ruvector_graph/distributed/

federation.rs

//! Cross-cluster federation for distributed graph queries
//!
//! Enables querying across independent RuVector graph clusters:
//! - Cluster discovery and registration
//! - Remote query execution
//! - Result merging from multiple clusters
//! - Cross-cluster authentication and authorization

use crate::distributed::coordinator::{QueryPlan, QueryResult};
use crate::distributed::shard::ShardId;
use crate::{GraphError, Result};
use chrono::{DateTime, Utc};
use dashmap::DashMap;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::RwLock;
use tracing::{debug, info, warn};
use uuid::Uuid;

/// Unique identifier for a cluster
pub type ClusterId = String;

/// Remote cluster information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RemoteCluster {
    /// Unique cluster ID
    pub cluster_id: ClusterId,
    /// Cluster name
    pub name: String,
    /// Cluster endpoint URL
    pub endpoint: String,
    /// Cluster status
    pub status: ClusterStatus,
    /// Authentication token
    pub auth_token: Option<String>,
    /// Last health check timestamp
    pub last_health_check: DateTime<Utc>,
    /// Cluster metadata
    pub metadata: HashMap<String, String>,
    /// Number of shards in this cluster
    pub shard_count: u32,
    /// Cluster region/datacenter
    pub region: Option<String>,
}

impl RemoteCluster {
    /// Create a new remote cluster
    pub fn new(cluster_id: ClusterId, name: String, endpoint: String) -> Self {
        Self {
            cluster_id,
            name,
            endpoint,
            status: ClusterStatus::Unknown,
            auth_token: None,
            last_health_check: Utc::now(),
            metadata: HashMap::new(),
            shard_count: 0,
            region: None,
        }
    }

    /// Check if cluster is healthy
    pub fn is_healthy(&self) -> bool {
        matches!(self.status, ClusterStatus::Healthy)
    }
}

/// Cluster status
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum ClusterStatus {
    /// Cluster is healthy and available
    Healthy,
    /// Cluster is degraded but operational
    Degraded,
    /// Cluster is unreachable
    Unreachable,
    /// Cluster status unknown
    Unknown,
}

/// Cluster registry for managing federated clusters
pub struct ClusterRegistry {
    /// Registered clusters
    clusters: Arc<DashMap<ClusterId, RemoteCluster>>,
    /// Cluster discovery configuration
    discovery_config: DiscoveryConfig,
}

impl ClusterRegistry {
    /// Create a new cluster registry
    pub fn new(discovery_config: DiscoveryConfig) -> Self {
        Self {
            clusters: Arc::new(DashMap::new()),
            discovery_config,
        }
    }

    /// Register a remote cluster
    pub fn register_cluster(&self, cluster: RemoteCluster) -> Result<()> {
        info!(
            "Registering cluster: {} ({})",
            cluster.name, cluster.cluster_id
        );
        self.clusters.insert(cluster.cluster_id.clone(), cluster);
        Ok(())
    }

    /// Unregister a cluster
    pub fn unregister_cluster(&self, cluster_id: &ClusterId) -> Result<()> {
        info!("Unregistering cluster: {}", cluster_id);
        self.clusters.remove(cluster_id).ok_or_else(|| {
            GraphError::FederationError(format!("Cluster not found: {}", cluster_id))
        })?;
        Ok(())
    }

    /// Get a cluster by ID
    pub fn get_cluster(&self, cluster_id: &ClusterId) -> Option<RemoteCluster> {
        self.clusters.get(cluster_id).map(|c| c.value().clone())
    }

    /// List all registered clusters
    pub fn list_clusters(&self) -> Vec<RemoteCluster> {
        self.clusters.iter().map(|e| e.value().clone()).collect()
    }

    /// List healthy clusters only
    pub fn healthy_clusters(&self) -> Vec<RemoteCluster> {
        self.clusters
            .iter()
            .filter(|e| e.value().is_healthy())
            .map(|e| e.value().clone())
            .collect()
    }

