oxirs-vec 0.2.4

//! Federated Vector Search - Advanced Multi-Organization Search
//!
//! This module implements advanced federated vector search capabilities that extend
//! beyond basic distributed search to enable cross-organizational, semantic, and
//! trust-based federation. It supports federating across different vector schemas,
//! organizations, and trust domains while maintaining security and privacy.

use crate::{
    distributed_vector_search::{DistributedVectorSearch, NodeHealthStatus},
    quantum_search::QuantumVectorSearch,
    similarity::{SimilarityMetric, SimilarityResult},
    Vector,
};

use anyhow::{anyhow, Context, Result};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::{Arc, RwLock};
use std::time::{Duration, Instant, SystemTime};
use tracing::{debug, info, span, Level};

/// Federated search configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederatedSearchConfig {
    /// Maximum number of federations to query simultaneously
    pub max_concurrent_federations: usize,
    /// Default timeout for federated queries
    pub default_timeout: Duration,
    /// Enable semantic query routing
    pub enable_semantic_routing: bool,
    /// Enable cross-organization trust verification
    pub enable_trust_verification: bool,
    /// Enable result aggregation across federations
    pub enable_result_aggregation: bool,
    /// Privacy preservation mode
    pub privacy_mode: PrivacyMode,
    /// Schema compatibility checking
    pub schema_compatibility: SchemaCompatibility,
}

impl Default for FederatedSearchConfig {
    fn default() -> Self {
        Self {
            max_concurrent_federations: 10,
            default_timeout: Duration::from_secs(30),
            enable_semantic_routing: true,
            enable_trust_verification: true,
            enable_result_aggregation: true,
            privacy_mode: PrivacyMode::Balanced,
            schema_compatibility: SchemaCompatibility::Strict,
        }
    }
}

/// Privacy preservation modes for federated search
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, PartialOrd)]
pub enum PrivacyMode {
    /// No privacy preservation
    None,
    /// Basic anonymization
    Basic,
    /// Balanced privacy and functionality
    Balanced,
    /// Maximum privacy with differential privacy
    Strict,
}

/// Schema compatibility levels
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, PartialOrd)]
pub enum SchemaCompatibility {
    /// Best-effort compatibility with loss tolerance
    BestEffort,
    /// Compatible schemas allowed with transformation
    Compatible,
    /// Strict schema matching required
    Strict,
}

/// Federation endpoint configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederationEndpoint {
    /// Unique federation identifier
    pub federation_id: String,
    /// Federation name
    pub name: String,
    /// Base URL for federation API
    pub base_url: String,
    /// Organization identifier
    pub organization_id: String,
    /// Trust level (0.0 to 1.0)
    pub trust_level: f32,
    /// API version supported
    pub api_version: String,
    /// Authentication credentials
    pub auth_config: AuthenticationConfig,
    /// Supported vector dimensions
    pub supported_dimensions: Vec<usize>,
    /// Supported similarity metrics
    pub supported_metrics: Vec<SimilarityMetric>,
    /// Privacy capabilities
    pub privacy_capabilities: PrivacyCapabilities,
    /// Schema information
    pub schema_info: SchemaInfo,
    /// Performance characteristics
    pub performance_profile: PerformanceProfile,
}

/// Authentication configuration for federation
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AuthenticationConfig {
    /// Authentication type
    pub auth_type: AuthenticationType,
    /// API key (if applicable)
    pub api_key: Option<String>,
    /// OAuth configuration (if applicable)
    pub oauth_config: Option<OAuthConfig>,
    /// Certificate-based auth (if applicable)
    pub cert_config: Option<CertificateConfig>,
}

/// Authentication types supported
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum AuthenticationType {
    ApiKey,
    OAuth2,
    Certificate,
    Bearer,
    Custom(String),
}

/// OAuth configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct OAuthConfig {
    pub client_id: String,
    pub client_secret: String,
    pub token_url: String,
    pub scope: String,
}

/// Certificate-based authentication
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CertificateConfig {
    pub cert_path: String,
    pub key_path: String,
    pub ca_path: Option<String>,
}

/// Privacy capabilities of a federation endpoint
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PrivacyCapabilities {
    /// Supports differential privacy
    pub differential_privacy: bool,
    /// Supports k-anonymity
    pub k_anonymity: bool,
    /// Supports secure multiparty computation
    pub secure_mpc: bool,
    /// Supports homomorphic encryption
    pub homomorphic_encryption: bool,
    /// Privacy budget available
    pub privacy_budget: Option<f32>,
}

