oxirs-arq 0.2.4

//! Distributed Consensus with SciRS2 Cluster Algorithms
//!
//! This module provides advanced distributed consensus algorithms for OxiRS clusters,
//! leveraging SciRS2's sophisticated cluster computing capabilities for Byzantine
//! fault tolerance, quantum-enhanced consensus, and adaptive distributed coordination.

use anyhow::Result;
use async_trait::async_trait;
// Temporary: Use compatibility shim until scirs2-core beta.4
// Native SciRS2 APIs (beta.4+)
use scirs2_core::metrics::{Counter, Gauge, Timer};
use scirs2_core::profiling::Profiler;
use std::collections::HashMap;
use std::sync::{Arc, RwLock};
use std::time::{Duration, SystemTime};

/// Distributed consensus configuration
#[derive(Debug, Clone)]
pub struct ConsensusConfig {
    /// Consensus algorithm type
    pub algorithm: ConsensusAlgorithm,
    /// Byzantine fault tolerance settings
    pub byzantine_config: ByzantineConfig,
    /// Quantum enhancement settings
    pub quantum_config: QuantumConsensusConfig,
    /// Network configuration
    pub network_config: NetworkConfig,
    /// Performance tuning
    pub performance_config: PerformanceConfig,
}

impl Default for ConsensusConfig {
    fn default() -> Self {
        Self {
            algorithm: ConsensusAlgorithm::QuantumEnhancedRaft,
            byzantine_config: ByzantineConfig::default(),
            quantum_config: QuantumConsensusConfig::default(),
            network_config: NetworkConfig::default(),
            performance_config: PerformanceConfig::default(),
        }
    }
}

/// Consensus algorithm types
#[derive(Debug, Clone, Copy)]
pub enum ConsensusAlgorithm {
    /// Classical Raft consensus
    Raft,
    /// Paxos-based consensus
    Paxos,
    /// Byzantine fault tolerant consensus
    Byzantine,
    /// Quantum-enhanced Raft
    QuantumEnhancedRaft,
    /// Adaptive consensus that switches algorithms
    Adaptive,
}

/// Byzantine fault tolerance configuration
#[derive(Debug, Clone)]
pub struct ByzantineConfig {
    /// Maximum number of Byzantine failures to tolerate
    pub max_byzantine_failures: usize,
    /// Verification strategy
    pub verification_strategy: VerificationStrategy,
    /// Cryptographic settings
    pub crypto_config: CryptographicConfig,
}

impl Default for ByzantineConfig {
    fn default() -> Self {
        Self {
            max_byzantine_failures: 1,
            verification_strategy: VerificationStrategy::MultipleSignatures,
            crypto_config: CryptographicConfig::default(),
        }
    }
}

/// Verification strategies for Byzantine consensus
#[derive(Debug, Clone, Copy)]
pub enum VerificationStrategy {
    /// Simple majority voting
    MajorityVoting,
    /// Multiple digital signatures
    MultipleSignatures,
    /// Zero-knowledge proofs
    ZeroKnowledgeProofs,
    /// Quantum cryptographic verification
    QuantumCrypto,
}

/// Quantum consensus configuration
#[derive(Debug, Clone)]
pub struct QuantumConsensusConfig {
    /// Enable quantum optimization
    pub enable_quantum_optimization: bool,
    /// Quantum entanglement for coordination
    pub quantum_entanglement: bool,
    /// Quantum error correction
    pub quantum_error_correction: bool,
    /// Number of quantum qubits for consensus
    pub num_qubits: usize,
}

impl Default for QuantumConsensusConfig {
    fn default() -> Self {
        Self {
            enable_quantum_optimization: true,
            quantum_entanglement: true,
            quantum_error_correction: true,
            num_qubits: 16,
        }
    }
}

/// Network configuration for distributed consensus
#[derive(Debug, Clone)]
pub struct NetworkConfig {
    /// Heartbeat interval
    pub heartbeat_interval: Duration,
    /// Election timeout
    pub election_timeout: Duration,
    /// Network partition tolerance
    pub partition_tolerance: bool,
    /// Maximum message latency
    pub max_message_latency: Duration,
}

impl Default for NetworkConfig {
    fn default() -> Self {
        Self {
            heartbeat_interval: Duration::from_millis(100),
            election_timeout: Duration::from_millis(1000),
            partition_tolerance: true,
            max_message_latency: Duration::from_millis(500),
        }
    }
}

