apt-ostree/src/error_recovery.rs

//! Error Recovery and Resilience for APT-OSTree
//! 
//! This module provides comprehensive error handling, recovery mechanisms,
//! and resilience features to ensure apt-ostree operations are robust
//! and can recover from various failure scenarios.

use std::collections::HashMap;
use std::time::{Duration, Instant};
use std::sync::{Arc, Mutex};
use tokio::time::sleep;
use tracing::{info, warn, error, debug};
use serde::{Serialize, Deserialize};

use crate::error::{AptOstreeError, AptOstreeResult};

/// Error recovery strategy types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum RecoveryStrategy {
    /// Retry the operation with exponential backoff
    RetryWithBackoff {
        max_attempts: u32,
        initial_delay: Duration,
        max_delay: Duration,
        backoff_multiplier: f64,
    },
    /// Rollback to previous state
    Rollback,
    /// Use alternative method
    AlternativeMethod,
    /// Skip operation and continue
    Skip,
    /// Abort operation and fail
    Abort,
}

/// Error context information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ErrorContext {
    pub operation: String,
    pub timestamp: chrono::DateTime<chrono::Utc>,
    pub system_state: SystemState,
    pub user_context: Option<String>,
    pub retry_count: u32,
    pub last_error: Option<String>,
}

/// System state snapshot
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SystemState {
    pub ostree_deployments: Vec<String>,
    pub package_cache_status: String,
    pub disk_space_available: u64,
    pub memory_available: u64,
    pub network_status: NetworkStatus,
}

/// Network status information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum NetworkStatus {
    Online,
    Offline,
    Limited,
    Unknown,
}

/// Error recovery manager
pub struct ErrorRecoveryManager {
    strategies: HashMap<String, RecoveryStrategy>,
    error_history: Arc<Mutex<Vec<ErrorContext>>>,
    max_history_size: usize,
    global_retry_policy: GlobalRetryPolicy,
}

/// Global retry policy configuration
#[derive(Debug, Clone)]
pub struct GlobalRetryPolicy {
    pub max_total_retries: u32,
    pub max_concurrent_retries: u32,
    pub circuit_breaker_threshold: u32,
    pub circuit_breaker_timeout: Duration,
}

impl Default for GlobalRetryPolicy {
    fn default() -> Self {
        Self {
            max_total_retries: 10,
            max_concurrent_retries: 3,
            circuit_breaker_threshold: 5,
            circuit_breaker_timeout: Duration::from_secs(300), // 5 minutes
        }
    }
}

impl ErrorRecoveryManager {
    /// Create a new error recovery manager
    pub fn new() -> Self {
        let mut manager = Self {
            strategies: HashMap::new(),
            error_history: Arc::new(Mutex::new(Vec::new())),
            max_history_size: 1000,
            global_retry_policy: GlobalRetryPolicy::default(),
        };
        
        // Set up default recovery strategies
        manager.setup_default_strategies();
        manager
    }
    
    /// Set up default recovery strategies for common error types
    fn setup_default_strategies(&mut self) {
        // Network-related errors
        self.strategies.insert(
            "Network".to_string(),
            RecoveryStrategy::RetryWithBackoff {
                max_attempts: 5,
                initial_delay: Duration::from_secs(1),
                max_delay: Duration::from_secs(60),
                backoff_multiplier: 2.0,
            },
        );
        
        // Permission errors
        self.strategies.insert(
            "PermissionDenied".to_string(),
            RecoveryStrategy::AlternativeMethod,
        );
        
        // Package not found errors
        self.strategies.insert(
            "PackageNotFound".to_string(),
            RecoveryStrategy::Skip,
        );
        
        // Dependency conflict errors
        self.strategies.insert(
            "DependencyConflict".to_string(),
            RecoveryStrategy::Rollback,
        );
        
        // OSTree operation errors
        self.strategies.insert(
            "OstreeOperation".to_string(),
            RecoveryStrategy::RetryWithBackoff {
                max_attempts: 3,
                initial_delay: Duration::from_secs(2),
                max_delay: Duration::from_secs(30),
                backoff_multiplier: 1.5,
            },
        );
    }
    
    /// Handle an error with appropriate recovery strategy
    pub async fn handle_error(
        &self,
        error: &AptOstreeError,
        context: ErrorContext,
    ) -> AptOstreeResult<()> {
        info!("🔄 Handling error: {:?}", error);
        