/// Schema information for federation compatibility
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SchemaInfo {
    /// Vector schema version
    pub schema_version: String,
    /// Metadata schema
    pub metadata_schema: HashMap<String, String>,
    /// Supported data types
    pub supported_types: Vec<String>,
    /// Dimension constraints
    pub dimension_constraints: DimensionConstraints,
}

/// Vector dimension constraints
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DimensionConstraints {
    pub min_dimensions: usize,
    pub max_dimensions: usize,
    pub preferred_dimensions: Vec<usize>,
}

/// Performance profile of federation endpoint
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PerformanceProfile {
    /// Average latency in milliseconds
    pub avg_latency_ms: u64,
    /// Maximum concurrent queries supported
    pub max_concurrent_queries: usize,
    /// Rate limit (queries per second)
    pub rate_limit_qps: f32,
    /// Data freshness guarantee
    pub data_freshness_seconds: u64,
}

/// Federated query specification
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederatedQuery {
    /// Unique query identifier
    pub query_id: String,
    /// Query vector
    pub vector: Vector,
    /// Number of results requested
    pub k: usize,
    /// Similarity metric
    pub metric: SimilarityMetric,
    /// Query filters
    pub filters: HashMap<String, String>,
    /// Target federations (empty = all)
    pub target_federations: Vec<String>,
    /// Privacy requirements
    pub privacy_requirements: PrivacyRequirements,
    /// Quality requirements
    pub quality_requirements: QualityRequirements,
    /// Timeout
    pub timeout: Duration,
}

/// Privacy requirements for federated query
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PrivacyRequirements {
    /// Minimum privacy level required
    pub min_privacy_level: PrivacyMode,
    /// Allow result aggregation
    pub allow_aggregation: bool,
    /// Maximum data exposure tolerance
    pub max_exposure_tolerance: f32,
}

/// Quality requirements for federated query
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct QualityRequirements {
    /// Minimum result quality threshold
    pub min_quality_threshold: f32,
    /// Maximum latency tolerance
    pub max_latency_ms: u64,
    /// Minimum number of results required
    pub min_results: usize,
    /// Result freshness requirements
    pub max_staleness_seconds: u64,
}

/// Federated search result
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederatedSearchResult {
    /// Query ID that generated this result
    pub query_id: String,
    /// Federation that provided this result
    pub federation_id: String,
    /// Original result from federation
    pub result: SimilarityResult,
    /// Confidence in result quality (0.0 to 1.0)
    pub confidence: f32,
    /// Privacy level of this result
    pub privacy_level: PrivacyMode,
    /// Trust score for the source (0.0 to 1.0)
    pub trust_score: f32,
    /// Result metadata
    pub metadata: ResultMetadata,
}

/// Metadata for federated search results
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ResultMetadata {
    /// Timestamp when result was generated
    pub timestamp: SystemTime,
    /// Processing time in milliseconds
    pub processing_time_ms: u64,
    /// Schema version used
    pub schema_version: String,
    /// Data provenance information
    pub provenance: DataProvenance,
}

/// Data provenance tracking
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DataProvenance {
    /// Original data source
    pub source: String,
    /// Data transformation pipeline
    pub transformations: Vec<String>,
    /// Quality assurance steps
    pub quality_checks: Vec<String>,
    /// Data lineage hash
    pub lineage_hash: String,
}

/// Aggregated federated search response
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederatedSearchResponse {
    /// Query ID
    pub query_id: String,
    /// Aggregated results
    pub results: Vec<FederatedSearchResult>,
    /// Federation statistics
    pub federation_stats: FederationStatistics,
    /// Aggregation metadata
    pub aggregation_metadata: AggregationMetadata,
}

/// Statistics for federated search execution
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederationStatistics {
    /// Total federations contacted
    pub federations_contacted: usize,
    /// Federations that responded
    pub federations_responded: usize,
    /// Total results before aggregation
    pub total_raw_results: usize,
    /// Results after aggregation
    pub aggregated_results: usize,
    /// Average response time
    pub avg_response_time_ms: u64,
    /// Trust-weighted quality score
    pub trust_weighted_quality: f32,
}

/// Metadata about result aggregation
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AggregationMetadata {
    /// Aggregation strategy used
    pub strategy: AggregationStrategy,
    /// Duplicate removal statistics
    pub duplicate_removal_stats: DuplicateRemovalStats,
    /// Privacy preservation applied
    pub privacy_preservation: Vec<String>,
    /// Quality enhancement applied
    pub quality_enhancements: Vec<String>,
}

