oxirs_core/distributed/

replication.rs

//! Multi-region active-active replication
//!
//! This module implements multi-region replication with active-active support,
//! optimized for low latency and high availability across geographic regions.

#![allow(dead_code)]

use crate::model::{Triple, TriplePattern};
use crate::OxirsError;
use serde::{Deserialize, Serialize};
use std::collections::{HashMap, VecDeque};
use std::net::SocketAddr;
use std::sync::Arc;
use std::time::{Duration, Instant};
use tokio::sync::{mpsc, Mutex, RwLock};
use tokio::time::interval;

/// Replication configuration
#[derive(Debug, Clone)]
pub struct ReplicationConfig {
    /// Region ID
    pub region_id: String,
    /// Region configuration
    pub region: RegionConfig,
    /// Peer regions
    pub peers: Vec<RegionPeer>,
    /// Replication strategy
    pub strategy: ReplicationStrategy,
    /// Conflict resolution
    pub conflict_resolution: ConflictResolution,
    /// Network configuration
    pub network: NetworkConfig,
    /// Persistence configuration
    pub persistence: PersistenceConfig,
}

/// Region configuration
#[derive(Debug, Clone)]
pub struct RegionConfig {
    /// Region name
    pub name: String,
    /// Geographic location
    pub location: GeographicLocation,
    /// Availability zones
    pub availability_zones: Vec<String>,
    /// Read/write capacity
    pub capacity: RegionCapacity,
}

/// Geographic location
#[derive(Debug, Clone)]
pub struct GeographicLocation {
    /// Latitude
    pub latitude: f64,
    /// Longitude
    pub longitude: f64,
    /// Continent
    pub continent: String,
    /// Country
    pub country: String,
}

/// Region capacity configuration
#[derive(Debug, Clone)]
pub struct RegionCapacity {
    /// Read units per second
    pub read_units: u32,
    /// Write units per second
    pub write_units: u32,
    /// Storage capacity (GB)
    pub storage_gb: u32,
    /// Auto-scaling enabled
    pub auto_scaling: bool,
}

/// Region peer information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RegionPeer {
    /// Region ID
    pub region_id: String,
    /// Endpoint addresses
    pub endpoints: Vec<SocketAddr>,
    /// Priority (lower is higher priority)
    pub priority: u32,
    /// Active status
    pub active: bool,
}

/// Replication strategy
#[derive(Debug, Clone)]
pub enum ReplicationStrategy {
    /// Synchronous replication to all regions
    SyncAll,
    /// Synchronous to N regions
    SyncQuorum { n: usize },
    /// Asynchronous to all regions
    AsyncAll,
    /// Chain replication
    Chain { order: Vec<String> },
    /// Hierarchical replication
    Hierarchical { topology: ReplicationTopology },
    /// Adaptive based on network conditions
    Adaptive,
}

/// Replication topology for hierarchical strategy
#[derive(Debug, Clone)]
pub struct ReplicationTopology {
    /// Primary regions
    pub primary: Vec<String>,
    /// Secondary regions
    pub secondary: Vec<String>,
    /// Edge regions
    pub edge: Vec<String>,
}

/// Conflict resolution strategy
#[derive(Debug, Clone)]
pub enum ConflictResolution {
    /// Last write wins based on timestamp
    LastWriteWins,
    /// Use vector clocks
    VectorClock,
    /// Custom resolver function
    Custom(String),
    /// Multi-value (keep all conflicting values)
    MultiValue,
    /// Region priority based
    RegionPriority,
}

/// Network configuration
#[derive(Debug, Clone)]
pub struct NetworkConfig {
    /// Connection timeout
    pub connect_timeout: Duration,
    /// Request timeout
    pub request_timeout: Duration,
    /// Maximum retries
    pub max_retries: u32,
    /// Compression enabled
    pub compression: bool,
    /// Encryption configuration
    pub encryption: EncryptionConfig,
}

/// Encryption configuration
#[derive(Debug, Clone)]
pub struct EncryptionConfig {
    /// Enable TLS
    pub tls_enabled: bool,
    /// Certificate path
    pub cert_path: Option<String>,
    /// Key path
    pub key_path: Option<String>,
    /// CA path
    pub ca_path: Option<String>,
}