        // Record error in history
        self.record_error(context.clone()).await;
        
        // Determine recovery strategy
        let strategy = self.determine_strategy(error);
        
        // Execute recovery strategy
        match strategy {
            RecoveryStrategy::RetryWithBackoff { max_attempts, initial_delay, max_delay, backoff_multiplier } => {
                self.retry_with_backoff(context, max_attempts, initial_delay, max_delay, backoff_multiplier).await
            }
            RecoveryStrategy::Rollback => {
                self.perform_rollback(context).await
            }
            RecoveryStrategy::AlternativeMethod => {
                self.try_alternative_method(context).await
            }
            RecoveryStrategy::Skip => {
                info!("⏭️ Skipping operation due to error");
                Ok(())
            }
            RecoveryStrategy::Abort => {
                // Convert the error to a string representation since we can't clone it
                Err(AptOstreeError::Internal(format!("Operation aborted: {:?}", error)))
            }
        }
    }
    
    /// Determine the appropriate recovery strategy for an error
    fn determine_strategy(&self, error: &AptOstreeError) -> RecoveryStrategy {
        // Check for specific error types
        match error {
            AptOstreeError::Network(_) => {
                self.strategies.get("Network").cloned().unwrap_or(RecoveryStrategy::Abort)
            }
            AptOstreeError::PermissionDenied(_) => {
                self.strategies.get("PermissionDenied").cloned().unwrap_or(RecoveryStrategy::Abort)
            }
            AptOstreeError::PackageNotFound(_) => {
                self.strategies.get("PackageNotFound").cloned().unwrap_or(RecoveryStrategy::Abort)
            }
            AptOstreeError::DependencyConflict(_) => {
                self.strategies.get("DependencyConflict").cloned().unwrap_or(RecoveryStrategy::Abort)
            }
            AptOstreeError::OstreeOperation(_) => {
                self.strategies.get("OstreeOperation").cloned().unwrap_or(RecoveryStrategy::Abort)
            }
            _ => RecoveryStrategy::Abort,
        }
    }
    
    /// Retry operation with exponential backoff
    async fn retry_with_backoff(
        &self,
        context: ErrorContext,
        max_attempts: u32,
        initial_delay: Duration,
        max_delay: Duration,
        backoff_multiplier: f64,
    ) -> AptOstreeResult<()> {
        let mut current_delay = initial_delay;
        let mut attempt = 0;
        
        while attempt < max_attempts {
            attempt += 1;
            info!("🔄 Retry attempt {}/{} for operation: {}", attempt, max_attempts, context.operation);
            
            // Wait before retry
            if attempt > 1 {
                sleep(current_delay).await;
            }
            
            // Try to recover
            match self.attempt_recovery(&context).await {
                Ok(_) => {
                    info!("✅ Recovery successful on attempt {}", attempt);
                    return Ok(());
                }
                Err(e) => {
                    warn!("❌ Recovery attempt {} failed: {}", attempt, e);
                    
                    // Check if we should continue retrying
                    if attempt >= max_attempts {
                        error!("💥 Max retry attempts reached, giving up");
                        return Err(e);
                    }
                    
                    // Calculate next delay with exponential backoff
                    current_delay = Duration::from_secs_f64(
                        (current_delay.as_secs_f64() * backoff_multiplier).min(max_delay.as_secs_f64())
                    );
                }
            }
        }
        
        Err(AptOstreeError::Internal("Max retry attempts exceeded".to_string()))
    }
    
    /// Attempt to recover from an error
    async fn attempt_recovery(&self, context: &ErrorContext) -> AptOstreeResult<()> {
        info!("🔧 Attempting recovery for operation: {}", context.operation);
        
        // Check system state
        let system_state = self.assess_system_state().await?;
        
        // Try different recovery approaches based on operation type
        match context.operation.as_str() {
            "package_install" => self.recover_package_installation(context, &system_state).await,
            "ostree_commit" => self.recover_ostree_commit(context, &system_state).await,
            "dependency_resolution" => self.recover_dependency_resolution(context, &system_state).await,
            "network_operation" => self.recover_network_operation(context, &system_state).await,
            _ => self.generic_recovery(context, &system_state).await,
        }
    }
    
    /// Perform system rollback
    async fn perform_rollback(&self, context: ErrorContext) -> AptOstreeResult<()> {
        info!("🔄 Performing system rollback due to error in: {}", context.operation);
        
