quantrs2-device 0.1.3

//! Fault tolerance types and implementations for distributed quantum computation

use super::super::types::*;
use async_trait::async_trait;
use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use std::time::Duration;
use uuid::Uuid;

/// Fault tolerance management system
#[derive(Debug)]
pub struct FaultToleranceManager {
    pub fault_detectors: Vec<Box<dyn FaultDetector + Send + Sync>>,
    pub recovery_strategies: HashMap<String, Box<dyn RecoveryStrategy + Send + Sync>>,
    pub checkpointing_system: Arc<CheckpointingSystem>,
    pub redundancy_manager: Arc<RedundancyManager>,
}

/// Trait for fault detection
#[async_trait]
pub trait FaultDetector: std::fmt::Debug {
    async fn detect_faults(&self, nodes: &HashMap<NodeId, NodeInfo>) -> Vec<Fault>;
    fn get_detection_confidence(&self) -> f64;
    fn get_false_positive_rate(&self) -> f64;
}

/// Fault representation
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Fault {
    pub fault_id: Uuid,
    pub fault_type: FaultType,
    pub affected_nodes: Vec<NodeId>,
    pub severity: Severity,
    pub detection_time: DateTime<Utc>,
    pub predicted_impact: Impact,
}

/// Types of faults in distributed quantum systems
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum FaultType {
    NodeFailure,
    NetworkPartition,
    QuantumDecoherence,
    HardwareCalibrationDrift,
    SoftwareBug,
    ResourceExhaustion,
    SecurityBreach,
}

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

/// Predicted impact of a fault
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Impact {
    pub affected_computations: Vec<Uuid>,
    pub estimated_downtime: Duration,
    pub performance_degradation: f64,
    pub recovery_cost: f64,
}

/// Trait for recovery strategies
#[async_trait]
pub trait RecoveryStrategy: std::fmt::Debug {
    async fn recover_from_fault(
        &self,
        fault: &Fault,
        system_state: &SystemState,
    ) -> Result<RecoveryResult>;

    fn estimate_recovery_time(&self, fault: &Fault) -> Duration;
    fn calculate_recovery_cost(&self, fault: &Fault) -> f64;
}

/// System state snapshot
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SystemState {
    pub nodes: HashMap<NodeId, NodeInfo>,
    pub active_computations: HashMap<Uuid, ExecutionRequest>,
    pub distributed_states: HashMap<Uuid, DistributedQuantumState>,
    pub network_topology: NetworkTopology,
    pub resource_allocation: HashMap<NodeId, ResourceAllocation>,
}

/// Network topology representation
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NetworkTopology {
    pub nodes: Vec<NodeId>,
    pub edges: Vec<(NodeId, NodeId)>,
    pub edge_weights: HashMap<(NodeId, NodeId), f64>,
    pub clustering_coefficient: f64,
    pub diameter: u32,
}

/// Resource allocation per node
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ResourceAllocation {
    pub allocated_qubits: Vec<QubitId>,
    pub memory_allocated_mb: u32,
    pub cpu_allocated_percentage: f64,
    pub network_bandwidth_allocated_mbps: f64,
}

/// Recovery result
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RecoveryResult {
    pub success: bool,
    pub recovery_time: Duration,
    pub restored_computations: Vec<Uuid>,
    pub failed_computations: Vec<Uuid>,
    pub performance_impact: f64,
}

/// Checkpointing system for fault tolerance
#[derive(Debug)]
pub struct CheckpointingSystem {
    pub checkpoint_storage: Arc<dyn CheckpointStorage + Send + Sync>,
    pub checkpoint_frequency: Duration,
    pub compression_enabled: bool,
    pub incremental_checkpoints: bool,
}

/// Trait for checkpoint storage
#[async_trait]
pub trait CheckpointStorage: std::fmt::Debug {
    async fn store_checkpoint(&self, checkpoint_id: Uuid, data: &CheckpointData) -> Result<()>;
    async fn load_checkpoint(&self, checkpoint_id: Uuid) -> Result<CheckpointData>;
    async fn list_checkpoints(&self) -> Result<Vec<Uuid>>;
    async fn delete_checkpoint(&self, checkpoint_id: Uuid) -> Result<()>;
}

/// Checkpoint data structure
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CheckpointData {
    pub timestamp: DateTime<Utc>,
    pub system_state: SystemState,
    pub computation_progress: HashMap<Uuid, ComputationProgress>,
    pub quantum_states: HashMap<Uuid, DistributedQuantumState>,
    pub metadata: HashMap<String, String>,
}

