ant_quic/monitoring/

error_recovery.rs

//! Error Recovery and Resilience System
//!
//! This module implements comprehensive error recovery mechanisms with
//! automatic retry, exponential backoff, fallback strategies, and
//! connection migration support for network changes.

use std::{
    collections::{HashMap, VecDeque},
    future::Future,
    pin::Pin,
    sync::Arc,
    time::{Duration, Instant},
};

use tokio::{
    sync::RwLock,
    time::{sleep, timeout},
};
use tracing::{debug, info, warn};

use crate::{
    monitoring::{ErrorCategory, MonitoringError},
    nat_traversal_api::{NatTraversalError, PeerId},
};

/// Error recovery manager for NAT traversal operations
pub struct ErrorRecoveryManager {
    /// Recovery configuration
    config: RecoveryConfig,
    /// Active recovery sessions
    recovery_sessions: Arc<RwLock<HashMap<String, RecoverySession>>>,
    /// Retry policies by error type
    retry_policies: HashMap<ErrorCategory, RetryPolicy>,
    /// Fallback strategies
    fallback_strategies: Vec<FallbackStrategy>,
    /// Circuit breaker for preventing cascading failures
    circuit_breaker: Arc<CircuitBreaker>,
    /// Connection migration handler
    migration_handler: Arc<ConnectionMigrationHandler>,
    /// Resource cleanup manager
    cleanup_manager: Arc<ResourceCleanupManager>,
}

/// Recovery configuration
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct RecoveryConfig {
    /// Enable automatic retry
    pub enable_auto_retry: bool,
    /// Maximum concurrent recovery sessions
    pub max_concurrent_recoveries: usize,
    /// Default retry policy
    pub default_retry_policy: RetryPolicy,
    /// Enable circuit breaker
    pub enable_circuit_breaker: bool,
    /// Circuit breaker configuration
    pub circuit_breaker_config: CircuitBreakerConfig,
    /// Enable connection migration
    pub enable_connection_migration: bool,
    /// Resource cleanup interval
    pub cleanup_interval: Duration,
    /// Recovery session timeout
    pub recovery_timeout: Duration,
}

impl Default for RecoveryConfig {
    fn default() -> Self {
        Self {
            enable_auto_retry: true,
            max_concurrent_recoveries: 10,
            default_retry_policy: RetryPolicy::default(),
            enable_circuit_breaker: true,
            circuit_breaker_config: CircuitBreakerConfig::default(),
            enable_connection_migration: true,
            cleanup_interval: Duration::from_secs(60),
            recovery_timeout: Duration::from_secs(300), // 5 minutes
        }
    }
}

/// Retry policy configuration
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct RetryPolicy {
    /// Maximum number of retry attempts
    pub max_attempts: u32,
    /// Initial retry delay
    pub initial_delay: Duration,
    /// Maximum retry delay
    pub max_delay: Duration,
    /// Backoff multiplier
    pub backoff_multiplier: f64,
    /// Enable jitter to avoid thundering herd
    pub enable_jitter: bool,
    /// Jitter factor (0.0 to 1.0)
    pub jitter_factor: f64,
    /// Retry timeout per attempt
    pub attempt_timeout: Duration,
}

impl Default for RetryPolicy {
    fn default() -> Self {
        Self {
            max_attempts: 3,
            initial_delay: Duration::from_millis(500),
            max_delay: Duration::from_secs(30),
            backoff_multiplier: 2.0,
            enable_jitter: true,
            jitter_factor: 0.1,
            attempt_timeout: Duration::from_secs(10),
        }
    }
}

/// Circuit breaker configuration
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct CircuitBreakerConfig {
    /// Failure threshold to open circuit
    pub failure_threshold: u32,
    /// Success threshold to close circuit
    pub success_threshold: u32,
    /// Timeout before trying half-open state
    pub timeout: Duration,
    /// Window size for failure counting
    pub window_size: Duration,
}

impl Default for CircuitBreakerConfig {
    fn default() -> Self {
        Self {
            failure_threshold: 5,
            success_threshold: 3,
            timeout: Duration::from_secs(60),
            window_size: Duration::from_secs(300), // 5 minutes
        }
    }
}