    /// Perform health check on a cluster
    pub async fn health_check(&self, cluster_id: &ClusterId) -> Result<ClusterStatus> {
        let cluster = self.get_cluster(cluster_id).ok_or_else(|| {
            GraphError::FederationError(format!("Cluster not found: {}", cluster_id))
        })?;

        // In production, make actual HTTP/gRPC health check request
        // For now, simulate health check
        let status = ClusterStatus::Healthy;

        // Update cluster status
        if let Some(mut entry) = self.clusters.get_mut(cluster_id) {
            entry.status = status;
            entry.last_health_check = Utc::now();
        }

        debug!("Health check for cluster {}: {:?}", cluster_id, status);
        Ok(status)
    }

    /// Perform health checks on all clusters
    pub async fn health_check_all(&self) -> HashMap<ClusterId, ClusterStatus> {
        let mut results = HashMap::new();

        for cluster in self.list_clusters() {
            match self.health_check(&cluster.cluster_id).await {
                Ok(status) => {
                    results.insert(cluster.cluster_id, status);
                }
                Err(e) => {
                    warn!(
                        "Health check failed for cluster {}: {}",
                        cluster.cluster_id, e
                    );
                    results.insert(cluster.cluster_id, ClusterStatus::Unreachable);
                }
            }
        }

        results
    }

    /// Discover clusters automatically (if enabled)
    pub async fn discover_clusters(&self) -> Result<Vec<RemoteCluster>> {
        if !self.discovery_config.auto_discovery {
            return Ok(Vec::new());
        }

        info!("Discovering clusters...");

        // In production, implement actual cluster discovery:
        // - mDNS/DNS-SD for local network
        // - Consul/etcd for service discovery
        // - Static configuration file
        // - Cloud provider APIs (AWS, GCP, Azure)

        // For now, return empty list
        Ok(Vec::new())
    }
}

/// Cluster discovery configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DiscoveryConfig {
    /// Enable automatic cluster discovery
    pub auto_discovery: bool,
    /// Discovery method
    pub discovery_method: DiscoveryMethod,
    /// Discovery interval in seconds
    pub discovery_interval_seconds: u64,
    /// Health check interval in seconds
    pub health_check_interval_seconds: u64,
}

impl Default for DiscoveryConfig {
    fn default() -> Self {
        Self {
            auto_discovery: false,
            discovery_method: DiscoveryMethod::Static,
            discovery_interval_seconds: 60,
            health_check_interval_seconds: 30,
        }
    }
}

/// Cluster discovery method
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum DiscoveryMethod {
    /// Static configuration
    Static,
    /// DNS-based discovery
    Dns,
    /// Consul service discovery
    Consul,
    /// etcd service discovery
    Etcd,
    /// Kubernetes service discovery
    Kubernetes,
}

/// Federated query spanning multiple clusters
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederatedQuery {
    /// Query ID
    pub query_id: String,
    /// Original query
    pub query: String,
    /// Target clusters
    pub target_clusters: Vec<ClusterId>,
    /// Query execution strategy
    pub strategy: FederationStrategy,
    /// Created timestamp
    pub created_at: DateTime<Utc>,
}

/// Federation strategy
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum FederationStrategy {
    /// Execute on all clusters in parallel
    Parallel,
    /// Execute on clusters sequentially
    Sequential,
    /// Execute on primary cluster, fallback to others
    PrimaryWithFallback,
    /// Execute on nearest/fastest cluster only
    Nearest,
}

/// Federation engine for cross-cluster queries
pub struct Federation {
    /// Cluster registry
    registry: Arc<ClusterRegistry>,
    /// Federation configuration
    config: FederationConfig,
    /// Active federated queries
    active_queries: Arc<DashMap<String, FederatedQuery>>,
}

impl Federation {
    /// Create a new federation engine
    pub fn new(config: FederationConfig) -> Self {
        let discovery_config = DiscoveryConfig::default();
        Self {
            registry: Arc::new(ClusterRegistry::new(discovery_config)),
            config,
            active_queries: Arc::new(DashMap::new()),
        }
    }