/// Persistence configuration
#[derive(Debug, Clone)]
pub struct PersistenceConfig {
    /// Write-ahead log path
    pub wal_path: String,
    /// Checkpoint interval
    pub checkpoint_interval: Duration,
    /// Maximum WAL size
    pub max_wal_size: usize,
    /// Compression for WAL
    pub wal_compression: bool,
}

/// Replication operation types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ReplicationOp {
    /// Insert triple
    Insert(VersionedTriple),
    /// Delete triple
    Delete(VersionedTriple),
    /// Batch operations
    Batch(Vec<ReplicationOp>),
    /// Snapshot chunk
    SnapshotChunk(SnapshotChunk),
    /// Heartbeat
    Heartbeat(HeartbeatInfo),
}

/// Versioned triple with metadata
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct VersionedTriple {
    /// The triple
    pub triple: Triple,
    /// Version vector
    pub version: VectorClock,
    /// Timestamp
    pub timestamp: u64,
    /// Origin region
    pub origin_region: String,
    /// Transaction ID
    pub tx_id: Option<String>,
}

/// Vector clock for causality tracking
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub struct VectorClock {
    /// Clock entries by region
    pub entries: HashMap<String, u64>,
}

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

impl VectorClock {
    /// Create new vector clock
    pub fn new() -> Self {
        VectorClock {
            entries: HashMap::new(),
        }
    }

    /// Increment clock for region
    pub fn increment(&mut self, region: &str) {
        let counter = self.entries.entry(region.to_string()).or_insert(0);
        *counter += 1;
    }

    /// Merge with another clock
    pub fn merge(&mut self, other: &VectorClock) {
        for (region, &count) in &other.entries {
            let entry = self.entries.entry(region.clone()).or_insert(0);
            *entry = (*entry).max(count);
        }
    }

    /// Check if this clock is concurrent with another
    pub fn is_concurrent(&self, other: &VectorClock) -> bool {
        !self.happens_before(other) && !other.happens_before(self)
    }

    /// Check if this clock happens before another
    pub fn happens_before(&self, other: &VectorClock) -> bool {
        let mut all_leq = true;
        let mut exists_lt = false;

        for (region, &count) in &self.entries {
            let other_count = other.entries.get(region).copied().unwrap_or(0);
            if count > other_count {
                all_leq = false;
                break;
            }
            if count < other_count {
                exists_lt = true;
            }
        }

        // Check regions in other but not in self
        for region in other.entries.keys() {
            if !self.entries.contains_key(region) && other.entries[region] > 0 {
                exists_lt = true;
            }
        }

        all_leq && exists_lt
    }
}

/// Snapshot chunk for initial sync
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SnapshotChunk {
    /// Snapshot ID
    pub snapshot_id: String,
    /// Chunk index
    pub chunk_index: u64,
    /// Total chunks
    pub total_chunks: u64,
    /// Data
    pub data: Vec<u8>,
    /// Checksum
    pub checksum: String,
}

/// Heartbeat information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HeartbeatInfo {
    /// Region ID
    pub region_id: String,
    /// Timestamp
    pub timestamp: u64,
    /// Load metrics
    pub load: LoadMetrics,
    /// Replication lag
    pub lag_ms: u64,
}

/// Load metrics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LoadMetrics {
    /// CPU usage percentage
    pub cpu_percent: f32,
    /// Memory usage percentage
    pub memory_percent: f32,
    /// Disk usage percentage
    pub disk_percent: f32,
    /// Network bandwidth usage
    pub network_mbps: f32,
    /// Active connections
    pub connections: u32,
}

/// Multi-region replication manager
pub struct ReplicationManager {
    /// Configuration
    config: ReplicationConfig,
    /// Local storage
    storage: Arc<RwLock<ReplicationStorage>>,
    /// Replication state
    state: Arc<RwLock<ReplicationState>>,
    /// Network manager
    network: Arc<NetworkManager>,
    /// Conflict resolver
    resolver: Arc<ConflictResolver>,
    /// WAL manager
    wal: Arc<RwLock<WriteAheadLog>>,
    /// Statistics
    stats: Arc<RwLock<ReplicationStats>>,
}

/// Replication storage
#[allow(dead_code)]
struct ReplicationStorage {
    /// Current triples with versions
    triples: HashMap<Triple, VersionedTriple>,
    /// Conflict storage
    conflicts: HashMap<Triple, Vec<VersionedTriple>>,
    /// Pending operations
    #[allow(dead_code)]
    pending_ops: VecDeque<ReplicationOp>,
}