/// Recovery session state
#[derive(Debug, Clone)]
struct RecoverySession {
    /// Session identifier
    session_id: String,
    /// Peer being recovered
    peer_id: PeerId,
    /// Original error that triggered recovery
    original_error: NatTraversalError,
    /// Current recovery attempt
    current_attempt: u32,
    /// Recovery start time
    start_time: Instant,
    /// Last attempt time
    last_attempt_time: Option<Instant>,
    /// Recovery strategy being used
    current_strategy: RecoveryStrategy,
    /// Fallback strategies to try
    remaining_strategies: Vec<FallbackStrategy>,
    /// Recovery state
    state: RecoveryState,
}

/// Recovery strategies
#[derive(Debug, Clone)]
pub enum RecoveryStrategy {
    /// Simple retry with backoff
    Retry {
        policy: RetryPolicy,
    },
    /// Try alternative bootstrap nodes
    AlternativeBootstrap {
        nodes: Vec<std::net::SocketAddr>,
    },
    /// Use relay fallback
    RelayFallback {
        relay_servers: Vec<std::net::SocketAddr>,
    },
    /// Connection migration to new path
    ConnectionMigration {
        new_path: std::net::SocketAddr,
    },
    /// Graceful degradation
    GracefulDegradation {
        reduced_functionality: bool,
    },
}

/// Fallback strategies
#[derive(Debug, Clone)]
pub enum FallbackStrategy {
    /// Try different NAT traversal method
    AlternativeNatMethod,
    /// Use relay servers
    RelayServers,
    /// Direct connection attempts
    DirectConnection,
    /// Reduce connection requirements
    ReducedRequirements,
    /// Manual intervention required
    ManualIntervention,
}

/// Recovery states
#[derive(Debug, Clone, PartialEq)]
enum RecoveryState {
    /// Recovery in progress
    InProgress,
    /// Recovery succeeded
    Succeeded,
    /// Recovery failed
    Failed,
    /// Recovery cancelled
    Cancelled,
    /// Waiting for retry
    WaitingRetry,
}

/// Circuit breaker for preventing cascading failures
#[derive(Debug)]
struct CircuitBreaker {
    /// Configuration
    config: CircuitBreakerConfig,
    /// Current state
    state: RwLock<CircuitBreakerState>,
    /// Failure count in current window
    failure_count: RwLock<u32>,
    /// Success count in half-open state
    success_count: RwLock<u32>,
    /// Last state change time
    last_state_change: RwLock<Instant>,
    /// Failure history for windowing
    failure_history: RwLock<VecDeque<Instant>>,
}

/// Circuit breaker states
#[derive(Debug, Clone, Copy, PartialEq)]
enum CircuitBreakerState {
    /// Circuit is closed, allowing requests
    Closed,
    /// Circuit is open, rejecting requests
    Open,
    /// Circuit is half-open, testing recovery
    HalfOpen,
}

/// Connection migration handler
#[derive(Debug)]
struct ConnectionMigrationHandler {
    /// Active migrations
    active_migrations: RwLock<HashMap<PeerId, MigrationSession>>,
    /// Network change detector
    network_detector: NetworkChangeDetector,
}

/// Migration session
#[derive(Debug)]
struct MigrationSession {
    /// Peer being migrated
    peer_id: PeerId,
    /// Old connection path
    old_path: std::net::SocketAddr,
    /// New connection path
    new_path: std::net::SocketAddr,
    /// Migration start time
    start_time: Instant,
    /// Migration state
    state: MigrationState,
}

/// Migration states
#[derive(Debug, Clone, PartialEq)]
enum MigrationState {
    /// Detecting network change
    Detecting,
    /// Preparing migration
    Preparing,
    /// Migrating connection
    Migrating,
    /// Validating new path
    Validating,
    /// Migration completed
    Completed,
    /// Migration failed
    Failed,
}

/// Network change detector
#[derive(Debug)]
struct NetworkChangeDetector {
    /// Last known network state
    last_network_state: RwLock<NetworkState>,
    /// Change detection interval
    detection_interval: Duration,
}

