oxirs_core/query/

distributed.rs

//! Distributed query engine for federated SPARQL execution
//!
//! This module provides federated query capabilities, cross-datacenter optimization,
//! edge computing distribution, and real-time collaborative filtering.

#![allow(dead_code)]

use crate::model::*;
use crate::query::algebra::{self, *};
// use crate::query::plan::ExecutionPlan; // For future distributed execution
use crate::OxirsError;
use async_trait::async_trait;
use std::collections::{HashMap, HashSet};
use std::sync::{Arc, RwLock};
use std::time::{Duration, Instant};
#[cfg(feature = "async")]
#[allow(unused_imports)] // Used in CollaborativeFilter when async feature is enabled
use tokio::sync::mpsc;

/// Distributed query coordinator
pub struct DistributedQueryEngine {
    /// Known federated endpoints
    endpoints: Arc<RwLock<HashMap<String, FederatedEndpoint>>>,
    /// Query routing strategy
    router: Arc<QueryRouter>,
    /// Network statistics
    network_stats: Arc<RwLock<NetworkStatistics>>,
    /// Edge computing nodes
    edge_nodes: Arc<RwLock<Vec<EdgeNode>>>,
    /// Configuration
    config: DistributedConfig,
}

/// Federated SPARQL endpoint
#[derive(Debug, Clone)]
pub struct FederatedEndpoint {
    /// Endpoint URL
    pub url: String,
    /// Supported features
    pub features: EndpointFeatures,
    /// Network latency (moving average)
    pub latency_ms: f64,
    /// Throughput estimate (triples/sec)
    pub throughput: f64,
    /// Available datasets
    pub datasets: Vec<String>,
    /// Last health check
    pub last_health_check: Instant,
    /// Endpoint status
    pub status: EndpointStatus,
}

/// Endpoint feature capabilities
#[derive(Debug, Clone)]
pub struct EndpointFeatures {
    /// SPARQL version support
    pub sparql_version: String,
    /// Supports SPARQL update
    pub update_support: bool,
    /// Supports federated queries
    pub federation_support: bool,
    /// Supports full-text search
    pub text_search: bool,
    /// Supports geospatial queries
    pub geospatial: bool,
    /// Custom extensions
    pub extensions: HashSet<String>,
}

/// Endpoint status
#[derive(Debug, Clone, PartialEq)]
pub enum EndpointStatus {
    /// Endpoint is healthy
    Healthy,
    /// Endpoint is degraded but operational
    Degraded,
    /// Endpoint is unreachable
    Unreachable,
    /// Endpoint is overloaded
    Overloaded,
}

/// Query routing strategy
pub struct QueryRouter {
    /// Routing policy
    policy: RoutingPolicy,
    /// Data locality map
    data_locality: Arc<RwLock<DataLocalityMap>>,
    /// Query pattern cache
    pattern_cache: Arc<RwLock<PatternCache>>,
}

/// Custom routing function type
pub type RoutingFunction =
    Arc<dyn Fn(&Query, &[FederatedEndpoint]) -> Vec<QueryRoute> + Send + Sync>;

/// Routing policy for distributed queries
#[derive(Clone)]
pub enum RoutingPolicy {
    /// Route to nearest endpoint
    NearestEndpoint,
    /// Load balance across endpoints
    LoadBalanced,
    /// Route based on data locality
    DataLocality,
    /// Minimize network transfers
    MinimizeTransfers,
    /// Custom routing function
    Custom(RoutingFunction),
}

impl std::fmt::Debug for RoutingPolicy {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::NearestEndpoint => write!(f, "NearestEndpoint"),
            Self::LoadBalanced => write!(f, "LoadBalanced"),
            Self::DataLocality => write!(f, "DataLocality"),
            Self::MinimizeTransfers => write!(f, "MinimizeTransfers"),
            Self::Custom(_) => write!(f, "Custom(<function>)"),
        }
    }
}

/// Data locality information
pub struct DataLocalityMap {
    /// Dataset to endpoint mapping
    dataset_locations: HashMap<String, Vec<String>>,
    /// Predicate distribution
    predicate_distribution: HashMap<NamedNode, Vec<String>>,
    /// Data affinity scores
    affinity_scores: HashMap<(String, String), f64>,
}

/// Query pattern cache for optimization
pub struct PatternCache {
    /// Cached execution plans
    plans: HashMap<QueryHash, CachedPlan>,
    /// Pattern statistics
    stats: HashMap<QueryPattern, PatternStats>,
    /// Cache size limit
    max_size: usize,
}

/// Query hash for caching
type QueryHash = u64;

/// Cached execution plan
pub struct CachedPlan {
    /// The execution plan
    plan: DistributedPlan,
    /// Creation time
    created: Instant,
    /// Hit count
    hits: usize,
    /// Average execution time
    avg_exec_time: Duration,
}

/// Query pattern for analysis - using unified pattern representation
#[derive(Debug, Clone, Hash, PartialEq, Eq)]
struct QueryPattern {
    /// Triple patterns (using algebra representation for consistency)
    patterns: Vec<algebra::TriplePattern>,
    /// Join structure
    joins: Vec<JoinType>,
    /// Filter types
    filters: Vec<FilterType>,
}