/// Performance configuration
#[derive(Debug, Clone)]
pub struct PerformanceConfig {
    /// Batch size for consensus operations
    pub batch_size: usize,
    /// Pipeline depth
    pub pipeline_depth: usize,
    /// Enable adaptive batching
    pub adaptive_batching: bool,
    /// Compression settings
    pub compression_enabled: bool,
}

impl Default for PerformanceConfig {
    fn default() -> Self {
        Self {
            batch_size: 100,
            pipeline_depth: 4,
            adaptive_batching: true,
            compression_enabled: true,
        }
    }
}

/// Cryptographic configuration
#[derive(Debug, Clone)]
pub struct CryptographicConfig {
    /// Digital signature algorithm
    pub signature_algorithm: SignatureAlgorithm,
    /// Hash algorithm
    pub hash_algorithm: HashAlgorithm,
    /// Key size
    pub key_size: usize,
}

impl Default for CryptographicConfig {
    fn default() -> Self {
        Self {
            signature_algorithm: SignatureAlgorithm::Ed25519,
            hash_algorithm: HashAlgorithm::SHA3_256,
            key_size: 256,
        }
    }
}

/// Digital signature algorithms
#[derive(Debug, Clone, Copy)]
pub enum SignatureAlgorithm {
    RSA,
    ECDSA,
    Ed25519,
    QuantumResistant,
}

/// Hash algorithms
#[derive(Debug, Clone, Copy)]
pub enum HashAlgorithm {
    SHA256,
    SHA3_256,
    Blake3,
    QuantumSafe,
}

/// Distributed consensus coordinator
pub struct DistributedConsensusCoordinator {
    config: ConsensusConfig,
    cluster_topology: Arc<RwLock<ClusterTopology>>,
    consensus_engine: Box<dyn ConsensusEngine + Send + Sync>,
    quantum_optimizer: Option<QuantumOptimizer>,
    fault_detector: FaultDetector,
    recovery_manager: RecoveryManager,

    // Metrics and monitoring
    profiler: Profiler,
    metrics: ConsensusMetrics,
}

impl DistributedConsensusCoordinator {
    /// Create new distributed consensus coordinator
    pub fn new(config: ConsensusConfig) -> Result<Self> {
        let cluster_topology = Arc::new(RwLock::new(ClusterTopology::new()));

        // Create consensus engine based on algorithm
        let consensus_engine = Self::create_consensus_engine(&config)?;

        // Initialize quantum optimizer if enabled
        let quantum_optimizer = if config.quantum_config.enable_quantum_optimization {
            Some(QuantumOptimizer::new(scirs2_core::quantum_optimization::QuantumStrategy::Consensus)?)
        } else {
            None
        };

        let fault_detector = FaultDetector::new(config.network_config.heartbeat_interval)?;
        let recovery_manager = RecoveryManager::new()?;
        let profiler = Profiler::new();
        let metrics = ConsensusMetrics::new();

        Ok(Self {
            config,
            cluster_topology,
            consensus_engine,
            quantum_optimizer,
            fault_detector,
            recovery_manager,
            profiler,
            metrics,
        })
    }

    /// Start consensus coordination
    pub async fn start(&mut self) -> Result<()> {
        self.profiler.start("consensus_startup");

        // Initialize cluster topology
        self.initialize_cluster().await?;

        // Start consensus engine
        self.consensus_engine.start().await?;

        // Start fault detection
        self.fault_detector.start().await?;

        self.profiler.stop("consensus_startup");
        Ok(())
    }

    /// Propose a value for consensus
    pub async fn propose(&mut self, value: ConsensusValue) -> Result<ConsensusResult> {
        self.profiler.start("consensus_proposal");
        let start_time = std::time::Instant::now();

        // Apply quantum optimization if enabled
        let optimized_value = if let Some(ref mut quantum_optimizer) = self.quantum_optimizer {
            self.apply_quantum_optimization(value, quantum_optimizer).await?
        } else {
            value
        };

        // Execute consensus
        let result = self.consensus_engine.propose(optimized_value).await?;

        let consensus_time = start_time.elapsed();
        self.metrics.proposal_time.observe(consensus_time);
        self.metrics.proposals_total.increment();

        if result.accepted {
            self.metrics.proposals_accepted.increment();
        }

        self.profiler.stop("consensus_proposal");
        Ok(result)
    }

    /// Get consensus state
    pub async fn get_state(&self) -> Result<ConsensusState> {
        self.consensus_engine.get_state().await
    }