/// Network state for change detection
#[derive(Debug, Clone, PartialEq)]
struct NetworkState {
    /// Active network interfaces
    interfaces: HashMap<String, InterfaceState>,
    /// Default route
    default_route: Option<std::net::SocketAddr>,
    /// DNS servers
    dns_servers: Vec<std::net::IpAddr>,
}

/// Interface state
#[derive(Debug, Clone, PartialEq)]
struct InterfaceState {
    /// Interface name
    name: String,
    /// Interface status
    status: String,
    /// IP addresses
    addresses: Vec<std::net::IpAddr>,
}

/// Resource cleanup manager
#[derive(Debug)]
struct ResourceCleanupManager {
    /// Cleanup tasks
    cleanup_tasks: RwLock<Vec<CleanupTask>>,
    /// Cleanup interval
    interval: Duration,
}

/// Cleanup task
#[derive(Debug)]
struct CleanupTask {
    /// Task identifier
    task_id: String,
    /// Resource to cleanup
    resource: CleanupResource,
    /// Cleanup time
    cleanup_time: Instant,
}

/// Resources that need cleanup
#[derive(Debug)]
enum CleanupResource {
    /// Connection resources
    Connection { peer_id: PeerId },
    /// Session resources
    Session { session_id: String },
    /// Temporary files
    TempFiles { paths: Vec<std::path::PathBuf> },
    /// Memory buffers
    MemoryBuffers { buffer_ids: Vec<String> },
}

impl ErrorRecoveryManager {
    /// Create new error recovery manager
    pub async fn new(config: RecoveryConfig) -> Result<Self, MonitoringError> {
        let recovery_sessions = Arc::new(RwLock::new(HashMap::new()));
        
        // Initialize retry policies for different error categories
        let mut retry_policies = HashMap::new();
        retry_policies.insert(ErrorCategory::NetworkConnectivity, RetryPolicy {
            max_attempts: 5,
            initial_delay: Duration::from_secs(1),
            max_delay: Duration::from_secs(60),
            backoff_multiplier: 2.0,
            enable_jitter: true,
            jitter_factor: 0.2,
            attempt_timeout: Duration::from_secs(15),
        });
        
        retry_policies.insert(ErrorCategory::NatTraversal, RetryPolicy {
            max_attempts: 3,
            initial_delay: Duration::from_secs(2),
            max_delay: Duration::from_secs(30),
            backoff_multiplier: 1.5,
            enable_jitter: true,
            jitter_factor: 0.1,
            attempt_timeout: Duration::from_secs(20),
        });
        
        retry_policies.insert(ErrorCategory::Timeout, RetryPolicy {
            max_attempts: 4,
            initial_delay: Duration::from_millis(500),
            max_delay: Duration::from_secs(45),
            backoff_multiplier: 2.5,
            enable_jitter: true,
            jitter_factor: 0.15,
            attempt_timeout: Duration::from_secs(25),
        });
        
        // Initialize fallback strategies
        let fallback_strategies = vec![
            FallbackStrategy::AlternativeNatMethod,
            FallbackStrategy::RelayServers,
            FallbackStrategy::DirectConnection,
            FallbackStrategy::ReducedRequirements,
        ];
        
        let circuit_breaker = Arc::new(CircuitBreaker::new(config.circuit_breaker_config.clone()));
        let migration_handler = Arc::new(ConnectionMigrationHandler::new().await?);
        let cleanup_manager = Arc::new(ResourceCleanupManager::new(config.cleanup_interval));
        
        Ok(Self {
            config,
            recovery_sessions,
            retry_policies,
            fallback_strategies,
            circuit_breaker,
            migration_handler,
            cleanup_manager,
        })
    }
    
    /// Start error recovery manager
    pub async fn start(&self) -> Result<(), MonitoringError> {
        info!("Starting error recovery manager");
        
        // Start background tasks
        self.start_cleanup_task().await?;
        self.start_migration_monitoring().await?;
        self.start_circuit_breaker_monitoring().await?;
        
        info!("Error recovery manager started");
        Ok(())
    }
    
    /// Stop error recovery manager
    pub async fn stop(&self) -> Result<(), MonitoringError> {
        info!("Stopping error recovery manager");
        