/// Pattern execution statistics
struct PatternStats {
    /// Execution count
    count: usize,
    /// Success rate
    success_rate: f64,
    /// Average result size
    avg_result_size: usize,
    /// Preferred endpoints
    preferred_endpoints: Vec<String>,
}

/// Join type for pattern analysis
#[derive(Debug, Clone, Hash, PartialEq, Eq)]
enum JoinType {
    InnerJoin,
    LeftJoin,
    Union,
    Optional,
}

/// Filter type for pattern analysis
#[derive(Debug, Clone, Hash, PartialEq, Eq)]
enum FilterType {
    Comparison,
    Regex,
    Exists,
    Function(String),
}

/// Network statistics for optimization
pub struct NetworkStatistics {
    /// Endpoint latencies
    latencies: HashMap<String, Vec<Duration>>,
    /// Transfer rates
    transfer_rates: HashMap<String, Vec<f64>>,
    /// Error rates
    error_rates: HashMap<String, f64>,
    /// Last update time
    last_update: Instant,
}

/// Edge computing node
#[derive(Debug, Clone)]
pub struct EdgeNode {
    /// Node identifier
    pub id: String,
    /// Geographic location
    pub location: GeoLocation,
    /// Compute capacity
    pub capacity: ComputeCapacity,
    /// Cached data
    pub cached_data: HashSet<String>,
    /// Current load
    pub load: f64,
}

/// Geographic location
#[derive(Debug, Clone)]
pub struct GeoLocation {
    /// Latitude
    pub latitude: f64,
    /// Longitude
    pub longitude: f64,
    /// Region identifier
    pub region: String,
}

/// Compute capacity specification
#[derive(Debug, Clone)]
pub struct ComputeCapacity {
    /// CPU cores
    pub cpu_cores: u32,
    /// Memory in GB
    pub memory_gb: u32,
    /// Storage in GB
    pub storage_gb: u32,
    /// Network bandwidth in Gbps
    pub bandwidth_gbps: f64,
}

/// Distributed query configuration
#[derive(Debug, Clone)]
pub struct DistributedConfig {
    /// Query timeout
    pub query_timeout: Duration,
    /// Maximum parallel queries
    pub max_parallel_queries: usize,
    /// Enable edge computing
    pub edge_computing_enabled: bool,
    /// Cache query results
    pub cache_results: bool,
    /// Result cache TTL
    pub cache_ttl: Duration,
    /// Network timeout
    pub network_timeout: Duration,
    /// Retry policy
    pub retry_policy: RetryPolicy,
}

/// Retry policy for failed queries
#[derive(Debug, Clone)]
pub struct RetryPolicy {
    /// Maximum retry attempts
    pub max_attempts: u32,
    /// Base delay between retries
    pub base_delay: Duration,
    /// Exponential backoff factor
    pub backoff_factor: f64,
    /// Maximum delay
    pub max_delay: Duration,
}

/// Query route for execution
pub struct QueryRoute {
    /// Target endpoint
    pub endpoint: String,
    /// Query fragment
    pub fragment: QueryFragment,
    /// Estimated cost
    pub estimated_cost: f64,
    /// Priority
    pub priority: u32,
}

/// Query fragment for distributed execution
pub struct QueryFragment {
    /// Original query
    pub query: Query,
    /// Assigned patterns (using algebra representation for performance)
    pub patterns: Vec<algebra::TriplePattern>,
    /// Required variables
    pub required_vars: HashSet<Variable>,
    /// Output variables
    pub output_vars: HashSet<Variable>,
}

/// Distributed execution plan
pub struct DistributedPlan {
    /// Query routes
    pub routes: Vec<QueryRoute>,
    /// Join order
    pub join_order: Vec<JoinOperation>,
    /// Result aggregation
    pub aggregation: AggregationStrategy,
    /// Estimated total cost
    pub total_cost: f64,
}

/// Join operation in distributed plan
pub struct JoinOperation {
    /// Left fragment
    pub left: usize,
    /// Right fragment
    pub right: usize,
    /// Join variables
    pub join_vars: Vec<Variable>,
    /// Join algorithm
    pub algorithm: JoinAlgorithm,
}

/// Join algorithm selection
#[derive(Debug, Clone)]
pub enum JoinAlgorithm {
    /// Hash join
    HashJoin,
    /// Sort-merge join
    SortMergeJoin,
    /// Nested loop join
    NestedLoop,
    /// Broadcast join
    BroadcastJoin,
    /// Adaptive selection
    Adaptive,
}

/// Result aggregation strategy
#[derive(Clone)]
pub enum AggregationStrategy {
    /// Simple union
    Union,
    /// Merge with deduplication
    MergeDistinct,
    /// Streaming aggregation
    Streaming,
    /// Custom aggregation
    Custom(Arc<dyn Fn(Vec<QueryResult>) -> QueryResult + Send + Sync>),
}

impl std::fmt::Debug for AggregationStrategy {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Union => write!(f, "Union"),
            Self::MergeDistinct => write!(f, "MergeDistinct"),
            Self::Streaming => write!(f, "Streaming"),
            Self::Custom(_) => write!(f, "Custom(<function>)"),
        }
    }
}