/// Aggregation strategies for federated results
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum AggregationStrategy {
    /// Simple union of all results
    Union,
    /// Intersection of common results
    Intersection,
    /// Trust-weighted ranking
    TrustWeighted,
    /// Quality-based filtering
    QualityFiltered,
    /// Semantic clustering
    SemanticClustered,
    /// Quantum-enhanced aggregation
    QuantumEnhanced,
}

/// Statistics for duplicate removal
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DuplicateRemovalStats {
    /// Original result count
    pub original_count: usize,
    /// Duplicates found
    pub duplicates_found: usize,
    /// Final result count
    pub final_count: usize,
    /// Similarity threshold used
    pub similarity_threshold: f32,
}

/// Main federated vector search coordinator
pub struct FederatedVectorSearch {
    /// Configuration
    config: FederatedSearchConfig,
    /// Registered federation endpoints
    federations: Arc<RwLock<HashMap<String, FederationEndpoint>>>,
    /// Distributed search coordinator
    distributed_search: Arc<DistributedVectorSearch>,
    /// Quantum search engine for enhanced aggregation
    quantum_search: Arc<QuantumVectorSearch>,
    /// Schema compatibility engine
    schema_engine: Arc<RwLock<SchemaCompatibilityEngine>>,
    /// Trust management system
    trust_manager: Arc<RwLock<TrustManager>>,
    /// Privacy preservation engine
    privacy_engine: Arc<RwLock<PrivacyEngine>>,
    /// Query cache for performance
    query_cache: Arc<RwLock<HashMap<String, FederatedSearchResponse>>>,
    /// Performance metrics
    metrics: Arc<RwLock<FederationMetrics>>,
}

/// Schema compatibility checking engine
#[derive(Debug)]
pub struct SchemaCompatibilityEngine {
    /// Known schema mappings
    schema_mappings: HashMap<String, SchemaMapping>,
    /// Transformation rules
    transformation_rules: Vec<TransformationRule>,
}

/// Schema mapping between different formats
#[derive(Debug, Clone)]
pub struct SchemaMapping {
    /// Source schema identifier
    pub source_schema: String,
    /// Target schema identifier
    pub target_schema: String,
    /// Field mappings
    pub field_mappings: HashMap<String, String>,
    /// Dimension transformation
    pub dimension_transform: Option<DimensionTransform>,
}

/// Dimension transformation specification
#[derive(Debug, Clone)]
pub struct DimensionTransform {
    /// Source dimensions
    pub source_dimensions: usize,
    /// Target dimensions
    pub target_dimensions: usize,
    /// Transformation method
    pub method: TransformMethod,
}

/// Transformation methods for dimension compatibility
#[derive(Debug, Clone)]
pub enum TransformMethod {
    /// Padding with zeros
    Padding,
    /// Truncation
    Truncation,
    /// PCA reduction
    PcaReduction,
    /// Linear transformation
    LinearTransform(Vec<Vec<f32>>),
}

/// Schema transformation rule
#[derive(Debug, Clone)]
pub struct TransformationRule {
    /// Rule identifier
    pub rule_id: String,
    /// Condition for applying rule
    pub condition: String,
    /// Transformation to apply
    pub transformation: String,
    /// Quality impact estimate
    pub quality_impact: f32,
}

/// Trust management system
#[derive(Debug)]
pub struct TrustManager {
    /// Trust scores for federations
    trust_scores: HashMap<String, f32>,
    /// Trust history
    trust_history: HashMap<String, Vec<TrustEvent>>,
    /// Trust verification rules
    verification_rules: Vec<TrustRule>,
}

/// Trust event for tracking federation reliability
#[derive(Debug, Clone)]
pub struct TrustEvent {
    /// Timestamp of event
    pub timestamp: SystemTime,
    /// Event type
    pub event_type: TrustEventType,
    /// Impact on trust score
    pub trust_impact: f32,
    /// Additional context
    pub context: String,
}

/// Types of trust events
#[derive(Debug, Clone)]
pub enum TrustEventType {
    /// Successful query response
    SuccessfulResponse,
    /// Failed query response
    FailedResponse,
    /// Quality degradation detected
    QualityDegradation,
    /// Privacy violation detected
    PrivacyViolation,
    /// Performance degradation
    PerformanceDegradation,
    /// Security incident
    SecurityIncident,
}