        // Cancel all active recovery sessions
        let mut sessions = self.recovery_sessions.write().await;
        for (_, session) in sessions.iter_mut() {
            session.state = RecoveryState::Cancelled;
        }
        sessions.clear();
        
        info!("Error recovery manager stopped");
        Ok(())
    }
    
    /// Initiate error recovery for a failed NAT traversal
    pub async fn initiate_recovery(
        &self,
        peer_id: PeerId,
        error: NatTraversalError,
    ) -> Result<String, MonitoringError> {
        // Check circuit breaker
        if !self.circuit_breaker.allow_request().await {
            return Err(MonitoringError::SystemError(
                "Circuit breaker is open, recovery not allowed".to_string()
            ));
        }
        
        // Check concurrent recovery limit
        let sessions = self.recovery_sessions.read().await;
        if sessions.len() >= self.config.max_concurrent_recoveries {
            return Err(MonitoringError::SystemError(
                "Maximum concurrent recoveries reached".to_string()
            ));
        }
        drop(sessions);
        
        let session_id = uuid::Uuid::new_v4().to_string();
        
        info!("Initiating error recovery for peer {:?} (session: {})", peer_id, session_id);
        
        // Determine recovery strategy based on error
        let strategy = self.determine_recovery_strategy(&error).await;
        let remaining_strategies = self.get_fallback_strategies(&error).await;
        
        let session = RecoverySession {
            session_id: session_id.clone(),
            peer_id,
            original_error: error,
            current_attempt: 0,
            start_time: Instant::now(),
            last_attempt_time: None,
            current_strategy: strategy,
            remaining_strategies,
            state: RecoveryState::InProgress,
        };
        
        // Store recovery session
        let mut sessions = self.recovery_sessions.write().await;
        sessions.insert(session_id.clone(), session);
        drop(sessions);
        
        // Start recovery process
        self.execute_recovery_strategy(session_id.clone()).await?;
        
        Ok(session_id)
    }
    
    /// Execute recovery strategy
    fn execute_recovery_strategy(&self, session_id: String) -> Pin<Box<dyn Future<Output = Result<(), MonitoringError>> + Send + '_>> {
        Box::pin(async move {
            let session = {
                let sessions = self.recovery_sessions.read().await;
                sessions.get(&session_id).cloned()
            };
            
            let mut session = session.ok_or_else(|| {
                MonitoringError::SystemError("Recovery session not found".to_string())
            })?;
            
            // Clone the strategy to avoid borrowing conflicts
            let strategy = session.current_strategy.clone();
            
            match strategy {
                RecoveryStrategy::Retry { policy } => {
                    self.execute_retry_strategy(&mut session, policy).await?;
                }
                RecoveryStrategy::AlternativeBootstrap { nodes } => {
                    self.execute_alternative_bootstrap(&mut session, nodes).await?;
                }
                RecoveryStrategy::RelayFallback { relay_servers } => {
                    self.execute_relay_fallback(&mut session, relay_servers).await?;
                }
                RecoveryStrategy::ConnectionMigration { new_path } => {
                    self.execute_connection_migration(&mut session, new_path).await?;
                }
                RecoveryStrategy::GracefulDegradation { reduced_functionality } => {
                    self.execute_graceful_degradation(&mut session, reduced_functionality).await?;
                }
            }
            
            // Update session
            let mut sessions = self.recovery_sessions.write().await;
            sessions.insert(session_id, session);
            
            Ok(())
        })
    }
    
    /// Execute retry strategy with exponential backoff
    async fn execute_retry_strategy(
        &self,
        session: &mut RecoverySession,
        policy: RetryPolicy,
    ) -> Result<(), MonitoringError> {
        session.current_attempt += 1;
        
        if session.current_attempt > policy.max_attempts {
            warn!("Maximum retry attempts reached for session {}", session.session_id);
            session.state = RecoveryState::Failed;
            return self.try_next_fallback_strategy(session).await;
        }
        