/// Query result from distributed execution
pub struct QueryResult {
    /// Result bindings
    pub bindings: Vec<HashMap<Variable, Term>>,
    /// Execution metadata
    pub metadata: ExecutionMetadata,
    /// Source endpoint
    pub source: String,
}

/// Execution metadata
#[derive(Debug, Clone)]
pub struct ExecutionMetadata {
    /// Execution time
    pub execution_time: Duration,
    /// Result count
    pub result_count: usize,
    /// Bytes transferred
    pub bytes_transferred: usize,
    /// Cache hit
    pub cache_hit: bool,
    /// Warnings
    pub warnings: Vec<String>,
}

impl DistributedQueryEngine {
    /// Create new distributed query engine
    pub fn new(config: DistributedConfig) -> Self {
        Self {
            endpoints: Arc::new(RwLock::new(HashMap::new())),
            router: Arc::new(QueryRouter::new(RoutingPolicy::DataLocality)),
            network_stats: Arc::new(RwLock::new(NetworkStatistics::new())),
            edge_nodes: Arc::new(RwLock::new(Vec::new())),
            config,
        }
    }

    /// Register a federated endpoint
    pub fn register_endpoint(&self, endpoint: FederatedEndpoint) -> Result<(), OxirsError> {
        let mut endpoints = self
            .endpoints
            .write()
            .map_err(|_| OxirsError::Query("Failed to acquire endpoints lock".to_string()))?;

        endpoints.insert(endpoint.url.clone(), endpoint);
        Ok(())
    }

    /// Execute distributed query
    pub async fn execute(&self, query: Query) -> Result<QueryResult, OxirsError> {
        // Plan query distribution
        let plan = self.plan_query(&query)?;

        // Execute fragments in parallel
        let fragment_results = self.execute_fragments(&plan).await?;

        // Join results according to plan
        let joined = self.join_results(fragment_results, &plan)?;

        // Apply final aggregation
        let aggregated = self.aggregate_results(joined, &plan)?;

        Ok(aggregated)
    }

    /// Plan distributed query execution
    fn plan_query(&self, query: &Query) -> Result<DistributedPlan, OxirsError> {
        let endpoints = self
            .endpoints
            .read()
            .map_err(|_| OxirsError::Query("Failed to read endpoints".to_string()))?;

        // Route query fragments
        let routes = self.router.route_query(query, &endpoints)?;

        // Optimize join order
        let join_order = self.optimize_join_order(&routes)?;

        // Select aggregation strategy
        let aggregation = self.select_aggregation_strategy(query)?;

        // Calculate total cost
        let total_cost = routes.iter().map(|r| r.estimated_cost).sum();

        Ok(DistributedPlan {
            routes,
            join_order,
            aggregation,
            total_cost,
        })
    }

    /// Execute query fragments in parallel
    async fn execute_fragments(
        &self,
        plan: &DistributedPlan,
    ) -> Result<Vec<QueryResult>, OxirsError> {
        use futures::future::join_all;

        let mut futures = Vec::new();

        for route in &plan.routes {
            let future = self.execute_fragment(route);
            futures.push(future);
        }

        let results = join_all(futures).await;

        // Collect successful results
        let mut fragment_results = Vec::new();
        for result in results {
            fragment_results.push(result?);
        }

        Ok(fragment_results)
    }

    /// Execute single query fragment
    async fn execute_fragment(&self, route: &QueryRoute) -> Result<QueryResult, OxirsError> {
        // This would actually send the query to the remote endpoint
        // For now, return a placeholder
        Ok(QueryResult {
            bindings: Vec::new(),
            metadata: ExecutionMetadata {
                execution_time: Duration::from_millis(100),
                result_count: 0,
                bytes_transferred: 0,
                cache_hit: false,
                warnings: Vec::new(),
            },
            source: route.endpoint.clone(),
        })
    }

    /// Join distributed results
    fn join_results(
        &self,
        results: Vec<QueryResult>,
        plan: &DistributedPlan,
    ) -> Result<Vec<QueryResult>, OxirsError> {
        // Apply joins according to plan
        let mut joined = results;

        for join_op in &plan.join_order {
            joined = self.apply_join(joined, join_op)?;
        }

        Ok(joined)
    }

    /// Apply single join operation
    fn apply_join(
        &self,
        results: Vec<QueryResult>,
        _join_op: &JoinOperation,
    ) -> Result<Vec<QueryResult>, OxirsError> {
        // Placeholder implementation
        Ok(results)
    }

    /// Aggregate final results
    fn aggregate_results(
        &self,
        results: Vec<QueryResult>,
        plan: &DistributedPlan,
    ) -> Result<QueryResult, OxirsError> {
        match &plan.aggregation {
            AggregationStrategy::Union => self.union_results(results),
            AggregationStrategy::MergeDistinct => self.merge_distinct(results),
            AggregationStrategy::Streaming => self.streaming_aggregate(results),
            AggregationStrategy::Custom(f) => Ok(f(results)),
        }
    }