/// Trust verification rule
#[derive(Debug, Clone)]
pub struct TrustRule {
    /// Rule identifier
    pub rule_id: String,
    /// Rule description
    pub description: String,
    /// Verification function
    pub verification_fn: String,
    /// Trust impact if rule passes
    pub positive_impact: f32,
    /// Trust impact if rule fails
    pub negative_impact: f32,
}

/// Privacy preservation engine
#[derive(Debug)]
pub struct PrivacyEngine {
    /// Privacy policies
    privacy_policies: HashMap<String, PrivacyPolicy>,
    /// Active privacy mechanisms
    mechanisms: Vec<PrivacyMechanism>,
    /// Privacy budget tracker
    budget_tracker: PrivacyBudgetTracker,
}

/// Privacy policy for federation
#[derive(Debug, Clone)]
pub struct PrivacyPolicy {
    /// Policy identifier
    pub policy_id: String,
    /// Applicable federation IDs
    pub applicable_federations: Vec<String>,
    /// Privacy requirements
    pub requirements: PrivacyRequirements,
    /// Enforcement mechanisms
    pub enforcement_mechanisms: Vec<String>,
}

/// Privacy preservation mechanism
#[derive(Debug, Clone)]
pub struct PrivacyMechanism {
    /// Mechanism identifier
    pub mechanism_id: String,
    /// Mechanism type
    pub mechanism_type: PrivacyMechanismType,
    /// Privacy parameters
    pub parameters: HashMap<String, f32>,
    /// Quality impact
    pub quality_impact: f32,
}

/// Types of privacy mechanisms
#[derive(Debug, Clone)]
pub enum PrivacyMechanismType {
    /// Differential privacy with noise addition
    DifferentialPrivacy,
    /// K-anonymity grouping
    KAnonymity,
    /// L-diversity
    LDiversity,
    /// T-closeness
    TCloseness,
    /// Secure multiparty computation
    SecureMpc,
    /// Homomorphic encryption
    HomomorphicEncryption,
}

/// Privacy budget tracker for differential privacy
#[derive(Debug)]
pub struct PrivacyBudgetTracker {
    /// Budget allocations per federation
    budget_allocations: HashMap<String, f32>,
    /// Budget usage tracking
    budget_usage: HashMap<String, f32>,
    /// Budget renewal policies
    renewal_policies: HashMap<String, BudgetRenewalPolicy>,
}

/// Budget renewal policy
#[derive(Debug, Clone)]
pub struct BudgetRenewalPolicy {
    /// Renewal interval
    pub renewal_interval: Duration,
    /// Budget amount per renewal
    pub budget_per_renewal: f32,
    /// Maximum accumulated budget
    pub max_accumulated_budget: f32,
}

/// Performance metrics for federation
#[derive(Debug, Default, Clone)]
pub struct FederationMetrics {
    /// Total queries processed
    pub total_queries: u64,
    /// Successful queries
    pub successful_queries: u64,
    /// Failed queries
    pub failed_queries: u64,
    /// Average response time
    pub avg_response_time_ms: f64,
    /// Privacy preservation overhead
    pub privacy_overhead_ms: f64,
    /// Schema transformation overhead
    pub schema_overhead_ms: f64,
    /// Trust verification overhead
    pub trust_overhead_ms: f64,
}

impl FederatedVectorSearch {
    /// Create a new federated vector search coordinator
    pub async fn new(config: FederatedSearchConfig) -> Result<Self> {
        let distributed_search = Arc::new(
            DistributedVectorSearch::new(
                crate::distributed_vector_search::PartitioningStrategy::Hash,
            )
            .context("Failed to create distributed search coordinator")?,
        );

        let quantum_search = Arc::new(QuantumVectorSearch::with_default_config());

        Ok(Self {
            config,
            federations: Arc::new(RwLock::new(HashMap::new())),
            distributed_search,
            quantum_search,
            schema_engine: Arc::new(RwLock::new(SchemaCompatibilityEngine::new())),
            trust_manager: Arc::new(RwLock::new(TrustManager::new())),
            privacy_engine: Arc::new(RwLock::new(PrivacyEngine::new())),
            query_cache: Arc::new(RwLock::new(HashMap::new())),
            metrics: Arc::new(RwLock::new(FederationMetrics::default())),
        })
    }

    /// Register a new federation endpoint
    pub async fn register_federation(&self, endpoint: FederationEndpoint) -> Result<()> {
        let span =
            span!(Level::DEBUG, "register_federation", federation_id = %endpoint.federation_id);
        let _enter = span.enter();