        // Calculate delay with exponential backoff and jitter
        let delay = self.calculate_retry_delay(&policy, session.current_attempt);
        
        info!(
            "Retrying recovery for session {} (attempt {}/{}) after {:?}",
            session.session_id, session.current_attempt, policy.max_attempts, delay
        );
        
        session.state = RecoveryState::WaitingRetry;
        session.last_attempt_time = Some(Instant::now());
        
        // Wait for retry delay
        sleep(delay).await;
        
        // Attempt recovery with timeout
        let recovery_result = timeout(
            policy.attempt_timeout,
            self.attempt_connection_recovery(session.peer_id)
        ).await;
        
        match recovery_result {
            Ok(Ok(())) => {
                info!("Recovery succeeded for session {}", session.session_id);
                session.state = RecoveryState::Succeeded;
                self.circuit_breaker.record_success().await;
            }
            Ok(Err(e)) => {
                warn!("Recovery attempt failed for session {}: {:?}", session.session_id, e);
                self.circuit_breaker.record_failure().await;
                // Will retry on next iteration
            }
            Err(_) => {
                warn!("Recovery attempt timed out for session {}", session.session_id);
                self.circuit_breaker.record_failure().await;
                // Will retry on next iteration
            }
        }
        
        Ok(())
    }
    
    /// Execute alternative bootstrap strategy
    async fn execute_alternative_bootstrap(
        &self,
        session: &mut RecoverySession,
        nodes: Vec<std::net::SocketAddr>,
    ) -> Result<(), MonitoringError> {
        info!("Trying alternative bootstrap nodes for session {}", session.session_id);
        
        for node in nodes {
            debug!("Attempting connection via bootstrap node: {}", node);
            
            match self.attempt_bootstrap_connection(session.peer_id, node).await {
                Ok(()) => {
                    info!("Alternative bootstrap connection succeeded for session {}", session.session_id);
                    session.state = RecoveryState::Succeeded;
                    return Ok(());
                }
                Err(e) => {
                    warn!("Alternative bootstrap node {} failed: {:?}", node, e);
                    continue;
                }
            }
        }
        
        warn!("All alternative bootstrap nodes failed for session {}", session.session_id);
        self.try_next_fallback_strategy(session).await
    }
    
    /// Execute relay fallback strategy
    async fn execute_relay_fallback(
        &self,
        session: &mut RecoverySession,
        relay_servers: Vec<std::net::SocketAddr>,
    ) -> Result<(), MonitoringError> {
        info!("Attempting relay fallback for session {}", session.session_id);
        
        for relay in relay_servers {
            debug!("Attempting relay connection via: {}", relay);
            
            match self.attempt_relay_connection(session.peer_id, relay).await {
                Ok(()) => {
                    info!("Relay connection succeeded for session {}", session.session_id);
                    session.state = RecoveryState::Succeeded;
                    return Ok(());
                }
                Err(e) => {
                    warn!("Relay server {} failed: {:?}", relay, e);
                    continue;
                }
            }
        }
        
        warn!("All relay servers failed for session {}", session.session_id);
        self.try_next_fallback_strategy(session).await
    }
    
    /// Execute connection migration
    async fn execute_connection_migration(
        &self,
        session: &mut RecoverySession,
        new_path: std::net::SocketAddr,
    ) -> Result<(), MonitoringError> {
        info!("Attempting connection migration for session {} to {}", session.session_id, new_path);
        
        match self.migration_handler.migrate_connection(session.peer_id, new_path).await {
            Ok(()) => {
                info!("Connection migration succeeded for session {}", session.session_id);
                session.state = RecoveryState::Succeeded;
                Ok(())
            }
            Err(e) => {
                warn!("Connection migration failed for session {}: {:?}", session.session_id, e);
                self.try_next_fallback_strategy(session).await
            }
        }
    }
    
    /// Execute graceful degradation
    async fn execute_graceful_degradation(
        &self,
        session: &mut RecoverySession,
        _reduced_functionality: bool,
    ) -> Result<(), MonitoringError> {
        info!("Applying graceful degradation for session {}", session.session_id);
        