    /// Simple union of results
    fn union_results(&self, results: Vec<QueryResult>) -> Result<QueryResult, OxirsError> {
        let mut all_bindings = Vec::new();
        let mut total_time = Duration::ZERO;
        let mut total_bytes = 0;

        for result in results {
            all_bindings.extend(result.bindings);
            total_time += result.metadata.execution_time;
            total_bytes += result.metadata.bytes_transferred;
        }

        let result_count = all_bindings.len();
        Ok(QueryResult {
            bindings: all_bindings,
            metadata: ExecutionMetadata {
                execution_time: total_time,
                result_count,
                bytes_transferred: total_bytes,
                cache_hit: false,
                warnings: Vec::new(),
            },
            source: "distributed".to_string(),
        })
    }

    /// Merge with deduplication
    fn merge_distinct(&self, results: Vec<QueryResult>) -> Result<QueryResult, OxirsError> {
        use std::collections::HashSet;

        let mut seen = HashSet::new();
        let mut unique_bindings = Vec::new();

        for result in results {
            for binding in result.bindings {
                let key = self.binding_key(&binding);
                if seen.insert(key) {
                    unique_bindings.push(binding);
                }
            }
        }

        let result_count = unique_bindings.len();
        Ok(QueryResult {
            bindings: unique_bindings,
            metadata: ExecutionMetadata {
                execution_time: Duration::from_millis(100),
                result_count,
                bytes_transferred: 0,
                cache_hit: false,
                warnings: Vec::new(),
            },
            source: "distributed".to_string(),
        })
    }

    /// Create key for binding deduplication
    fn binding_key(&self, binding: &HashMap<Variable, Term>) -> String {
        let mut key = String::new();
        let mut vars: Vec<_> = binding.keys().collect();
        vars.sort();

        for var in vars {
            key.push_str(&format!("{}={},", var, binding[var]));
        }

        key
    }

    /// Streaming aggregation
    fn streaming_aggregate(&self, results: Vec<QueryResult>) -> Result<QueryResult, OxirsError> {
        // Would implement streaming aggregation
        self.union_results(results)
    }

    /// Optimize join order for distributed execution
    fn optimize_join_order(
        &self,
        _routes: &[QueryRoute],
    ) -> Result<Vec<JoinOperation>, OxirsError> {
        // Placeholder - would use cost-based optimization
        Ok(Vec::new())
    }

    /// Select aggregation strategy based on query
    fn select_aggregation_strategy(
        &self,
        query: &Query,
    ) -> Result<AggregationStrategy, OxirsError> {
        // Check if query requires distinct results
        if let QueryForm::Select { distinct, .. } = &query.form {
            if *distinct {
                return Ok(AggregationStrategy::MergeDistinct);
            }
        }

        Ok(AggregationStrategy::Union)
    }
}

impl QueryRouter {
    /// Create new query router
    pub fn new(policy: RoutingPolicy) -> Self {
        Self {
            policy,
            data_locality: Arc::new(RwLock::new(DataLocalityMap::new())),
            pattern_cache: Arc::new(RwLock::new(PatternCache::new())),
        }
    }

    /// Route query to endpoints
    pub fn route_query(
        &self,
        query: &Query,
        endpoints: &HashMap<String, FederatedEndpoint>,
    ) -> Result<Vec<QueryRoute>, OxirsError> {
        match &self.policy {
            RoutingPolicy::NearestEndpoint => self.route_nearest(query, endpoints),
            RoutingPolicy::LoadBalanced => self.route_load_balanced(query, endpoints),
            RoutingPolicy::DataLocality => self.route_data_locality(query, endpoints),
            RoutingPolicy::MinimizeTransfers => self.route_minimize_transfers(query, endpoints),
            RoutingPolicy::Custom(f) => {
                let endpoint_vec: Vec<_> = endpoints.values().cloned().collect();
                Ok(f(query, &endpoint_vec))
            }
        }
    }

    /// Route to nearest endpoint
    fn route_nearest(
        &self,
        query: &Query,
        endpoints: &HashMap<String, FederatedEndpoint>,
    ) -> Result<Vec<QueryRoute>, OxirsError> {
        // Find endpoint with lowest latency
        let best_endpoint = endpoints
            .values()
            .filter(|e| e.status == EndpointStatus::Healthy)
            .min_by(|a, b| {
                a.latency_ms
                    .partial_cmp(&b.latency_ms)
                    .unwrap_or(std::cmp::Ordering::Equal)
            })
            .ok_or_else(|| OxirsError::Query("No healthy endpoints available".to_string()))?;

        Ok(vec![QueryRoute {
            endpoint: best_endpoint.url.clone(),
            fragment: QueryFragment {
                query: query.clone(),
                patterns: self.extract_patterns(query)?,
                required_vars: self.extract_variables(query)?,
                output_vars: self.extract_output_vars(query)?,
            },
            estimated_cost: 1.0,
            priority: 1,
        }])
    }