/// Replication state
#[allow(dead_code)]
struct ReplicationState {
    /// Vector clock for this region
    vector_clock: VectorClock,
    /// Peer states
    peer_states: HashMap<String, PeerState>,
    /// Active snapshot transfers
    active_snapshots: HashMap<String, SnapshotTransfer>,
    /// Replication status
    status: ReplicationStatus,
}

/// Peer state tracking
#[derive(Debug, Clone)]
#[allow(dead_code)]
struct PeerState {
    /// Last seen timestamp
    last_seen: Instant,
    /// Last known vector clock
    last_clock: VectorClock,
    /// Connection status
    connected: bool,
    /// Replication lag
    lag_ms: u64,
    /// In-flight operations
    in_flight: u64,
}

/// Snapshot transfer state
#[allow(dead_code)]
struct SnapshotTransfer {
    /// Snapshot ID
    id: String,
    /// Direction (send/receive)
    direction: TransferDirection,
    /// Progress
    chunks_transferred: u64,
    /// Total chunks
    total_chunks: u64,
    /// Start time
    start_time: Instant,
}

/// Transfer direction
#[derive(Debug)]
enum TransferDirection {
    Send,
    Receive,
}

/// Replication status
#[derive(Debug, Clone)]
enum ReplicationStatus {
    Healthy,
    Degraded,
    PartialOutage,
    FullOutage,
}

/// Network manager for peer communication
struct NetworkManager {
    /// Region connections
    connections: Arc<RwLock<HashMap<String, PeerConnection>>>,
    /// Message channels
    message_tx: mpsc::Sender<NetworkMessage>,
    message_rx: Arc<Mutex<mpsc::Receiver<NetworkMessage>>>,
}

/// Peer connection
struct PeerConnection {
    /// Region ID
    region_id: String,
    /// Connection handle
    handle: Arc<Mutex<Option<tokio::task::JoinHandle<()>>>>,
    /// Send channel
    send_tx: mpsc::Sender<ReplicationOp>,
}

/// Network message
#[derive(Debug)]
enum NetworkMessage {
    /// Incoming operation
    IncomingOp {
        _from_region: String,
        _op: Box<ReplicationOp>,
    },
    /// Connection event
    ConnectionEvent {
        region_id: String,
        event: ConnectionEvent,
    },
}

/// Connection events
#[derive(Debug)]
enum ConnectionEvent {
    Connected,
    Disconnected,
    Error(String),
}

/// Conflict resolver
struct ConflictResolver {
    /// Resolution strategy
    strategy: ConflictResolution,
    /// Region priorities
    region_priorities: HashMap<String, u32>,
}

/// Write-ahead log
struct WriteAheadLog {
    /// Current log file
    current_file: Option<std::fs::File>,
    /// Log entries
    entries: VecDeque<WalEntry>,
    /// Current size
    current_size: usize,
    /// Configuration
    config: PersistenceConfig,
}

/// WAL entry
#[derive(Debug, Serialize, Deserialize)]
struct WalEntry {
    /// Sequence number
    seq: u64,
    /// Timestamp
    timestamp: u64,
    /// Operation
    op: ReplicationOp,
    /// Checksum
    checksum: u32,
}

/// Replication statistics
#[derive(Debug, Default)]
struct ReplicationStats {
    /// Operations sent
    ops_sent: u64,
    /// Operations received
    ops_received: u64,
    /// Conflicts detected
    conflicts_detected: u64,
    /// Conflicts resolved
    conflicts_resolved: u64,
    /// Bytes sent
    bytes_sent: u64,
    /// Bytes received
    bytes_received: u64,
    /// Average replication lag
    avg_lag_ms: f64,
}

impl ReplicationManager {
    /// Create new replication manager
    pub async fn new(config: ReplicationConfig) -> Result<Self, OxirsError> {
        let (message_tx, message_rx) = mpsc::channel(10000);

        let storage = Arc::new(RwLock::new(ReplicationStorage {
            triples: HashMap::new(),
            conflicts: HashMap::new(),
            pending_ops: VecDeque::new(),
        }));