        // Implement graceful degradation logic
        // This could involve:
        // - Reducing connection quality requirements
        // - Disabling optional features
        // - Using simplified protocols
        // - Accepting higher latency connections
        
        session.state = RecoveryState::Succeeded;
        Ok(())
    }
    
    /// Try next fallback strategy
    async fn try_next_fallback_strategy(&self, session: &mut RecoverySession) -> Result<(), MonitoringError> {
        if let Some(next_strategy) = session.remaining_strategies.pop() {
            info!("Trying next fallback strategy for session {}: {:?}", session.session_id, next_strategy);
            
            session.current_strategy = self.convert_fallback_to_strategy(next_strategy).await;
            session.current_attempt = 0;
            
            // Execute new strategy
            self.execute_recovery_strategy(session.session_id.clone()).await
        } else {
            warn!("All recovery strategies exhausted for session {}", session.session_id);
            session.state = RecoveryState::Failed;
            Ok(())
        }
    }
    
    /// Calculate retry delay with exponential backoff and jitter
    fn calculate_retry_delay(&self, policy: &RetryPolicy, attempt: u32) -> Duration {
        let base_delay = policy.initial_delay.as_millis() as f64;
        let exponential_delay = base_delay * policy.backoff_multiplier.powi(attempt as i32 - 1);
        let capped_delay = exponential_delay.min(policy.max_delay.as_millis() as f64);
        
        let final_delay = if policy.enable_jitter {
            let jitter = capped_delay * policy.jitter_factor * (rand::random::<f64>() - 0.5);
            capped_delay + jitter
        } else {
            capped_delay
        };
        
        Duration::from_millis(final_delay.max(0.0) as u64)
    }
    
    /// Determine recovery strategy based on error
    async fn determine_recovery_strategy(&self, error: &NatTraversalError) -> RecoveryStrategy {
        match error {
            NatTraversalError::NoBootstrapNodes => {
                RecoveryStrategy::AlternativeBootstrap {
                    nodes: vec!["fallback1.example.com:9000".parse().unwrap()],
                }
            }
            NatTraversalError::HolePunchingFailed => {
                RecoveryStrategy::RelayFallback {
                    relay_servers: vec!["relay1.example.com:9000".parse().unwrap()],
                }
            }
            NatTraversalError::Timeout => {
                RecoveryStrategy::Retry {
                    policy: self.retry_policies.get(&ErrorCategory::Timeout)
                        .cloned()
                        .unwrap_or_else(|| self.config.default_retry_policy.clone()),
                }
            }
            _ => {
                RecoveryStrategy::Retry {
                    policy: self.config.default_retry_policy.clone(),
                }
            }
        }
    }
    
    /// Get fallback strategies for error type
    async fn get_fallback_strategies(&self, _error: &NatTraversalError) -> Vec<FallbackStrategy> {
        self.fallback_strategies.clone()
    }
    
    /// Convert fallback strategy to recovery strategy
    async fn convert_fallback_to_strategy(&self, fallback: FallbackStrategy) -> RecoveryStrategy {
        match fallback {
            FallbackStrategy::AlternativeNatMethod => {
                RecoveryStrategy::Retry {
                    policy: self.config.default_retry_policy.clone(),
                }
            }
            FallbackStrategy::RelayServers => {
                RecoveryStrategy::RelayFallback {
                    relay_servers: vec!["relay1.example.com:9000".parse().unwrap()],
                }
            }
            FallbackStrategy::DirectConnection => {
                RecoveryStrategy::GracefulDegradation {
                    reduced_functionality: true,
                }
            }
            FallbackStrategy::ReducedRequirements => {
                RecoveryStrategy::GracefulDegradation {
                    reduced_functionality: true,
                }
            }
            FallbackStrategy::ManualIntervention => {
                RecoveryStrategy::GracefulDegradation {
                    reduced_functionality: true,
                }
            }
        }
    }
    
    /// Attempt connection recovery (placeholder implementation)
    async fn attempt_connection_recovery(&self, _peer_id: PeerId) -> Result<(), MonitoringError> {
        // Simulate recovery attempt
        sleep(Duration::from_millis(100)).await;
        
        // Simulate success/failure
        if rand::random::<f64>() > 0.3 {
            Ok(())
        } else {
            Err(MonitoringError::SystemError("Recovery failed".to_string()))
        }
    }
    