    /// Load balanced routing
    fn route_load_balanced(
        &self,
        query: &Query,
        endpoints: &HashMap<String, FederatedEndpoint>,
    ) -> Result<Vec<QueryRoute>, OxirsError> {
        // Distribute patterns across healthy endpoints
        let healthy_endpoints: Vec<_> = endpoints
            .values()
            .filter(|e| e.status == EndpointStatus::Healthy)
            .collect();

        if healthy_endpoints.is_empty() {
            return Err(OxirsError::Query(
                "No healthy endpoints available".to_string(),
            ));
        }

        let patterns = self.extract_patterns(query)?;
        let mut routes = Vec::new();

        // Round-robin distribution
        for (i, pattern) in patterns.into_iter().enumerate() {
            let endpoint = &healthy_endpoints[i % healthy_endpoints.len()];

            routes.push(QueryRoute {
                endpoint: endpoint.url.clone(),
                fragment: QueryFragment {
                    query: query.clone(),
                    patterns: vec![pattern],
                    required_vars: HashSet::new(),
                    output_vars: HashSet::new(),
                },
                estimated_cost: 1.0 / healthy_endpoints.len() as f64,
                priority: 1,
            });
        }

        Ok(routes)
    }

    /// Route based on data locality
    fn route_data_locality(
        &self,
        query: &Query,
        endpoints: &HashMap<String, FederatedEndpoint>,
    ) -> Result<Vec<QueryRoute>, OxirsError> {
        // Would analyze data distribution and route accordingly
        self.route_load_balanced(query, endpoints)
    }

    /// Route to minimize network transfers
    fn route_minimize_transfers(
        &self,
        query: &Query,
        endpoints: &HashMap<String, FederatedEndpoint>,
    ) -> Result<Vec<QueryRoute>, OxirsError> {
        // Would analyze join patterns and minimize data movement
        self.route_load_balanced(query, endpoints)
    }

    /// Extract triple patterns from query (returning algebra patterns for consistency)
    fn extract_patterns(&self, query: &Query) -> Result<Vec<algebra::TriplePattern>, OxirsError> {
        match &query.form {
            QueryForm::Select { where_clause, .. } => {
                self.extract_patterns_from_graph_pattern(where_clause)
            }
            _ => Ok(Vec::new()),
        }
    }

    /// Extract patterns from graph pattern (returning algebra patterns)
    fn extract_patterns_from_graph_pattern(
        &self,
        pattern: &GraphPattern,
    ) -> Result<Vec<algebra::TriplePattern>, OxirsError> {
        match pattern {
            GraphPattern::Bgp(patterns) => {
                // Convert algebra patterns to model patterns
                let model_patterns: Vec<algebra::TriplePattern> = patterns
                    .iter()
                    .filter_map(|p| self.convert_algebra_to_model_pattern(p))
                    .collect();
                Ok(model_patterns)
            }
            GraphPattern::Join(left, right) => {
                let mut left_patterns = self.extract_patterns_from_graph_pattern(left)?;
                let mut right_patterns = self.extract_patterns_from_graph_pattern(right)?;
                left_patterns.append(&mut right_patterns);
                Ok(left_patterns)
            }
            GraphPattern::Filter { inner, .. } => self.extract_patterns_from_graph_pattern(inner),
            GraphPattern::Union(left, right) => {
                let mut left_patterns = self.extract_patterns_from_graph_pattern(left)?;
                let mut right_patterns = self.extract_patterns_from_graph_pattern(right)?;
                left_patterns.append(&mut right_patterns);
                Ok(left_patterns)
            }
            _ => Ok(Vec::new()),
        }
    }

    /// Convert model pattern to algebra pattern
    fn convert_to_algebra_pattern(
        &self,
        pattern: &crate::model::pattern::TriplePattern,
    ) -> Result<algebra::TriplePattern, OxirsError> {
        let subject = match &pattern.subject {
            Some(crate::model::pattern::SubjectPattern::NamedNode(n)) => {
                algebra::TermPattern::NamedNode(n.clone())
            }
            Some(crate::model::pattern::SubjectPattern::BlankNode(b)) => {
                algebra::TermPattern::BlankNode(b.clone())
            }
            Some(crate::model::pattern::SubjectPattern::Variable(v)) => {
                algebra::TermPattern::Variable(v.clone())
            }
            Some(crate::model::pattern::SubjectPattern::QuotedTriple(qt)) => {
                algebra::TermPattern::QuotedTriple(qt.clone())
            }
            None => {
                return Err(OxirsError::Query(
                    "Subject pattern cannot be None in basic graph pattern".to_string(),
                ))
            }
        };

        let predicate = match &pattern.predicate {
            Some(crate::model::pattern::PredicatePattern::NamedNode(n)) => {
                algebra::TermPattern::NamedNode(n.clone())
            }
            Some(crate::model::pattern::PredicatePattern::Variable(v)) => {
                algebra::TermPattern::Variable(v.clone())
            }
            None => {
                return Err(OxirsError::Query(
                    "Predicate pattern cannot be None in basic graph pattern".to_string(),
                ))
            }
        };