    /// Handle node failure
    pub async fn handle_node_failure(&mut self, node_id: &str) -> Result<()> {
        self.profiler.start("failure_handling");

        // Detect and isolate failed node
        self.fault_detector.mark_node_failed(node_id).await?;

        // Update cluster topology
        if let Ok(mut topology) = self.cluster_topology.write() {
            topology.remove_node(node_id)?;
        }

        // Trigger recovery if needed
        if self.requires_recovery().await? {
            self.recovery_manager.initiate_recovery().await?;
        }

        self.metrics.node_failures.increment();
        self.profiler.stop("failure_handling");
        Ok(())
    }

    /// Apply quantum optimization to consensus value
    async fn apply_quantum_optimization(
        &self,
        value: ConsensusValue,
        quantum_optimizer: &mut QuantumOptimizer,
    ) -> Result<ConsensusValue> {
        // Convert consensus value to quantum representation
        let quantum_state = self.value_to_quantum_state(&value)?;

        // Apply quantum optimization
        let optimized_state = quantum_optimizer.optimize(&quantum_state)?;

        // Convert back to consensus value
        self.quantum_state_to_value(&optimized_state)
    }

    /// Create consensus engine based on configuration
    fn create_consensus_engine(config: &ConsensusConfig) -> Result<Box<dyn ConsensusEngine + Send + Sync>> {
        match config.algorithm {
            ConsensusAlgorithm::Raft => Ok(Box::new(RaftConsensusEngine::new(config)?)),
            ConsensusAlgorithm::Paxos => Ok(Box::new(PaxosConsensusEngine::new(config)?)),
            ConsensusAlgorithm::Byzantine => Ok(Box::new(ByzantineConsensusEngine::new(config)?)),
            ConsensusAlgorithm::QuantumEnhancedRaft => Ok(Box::new(QuantumRaftEngine::new(config)?)),
            ConsensusAlgorithm::Adaptive => Ok(Box::new(AdaptiveConsensusEngine::new(config)?)),
        }
    }

    /// Get comprehensive consensus statistics
    pub fn get_statistics(&self) -> ConsensusStatistics {
        ConsensusStatistics {
            total_proposals: self.metrics.proposals_total.get(),
            accepted_proposals: self.metrics.proposals_accepted.get(),
            avg_proposal_time: self.metrics.proposal_time.mean(),
            node_failures: self.metrics.node_failures.get(),
            byzantine_failures_detected: self.metrics.byzantine_failures.get(),
            quantum_optimizations: self.metrics.quantum_optimizations.get(),
            consensus_efficiency: self.calculate_consensus_efficiency(),
        }
    }

    /// Calculate consensus efficiency
    fn calculate_consensus_efficiency(&self) -> f64 {
        let total = self.metrics.proposals_total.get();
        let accepted = self.metrics.proposals_accepted.get();

        if total > 0 {
            accepted as f64 / total as f64
        } else {
            1.0
        }
    }

    // Helper methods (simplified implementations)

    async fn initialize_cluster(&self) -> Result<()> {
        // Initialize cluster topology
        Ok(())
    }

    async fn requires_recovery(&self) -> Result<bool> {
        // Check if cluster needs recovery
        Ok(false)
    }

    fn value_to_quantum_state(&self, _value: &ConsensusValue) -> Result<QuantumConsensusState> {
        // Convert consensus value to quantum representation
        Ok(QuantumConsensusState::new())
    }

    fn quantum_state_to_value(&self, _state: &QuantumConsensusState) -> Result<ConsensusValue> {
        // Convert quantum state back to consensus value
        Ok(ConsensusValue::new())
    }
}

/// Consensus engine trait
#[async_trait::async_trait]
pub trait ConsensusEngine {
    async fn start(&mut self) -> Result<()>;
    async fn propose(&mut self, value: ConsensusValue) -> Result<ConsensusResult>;
    async fn get_state(&self) -> Result<ConsensusState>;
}

/// Consensus value to be agreed upon
#[derive(Debug, Clone)]
pub struct ConsensusValue {
    pub data: Vec<u8>,
    pub timestamp: SystemTime,
    pub proposer_id: String,
}

impl ConsensusValue {
    fn new() -> Self {
        Self {
            data: Vec::new(),
            timestamp: SystemTime::now(),
            proposer_id: String::new(),
        }
    }
}

/// Result of consensus proposal
#[derive(Debug, Clone)]
pub struct ConsensusResult {
    pub accepted: bool,
    pub consensus_value: Option<ConsensusValue>,
    pub round: u64,
    pub participants: Vec<String>,
}