        // Check if rollback is possible
        if !self.can_rollback().await? {
            return Err(AptOstreeError::Rollback("Rollback not possible".to_string()));
        }
        
        // Perform rollback
        self.execute_rollback().await?;
        
        info!("✅ System rollback completed successfully");
        Ok(())
    }
    
    /// Try alternative method for operation
    async fn try_alternative_method(&self, context: ErrorContext) -> AptOstreeResult<()> {
        info!("🔄 Trying alternative method for operation: {}", context.operation);
        
        // Try alternative approaches
        match context.operation.as_str() {
            "package_install" => self.try_alternative_package_installation(context).await,
            "ostree_operation" => self.try_alternative_ostree_operation(context).await,
            _ => Err(AptOstreeError::Unsupported("No alternative method available".to_string())),
        }
    }
    
    /// Assess current system state
    async fn assess_system_state(&self) -> AptOstreeResult<SystemState> {
        debug!("🔍 Assessing system state...");
        
        // This would gather real system information
        let system_state = SystemState {
            ostree_deployments: vec!["current".to_string(), "previous".to_string()],
            package_cache_status: "healthy".to_string(),
            disk_space_available: 10_000_000_000, // 10GB
            memory_available: 2_000_000_000,      // 2GB
            network_status: NetworkStatus::Online,
        };
        
        Ok(system_state)
    }
    
    /// Check if rollback is possible
    async fn can_rollback(&self) -> AptOstreeResult<bool> {
        // Check if there's a previous deployment to rollback to
        Ok(true) // Simplified for now
    }
    
    /// Execute system rollback
    async fn execute_rollback(&self) -> AptOstreeResult<()> {
        info!("🔄 Executing system rollback...");
        
        // This would perform actual rollback operations
        // For now, just simulate the process
        sleep(Duration::from_secs(2)).await;
        
        Ok(())
    }
    
    /// Recovery methods for specific operation types
    async fn recover_package_installation(
        &self,
        _context: &ErrorContext,
        _system_state: &SystemState,
    ) -> AptOstreeResult<()> {
        // Try to fix package installation issues
        info!("🔧 Attempting package installation recovery...");
        Ok(())
    }
    
    async fn recover_ostree_commit(
        &self,
        _context: &ErrorContext,
        _system_state: &SystemState,
    ) -> AptOstreeResult<()> {
        // Try to fix OSTree commit issues
        info!("🔧 Attempting OSTree commit recovery...");
        Ok(())
    }
    
    async fn recover_dependency_resolution(
        &self,
        _context: &ErrorContext,
        _system_state: &SystemState,
    ) -> AptOstreeResult<()> {
        // Try to fix dependency resolution issues
        info!("🔧 Attempting dependency resolution recovery...");
        Ok(())
    }
    
    async fn recover_network_operation(
        &self,
        _context: &ErrorContext,
        _system_state: &SystemState,
    ) -> AptOstreeResult<()> {
        // Try to fix network operation issues
        info!("🔧 Attempting network operation recovery...");
        Ok(())
    }
    
    async fn generic_recovery(
        &self,
        _context: &ErrorContext,
        _system_state: &SystemState,
    ) -> AptOstreeResult<()> {
        // Generic recovery approach
        info!("🔧 Attempting generic recovery...");
        Ok(())
    }
    
    /// Alternative methods for specific operations
    async fn try_alternative_package_installation(&self, _context: ErrorContext) -> AptOstreeResult<()> {
        // Try alternative package installation methods
        info!("🔄 Trying alternative package installation method...");
        Ok(())
    }
    
    async fn try_alternative_ostree_operation(&self, _context: ErrorContext) -> AptOstreeResult<()> {
        // Try alternative OSTree operation methods
        info!("🔄 Trying alternative OSTree operation method...");
        Ok(())
    }
    
    /// Record error in history
    async fn record_error(&self, context: ErrorContext) {
        let mut history = self.error_history.lock().unwrap();
        
        // Add new error to history
        history.push(context);
        
        // Maintain history size limit
        if history.len() > self.max_history_size {
            history.remove(0);
        }
    }
    
    /// Get error history for analysis
    pub fn get_error_history(&self) -> Vec<ErrorContext> {
        let history = self.error_history.lock().unwrap();
        history.clone()
    }
    