        let object = match &pattern.object {
            Some(crate::model::pattern::ObjectPattern::NamedNode(n)) => {
                algebra::TermPattern::NamedNode(n.clone())
            }
            Some(crate::model::pattern::ObjectPattern::BlankNode(b)) => {
                algebra::TermPattern::BlankNode(b.clone())
            }
            Some(crate::model::pattern::ObjectPattern::Literal(l)) => {
                algebra::TermPattern::Literal(l.clone())
            }
            Some(crate::model::pattern::ObjectPattern::Variable(v)) => {
                algebra::TermPattern::Variable(v.clone())
            }
            Some(crate::model::pattern::ObjectPattern::QuotedTriple(qt)) => {
                algebra::TermPattern::QuotedTriple(qt.clone())
            }
            None => {
                return Err(OxirsError::Query(
                    "Object pattern cannot be None in basic graph pattern".to_string(),
                ))
            }
        };

        use crate::model::pattern::{ObjectPattern, PredicatePattern, SubjectPattern};
        let subject_pattern = SubjectPattern::try_from(subject)
            .map_err(|e| OxirsError::Query(format!("Invalid subject pattern: {e}")))?;
        let predicate_pattern = PredicatePattern::try_from(predicate)
            .map_err(|e| OxirsError::Query(format!("Invalid predicate pattern: {e}")))?;
        let object_pattern = ObjectPattern::try_from(object)
            .map_err(|e| OxirsError::Query(format!("Invalid object pattern: {e}")))?;

        Ok(algebra::TriplePattern::new(
            Some(subject_pattern),
            Some(predicate_pattern),
            Some(object_pattern),
        ))
    }

    /// Convert AlgebraTriplePattern to model TriplePattern
    fn convert_algebra_to_model_pattern(
        &self,
        algebra_pattern: &AlgebraTriplePattern,
    ) -> Option<algebra::TriplePattern> {
        use crate::model::pattern::{ObjectPattern, PredicatePattern, SubjectPattern};

        let subject = match &algebra_pattern.subject {
            algebra::TermPattern::NamedNode(n) => Some(SubjectPattern::NamedNode(n.clone())),
            algebra::TermPattern::BlankNode(b) => Some(SubjectPattern::BlankNode(b.clone())),
            algebra::TermPattern::Variable(v) => Some(SubjectPattern::Variable(v.clone())),
            algebra::TermPattern::QuotedTriple(qt) => {
                Some(SubjectPattern::QuotedTriple(qt.clone()))
            }
            _ => None,
        };

        let predicate = match &algebra_pattern.predicate {
            algebra::TermPattern::NamedNode(n) => Some(PredicatePattern::NamedNode(n.clone())),
            algebra::TermPattern::Variable(v) => Some(PredicatePattern::Variable(v.clone())),
            _ => None,
        };

        let object = match &algebra_pattern.object {
            algebra::TermPattern::NamedNode(n) => Some(ObjectPattern::NamedNode(n.clone())),
            algebra::TermPattern::BlankNode(b) => Some(ObjectPattern::BlankNode(b.clone())),
            algebra::TermPattern::Literal(l) => Some(ObjectPattern::Literal(l.clone())),
            algebra::TermPattern::Variable(v) => Some(ObjectPattern::Variable(v.clone())),
            algebra::TermPattern::QuotedTriple(qt) => {
                // RDF-star quoted triples as objects are represented in the pattern.
                Some(ObjectPattern::QuotedTriple(qt.clone()))
            }
        };

        Some(algebra::TriplePattern::new(subject, predicate, object))
    }

    /// Extract variables from query
    fn extract_variables(&self, query: &Query) -> Result<HashSet<Variable>, OxirsError> {
        let mut vars = HashSet::new();

        if let QueryForm::Select { where_clause, .. } = &query.form {
            self.collect_variables_from_pattern(where_clause, &mut vars)?;
        }

        Ok(vars)
    }

    /// Collect variables from pattern
    fn collect_variables_from_pattern(
        &self,
        pattern: &GraphPattern,
        vars: &mut HashSet<Variable>,
    ) -> Result<(), OxirsError> {
        if let GraphPattern::Bgp(patterns) = pattern {
            for tp in patterns {
                if let TermPattern::Variable(v) = &tp.subject {
                    vars.insert(v.clone());
                }
                if let TermPattern::Variable(v) = &tp.predicate {
                    vars.insert(v.clone());
                }
                if let TermPattern::Variable(v) = &tp.object {
                    vars.insert(v.clone());
                }
            }
        }

        Ok(())
    }

    /// Extract output variables
    fn extract_output_vars(&self, query: &Query) -> Result<HashSet<Variable>, OxirsError> {
        match &query.form {
            QueryForm::Select { variables, .. } => match variables {
                SelectVariables::All => self.extract_variables(query),
                SelectVariables::Specific(vars) => Ok(vars.iter().cloned().collect()),
            },
            _ => Ok(HashSet::new()),
        }
    }
}