        // Validate endpoint configuration
        self.validate_federation_endpoint(&endpoint)?;

        // Perform trust verification if enabled
        if self.config.enable_trust_verification {
            self.verify_federation_trust(&endpoint).await?;
        }

        // Check schema compatibility
        if self.config.schema_compatibility != SchemaCompatibility::BestEffort {
            self.verify_schema_compatibility(&endpoint).await?;
        }

        // Register the federation
        {
            let mut federations = self
                .federations
                .write()
                .expect("rwlock should not be poisoned");
            federations.insert(endpoint.federation_id.clone(), endpoint.clone());
        }

        // Initialize trust tracking
        {
            let mut trust_manager = self
                .trust_manager
                .write()
                .expect("rwlock should not be poisoned");
            trust_manager
                .initialize_federation_trust(&endpoint.federation_id, endpoint.trust_level);
        }

        info!(
            "Successfully registered federation: {}",
            endpoint.federation_id
        );
        Ok(())
    }

    /// Perform federated vector search
    pub async fn federated_search(&self, query: FederatedQuery) -> Result<FederatedSearchResponse> {
        let span = span!(Level::INFO, "federated_search", query_id = %query.query_id);
        let _enter = span.enter();

        let start_time = Instant::now();

        // Check cache first
        if let Some(cached_response) = self.get_cached_response(&query.query_id) {
            debug!("Returning cached response for query {}", query.query_id);
            return Ok(cached_response);
        }

        // Select target federations
        let target_federations = self.select_target_federations(&query).await?;

        // Execute parallel federated queries
        let federation_results = self
            .execute_parallel_federated_queries(&query, &target_federations)
            .await?;

        // Apply privacy preservation
        let privacy_preserved_results = if self.config.enable_result_aggregation {
            self.apply_privacy_preservation(&federation_results, &query.privacy_requirements)
                .await?
        } else {
            federation_results
        };

        // Aggregate results
        let aggregated_response = self
            .aggregate_federated_results(&query, privacy_preserved_results, start_time)
            .await?;

        // Cache the response
        self.cache_response(&aggregated_response).await;

        // Update metrics
        self.update_metrics(&aggregated_response, start_time.elapsed())
            .await;

        info!(
            "Federated search completed for query {} with {} results",
            query.query_id,
            aggregated_response.results.len()
        );

        Ok(aggregated_response)
    }

    /// Get federation health status
    pub fn get_federation_health(&self) -> HashMap<String, NodeHealthStatus> {
        let federations = self
            .federations
            .read()
            .expect("rwlock should not be poisoned");
        federations
            .keys()
            .map(|id| {
                // Determine health based on trust scores and recent performance
                let trust_manager = self
                    .trust_manager
                    .read()
                    .expect("rwlock should not be poisoned");
                let trust_score = trust_manager.get_trust_score(id).unwrap_or(0.0);

                let health = if trust_score >= 0.8 {
                    NodeHealthStatus::Healthy
                } else if trust_score >= 0.5 {
                    NodeHealthStatus::Degraded
                } else if trust_score >= 0.2 {
                    NodeHealthStatus::Unhealthy
                } else {
                    NodeHealthStatus::Offline
                };

                (id.clone(), health)
            })
            .collect()
    }

    /// Get federation performance metrics
    pub fn get_federation_metrics(&self) -> FederationMetrics {
        (*self.metrics.read().expect("rwlock should not be poisoned")).clone()
    }

    // Private implementation methods

    fn validate_federation_endpoint(&self, endpoint: &FederationEndpoint) -> Result<()> {
        if endpoint.federation_id.is_empty() {
            return Err(anyhow!("Federation ID cannot be empty"));
        }

        if endpoint.base_url.is_empty() {
            return Err(anyhow!("Base URL cannot be empty"));
        }

        if endpoint.trust_level < 0.0 || endpoint.trust_level > 1.0 {
            return Err(anyhow!("Trust level must be between 0.0 and 1.0"));
        }

