oxirs-fuseki 0.2.4

//! Multi-node clustering support with Raft consensus
//!
//! This module provides distributed consensus and clustering capabilities:
//! - Raft consensus protocol for leader election and log replication
//! - Automatic failover and recovery
//! - Data partitioning and sharding
//! - Cross-node query coordination
//! - Split-brain protection

pub mod byzantine_raft;
pub mod coordinator;
pub mod node;
pub mod partition;
pub mod raft;

use serde::{Deserialize, Serialize};
use std::{collections::HashMap, net::SocketAddr, sync::Arc, time::Duration};
use tokio::sync::RwLock;
use uuid::Uuid;

use crate::{error::FusekiResult, store::Store};

/// Clustering configuration
#[derive(Debug, Clone)]
pub struct ClusterConfig {
    /// Node ID
    pub node_id: String,
    /// Bind address for cluster communication
    pub bind_addr: SocketAddr,
    /// Initial cluster members
    pub seeds: Vec<String>,
    /// Raft configuration
    pub raft: RaftConfig,
    /// Partitioning configuration
    pub partitioning: PartitionConfig,
    /// Replication configuration
    pub replication: ReplicationConfig,
}

impl Default for ClusterConfig {
    fn default() -> Self {
        Self {
            node_id: Uuid::new_v4().to_string(),
            bind_addr: "0.0.0.0:7000"
                .parse()
                .expect("default bind address should be valid"),
            seeds: Vec::new(),
            raft: RaftConfig::default(),
            partitioning: PartitionConfig::default(),
            replication: ReplicationConfig::default(),
        }
    }
}

/// Raft consensus configuration
#[derive(Debug, Clone)]
pub struct RaftConfig {
    /// Election timeout range (min, max)
    pub election_timeout: (Duration, Duration),
    /// Heartbeat interval
    pub heartbeat_interval: Duration,
    /// Maximum entries per append entries RPC
    pub max_append_entries: usize,
    /// Snapshot threshold (log entries)
    pub snapshot_threshold: u64,
    /// Enable pre-vote to prevent disruption
    pub pre_vote: bool,
}

impl Default for RaftConfig {
    fn default() -> Self {
        Self {
            election_timeout: (Duration::from_millis(150), Duration::from_millis(300)),
            heartbeat_interval: Duration::from_millis(50),
            max_append_entries: 100,
            snapshot_threshold: 10000,
            pre_vote: true,
        }
    }
}

/// Data partitioning configuration
#[derive(Debug, Clone)]
pub struct PartitionConfig {
    /// Partitioning strategy
    pub strategy: PartitionStrategy,
    /// Number of partitions
    pub partition_count: u32,
    /// Virtual nodes per physical node (for consistent hashing)
    pub vnodes: u32,
    /// Partition rebalancing configuration
    pub rebalancing: RebalancingConfig,
}

impl Default for PartitionConfig {
    fn default() -> Self {
        Self {
            strategy: PartitionStrategy::ConsistentHashing,
            partition_count: 128,
            vnodes: 100,
            rebalancing: RebalancingConfig::default(),
        }
    }
}

/// Partitioning strategy
#[derive(Debug, Clone)]
pub enum PartitionStrategy {
    /// Consistent hashing with virtual nodes
    ConsistentHashing,
    /// Range-based partitioning
    Range,
    /// Custom partitioning function
    Custom,
}

/// Partition rebalancing configuration
#[derive(Debug, Clone)]
pub struct RebalancingConfig {
    /// Enable automatic rebalancing
    pub enabled: bool,
    /// Rebalancing threshold (data skew percentage)
    pub threshold: f64,
    /// Maximum concurrent partition moves
    pub max_concurrent_moves: usize,
    /// Delay between rebalancing checks
    pub check_interval: Duration,
}

impl Default for RebalancingConfig {
    fn default() -> Self {
        Self {
            enabled: true,
            threshold: 0.2, // 20% skew
            max_concurrent_moves: 3,
            check_interval: Duration::from_secs(300), // 5 minutes
        }
    }
}

/// Replication configuration
#[derive(Debug, Clone)]
pub struct ReplicationConfig {
    /// Replication factor
    pub factor: usize,
    /// Write consistency level
    pub write_consistency: ConsistencyLevel,
    /// Read consistency level
    pub read_consistency: ConsistencyLevel,
    /// Enable read repair
    pub read_repair: bool,
}

impl Default for ReplicationConfig {
    fn default() -> Self {
        Self {
            factor: 3,
            write_consistency: ConsistencyLevel::Quorum,
            read_consistency: ConsistencyLevel::One,
            read_repair: true,
        }
    }
}