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

impl NetworkStatistics {
    /// Create new network statistics
    pub fn new() -> Self {
        Self {
            latencies: HashMap::new(),
            transfer_rates: HashMap::new(),
            error_rates: HashMap::new(),
            last_update: Instant::now(),
        }
    }

    /// Update endpoint latency
    pub fn update_latency(&mut self, endpoint: String, latency: Duration) {
        self.latencies.entry(endpoint).or_default().push(latency);
        self.last_update = Instant::now();
    }

    /// Get average latency for endpoint
    pub fn avg_latency(&self, endpoint: &str) -> Option<Duration> {
        self.latencies.get(endpoint).map(|samples| {
            let sum: Duration = samples.iter().sum();
            sum / samples.len() as u32
        })
    }
}

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

impl DataLocalityMap {
    /// Create new data locality map
    pub fn new() -> Self {
        Self {
            dataset_locations: HashMap::new(),
            predicate_distribution: HashMap::new(),
            affinity_scores: HashMap::new(),
        }
    }

    /// Update dataset location
    pub fn update_dataset_location(&mut self, dataset: String, endpoints: Vec<String>) {
        self.dataset_locations.insert(dataset, endpoints);
    }

    /// Get endpoints for dataset
    pub fn get_dataset_endpoints(&self, dataset: &str) -> Option<&Vec<String>> {
        self.dataset_locations.get(dataset)
    }
}

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

impl PatternCache {
    /// Create new pattern cache
    pub fn new() -> Self {
        Self {
            plans: HashMap::new(),
            stats: HashMap::new(),
            max_size: 1000,
        }
    }

    /// Get cached plan
    pub fn get_plan(&mut self, hash: QueryHash) -> Option<&mut CachedPlan> {
        self.plans.get_mut(&hash).map(|plan| {
            plan.hits += 1;
            plan
        })
    }

    /// Cache execution plan
    pub fn cache_plan(&mut self, hash: QueryHash, plan: DistributedPlan) {
        // Evict if at capacity
        if self.plans.len() >= self.max_size {
            // Remove least recently used
            if let Some(&oldest) = self.plans.keys().next() {
                self.plans.remove(&oldest);
            }
        }

        self.plans.insert(
            hash,
            CachedPlan {
                plan,
                created: Instant::now(),
                hits: 0,
                avg_exec_time: Duration::ZERO,
            },
        );
    }
}

impl Default for DistributedConfig {
    fn default() -> Self {
        Self {
            query_timeout: Duration::from_secs(30),
            max_parallel_queries: 100,
            edge_computing_enabled: true,
            cache_results: true,
            cache_ttl: Duration::from_secs(300),
            network_timeout: Duration::from_secs(10),
            retry_policy: RetryPolicy::default(),
        }
    }
}

impl Default for RetryPolicy {
    fn default() -> Self {
        Self {
            max_attempts: 3,
            base_delay: Duration::from_millis(100),
            backoff_factor: 2.0,
            max_delay: Duration::from_secs(10),
        }
    }
}

/// Async trait for federated query execution
#[async_trait]
pub trait FederatedQueryExecutor: Send + Sync {
    /// Execute query on federated endpoint
    async fn execute_query(
        &self,
        endpoint: &FederatedEndpoint,
        query: &Query,
    ) -> Result<QueryResult, OxirsError>;

    /// Check endpoint health
    async fn check_health(&self, endpoint: &FederatedEndpoint) -> EndpointStatus;

    /// Get endpoint capabilities
    async fn get_capabilities(
        &self,
        endpoint: &FederatedEndpoint,
    ) -> Result<EndpointFeatures, OxirsError>;
}

/// Real-time collaborative filtering for distributed queries
pub struct CollaborativeFilter {
    /// Active queries
    active_queries: Arc<RwLock<HashMap<QueryHash, ActiveQuery>>>,
    /// Query similarity threshold
    similarity_threshold: f64,
    /// Result sharing channel
    #[cfg(feature = "async")]
    result_channel: tokio::sync::mpsc::Sender<SharedResult>,
    #[cfg(not(feature = "async"))]
    result_channel: std::sync::mpsc::Sender<SharedResult>,
}

/// Active query tracking
struct ActiveQuery {
    /// Query pattern
    pattern: QueryPattern,
    /// Participating clients
    clients: HashSet<String>,
    /// Partial results
    partial_results: Vec<QueryResult>,
    /// Start time
    start_time: Instant,
}

/// Shared query result
pub struct SharedResult {
    /// Query hash
    query_hash: QueryHash,
    /// Result data
    result: QueryResult,
    /// Sharing client
    client_id: String,
}

impl CollaborativeFilter {
    /// Create new collaborative filter
    #[cfg(feature = "async")]
    pub fn new(similarity_threshold: f64) -> (Self, tokio::sync::mpsc::Receiver<SharedResult>) {
        let (tx, rx) = tokio::sync::mpsc::channel(1000);

        (
            Self {
                active_queries: Arc::new(RwLock::new(HashMap::new())),
                similarity_threshold,
                result_channel: tx,
            },
            rx,
        )
    }