        Ok(())
    }

    async fn verify_federation_trust(&self, _endpoint: &FederationEndpoint) -> Result<()> {
        // Placeholder for trust verification logic
        // In a real implementation, this would involve:
        // - Certificate validation
        // - Reputation checking
        // - Performance testing
        // - Security assessment
        Ok(())
    }

    async fn verify_schema_compatibility(&self, _endpoint: &FederationEndpoint) -> Result<()> {
        // Placeholder for schema compatibility verification
        // In a real implementation, this would involve:
        // - Schema version checking
        // - Dimension compatibility
        // - Metadata schema validation
        // - Transformation capability assessment
        Ok(())
    }

    async fn select_target_federations(&self, query: &FederatedQuery) -> Result<Vec<String>> {
        if !query.target_federations.is_empty() {
            return Ok(query.target_federations.clone());
        }

        let federations = self
            .federations
            .read()
            .expect("rwlock should not be poisoned");
        let trust_manager = self
            .trust_manager
            .read()
            .expect("rwlock should not be poisoned");

        let mut eligible_federations = Vec::new();

        for (federation_id, endpoint) in federations.iter() {
            // Check trust level
            let trust_score = trust_manager.get_trust_score(federation_id).unwrap_or(0.0);
            if trust_score < 0.3 {
                continue;
            }

            // Check dimension compatibility
            if !endpoint
                .supported_dimensions
                .contains(&query.vector.dimensions)
            {
                continue;
            }

            // Check metric support
            if !endpoint.supported_metrics.contains(&query.metric) {
                continue;
            }

            eligible_federations.push(federation_id.clone());
        }

        // Limit to max concurrent federations
        eligible_federations.truncate(self.config.max_concurrent_federations);

        Ok(eligible_federations)
    }

    async fn execute_parallel_federated_queries(
        &self,
        query: &FederatedQuery,
        target_federations: &[String],
    ) -> Result<Vec<FederatedSearchResult>> {
        let mut results = Vec::new();

        // For this implementation, we'll simulate federated query execution
        // In a real implementation, this would involve HTTP requests to federation endpoints

        for federation_id in target_federations {
            if let Some(endpoint) = self
                .federations
                .read()
                .expect("rwlock should not be poisoned")
                .get(federation_id)
            {
                // Simulate query execution with some example results
                let similarity_result = SimilarityResult {
                    id: format!(
                        "fed_{}_{}",
                        federation_id,
                        std::time::SystemTime::now()
                            .duration_since(std::time::UNIX_EPOCH)
                            .unwrap_or_default()
                            .as_millis()
                    ),
                    uri: format!("result_from_{federation_id}"),
                    similarity: 0.85,
                    metrics: std::collections::HashMap::new(),
                    metadata: None,
                };

                let federated_result = FederatedSearchResult {
                    query_id: query.query_id.clone(),
                    federation_id: federation_id.clone(),
                    result: similarity_result,
                    confidence: 0.9,
                    privacy_level: PrivacyMode::Balanced,
                    trust_score: endpoint.trust_level,
                    metadata: ResultMetadata {
                        timestamp: SystemTime::now(),
                        processing_time_ms: 50,
                        schema_version: endpoint.schema_info.schema_version.clone(),
                        provenance: DataProvenance {
                            source: federation_id.clone(),
                            transformations: vec!["normalization".to_string()],
                            quality_checks: vec!["similarity_validation".to_string()],
                            lineage_hash: "abc123".to_string(),
                        },
                    },
                };

                results.push(federated_result);
            }
        }

        Ok(results)
    }

    async fn apply_privacy_preservation(
        &self,
        results: &[FederatedSearchResult],
        _privacy_requirements: &PrivacyRequirements,
    ) -> Result<Vec<FederatedSearchResult>> {
        // For this implementation, we'll return results as-is
        // In a real implementation, this would apply various privacy mechanisms
        Ok(results.to_vec())
    }

    async fn aggregate_federated_results(
        &self,
        query: &FederatedQuery,
        results: Vec<FederatedSearchResult>,
        start_time: Instant,
    ) -> Result<FederatedSearchResponse> {
        let processing_time = start_time.elapsed();

        // Simple aggregation strategy for this implementation
        let mut aggregated_results = results.clone();

        // Sort by trust-weighted similarity score
        aggregated_results.sort_by(|a, b| {
            let score_a = a.result.similarity * a.trust_score * a.confidence;
            let score_b = b.result.similarity * b.trust_score * b.confidence;
            score_b
                .partial_cmp(&score_a)
                .expect("scores should be comparable")
        });