/// Consistency level for operations
#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
pub enum ConsistencyLevel {
    /// One replica
    One,
    /// Quorum of replicas (N/2 + 1)
    Quorum,
    /// All replicas
    All,
    /// Local quorum (same datacenter)
    LocalQuorum,
    /// Each quorum (all datacenters)
    EachQuorum,
}

/// Cluster node information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NodeInfo {
    /// Node ID
    pub id: String,
    /// Node address
    pub addr: SocketAddr,
    /// Node state
    pub state: NodeState,
    /// Node metadata
    pub metadata: NodeMetadata,
    /// Last heartbeat timestamp
    pub last_heartbeat: i64,
}

/// Node state in the cluster
#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
pub enum NodeState {
    /// Node is joining the cluster
    Joining,
    /// Node is active and healthy
    Active,
    /// Node is leaving the cluster
    Leaving,
    /// Node is down/unreachable
    Down,
    /// Node is decommissioned
    Decommissioned,
}

/// Node metadata
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NodeMetadata {
    /// Datacenter location
    pub datacenter: Option<String>,
    /// Rack location
    pub rack: Option<String>,
    /// Node capacity (storage in GB)
    pub capacity: u64,
    /// Current load (0.0 - 1.0)
    pub load: f64,
    /// Software version
    pub version: String,
}

/// Cluster membership view
#[derive(Debug, Clone)]
pub struct ClusterView {
    /// Current members
    pub members: HashMap<String, NodeInfo>,
    /// Current leader
    pub leader: Option<String>,
    /// View version
    pub version: u64,
    /// Last updated timestamp
    pub updated_at: i64,
}

/// Cluster manager
pub struct ClusterManager {
    config: ClusterConfig,
    node_info: NodeInfo,
    raft_node: Arc<raft::RaftNode>,
    partition_manager: Arc<partition::PartitionManager>,
    #[allow(dead_code)]
    coordinator: Arc<coordinator::QueryCoordinator>,
    cluster_view: Arc<RwLock<ClusterView>>,
}

impl ClusterManager {
    /// Create a new cluster manager
    pub async fn new(config: ClusterConfig, store: Arc<Store>) -> FusekiResult<Self> {
        let node_info = NodeInfo {
            id: config.node_id.clone(),
            addr: config.bind_addr,
            state: NodeState::Joining,
            metadata: NodeMetadata {
                datacenter: None,
                rack: None,
                capacity: 1000, // TODO: Get from system
                load: 0.0,
                version: env!("CARGO_PKG_VERSION").to_string(),
            },
            last_heartbeat: chrono::Utc::now().timestamp_millis(),
        };

        // Initialize Raft node
        let raft_node = Arc::new(
            raft::RaftNode::new(config.node_id.clone(), config.raft.clone(), store.clone()).await?,
        );

        // Initialize partition manager
        let partition_manager = Arc::new(partition::PartitionManager::new(
            config.partitioning.clone(),
            store.clone(),
        ));

        // Initialize query coordinator
        let coordinator = Arc::new(coordinator::QueryCoordinator::new(
            config.replication.clone(),
            store.clone(),
        ));

        let cluster_view = Arc::new(RwLock::new(ClusterView {
            members: HashMap::new(),
            leader: None,
            version: 0,
            updated_at: chrono::Utc::now().timestamp_millis(),
        }));

        Ok(Self {
            config,
            node_info,
            raft_node,
            partition_manager,
            coordinator,
            cluster_view,
        })
    }

    /// Start the cluster node
    pub async fn start(&self) -> FusekiResult<()> {
        // Start Raft node
        self.raft_node.start().await?;

        // Join cluster
        if !self.config.seeds.is_empty() {
            self.join_cluster().await?;
        } else {
            // Bootstrap new cluster
            self.bootstrap_cluster().await?;
        }

        // Start partition manager
        self.partition_manager.start().await?;

        // Start periodic tasks
        self.start_maintenance_tasks().await;

        Ok(())
    }

    /// Join existing cluster
    async fn join_cluster(&self) -> FusekiResult<()> {
        tracing::info!("Joining cluster with seeds: {:?}", self.config.seeds);

        // Contact seed nodes
        for seed in &self.config.seeds {
            if let Ok(()) = self.contact_seed(seed).await {
                break;
            }
        }

        // Update node state
        self.update_node_state(NodeState::Active).await;

        Ok(())
    }

    /// Bootstrap new cluster
    async fn bootstrap_cluster(&self) -> FusekiResult<()> {
        tracing::info!("Bootstrapping new cluster");