    #[cfg(not(feature = "async"))]
    pub fn new(similarity_threshold: f64) -> (Self, std::sync::mpsc::Receiver<SharedResult>) {
        let (tx, rx) = std::sync::mpsc::channel();

        (
            Self {
                active_queries: Arc::new(RwLock::new(HashMap::new())),
                similarity_threshold,
                result_channel: tx,
            },
            rx,
        )
    }

    /// Register query for collaboration
    pub async fn register_query(
        &self,
        query: &Query,
        client_id: String,
    ) -> Result<QueryHash, OxirsError> {
        let pattern = self.extract_query_pattern(query)?;
        let hash = self.hash_pattern(&pattern);

        let mut active = self
            .active_queries
            .write()
            .map_err(|_| OxirsError::Query("Failed to acquire lock".to_string()))?;

        active
            .entry(hash)
            .or_insert_with(|| ActiveQuery {
                pattern: pattern.clone(),
                clients: HashSet::new(),
                partial_results: Vec::new(),
                start_time: Instant::now(),
            })
            .clients
            .insert(client_id);

        Ok(hash)
    }

    /// Share query results
    #[cfg(feature = "async")]
    pub async fn share_results(
        &self,
        hash: QueryHash,
        result: QueryResult,
        client_id: String,
    ) -> Result<(), OxirsError> {
        self.result_channel
            .send(SharedResult {
                query_hash: hash,
                result,
                client_id,
            })
            .await
            .map_err(|_| OxirsError::Query("Failed to share results".to_string()))
    }

    #[cfg(not(feature = "async"))]
    pub fn share_results(
        &self,
        hash: QueryHash,
        result: QueryResult,
        client_id: String,
    ) -> Result<(), OxirsError> {
        self.result_channel
            .send(SharedResult {
                query_hash: hash,
                result,
                client_id,
            })
            .map_err(|_| OxirsError::Query("Failed to share results".to_string()))
    }

    /// Extract pattern from query
    fn extract_query_pattern(&self, _query: &Query) -> Result<QueryPattern, OxirsError> {
        // Extract patterns, joins, and filters
        Ok(QueryPattern {
            patterns: Vec::new(),
            joins: Vec::new(),
            filters: Vec::new(),
        })
    }

    /// Hash query pattern
    fn hash_pattern(&self, pattern: &QueryPattern) -> QueryHash {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

        let mut hasher = DefaultHasher::new();
        pattern.hash(&mut hasher);
        hasher.finish()
    }
}

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

    #[test]
    fn test_distributed_engine_creation() {
        let config = DistributedConfig::default();
        let engine = DistributedQueryEngine::new(config);

        assert!(engine
            .endpoints
            .read()
            .expect("lock should not be poisoned")
            .is_empty());
    }

    #[test]
    fn test_endpoint_registration() {
        let config = DistributedConfig::default();
        let engine = DistributedQueryEngine::new(config);

        let endpoint = FederatedEndpoint {
            url: "http://example.org/sparql".to_string(),
            features: EndpointFeatures {
                sparql_version: "1.1".to_string(),
                update_support: true,
                federation_support: true,
                text_search: false,
                geospatial: false,
                extensions: HashSet::new(),
            },
            latency_ms: 50.0,
            throughput: 10000.0,
            datasets: vec!["dataset1".to_string()],
            last_health_check: Instant::now(),
            status: EndpointStatus::Healthy,
        };

        engine
            .register_endpoint(endpoint)
            .expect("operation should succeed");

        let endpoints = engine
            .endpoints
            .read()
            .expect("lock should not be poisoned");
        assert_eq!(endpoints.len(), 1);
        assert!(endpoints.contains_key("http://example.org/sparql"));
    }

    #[test]
    fn test_query_router() {
        let router = QueryRouter::new(RoutingPolicy::NearestEndpoint);
        let mut endpoints = HashMap::new();

        endpoints.insert(
            "endpoint1".to_string(),
            FederatedEndpoint {
                url: "http://endpoint1.org/sparql".to_string(),
                features: EndpointFeatures {
                    sparql_version: "1.1".to_string(),
                    update_support: false,
                    federation_support: true,
                    text_search: false,
                    geospatial: false,
                    extensions: HashSet::new(),
                },
                latency_ms: 20.0,
                throughput: 5000.0,
                datasets: vec![],
                last_health_check: Instant::now(),
                status: EndpointStatus::Healthy,
            },
        );

        let query = Query {
            base: None,
            prefixes: HashMap::new(),
            form: QueryForm::Select {
                variables: SelectVariables::All,
                where_clause: GraphPattern::Bgp(vec![]),
                distinct: false,
                reduced: false,
                order_by: vec![],
                offset: 0,
                limit: None,
            },
            dataset: crate::query::algebra::Dataset::default(),
        };

        let routes = router
            .route_query(&query, &endpoints)
            .expect("operation should succeed");
        assert_eq!(routes.len(), 1);
        assert_eq!(routes[0].endpoint, "http://endpoint1.org/sparql");
    }
}