        let state = Arc::new(RwLock::new(ReplicationState {
            vector_clock: VectorClock::new(),
            peer_states: HashMap::new(),
            active_snapshots: HashMap::new(),
            status: ReplicationStatus::Healthy,
        }));

        let network = Arc::new(NetworkManager {
            connections: Arc::new(RwLock::new(HashMap::new())),
            message_tx,
            message_rx: Arc::new(Mutex::new(message_rx)),
        });

        let resolver = Arc::new(ConflictResolver {
            strategy: config.conflict_resolution.clone(),
            region_priorities: HashMap::new(),
        });

        let wal = Arc::new(RwLock::new(WriteAheadLog {
            current_file: None,
            entries: VecDeque::new(),
            current_size: 0,
            config: config.persistence.clone(),
        }));

        Ok(ReplicationManager {
            config,
            storage,
            state,
            network,
            resolver,
            wal,
            stats: Arc::new(RwLock::new(ReplicationStats::default())),
        })
    }

    /// Start replication manager
    pub async fn start(&self) -> Result<(), OxirsError> {
        // Initialize WAL
        self.initialize_wal().await?;

        // Connect to peer regions
        self.connect_to_peers().await?;

        // Start message processor
        self.spawn_message_processor();

        // Start heartbeat sender
        self.spawn_heartbeat_sender();

        // Start lag monitor
        self.spawn_lag_monitor();

        // Start WAL checkpoint
        self.spawn_wal_checkpoint();

        Ok(())
    }

    /// Replicate a write operation
    pub async fn replicate_write(&self, triple: Triple, op_type: OpType) -> Result<(), OxirsError> {
        let mut state = self.state.write().await;
        state.vector_clock.increment(&self.config.region_id);

        let versioned = VersionedTriple {
            triple: triple.clone(),
            version: state.vector_clock.clone(),
            timestamp: std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .expect("SystemTime should be after UNIX_EPOCH")
                .as_secs(),
            origin_region: self.config.region_id.clone(),
            tx_id: Some(uuid::Uuid::new_v4().to_string()),
        };

        let op = match op_type {
            OpType::Insert => ReplicationOp::Insert(versioned.clone()),
            OpType::Delete => ReplicationOp::Delete(versioned.clone()),
        };

        // Write to WAL first
        self.write_to_wal(&op).await?;

        // Apply locally
        let mut storage = self.storage.write().await;
        match op_type {
            OpType::Insert => {
                storage.triples.insert(triple, versioned);
            }
            OpType::Delete => {
                storage.triples.remove(&triple);
            }
        }

        // Replicate based on strategy
        match &self.config.strategy {
            ReplicationStrategy::SyncAll => {
                self.replicate_sync_all(op).await?;
            }
            ReplicationStrategy::AsyncAll => {
                self.replicate_async_all(op).await?;
            }
            ReplicationStrategy::SyncQuorum { n } => {
                self.replicate_sync_quorum(op, *n).await?;
            }
            _ => {
                // Other strategies
                self.replicate_async_all(op).await?;
            }
        }

        Ok(())
    }

    /// Query with consistency level
    pub async fn query(
        &self,
        pattern: &TriplePattern,
        consistency: ConsistencyLevel,
    ) -> Result<Vec<Triple>, OxirsError> {
        match consistency {
            ConsistencyLevel::Strong => {
                // Ensure we have latest data from majority
                self.sync_with_quorum().await?;
            }
            ConsistencyLevel::BoundedStaleness { max_lag_ms } => {
                // Check if our data is within staleness bound
                let state = self.state.read().await;
                for peer in state.peer_states.values() {
                    if peer.lag_ms > max_lag_ms {
                        return Err(OxirsError::Store(
                            "Data staleness exceeds bound".to_string(),
                        ));
                    }
                }
            }
            ConsistencyLevel::Eventual => {
                // Return local data
            }
        }

        let storage = self.storage.read().await;
        let results: Vec<Triple> = storage
            .triples
            .values()
            .filter(|vt| pattern.matches(&vt.triple))
            .map(|vt| vt.triple.clone())
            .collect();

        Ok(results)
    }

    /// Handle incoming replication operation
    async fn handle_incoming_op(
        &self,
        from_region: String,
        op: ReplicationOp,
    ) -> Result<(), OxirsError> {
        let mut stats = self.stats.write().await;
        stats.ops_received += 1;
        drop(stats);

        match &op {
            ReplicationOp::Insert(versioned) | ReplicationOp::Delete(versioned) => {
                let mut storage = self.storage.write().await;
                let mut state = self.state.write().await;