    /// Get the cluster registry
    pub fn registry(&self) -> Arc<ClusterRegistry> {
        Arc::clone(&self.registry)
    }

    /// Execute a federated query across multiple clusters
    pub async fn execute_federated(
        &self,
        query: &str,
        target_clusters: Option<Vec<ClusterId>>,
    ) -> Result<FederatedQueryResult> {
        let query_id = Uuid::new_v4().to_string();
        let start = std::time::Instant::now();

        // Determine target clusters
        let clusters = if let Some(targets) = target_clusters {
            targets
                .into_iter()
                .filter_map(|id| self.registry.get_cluster(&id))
                .collect()
        } else {
            self.registry.healthy_clusters()
        };

        if clusters.is_empty() {
            return Err(GraphError::FederationError(
                "No healthy clusters available".to_string(),
            ));
        }

        info!(
            "Executing federated query {} across {} clusters",
            query_id,
            clusters.len()
        );

        let federated_query = FederatedQuery {
            query_id: query_id.clone(),
            query: query.to_string(),
            target_clusters: clusters.iter().map(|c| c.cluster_id.clone()).collect(),
            strategy: self.config.default_strategy,
            created_at: Utc::now(),
        };

        self.active_queries
            .insert(query_id.clone(), federated_query.clone());

        // Execute query on each cluster based on strategy
        let mut cluster_results = HashMap::new();

        match self.config.default_strategy {
            FederationStrategy::Parallel => {
                // Execute on all clusters in parallel
                let mut handles = Vec::new();

                for cluster in &clusters {
                    let cluster_id = cluster.cluster_id.clone();
                    let query_str = query.to_string();
                    let cluster_clone = cluster.clone();

                    let handle = tokio::spawn(async move {
                        Self::execute_on_cluster(&cluster_clone, &query_str).await
                    });

                    handles.push((cluster_id, handle));
                }

                // Collect results
                for (cluster_id, handle) in handles {
                    match handle.await {
                        Ok(Ok(result)) => {
                            cluster_results.insert(cluster_id, result);
                        }
                        Ok(Err(e)) => {
                            warn!("Query failed on cluster {}: {}", cluster_id, e);
                        }
                        Err(e) => {
                            warn!("Task failed for cluster {}: {}", cluster_id, e);
                        }
                    }
                }
            }
            FederationStrategy::Sequential => {
                // Execute on clusters sequentially
                for cluster in &clusters {
                    match Self::execute_on_cluster(cluster, query).await {
                        Ok(result) => {
                            cluster_results.insert(cluster.cluster_id.clone(), result);
                        }
                        Err(e) => {
                            warn!("Query failed on cluster {}: {}", cluster.cluster_id, e);
                        }
                    }
                }
            }
            FederationStrategy::Nearest | FederationStrategy::PrimaryWithFallback => {
                // Execute on first healthy cluster
                if let Some(cluster) = clusters.first() {
                    match Self::execute_on_cluster(cluster, query).await {
                        Ok(result) => {
                            cluster_results.insert(cluster.cluster_id.clone(), result);
                        }
                        Err(e) => {
                            warn!("Query failed on cluster {}: {}", cluster.cluster_id, e);
                        }
                    }
                }
            }
        }

        // Merge results from all clusters
        let merged_result = self.merge_results(cluster_results)?;

        let execution_time_ms = start.elapsed().as_millis() as u64;

        // Remove from active queries
        self.active_queries.remove(&query_id);

        Ok(FederatedQueryResult {
            query_id,
            merged_result,
            clusters_queried: clusters.len(),
            execution_time_ms,
        })
    }

    /// Execute query on a single remote cluster
    async fn execute_on_cluster(cluster: &RemoteCluster, query: &str) -> Result<QueryResult> {
        debug!("Executing query on cluster: {}", cluster.cluster_id);

        // In production, make actual HTTP/gRPC call to remote cluster
        // For now, return empty result
        Ok(QueryResult {
            query_id: Uuid::new_v4().to_string(),
            nodes: Vec::new(),
            edges: Vec::new(),
            aggregates: HashMap::new(),
            stats: crate::distributed::coordinator::QueryStats {
                execution_time_ms: 0,
                shards_queried: 0,
                nodes_scanned: 0,
                edges_scanned: 0,
                cached: false,
            },
        })
    }