        // Limit to requested k
        aggregated_results.truncate(query.k);

        let federation_stats = FederationStatistics {
            federations_contacted: results.len(),
            federations_responded: results.len(),
            total_raw_results: results.len(),
            aggregated_results: aggregated_results.len(),
            avg_response_time_ms: processing_time.as_millis() as u64,
            trust_weighted_quality: aggregated_results
                .iter()
                .map(|r| r.result.similarity * r.trust_score)
                .sum::<f32>()
                / aggregated_results.len() as f32,
        };

        let aggregation_metadata = AggregationMetadata {
            strategy: AggregationStrategy::TrustWeighted,
            duplicate_removal_stats: DuplicateRemovalStats {
                original_count: results.len(),
                duplicates_found: 0,
                final_count: aggregated_results.len(),
                similarity_threshold: 0.95,
            },
            privacy_preservation: vec!["basic_anonymization".to_string()],
            quality_enhancements: vec!["trust_weighting".to_string()],
        };

        Ok(FederatedSearchResponse {
            query_id: query.query_id.clone(),
            results: aggregated_results,
            federation_stats,
            aggregation_metadata,
        })
    }

    fn get_cached_response(&self, query_id: &str) -> Option<FederatedSearchResponse> {
        self.query_cache
            .read()
            .expect("rwlock should not be poisoned")
            .get(query_id)
            .cloned()
    }

    async fn cache_response(&self, response: &FederatedSearchResponse) {
        let mut cache = self
            .query_cache
            .write()
            .expect("rwlock should not be poisoned");
        cache.insert(response.query_id.clone(), response.clone());
    }

    async fn update_metrics(&self, response: &FederatedSearchResponse, elapsed: Duration) {
        let mut metrics = self.metrics.write().expect("rwlock should not be poisoned");
        metrics.total_queries += 1;

        if !response.results.is_empty() {
            metrics.successful_queries += 1;
        } else {
            metrics.failed_queries += 1;
        }

        metrics.avg_response_time_ms = (metrics.avg_response_time_ms
            * (metrics.total_queries - 1) as f64
            + elapsed.as_millis() as f64)
            / metrics.total_queries as f64;
    }
}

// Implementation of helper structures

impl SchemaCompatibilityEngine {
    fn new() -> Self {
        Self {
            schema_mappings: HashMap::new(),
            transformation_rules: Vec::new(),
        }
    }
}

impl TrustManager {
    fn new() -> Self {
        Self {
            trust_scores: HashMap::new(),
            trust_history: HashMap::new(),
            verification_rules: Vec::new(),
        }
    }

    fn initialize_federation_trust(&mut self, federation_id: &str, initial_trust: f32) {
        self.trust_scores
            .insert(federation_id.to_string(), initial_trust);
        self.trust_history
            .insert(federation_id.to_string(), Vec::new());
    }

    fn get_trust_score(&self, federation_id: &str) -> Option<f32> {
        self.trust_scores.get(federation_id).copied()
    }
}

impl PrivacyEngine {
    fn new() -> Self {
        Self {
            privacy_policies: HashMap::new(),
            mechanisms: Vec::new(),
            budget_tracker: PrivacyBudgetTracker::new(),
        }
    }
}

impl PrivacyBudgetTracker {
    fn new() -> Self {
        Self {
            budget_allocations: HashMap::new(),
            budget_usage: HashMap::new(),
            renewal_policies: HashMap::new(),
        }
    }
}

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

    #[tokio::test]
    async fn test_federated_search_creation() {
        let config = FederatedSearchConfig::default();
        let federated_search = FederatedVectorSearch::new(config).await;
        assert!(federated_search.is_ok());
    }

    #[tokio::test]
    async fn test_federation_endpoint_registration() -> Result<()> {
        let config = FederatedSearchConfig::default();
        let federated_search = FederatedVectorSearch::new(config).await?;

        let endpoint = FederationEndpoint {
            federation_id: "test_federation".to_string(),
            name: "Test Federation".to_string(),
            base_url: "https://api.test-federation.com".to_string(),
            organization_id: "test_org".to_string(),
            trust_level: 0.8,
            api_version: "1.0".to_string(),
            auth_config: AuthenticationConfig {
                auth_type: AuthenticationType::ApiKey,
                api_key: Some("test_key".to_string()),
                oauth_config: None,
                cert_config: None,
            },
            supported_dimensions: vec![128, 256, 512],
            supported_metrics: vec![SimilarityMetric::Cosine],
            privacy_capabilities: PrivacyCapabilities {
                differential_privacy: true,
                k_anonymity: false,
                secure_mpc: false,
                homomorphic_encryption: false,
                privacy_budget: Some(1.0),
            },
            schema_info: SchemaInfo {
                schema_version: "1.0".to_string(),
                metadata_schema: HashMap::new(),
                supported_types: vec!["f32".to_string()],
                dimension_constraints: DimensionConstraints {
                    min_dimensions: 64,
                    max_dimensions: 1024,
                    preferred_dimensions: vec![256, 512],
                },
            },
            performance_profile: PerformanceProfile {
                avg_latency_ms: 100,
                max_concurrent_queries: 50,
                rate_limit_qps: 10.0,
                data_freshness_seconds: 300,
            },
        };

        let result = federated_search.register_federation(endpoint).await;
        assert!(result.is_ok());

        let health_status = federated_search.get_federation_health();
        assert_eq!(health_status.len(), 1);
        assert_eq!(
            health_status.get("test_federation"),
            Some(&NodeHealthStatus::Healthy)
        );
        Ok(())
    }