                // Check for conflicts
                if let Some(existing) = storage.triples.get(&versioned.triple) {
                    if existing.version.is_concurrent(&versioned.version) {
                        // Conflict detected
                        let mut stats = self.stats.write().await;
                        stats.conflicts_detected += 1;
                        drop(stats);

                        // Resolve conflict
                        let winner = self.resolver.resolve_conflict(existing, versioned).await?;
                        storage.triples.insert(versioned.triple.clone(), winner);

                        // Store conflict for later analysis
                        storage
                            .conflicts
                            .entry(versioned.triple.clone())
                            .or_insert_with(Vec::new)
                            .push(versioned.clone());
                    } else if versioned.version.happens_before(&existing.version) {
                        // Incoming is older, ignore
                        return Ok(());
                    } else {
                        // Incoming is newer, apply
                        storage
                            .triples
                            .insert(versioned.triple.clone(), versioned.clone());
                    }
                } else {
                    // No conflict, apply
                    if matches!(op, ReplicationOp::Insert(_)) {
                        storage
                            .triples
                            .insert(versioned.triple.clone(), versioned.clone());
                    }
                }

                // Update vector clock
                state.vector_clock.merge(&versioned.version);
            }
            ReplicationOp::Batch(ops) => {
                for op in ops {
                    Box::pin(self.handle_incoming_op(from_region.clone(), op.clone())).await?;
                }
            }
            ReplicationOp::Heartbeat(info) => {
                self.handle_heartbeat(from_region, info.clone()).await?;
            }
            _ => {}
        }

        Ok(())
    }

    /// Initialize WAL
    async fn initialize_wal(&self) -> Result<(), OxirsError> {
        let mut wal = self.wal.write().await;
        std::fs::create_dir_all(&wal.config.wal_path)?;

        // Open or create WAL file
        let wal_file = std::fs::OpenOptions::new()
            .create(true)
            .append(true)
            .open(format!("{}/wal.log", wal.config.wal_path))?;

        wal.current_file = Some(wal_file);
        Ok(())
    }

    /// Connect to peer regions
    async fn connect_to_peers(&self) -> Result<(), OxirsError> {
        for peer in &self.config.peers {
            if peer.active {
                // In real implementation, would establish actual network connection
                tracing::info!("Connecting to peer region: {}", peer.region_id);

                // Update peer state
                let mut state = self.state.write().await;
                state.peer_states.insert(
                    peer.region_id.clone(),
                    PeerState {
                        last_seen: Instant::now(),
                        last_clock: VectorClock::new(),
                        connected: true,
                        lag_ms: 0,
                        in_flight: 0,
                    },
                );
            }
        }
        Ok(())
    }

    /// Spawn message processor
    fn spawn_message_processor(&self) {
        let storage = self.storage.clone();
        let state = self.state.clone();
        let network = self.network.clone();
        let resolver = self.resolver.clone();
        let stats = self.stats.clone();

        tokio::spawn(async move {
            let mut rx = network.message_rx.lock().await;
            while let Some(msg) = rx.recv().await {
                match msg {
                    NetworkMessage::IncomingOp { _from_region, _op } => {
                        // Handle in separate task to avoid blocking
                        let storage = storage.clone();
                        let state = state.clone();
                        let resolver = resolver.clone();
                        let stats = stats.clone();

                        tokio::spawn(async move {
                            if let Err(e) = Self::handle_incoming_op_static(
                                _from_region,
                                *_op,
                                storage,
                                state,
                                resolver,
                                stats,
                            )
                            .await
                            {
                                tracing::error!("Error handling incoming op: {}", e);
                            }
                        });
                    }
                    NetworkMessage::ConnectionEvent { region_id, event } => {
                        let mut state_guard = state.write().await;
                        if let Some(peer_state) = state_guard.peer_states.get_mut(&region_id) {
                            match event {
                                ConnectionEvent::Connected => {
                                    peer_state.connected = true;
                                    peer_state.last_seen = Instant::now();
                                }
                                ConnectionEvent::Disconnected => {
                                    peer_state.connected = false;
                                }
                                ConnectionEvent::Error(err) => {
                                    tracing::error!("Connection error for {}: {}", region_id, err);
                                    peer_state.connected = false;
                                }
                            }
                        }
                    }
                }
            }
        });
    }