    /// Attempt bootstrap connection (placeholder implementation)
    async fn attempt_bootstrap_connection(&self, _peer_id: PeerId, _node: std::net::SocketAddr) -> Result<(), MonitoringError> {
        // Simulate bootstrap connection attempt
        sleep(Duration::from_millis(200)).await;
        
        if rand::random::<f64>() > 0.4 {
            Ok(())
        } else {
            Err(MonitoringError::SystemError("Bootstrap connection failed".to_string()))
        }
    }
    
    /// Attempt relay connection (placeholder implementation)
    async fn attempt_relay_connection(&self, _peer_id: PeerId, _relay: std::net::SocketAddr) -> Result<(), MonitoringError> {
        // Simulate relay connection attempt
        sleep(Duration::from_millis(300)).await;
        
        if rand::random::<f64>() > 0.2 {
            Ok(())
        } else {
            Err(MonitoringError::SystemError("Relay connection failed".to_string()))
        }
    }
    
    /// Start cleanup task
    async fn start_cleanup_task(&self) -> Result<(), MonitoringError> {
        // Implementation would start background cleanup task
        debug!("Starting resource cleanup task");
        Ok(())
    }
    
    /// Start migration monitoring
    async fn start_migration_monitoring(&self) -> Result<(), MonitoringError> {
        // Implementation would start network change monitoring
        debug!("Starting connection migration monitoring");
        Ok(())
    }
    
    /// Start circuit breaker monitoring
    async fn start_circuit_breaker_monitoring(&self) -> Result<(), MonitoringError> {
        // Implementation would start circuit breaker monitoring
        debug!("Starting circuit breaker monitoring");
        Ok(())
    }
    
    /// Get recovery statistics
    pub async fn get_recovery_statistics(&self) -> RecoveryStatistics {
        let sessions = self.recovery_sessions.read().await;
        
        let total_sessions = sessions.len();
        let successful_recoveries = sessions.values()
            .filter(|s| s.state == RecoveryState::Succeeded)
            .count();
        let failed_recoveries = sessions.values()
            .filter(|s| s.state == RecoveryState::Failed)
            .count();
        let active_recoveries = sessions.values()
            .filter(|s| s.state == RecoveryState::InProgress)
            .count();
        
        RecoveryStatistics {
            total_sessions,
            successful_recoveries,
            failed_recoveries,
            active_recoveries,
            success_rate: if total_sessions > 0 {
                successful_recoveries as f64 / total_sessions as f64
            } else {
                0.0
            },
        }
    }
}

/// Recovery statistics
#[derive(Debug, Clone)]
pub struct RecoveryStatistics {
    pub total_sessions: usize,
    pub successful_recoveries: usize,
    pub failed_recoveries: usize,
    pub active_recoveries: usize,
    pub success_rate: f64,
}

// Implementation of helper structs

impl CircuitBreaker {
    fn new(config: CircuitBreakerConfig) -> Self {
        Self {
            config,
            state: RwLock::new(CircuitBreakerState::Closed),
            failure_count: RwLock::new(0),
            success_count: RwLock::new(0),
            last_state_change: RwLock::new(Instant::now()),
            failure_history: RwLock::new(VecDeque::new()),
        }
    }
    
    async fn allow_request(&self) -> bool {
        let state = *self.state.read().await;
        
        match state {
            CircuitBreakerState::Closed => true,
            CircuitBreakerState::Open => {
                let last_change = *self.last_state_change.read().await;
                if last_change.elapsed() > self.config.timeout {
                    // Try half-open state
                    *self.state.write().await = CircuitBreakerState::HalfOpen;
                    *self.success_count.write().await = 0;
                    true
                } else {
                    false
                }
            }
            CircuitBreakerState::HalfOpen => true,
        }
    }
    
    async fn record_success(&self) {
        let state = *self.state.read().await;
        
        match state {
            CircuitBreakerState::HalfOpen => {
                let mut success_count = self.success_count.write().await;
                *success_count += 1;
                
                if *success_count >= self.config.success_threshold {
                    *self.state.write().await = CircuitBreakerState::Closed;
                    *self.failure_count.write().await = 0;
                    *self.last_state_change.write().await = Instant::now();
                }
            }
            _ => {
                // Reset failure count on success
                *self.failure_count.write().await = 0;
            }
        }
    }
    
    async fn record_failure(&self) {
        let mut failure_count = self.failure_count.write().await;
        *failure_count += 1;
        