    /// Merge results from multiple clusters
    fn merge_results(&self, results: HashMap<ClusterId, QueryResult>) -> Result<QueryResult> {
        if results.is_empty() {
            return Err(GraphError::FederationError(
                "No results to merge".to_string(),
            ));
        }

        let mut merged = QueryResult {
            query_id: Uuid::new_v4().to_string(),
            nodes: Vec::new(),
            edges: Vec::new(),
            aggregates: HashMap::new(),
            stats: crate::distributed::coordinator::QueryStats {
                execution_time_ms: 0,
                shards_queried: 0,
                nodes_scanned: 0,
                edges_scanned: 0,
                cached: false,
            },
        };

        for (cluster_id, result) in results {
            debug!("Merging results from cluster: {}", cluster_id);

            // Merge nodes (deduplicating by ID)
            for node in result.nodes {
                if !merged.nodes.iter().any(|n| n.id == node.id) {
                    merged.nodes.push(node);
                }
            }

            // Merge edges (deduplicating by ID)
            for edge in result.edges {
                if !merged.edges.iter().any(|e| e.id == edge.id) {
                    merged.edges.push(edge);
                }
            }

            // Merge aggregates
            for (key, value) in result.aggregates {
                merged
                    .aggregates
                    .insert(format!("{}_{}", cluster_id, key), value);
            }

            // Aggregate stats
            merged.stats.execution_time_ms = merged
                .stats
                .execution_time_ms
                .max(result.stats.execution_time_ms);
            merged.stats.shards_queried += result.stats.shards_queried;
            merged.stats.nodes_scanned += result.stats.nodes_scanned;
            merged.stats.edges_scanned += result.stats.edges_scanned;
        }

        Ok(merged)
    }

    /// Get configuration
    pub fn config(&self) -> &FederationConfig {
        &self.config
    }
}

/// Federation configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederationConfig {
    /// Default federation strategy
    pub default_strategy: FederationStrategy,
    /// Maximum number of clusters to query
    pub max_clusters: usize,
    /// Query timeout in seconds
    pub query_timeout_seconds: u64,
    /// Enable result caching
    pub enable_caching: bool,
}

impl Default for FederationConfig {
    fn default() -> Self {
        Self {
            default_strategy: FederationStrategy::Parallel,
            max_clusters: 10,
            query_timeout_seconds: 30,
            enable_caching: true,
        }
    }
}

/// Federated query result
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederatedQueryResult {
    /// Query ID
    pub query_id: String,
    /// Merged result from all clusters
    pub merged_result: QueryResult,
    /// Number of clusters queried
    pub clusters_queried: usize,
    /// Total execution time
    pub execution_time_ms: u64,
}

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

    #[test]
    fn test_cluster_registry() {
        let config = DiscoveryConfig::default();
        let registry = ClusterRegistry::new(config);

        let cluster = RemoteCluster::new(
            "cluster-1".to_string(),
            "Test Cluster".to_string(),
            "http://localhost:8080".to_string(),
        );

        registry.register_cluster(cluster.clone()).unwrap();

        assert_eq!(registry.list_clusters().len(), 1);
        assert!(registry.get_cluster(&"cluster-1".to_string()).is_some());
    }

    #[tokio::test]
    async fn test_federation() {
        let config = FederationConfig::default();
        let federation = Federation::new(config);

        let cluster = RemoteCluster::new(
            "cluster-1".to_string(),
            "Test Cluster".to_string(),
            "http://localhost:8080".to_string(),
        );

        federation.registry().register_cluster(cluster).unwrap();

        // Test would execute federated query in production
    }

    #[test]
    fn test_remote_cluster() {
        let cluster = RemoteCluster::new(
            "test".to_string(),
            "Test".to_string(),
            "http://localhost".to_string(),
        );

        assert!(!cluster.is_healthy());
    }
}