    /// Static handler for incoming operations
    async fn handle_incoming_op_static(
        from_region: String,
        op: ReplicationOp,
        storage: Arc<RwLock<ReplicationStorage>>,
        state: Arc<RwLock<ReplicationState>>,
        resolver: Arc<ConflictResolver>,
        stats: Arc<RwLock<ReplicationStats>>,
    ) -> Result<(), OxirsError> {
        // Implementation similar to instance method
        let mut stats_guard = stats.write().await;
        stats_guard.ops_received += 1;
        drop(stats_guard);

        match &op {
            ReplicationOp::Insert(versioned) | ReplicationOp::Delete(versioned) => {
                let mut storage_guard = storage.write().await;
                let mut state_guard = state.write().await;

                // Check for conflicts
                if let Some(existing) = storage_guard.triples.get(&versioned.triple) {
                    if existing.version.is_concurrent(&versioned.version) {
                        // Conflict detected
                        let mut stats_guard = stats.write().await;
                        stats_guard.conflicts_detected += 1;
                        drop(stats_guard);

                        // Resolve conflict
                        let winner = resolver.resolve_conflict(existing, versioned).await?;
                        storage_guard
                            .triples
                            .insert(versioned.triple.clone(), winner);

                        // Store conflict for later analysis
                        storage_guard
                            .conflicts
                            .entry(versioned.triple.clone())
                            .or_insert_with(Vec::new)
                            .push(versioned.clone());
                    } else if versioned.version.happens_before(&existing.version) {
                        // Incoming is older, ignore
                        return Ok(());
                    } else {
                        // Incoming is newer, apply
                        storage_guard
                            .triples
                            .insert(versioned.triple.clone(), versioned.clone());
                    }
                } else {
                    // No conflict, apply
                    if matches!(op, ReplicationOp::Insert(_)) {
                        storage_guard
                            .triples
                            .insert(versioned.triple.clone(), versioned.clone());
                    }
                }

                // Update vector clock
                state_guard.vector_clock.merge(&versioned.version);
            }
            ReplicationOp::Batch(ops) => {
                for op_item in ops {
                    Box::pin(Self::handle_incoming_op_static(
                        from_region.clone(),
                        op_item.clone(),
                        storage.clone(),
                        state.clone(),
                        resolver.clone(),
                        stats.clone(),
                    ))
                    .await?;
                }
            }
            ReplicationOp::Heartbeat(info) => {
                let mut state_guard = state.write().await;
                if let Some(peer) = state_guard.peer_states.get_mut(&from_region) {
                    peer.last_seen = std::time::Instant::now();
                    peer.lag_ms = info.lag_ms;
                }
            }
            _ => {}
        }

        Ok(())
    }

    /// Spawn heartbeat sender
    fn spawn_heartbeat_sender(&self) {
        let config = self.config.clone();
        let _state = self.state.clone();
        let network = self.network.clone();

        tokio::spawn(async move {
            let mut interval = interval(Duration::from_secs(5));

            loop {
                interval.tick().await;

                let heartbeat = ReplicationOp::Heartbeat(HeartbeatInfo {
                    region_id: config.region_id.clone(),
                    timestamp: std::time::SystemTime::now()
                        .duration_since(std::time::UNIX_EPOCH)
                        .expect("SystemTime should be after UNIX_EPOCH")
                        .as_secs(),
                    load: LoadMetrics {
                        cpu_percent: 0.0, // Would get actual metrics
                        memory_percent: 0.0,
                        disk_percent: 0.0,
                        network_mbps: 0.0,
                        connections: 0,
                    },
                    lag_ms: 0,
                });

                // Send to all connected peers
                let connections = network.connections.read().await;
                for (_, conn) in connections.iter() {
                    let _ = conn.send_tx.send(heartbeat.clone()).await;
                }
            }
        });
    }