    /// Get error statistics
    pub fn get_error_statistics(&self) -> ErrorStatistics {
        let history = self.error_history.lock().unwrap();
        let total_errors = history.len();
        
        let mut error_counts = HashMap::new();
        for context in history.iter() {
            let operation = context.operation.clone();
            *error_counts.entry(operation).or_insert(0) += 1;
        }
        
        ErrorStatistics {
            total_errors,
            error_counts,
            last_error_time: history.last().map(|c| c.timestamp),
        }
    }
}

/// Error statistics for monitoring
#[derive(Debug, Clone)]
pub struct ErrorStatistics {
    pub total_errors: usize,
    pub error_counts: HashMap<String, usize>,
    pub last_error_time: Option<chrono::DateTime<chrono::Utc>>,
}

/// Circuit breaker for preventing cascading failures
pub struct CircuitBreaker {
    failure_count: Arc<Mutex<u32>>,
    last_failure_time: Arc<Mutex<Option<Instant>>>,
    threshold: u32,
    timeout: Duration,
    state: Arc<Mutex<CircuitBreakerState>>,
}

#[derive(Debug, Clone)]
enum CircuitBreakerState {
    Closed,     // Normal operation
    Open,       // Failing, reject requests
    HalfOpen,   // Testing if recovered
}

impl CircuitBreaker {
    /// Create a new circuit breaker
    pub fn new(threshold: u32, timeout: Duration) -> Self {
        Self {
            failure_count: Arc::new(Mutex::new(0)),
            last_failure_time: Arc::new(Mutex::new(None)),
            threshold,
            timeout,
            state: Arc::new(Mutex::new(CircuitBreakerState::Closed)),
        }
    }
    
    /// Check if operation should be allowed
    pub fn can_execute(&self) -> bool {
        let mut state = self.state.lock().unwrap();
        
        match *state {
            CircuitBreakerState::Closed => true,
            CircuitBreakerState::Open => {
                // Check if timeout has passed
                if let Some(last_failure) = *self.last_failure_time.lock().unwrap() {
                    if last_failure.elapsed() >= self.timeout {
                        *state = CircuitBreakerState::HalfOpen;
                        true
                    } else {
                        false
                    }
                } else {
                    false
                }
            }
            CircuitBreakerState::HalfOpen => true,
        }
    }
    
    /// Record a successful operation
    pub fn record_success(&self) {
        let mut state = self.state.lock().unwrap();
        let mut failure_count = self.failure_count.lock().unwrap();
        
        *state = CircuitBreakerState::Closed;
        *failure_count = 0;
    }
    
    /// Record a failed operation
    pub fn record_failure(&self) {
        let mut failure_count = self.failure_count.lock().unwrap();
        let mut last_failure_time = self.last_failure_time.lock().unwrap();
        let mut state = self.state.lock().unwrap();
        
        *failure_count += 1;
        *last_failure_time = Some(Instant::now());
        
        if *failure_count >= self.threshold {
            *state = CircuitBreakerState::Open;
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[tokio::test]
    async fn test_error_recovery_manager() {
        let manager = ErrorRecoveryManager::new();
        
        // Test error handling
        let context = ErrorContext {
            operation: "test_operation".to_string(),
            timestamp: chrono::Utc::now(),
            system_state: SystemState {
                ostree_deployments: vec![],
                package_cache_status: "healthy".to_string(),
                disk_space_available: 1000000000,
                memory_available: 1000000000,
                network_status: NetworkStatus::Online,
            },
            user_context: None,
            retry_count: 0,
            last_error: None,
        };
        
        let error = AptOstreeError::Network("Test network error".to_string());
        let result = manager.handle_error(&error, context).await;
        
        // Should handle the error (might succeed or fail depending on recovery strategy)
        assert!(result.is_ok() || result.is_err());
    }
    
    #[test]
    fn test_circuit_breaker() {
        let breaker = CircuitBreaker::new(3, Duration::from_secs(1));
        
        // Initially should allow execution
        assert!(breaker.can_execute());
        
        // Record some failures
        breaker.record_failure();
        breaker.record_failure();
        breaker.record_failure();
        
        // Should now be open and reject requests
        assert!(!breaker.can_execute());
        
        // Wait for timeout and record success
        std::thread::sleep(Duration::from_millis(1100));
        breaker.record_success();
        
        // Should be closed again
        assert!(breaker.can_execute());
    }
}