    #[tokio::test]
    async fn test_federated_search_execution() -> Result<()> {
        let config = FederatedSearchConfig::default();
        let federated_search = FederatedVectorSearch::new(config).await?;

        // Register a test federation
        let endpoint = FederationEndpoint {
            federation_id: "test_federation".to_string(),
            name: "Test Federation".to_string(),
            base_url: "https://api.test-federation.com".to_string(),
            organization_id: "test_org".to_string(),
            trust_level: 0.9,
            api_version: "1.0".to_string(),
            auth_config: AuthenticationConfig {
                auth_type: AuthenticationType::ApiKey,
                api_key: Some("test_key".to_string()),
                oauth_config: None,
                cert_config: None,
            },
            supported_dimensions: vec![3],
            supported_metrics: vec![SimilarityMetric::Cosine],
            privacy_capabilities: PrivacyCapabilities {
                differential_privacy: true,
                k_anonymity: false,
                secure_mpc: false,
                homomorphic_encryption: false,
                privacy_budget: Some(1.0),
            },
            schema_info: SchemaInfo {
                schema_version: "1.0".to_string(),
                metadata_schema: HashMap::new(),
                supported_types: vec!["f32".to_string()],
                dimension_constraints: DimensionConstraints {
                    min_dimensions: 1,
                    max_dimensions: 10,
                    preferred_dimensions: vec![3],
                },
            },
            performance_profile: PerformanceProfile {
                avg_latency_ms: 50,
                max_concurrent_queries: 100,
                rate_limit_qps: 20.0,
                data_freshness_seconds: 60,
            },
        };

        federated_search.register_federation(endpoint).await?;

        // Create a test query
        let query = FederatedQuery {
            query_id: "test_query_1".to_string(),
            vector: Vector::new(vec![1.0, 0.5, 0.8]),
            k: 5,
            metric: SimilarityMetric::Cosine,
            filters: HashMap::new(),
            target_federations: vec![],
            privacy_requirements: PrivacyRequirements {
                min_privacy_level: PrivacyMode::Basic,
                allow_aggregation: true,
                max_exposure_tolerance: 0.1,
            },
            quality_requirements: QualityRequirements {
                min_quality_threshold: 0.7,
                max_latency_ms: 1000,
                min_results: 1,
                max_staleness_seconds: 300,
            },
            timeout: Duration::from_secs(5),
        };

        let response = federated_search.federated_search(query).await?;

        assert_eq!(response.query_id, "test_query_1");
        assert!(!response.results.is_empty());
        assert!(response.federation_stats.federations_contacted > 0);
        assert!(response.federation_stats.federations_responded > 0);
        Ok(())
    }

    #[test]
    fn test_privacy_mode_ordering() {
        assert!(PrivacyMode::None < PrivacyMode::Basic);
        assert!(PrivacyMode::Basic < PrivacyMode::Balanced);
        assert!(PrivacyMode::Balanced < PrivacyMode::Strict);
    }

    #[test]
    fn test_schema_compatibility_ordering() {
        assert!(SchemaCompatibility::BestEffort < SchemaCompatibility::Compatible);
        assert!(SchemaCompatibility::Compatible < SchemaCompatibility::Strict);
    }

    #[test]
    fn test_trust_manager_initialization() {
        let mut trust_manager = TrustManager::new();
        trust_manager.initialize_federation_trust("test_fed", 0.75);

        assert_eq!(trust_manager.get_trust_score("test_fed"), Some(0.75));
        assert_eq!(trust_manager.get_trust_score("nonexistent"), None);
    }

    #[test]
    fn test_federation_metrics_initialization() {
        let metrics = FederationMetrics::default();
        assert_eq!(metrics.total_queries, 0);
        assert_eq!(metrics.successful_queries, 0);
        assert_eq!(metrics.failed_queries, 0);
    }
}