    /// Spawn lag monitor
    fn spawn_lag_monitor(&self) {
        let state = self.state.clone();
        let stats = self.stats.clone();

        tokio::spawn(async move {
            let mut interval = interval(Duration::from_secs(10));

            loop {
                interval.tick().await;

                let state_guard = state.read().await;
                let mut total_lag = 0u64;
                let mut peer_count = 0u64;

                for peer_state in state_guard.peer_states.values() {
                    total_lag += peer_state.lag_ms;
                    peer_count += 1;
                }

                if peer_count > 0 {
                    let mut stats_guard = stats.write().await;
                    stats_guard.avg_lag_ms = total_lag as f64 / peer_count as f64;
                }
            }
        });
    }

    /// Spawn WAL checkpoint
    fn spawn_wal_checkpoint(&self) {
        let wal = self.wal.clone();
        let config = self.config.persistence.clone();

        tokio::spawn(async move {
            let mut interval = interval(config.checkpoint_interval);

            loop {
                interval.tick().await;

                // Perform checkpoint
                let mut wal_guard = wal.write().await;
                if wal_guard.current_size > config.max_wal_size {
                    // Rotate WAL file
                    tracing::info!("Rotating WAL file");
                    // Implementation would rotate and compress old WAL
                    wal_guard.current_size = 0;
                }
            }
        });
    }

    /// Write operation to WAL
    async fn write_to_wal(&self, op: &ReplicationOp) -> Result<(), OxirsError> {
        let mut wal = self.wal.write().await;

        let entry = WalEntry {
            seq: wal.entries.len() as u64,
            timestamp: std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .expect("SystemTime should be after UNIX_EPOCH")
                .as_secs(),
            op: op.clone(),
            checksum: 0, // Would calculate actual checksum
        };

        // Serialize and write
        let serialized = oxicode::serde::encode_to_vec(&entry, oxicode::config::standard())?;
        if let Some(ref mut file) = wal.current_file {
            use std::io::Write;
            file.write_all(&serialized)?;
            file.sync_all()?;
        }

        wal.entries.push_back(entry);
        wal.current_size += serialized.len();

        Ok(())
    }

    /// Replicate synchronously to all regions
    async fn replicate_sync_all(&self, op: ReplicationOp) -> Result<(), OxirsError> {
        let connections = self.network.connections.read().await;
        let mut futures = Vec::new();

        for (_region_id, conn) in connections.iter() {
            let tx = conn.send_tx.clone();
            let op_clone = op.clone();
            let future = async move { tx.send(op_clone).await };
            futures.push(future);
        }

        // Wait for all to complete
        let results = futures::future::join_all(futures).await;

        // Check if any failed
        for result in results {
            if result.is_err() {
                return Err(OxirsError::Store("Replication failed".to_string()));
            }
        }

        Ok(())
    }

    /// Replicate asynchronously to all regions
    async fn replicate_async_all(&self, op: ReplicationOp) -> Result<(), OxirsError> {
        let connections = self.network.connections.read().await;

        for (_, conn) in connections.iter() {
            // Fire and forget
            let _ = conn.send_tx.try_send(op.clone());
        }

        Ok(())
    }

    /// Replicate synchronously to quorum
    async fn replicate_sync_quorum(&self, op: ReplicationOp, n: usize) -> Result<(), OxirsError> {
        let connections = self.network.connections.read().await;

        if connections.len() < n - 1 {
            return Err(OxirsError::Store(format!(
                "Not enough regions for quorum: need {}, have {}",
                n,
                connections.len() + 1
            )));
        }

        let mut futures = Vec::new();
        for (_, conn) in connections.iter().take(n - 1) {
            let tx = conn.send_tx.clone();
            let op_clone = op.clone();
            let future = async move { tx.send(op_clone).await };
            futures.push(future);
        }

        // Wait for quorum
        let results = futures::future::join_all(futures).await;

        let successes = results.iter().filter(|r| r.is_ok()).count();
        if successes + 1 >= n {
            Ok(())
        } else {
            Err(OxirsError::Store("Quorum not achieved".to_string()))
        }
    }

    /// Sync with quorum for strong consistency
    async fn sync_with_quorum(&self) -> Result<(), OxirsError> {
        // Implementation would sync vector clocks with majority of regions
        Ok(())
    }

