//! Fault tolerance and recovery mechanisms
//!
//! This module handles failure detection, recovery strategies, redundancy management,
//! and checkpointing for the distributed computing framework.

use super::communication::CompressionSettings;
use super::scheduling::TaskId;
use super::types::DistributedComputingConfig;
use crate::error::{CoreError, CoreResult};
use std::collections::HashMap;
use std::time::Duration;

/// Fault tolerance manager
#[derive(Debug)]
pub struct FaultToleranceManager {
    /// Failure detection
    #[allow(dead_code)]
    failure_detection: FailureDetection,
    /// Recovery strategies
    #[allow(dead_code)]
    recovery_strategies: Vec<RecoveryStrategy>,
    /// Redundancy management
    #[allow(dead_code)]
    redundancy: RedundancyManager,
    /// Checkpointing system
    #[allow(dead_code)]
    checkpointing: CheckpointingSystem,
}

/// Failure detection
#[derive(Debug)]
pub struct FailureDetection {
    /// Detection algorithms
    #[allow(dead_code)]
    algorithms: Vec<FailureDetectionAlgorithm>,
    /// Failure patterns
    #[allow(dead_code)]
    patterns: HashMap<String, FailurePattern>,
    /// Detection thresholds
    #[allow(dead_code)]
    thresholds: FailureThresholds,
}

/// Failure detection algorithms
#[derive(Debug, Clone)]
pub enum FailureDetectionAlgorithm {
    Heartbeat,
    StatisticalAnomalyDetection,
    MachineLearningBased,
    NetworkTopologyAnalysis,
    ResourceUsageAnalysis,
}

/// Failure pattern
#[derive(Debug, Clone)]
pub struct FailurePattern {
    /// Pattern name
    pub name: String,
    /// Symptoms
    pub symptoms: Vec<String>,
    /// Probability indicators
    pub indicators: HashMap<String, f64>,
    /// Historical occurrences
    pub occurrences: u32,
}

/// Failure detection thresholds
#[derive(Debug, Clone)]
pub struct FailureThresholds {
    /// Heartbeat timeout
    pub heartbeat_timeout: Duration,
    /// Response time threshold
    pub response_time_threshold: Duration,
    /// Error rate threshold
    pub error_rate_threshold: f64,
    /// Resource usage anomaly threshold
    pub resource_anomaly_threshold: f64,
}

/// Recovery strategies
#[derive(Debug, Clone)]
pub enum RecoveryStrategy {
    TaskMigration,
    NodeRestart,
    ResourceReallocation,
    Checkpointing,
    Redundancy,
    GracefulDegradation,
}

/// Redundancy manager
#[derive(Debug)]
pub struct RedundancyManager {
    /// Replication factor
    #[allow(dead_code)]
    replication_factor: u32,
    /// Replica placement strategy
    #[allow(dead_code)]
    placement_strategy: ReplicaPlacementStrategy,
    /// Consistency level
    #[allow(dead_code)]
    consistency_level: ConsistencyLevel,
}

/// Replica placement strategies
#[derive(Debug, Clone)]
pub enum ReplicaPlacementStrategy {
    Random,
    GeographicallyDistributed,
    ResourceBased,
    FaultDomainAware,
    LatencyOptimized,
}

/// Consistency levels
#[derive(Debug, Clone)]
pub enum ConsistencyLevel {
    Strong,
    Eventual,
    Weak,
    Causal,
}

/// Checkpointing system
#[derive(Debug)]
pub struct CheckpointingSystem {
    /// Checkpoint storage
    #[allow(dead_code)]
    storage: CheckpointStorage,
    /// Checkpoint frequency
    #[allow(dead_code)]
    frequency: CheckpointFrequency,
    /// Compression settings
    #[allow(dead_code)]
    compression: CompressionSettings,
}

/// Checkpoint storage
#[derive(Debug, Clone)]
pub enum CheckpointStorage {
    LocalDisk,
    DistributedFileSystem,
    ObjectStorage,
    InMemory,
    Hybrid,
}