/// Computation progress tracking
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ComputationProgress {
    pub completed_partitions: Vec<Uuid>,
    pub in_progress_partitions: Vec<Uuid>,
    pub pending_partitions: Vec<Uuid>,
    pub intermediate_results: HashMap<String, Vec<f64>>,
    pub execution_statistics: ExecutionStatistics,
}

/// Execution statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ExecutionStatistics {
    pub start_time: DateTime<Utc>,
    pub estimated_completion_time: DateTime<Utc>,
    pub gates_executed: u32,
    pub measurements_completed: u32,
    pub average_fidelity: f64,
    pub error_rate: f64,
}

/// Redundancy management for fault tolerance
#[derive(Debug)]
pub struct RedundancyManager {
    pub redundancy_strategies: HashMap<String, Box<dyn RedundancyStrategy + Send + Sync>>,
    pub replication_factor: u32,
    pub consistency_protocol: String,
}

/// Trait for redundancy strategies
pub trait RedundancyStrategy: std::fmt::Debug {
    fn replicate_computation(
        &self,
        computation: &ExecutionRequest,
        replication_factor: u32,
    ) -> Vec<ExecutionRequest>;

    fn aggregate_results(&self, results: &[ComputationResult]) -> Result<ComputationResult>;

    fn detect_byzantine_faults(&self, results: &[ComputationResult]) -> Vec<NodeId>;
}

/// Computation result
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ComputationResult {
    pub result_id: Uuid,
    pub computation_id: Uuid,
    pub node_id: NodeId,
    pub measurements: HashMap<u32, bool>,
    pub final_state: Option<LocalQuantumState>,
    pub execution_time: Duration,
    pub fidelity: f64,
    pub error_rate: f64,
    pub metadata: HashMap<String, String>,
}

/// In-memory checkpoint storage for testing
#[derive(Debug)]
pub struct InMemoryCheckpointStorage {
    pub checkpoints: Arc<std::sync::RwLock<HashMap<Uuid, CheckpointData>>>,
}

impl Default for InMemoryCheckpointStorage {
    fn default() -> Self {
        Self::new()
    }
}

impl InMemoryCheckpointStorage {
    pub fn new() -> Self {
        Self {
            checkpoints: Arc::new(std::sync::RwLock::new(HashMap::new())),
        }
    }
}

#[async_trait]
impl CheckpointStorage for InMemoryCheckpointStorage {
    async fn store_checkpoint(&self, checkpoint_id: Uuid, data: &CheckpointData) -> Result<()> {
        let mut checkpoints = self
            .checkpoints
            .write()
            .expect("Checkpoints RwLock poisoned");
        checkpoints.insert(checkpoint_id, data.clone());
        Ok(())
    }

    async fn load_checkpoint(&self, checkpoint_id: Uuid) -> Result<CheckpointData> {
        let checkpoints = self
            .checkpoints
            .read()
            .expect("Checkpoints RwLock poisoned");
        checkpoints.get(&checkpoint_id).cloned().ok_or_else(|| {
            DistributedComputationError::ResourceAllocation("Checkpoint not found".to_string())
        })
    }

    async fn list_checkpoints(&self) -> Result<Vec<Uuid>> {
        let checkpoints = self
            .checkpoints
            .read()
            .expect("Checkpoints RwLock poisoned");
        Ok(checkpoints.keys().copied().collect())
    }

    async fn delete_checkpoint(&self, checkpoint_id: Uuid) -> Result<()> {
        let mut checkpoints = self
            .checkpoints
            .write()
            .expect("Checkpoints RwLock poisoned");
        checkpoints.remove(&checkpoint_id);
        Ok(())
    }
}

impl Default for FaultToleranceManager {
    fn default() -> Self {
        Self::new()
    }
}

impl FaultToleranceManager {
    pub fn new() -> Self {
        Self {
            fault_detectors: vec![],
            recovery_strategies: HashMap::new(),
            checkpointing_system: Arc::new(CheckpointingSystem::new()),
            redundancy_manager: Arc::new(RedundancyManager::new()),
        }
    }
}

impl Default for CheckpointingSystem {
    fn default() -> Self {
        Self::new()
    }
}

impl CheckpointingSystem {
    pub fn new() -> Self {
        Self {
            checkpoint_storage: Arc::new(InMemoryCheckpointStorage::new()),
            checkpoint_frequency: Duration::from_secs(60),
            compression_enabled: true,
            incremental_checkpoints: true,
        }
    }
}

impl Default for RedundancyManager {
    fn default() -> Self {
        Self::new()
    }
}

impl RedundancyManager {
    pub fn new() -> Self {
        Self {
            redundancy_strategies: HashMap::new(),
            replication_factor: 3,
            consistency_protocol: "eventual_consistency".to_string(),
        }
    }
}