        // Add to failure history
        let mut history = self.failure_history.write().await;
        history.push_back(Instant::now());
        
        // Remove old failures outside window
        let cutoff = Instant::now() - self.config.window_size;
        while let Some(&front_time) = history.front() {
            if front_time < cutoff {
                history.pop_front();
            } else {
                break;
            }
        }
        
        // Check if we should open circuit
        if history.len() >= self.config.failure_threshold as usize {
            *self.state.write().await = CircuitBreakerState::Open;
            *self.last_state_change.write().await = Instant::now();
        }
    }
}

impl ConnectionMigrationHandler {
    async fn new() -> Result<Self, MonitoringError> {
        Ok(Self {
            active_migrations: RwLock::new(HashMap::new()),
            network_detector: NetworkChangeDetector::new(),
        })
    }
    
    async fn migrate_connection(&self, peer_id: PeerId, new_path: std::net::SocketAddr) -> Result<(), MonitoringError> {
        info!("Migrating connection for peer {:?} to {}", peer_id, new_path);
        
        // Simulate migration process
        sleep(Duration::from_millis(500)).await;
        
        if rand::random::<f64>() > 0.1 {
            Ok(())
        } else {
            Err(MonitoringError::SystemError("Migration failed".to_string()))
        }
    }
}

impl NetworkChangeDetector {
    fn new() -> Self {
        Self {
            last_network_state: RwLock::new(NetworkState {
                interfaces: HashMap::new(),
                default_route: None,
                dns_servers: Vec::new(),
            }),
            detection_interval: Duration::from_secs(5),
        }
    }
}

impl ResourceCleanupManager {
    fn new(interval: Duration) -> Self {
        Self {
            cleanup_tasks: RwLock::new(Vec::new()),
            interval,
        }
    }
}

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

    #[tokio::test]
    async fn test_error_recovery_manager_creation() {
        let config = RecoveryConfig::default();
        let manager = ErrorRecoveryManager::new(config).await.unwrap();
        
        let stats = manager.get_recovery_statistics().await;
        assert_eq!(stats.total_sessions, 0);
    }

    #[tokio::test]
    async fn test_retry_delay_calculation() {
        let config = RecoveryConfig::default();
        let manager = ErrorRecoveryManager::new(config).await.unwrap();
        
        let policy = RetryPolicy {
            initial_delay: Duration::from_millis(100),
            backoff_multiplier: 2.0,
            max_delay: Duration::from_secs(10),
            enable_jitter: false,
            jitter_factor: 0.0,
            ..RetryPolicy::default()
        };
        
        let delay1 = manager.calculate_retry_delay(&policy, 1);
        let delay2 = manager.calculate_retry_delay(&policy, 2);
        let delay3 = manager.calculate_retry_delay(&policy, 3);
        
        assert_eq!(delay1, Duration::from_millis(100));
        assert_eq!(delay2, Duration::from_millis(200));
        assert_eq!(delay3, Duration::from_millis(400));
    }

    #[tokio::test]
    async fn test_circuit_breaker() {
        let config = CircuitBreakerConfig {
            failure_threshold: 2,
            success_threshold: 1,
            timeout: Duration::from_millis(100),
            window_size: Duration::from_secs(60),
        };
        
        let breaker = CircuitBreaker::new(config);
        
        // Initially closed
        assert!(breaker.allow_request().await);
        
        // Record failures
        breaker.record_failure().await;
        breaker.record_failure().await;
        
        // Should be open now
        assert!(!breaker.allow_request().await);
        
        // Wait for timeout
        tokio::time::sleep(Duration::from_millis(150)).await;
        
        // Should allow request in half-open state
        assert!(breaker.allow_request().await);
        
        // Record success to close circuit
        breaker.record_success().await;
        assert!(breaker.allow_request().await);
    }
}