/// Checkpoint frequency
#[derive(Debug, Clone)]
pub enum CheckpointFrequency {
    TimeBased(Duration),
    OperationBased(u32),
    AdaptiveBased,
    Manual,
}

// Implementations
impl FaultToleranceManager {
    pub fn new(config: &DistributedComputingConfig) -> CoreResult<Self> {
        Ok(Self {
            failure_detection: FailureDetection {
                algorithms: vec![
                    FailureDetectionAlgorithm::Heartbeat,
                    FailureDetectionAlgorithm::MachineLearningBased,
                ],
                patterns: HashMap::new(),
                thresholds: FailureThresholds {
                    heartbeat_timeout: Duration::from_secs(30),
                    response_time_threshold: Duration::from_millis(5000),
                    error_rate_threshold: 0.1,
                    resource_anomaly_threshold: 2.0,
                },
            },
            recovery_strategies: vec![
                RecoveryStrategy::TaskMigration,
                RecoveryStrategy::Redundancy,
                RecoveryStrategy::Checkpointing,
            ],
            redundancy: RedundancyManager {
                replication_factor: 3,
                placement_strategy: ReplicaPlacementStrategy::FaultDomainAware,
                consistency_level: ConsistencyLevel::Strong,
            },
            checkpointing: CheckpointingSystem {
                storage: CheckpointStorage::DistributedFileSystem,
                frequency: CheckpointFrequency::AdaptiveBased,
                compression: CompressionSettings {
                    algorithm: super::communication::CompressionAlgorithm::Zstd,
                    level: 5,
                    minsize_bytes: 1024,
                    adaptive: true,
                },
            },
        })
    }

    /// Register a task for advanced monitoring
    pub fn register_task_for_advancedmonitoring(&self, _taskid: &TaskId) -> CoreResult<()> {
        // Advanced monitoring registration logic
        println!("📊 Registering task for advanced monitoring");
        Ok(())
    }

    /// Set up predictive monitoring for a task
    pub fn cancel_task(&self, _taskid: &TaskId) -> CoreResult<()> {
        // Predictive monitoring setup logic
        println!("🔮 Setting up predictive monitoring");
        Ok(())
    }

    /// Enable fault prediction for a task
    pub fn enable_fault_prediction(&self, _taskid: &TaskId) -> CoreResult<()> {
        // Fault prediction enablement logic
        println!("🎯 Enabling fault prediction");
        Ok(())
    }

    /// Setup anomaly detection for a task
    pub fn setup_anomaly_detection(&self, _taskid: &TaskId) -> CoreResult<()> {
        // Anomaly detection setup logic
        println!("🚨 Setting up anomaly detection");
        Ok(())
    }

    /// Setup cascading failure prevention for a task
    pub fn setup_cascading_failure_prevention(&self, _taskid: &TaskId) -> CoreResult<()> {
        // Cascading failure prevention setup logic
        println!("🛡️ Setting up cascading failure prevention");
        Ok(())
    }

    /// Setup adaptive recovery strategies for a task
    pub fn setup_adaptive_recovery_strategies(&self, _taskid: &TaskId) -> CoreResult<()> {
        // Adaptive recovery strategies setup logic
        println!("♻️ Setting up adaptive recovery strategies");
        Ok(())
    }

    /// Enable proactive checkpoint creation for a task
    pub fn enable_proactive_checkpoint_creation(&self, _taskid: &TaskId) -> CoreResult<()> {
        // Proactive checkpoint creation enablement logic
        println!("💾 Enabling proactive checkpoint creation");
        Ok(())
    }

    /// Setup intelligent load balancing for a task
    pub fn setup_intelligent_load_balancing(&self, _taskid: &TaskId) -> CoreResult<()> {
        // Intelligent load balancing setup logic
        println!("⚖️ Setting up intelligent load balancing");
        Ok(())
    }
}