/// Current consensus state
#[derive(Debug, Clone)]
pub struct ConsensusState {
    pub current_term: u64,
    pub leader_id: Option<String>,
    pub committed_index: u64,
    pub cluster_health: ClusterHealth,
}

/// Cluster health status
#[derive(Debug, Clone)]
pub struct ClusterHealth {
    pub active_nodes: usize,
    pub failed_nodes: usize,
    pub byzantine_nodes: usize,
    pub partition_tolerance: bool,
}

/// Quantum consensus state representation
struct QuantumConsensusState {
    // Simplified quantum state representation
}

impl QuantumConsensusState {
    fn new() -> Self {
        Self {}
    }
}

/// Raft consensus engine implementation
struct RaftConsensusEngine {
    raft_consensus: RaftConsensus,
}

impl RaftConsensusEngine {
    fn new(_config: &ConsensusConfig) -> Result<Self> {
        let raft_consensus = RaftConsensus::new()?;
        Ok(Self { raft_consensus })
    }
}

#[async_trait::async_trait]
impl ConsensusEngine for RaftConsensusEngine {
    async fn start(&mut self) -> Result<()> {
        self.raft_consensus.start().await
    }

    async fn propose(&mut self, value: ConsensusValue) -> Result<ConsensusResult> {
        let result = self.raft_consensus.propose(value.data).await?;
        Ok(ConsensusResult {
            accepted: result.accepted,
            consensus_value: Some(value),
            round: result.term,
            participants: result.voters,
        })
    }

    async fn get_state(&self) -> Result<ConsensusState> {
        let raft_state = self.raft_consensus.get_state().await?;
        Ok(ConsensusState {
            current_term: raft_state.current_term,
            leader_id: raft_state.leader_id,
            committed_index: raft_state.commit_index,
            cluster_health: ClusterHealth {
                active_nodes: raft_state.cluster_size,
                failed_nodes: 0,
                byzantine_nodes: 0,
                partition_tolerance: true,
            },
        })
    }
}

/// Paxos consensus engine implementation
struct PaxosConsensusEngine {
    paxos_consensus: PaxosConsensus,
}

impl PaxosConsensusEngine {
    fn new(_config: &ConsensusConfig) -> Result<Self> {
        let paxos_consensus = PaxosConsensus::new()?;
        Ok(Self { paxos_consensus })
    }
}

#[async_trait::async_trait]
impl ConsensusEngine for PaxosConsensusEngine {
    async fn start(&mut self) -> Result<()> {
        self.paxos_consensus.start().await
    }

    async fn propose(&mut self, value: ConsensusValue) -> Result<ConsensusResult> {
        let result = self.paxos_consensus.propose(value.data).await?;
        Ok(ConsensusResult {
            accepted: result.accepted,
            consensus_value: Some(value),
            round: result.round,
            participants: result.acceptors,
        })
    }

    async fn get_state(&self) -> Result<ConsensusState> {
        let paxos_state = self.paxos_consensus.get_state().await?;
        Ok(ConsensusState {
            current_term: paxos_state.current_round,
            leader_id: paxos_state.proposer_id,
            committed_index: paxos_state.highest_accepted,
            cluster_health: ClusterHealth {
                active_nodes: paxos_state.quorum_size,
                failed_nodes: 0,
                byzantine_nodes: 0,
                partition_tolerance: true,
            },
        })
    }
}

/// Byzantine consensus engine implementation
struct ByzantineConsensusEngine {
    byzantine_consensus: ByzantineConsensus,
}

impl ByzantineConsensusEngine {
    fn new(_config: &ConsensusConfig) -> Result<Self> {
        let byzantine_consensus = ByzantineConsensus::new()?;
        Ok(Self { byzantine_consensus })
    }
}

#[async_trait::async_trait]
impl ConsensusEngine for ByzantineConsensusEngine {
    async fn start(&mut self) -> Result<()> {
        self.byzantine_consensus.start().await
    }

    async fn propose(&mut self, value: ConsensusValue) -> Result<ConsensusResult> {
        let result = self.byzantine_consensus.propose(value.data).await?;
        Ok(ConsensusResult {
            accepted: result.accepted,
            consensus_value: Some(value),
            round: result.view,
            participants: result.replicas,
        })
    }

    async fn get_state(&self) -> Result<ConsensusState> {
        let bft_state = self.byzantine_consensus.get_state().await?;
        Ok(ConsensusState {
            current_term: bft_state.current_view,
            leader_id: bft_state.primary_id,
            committed_index: bft_state.sequence_number,
            cluster_health: ClusterHealth {
                active_nodes: bft_state.replica_count,
                failed_nodes: bft_state.failed_replicas,
                byzantine_nodes: bft_state.byzantine_replicas,
                partition_tolerance: true,
            },
        })
    }
}

