> ClusterResult<()> {
        if success {
            info!("Recovery successful for request {}: {}", request_id, message);
        } else {
            error!("Recovery failed for request {}: {}", request_id, message);
        }

        Ok(())
    }

    /// Add cluster node
    pub async fn add_node(&self, node_id: Uuid) {
        let mut nodes = self.cluster_nodes.write().await;
        nodes.insert(node_id);
        
        // Initialize health status
        let mut health = self.node_health.write().await;
        health.insert(node_id, NodeHealthStatus::Healthy);
    }

    /// Remove cluster node
    pub async fn remove_node(&self, node_id: Uuid) {
        let mut nodes = self.cluster_nodes.write().await;
        nodes.remove(&node_id);
        
        // Clean up health status
        let mut health = self.node_health.write().await;
        health.remove(&node_id);
    }

    /// Add failover callback
    pub async fn add_callback(&self, callback: Box<dyn FailoverCallback + Send + Sync>) {
        let mut callbacks = self.callbacks.lock().await;
        callbacks.push(callback);
    }

    /// Get current leader
    pub async fn get_current_leader(&self) -> Option<Uuid> {
        *self.current_leader.read().await
    }

    /// Get node health status
    pub async fn get_node_health(&self, node_id: Uuid) -> Option<NodeHealthStatus> {
        self.node_health.read().await.get(&node_id).cloned()
    }

    /// Get all failover events
    pub async fn get_failover_events(&self) -> Vec<FailoverEvent> {
        self.failover_events.read().await.clone()
    }
}

impl Clone for FailoverManager {
    fn clone(&self) -> Self {
        Self {
            node_id: self.node_id,
            config: self.config.clone(),
            cluster_nodes: Arc::clone(&self.cluster_nodes),
            node_health: Arc::clone(&self.node_health),
            failover_events: Arc::clone(&self.failover_events),
            current_leader: Arc::clone(&self.current_leader),
            callbacks: Arc::clone(&self.callbacks),
            network_sender: Arc::clone(&self.network_sender),
            recovery_manager: Arc::clone(&self.recovery_manager),
        }
    }
}