    /// Handle heartbeat
    async fn handle_heartbeat(
        &self,
        from_region: String,
        info: HeartbeatInfo,
    ) -> Result<(), OxirsError> {
        let mut state = self.state.write().await;
        if let Some(peer) = state.peer_states.get_mut(&from_region) {
            peer.last_seen = Instant::now();
            peer.lag_ms = info.lag_ms;
        }
        Ok(())
    }
}

impl ConflictResolver {
    /// Resolve conflict between two versions
    async fn resolve_conflict(
        &self,
        existing: &VersionedTriple,
        incoming: &VersionedTriple,
    ) -> Result<VersionedTriple, OxirsError> {
        match &self.strategy {
            ConflictResolution::LastWriteWins => {
                if incoming.timestamp > existing.timestamp {
                    Ok(incoming.clone())
                } else {
                    Ok(existing.clone())
                }
            }
            ConflictResolution::VectorClock => {
                // Already handled by vector clock comparison
                Ok(existing.clone())
            }
            ConflictResolution::RegionPriority => {
                let existing_priority = self
                    .region_priorities
                    .get(&existing.origin_region)
                    .copied()
                    .unwrap_or(999);
                let incoming_priority = self
                    .region_priorities
                    .get(&incoming.origin_region)
                    .copied()
                    .unwrap_or(999);

                if incoming_priority < existing_priority {
                    Ok(incoming.clone())
                } else {
                    Ok(existing.clone())
                }
            }
            _ => Ok(existing.clone()),
        }
    }
}

/// Operation type
#[derive(Debug, Clone)]
pub enum OpType {
    Insert,
    Delete,
}

/// Consistency level for queries
#[derive(Debug, Clone)]
pub enum ConsistencyLevel {
    /// Strong consistency (linearizable)
    Strong,
    /// Bounded staleness
    BoundedStaleness { max_lag_ms: u64 },
    /// Eventual consistency
    Eventual,
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::model::{Literal, NamedNode};

    #[test]
    fn test_vector_clock() {
        let mut clock1 = VectorClock::new();
        let mut clock2 = VectorClock::new();

        clock1.increment("region1");
        clock1.increment("region1");
        clock2.increment("region2");

        assert!(!clock1.happens_before(&clock2));
        assert!(!clock2.happens_before(&clock1));
        assert!(clock1.is_concurrent(&clock2));

        clock2.merge(&clock1);
        assert!(clock1.happens_before(&clock2));
    }

    #[tokio::test]
    async fn test_replication_manager() {
        let config = ReplicationConfig {
            region_id: "us-east-1".to_string(),
            region: RegionConfig {
                name: "US East".to_string(),
                location: GeographicLocation {
                    latitude: 38.7,
                    longitude: -77.0,
                    continent: "North America".to_string(),
                    country: "USA".to_string(),
                },
                availability_zones: vec!["us-east-1a".to_string(), "us-east-1b".to_string()],
                capacity: RegionCapacity {
                    read_units: 1000,
                    write_units: 500,
                    storage_gb: 100,
                    auto_scaling: true,
                },
            },
            peers: vec![],
            strategy: ReplicationStrategy::AsyncAll,
            conflict_resolution: ConflictResolution::LastWriteWins,
            network: NetworkConfig {
                connect_timeout: Duration::from_secs(5),
                request_timeout: Duration::from_secs(30),
                max_retries: 3,
                compression: true,
                encryption: EncryptionConfig {
                    tls_enabled: true,
                    cert_path: None,
                    key_path: None,
                    ca_path: None,
                },
            },
            persistence: PersistenceConfig {
                wal_path: "/tmp/wal".to_string(),
                checkpoint_interval: Duration::from_secs(300),
                max_wal_size: 100 * 1024 * 1024,
                wal_compression: true,
            },
        };

        let manager = ReplicationManager::new(config)
            .await
            .expect("async operation should succeed");

        // Test write replication
        let triple = Triple::new(
            NamedNode::new("http://example.org/s").expect("valid IRI"),
            NamedNode::new("http://example.org/p").expect("valid IRI"),
            crate::model::Object::Literal(Literal::new("test")),
        );

        manager
            .replicate_write(triple.clone(), OpType::Insert)
            .await
            .expect("operation should succeed");

        // Test query
        let pattern = TriplePattern::new(None, None, None);
        let results = manager
            .query(&pattern, ConsistencyLevel::Eventual)
            .await
            .expect("operation should succeed");
        assert_eq!(results.len(), 1);
        assert_eq!(results[0], triple);
    }
}