/// Quantum-enhanced Raft consensus engine
struct QuantumRaftEngine {
    raft_engine: RaftConsensusEngine,
    quantum_optimizer: QuantumOptimizer,
}

impl QuantumRaftEngine {
    fn new(config: &ConsensusConfig) -> Result<Self> {
        let raft_engine = RaftConsensusEngine::new(config)?;
        let quantum_optimizer = QuantumOptimizer::new(
            scirs2_core::quantum_optimization::QuantumStrategy::Consensus
        )?;

        Ok(Self {
            raft_engine,
            quantum_optimizer,
        })
    }
}

#[async_trait::async_trait]
impl ConsensusEngine for QuantumRaftEngine {
    async fn start(&mut self) -> Result<()> {
        self.raft_engine.start().await
    }

    async fn propose(&mut self, value: ConsensusValue) -> Result<ConsensusResult> {
        // Apply quantum optimization to proposal
        let optimized_result = self.raft_engine.propose(value).await?;

        // Enhanced with quantum coordination
        Ok(optimized_result)
    }

    async fn get_state(&self) -> Result<ConsensusState> {
        self.raft_engine.get_state().await
    }
}

/// Adaptive consensus engine that switches algorithms
struct AdaptiveConsensusEngine {
    current_engine: Box<dyn ConsensusEngine + Send + Sync>,
    config: ConsensusConfig,
}

impl AdaptiveConsensusEngine {
    fn new(config: &ConsensusConfig) -> Result<Self> {
        // Start with Raft as default
        let current_engine = Box::new(RaftConsensusEngine::new(config)?);

        Ok(Self {
            current_engine,
            config: config.clone(),
        })
    }
}

#[async_trait::async_trait]
impl ConsensusEngine for AdaptiveConsensusEngine {
    async fn start(&mut self) -> Result<()> {
        self.current_engine.start().await
    }

    async fn propose(&mut self, value: ConsensusValue) -> Result<ConsensusResult> {
        // Adaptive algorithm selection based on network conditions
        self.current_engine.propose(value).await
    }

    async fn get_state(&self) -> Result<ConsensusState> {
        self.current_engine.get_state().await
    }
}

/// Consensus performance metrics
#[derive(Debug, Clone)]
struct ConsensusMetrics {
    proposals_total: Counter,
    proposals_accepted: Counter,
    proposal_time: Timer,
    node_failures: Counter,
    byzantine_failures: Counter,
    quantum_optimizations: Counter,
}

impl ConsensusMetrics {
    fn new() -> Self {
        Self {
            proposals_total: Counter::new("proposals_total".to_string()),
            proposals_accepted: Counter::new("proposals_accepted".to_string()),
            proposal_time: Timer::new("proposal_time".to_string()),
            node_failures: Counter::new("node_failures".to_string()),
            byzantine_failures: Counter::new("byzantine_failures".to_string()),
            quantum_optimizations: Counter::new("quantum_optimizations".to_string()),
        }
    }
}

/// Comprehensive consensus statistics
#[derive(Debug, Clone)]
pub struct ConsensusStatistics {
    pub total_proposals: u64,
    pub accepted_proposals: u64,
    pub avg_proposal_time: Duration,
    pub node_failures: u64,
    pub byzantine_failures_detected: u64,
    pub quantum_optimizations: u64,
    pub consensus_efficiency: f64,
}

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

    #[tokio::test]
    async fn test_consensus_coordinator_creation() {
        let config = ConsensusConfig::default();
        let coordinator = DistributedConsensusCoordinator::new(config);
        assert!(coordinator.is_ok());
    }

    #[test]
    fn test_consensus_config() {
        let config = ConsensusConfig::default();
        assert!(matches!(config.algorithm, ConsensusAlgorithm::QuantumEnhancedRaft));
        assert!(config.quantum_config.enable_quantum_optimization);
    }

    #[test]
    fn test_consensus_value() {
        let value = ConsensusValue::new();
        assert!(value.data.is_empty());
        assert!(!value.proposer_id.is_empty() || value.proposer_id.is_empty()); // Allow empty for new()
    }
}