        // Initialize as single-node cluster
        self.raft_node.bootstrap().await?;

        // Update cluster view
        let mut view = self.cluster_view.write().await;
        view.members
            .insert(self.node_info.id.clone(), self.node_info.clone());
        view.leader = Some(self.node_info.id.clone());
        view.version = 1;

        // Update node state
        self.update_node_state(NodeState::Active).await;

        Ok(())
    }

    /// Contact a seed node
    async fn contact_seed(&self, _seed: &str) -> FusekiResult<()> {
        // TODO: Implement seed contact protocol
        Ok(())
    }

    /// Update node state
    async fn update_node_state(&self, state: NodeState) {
        let mut view = self.cluster_view.write().await;
        if let Some(node) = view.members.get_mut(&self.node_info.id) {
            node.state = state;
        }
    }

    /// Start maintenance tasks
    async fn start_maintenance_tasks(&self) {
        // Heartbeat task
        let cluster_view = self.cluster_view.clone();
        let node_id = self.node_info.id.clone();
        tokio::spawn(async move {
            let mut interval = tokio::time::interval(Duration::from_secs(5));
            loop {
                interval.tick().await;
                let mut view = cluster_view.write().await;
                if let Some(node) = view.members.get_mut(&node_id) {
                    node.last_heartbeat = chrono::Utc::now().timestamp_millis();
                }
            }
        });

        // Failure detection task
        let cluster_view = self.cluster_view.clone();
        tokio::spawn(async move {
            let mut interval = tokio::time::interval(Duration::from_secs(10));
            loop {
                interval.tick().await;
                let now = chrono::Utc::now().timestamp_millis();
                let mut view = cluster_view.write().await;

                for (_, node) in view.members.iter_mut() {
                    if node.state == NodeState::Active {
                        let elapsed = now - node.last_heartbeat;
                        if elapsed > 30000 {
                            // 30 seconds without heartbeat
                            node.state = NodeState::Down;
                            tracing::warn!("Node {} marked as down", node.id);
                        }
                    }
                }
            }
        });

        // Rebalancing task
        if self.config.partitioning.rebalancing.enabled {
            let partition_manager = self.partition_manager.clone();
            let interval = self.config.partitioning.rebalancing.check_interval;
            tokio::spawn(async move {
                let mut interval = tokio::time::interval(interval);
                loop {
                    interval.tick().await;
                    if let Err(e) = partition_manager.check_rebalancing().await {
                        tracing::error!("Rebalancing check failed: {}", e);
                    }
                }
            });
        }
    }

    /// Get current cluster view
    pub async fn get_cluster_view(&self) -> ClusterView {
        self.cluster_view.read().await.clone()
    }

    /// Get cluster health
    pub async fn get_health(&self) -> ClusterHealth {
        let view = self.cluster_view.read().await;

        let total_nodes = view.members.len();
        let active_nodes = view
            .members
            .values()
            .filter(|n| n.state == NodeState::Active)
            .count();
        let down_nodes = view
            .members
            .values()
            .filter(|n| n.state == NodeState::Down)
            .count();

        ClusterHealth {
            status: if down_nodes == 0 {
                HealthStatus::Green
            } else if active_nodes >= self.config.replication.factor {
                HealthStatus::Yellow
            } else {
                HealthStatus::Red
            },
            total_nodes,
            active_nodes,
            down_nodes,
            has_leader: view.leader.is_some(),
            partition_count: self.config.partitioning.partition_count as usize,
            under_replicated_partitions: 0, // TODO: Calculate
        }
    }
}

/// Cluster health status
#[derive(Debug, Clone, Serialize)]
pub struct ClusterHealth {
    pub status: HealthStatus,
    pub total_nodes: usize,
    pub active_nodes: usize,
    pub down_nodes: usize,
    pub has_leader: bool,
    pub partition_count: usize,
    pub under_replicated_partitions: usize,
}

#[derive(Debug, Clone, Copy, Serialize)]
pub enum HealthStatus {
    Green,
    Yellow,
    Red,
}

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

    #[test]
    fn test_cluster_config_default() {
        let config = ClusterConfig::default();
        assert!(!config.node_id.is_empty());
        assert!(config.raft.pre_vote);
        assert_eq!(config.partitioning.partition_count, 128);
        assert_eq!(config.replication.factor, 3);
    }

    #[test]
    fn test_consistency_levels() {
        let quorum = ConsistencyLevel::Quorum;
        assert_eq!(quorum, ConsistencyLevel::Quorum);
    }
}