trustformers-mobile 0.1.1

//! Advanced Privacy-Preserving Mechanisms for Mobile Federated Learning
//!
//! This module implements state-of-the-art privacy-preserving techniques for mobile
//! federated learning, including advanced differential privacy, secure multiparty
//! computation, homomorphic encryption, and zero-knowledge proofs.
//!
//! # Features
//!
//! - **Advanced Differential Privacy**: Rényi DP, concentrated DP, and privacy amplification
//! - **Secure Multiparty Computation**: Secret sharing and secure aggregation protocols
//! - **Homomorphic Encryption**: Lattice-based schemes for secure computation
//! - **Zero-Knowledge Proofs**: zk-SNARKs for model integrity verification
//! - **Private Information Retrieval**: Secure model updates without revealing patterns
//! - **Federated Analytics**: Privacy-preserving statistics and insights
//! - **Post-Quantum Cryptography**: Quantum-resistant privacy protection
//! - **Adaptive Privacy Budgeting**: Dynamic privacy budget allocation

use crate::RecommendationPriority;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::{Arc, Mutex, RwLock};
use std::time::{Duration, Instant};
use trustformers_core::error::Result;
use trustformers_core::Tensor;

/// Advanced privacy mechanisms configuration
#[derive(Debug, Clone, Serialize, Deserialize, Default)]
pub struct AdvancedPrivacyConfig {
    /// Differential privacy configuration
    pub differential_privacy: AdvancedDifferentialPrivacyConfig,
    /// Secure multiparty computation settings
    pub secure_mpc: SecureMultipartyConfig,
    /// Homomorphic encryption configuration
    pub homomorphic_encryption: HomomorphicEncryptionConfig,
    /// Zero-knowledge proof settings
    pub zero_knowledge: ZeroKnowledgeConfig,
    /// Private information retrieval configuration
    pub private_retrieval: PrivateRetrievalConfig,
    /// Federated analytics settings
    pub federated_analytics: FederatedAnalyticsConfig,
    /// Post-quantum cryptography configuration
    pub post_quantum: PostQuantumConfig,
    /// Adaptive privacy budgeting
    pub adaptive_budgeting: AdaptiveBudgetingConfig,
}

/// Advanced differential privacy configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AdvancedDifferentialPrivacyConfig {
    /// Privacy accounting mechanism
    pub accounting_mechanism: PrivacyAccountingMechanism,
    /// Rényi differential privacy parameters
    pub renyi_dp: RenyiDPConfig,
    /// Privacy amplification settings
    pub privacy_amplification: PrivacyAmplificationConfig,
    /// Concentrated differential privacy configuration
    pub concentrated_dp: ConcentratedDPConfig,
    /// Local differential privacy settings
    pub local_dp: LocalDPConfig,
}

impl Default for AdvancedDifferentialPrivacyConfig {
    fn default() -> Self {
        Self {
            accounting_mechanism: PrivacyAccountingMechanism::RenyiAccountant,
            renyi_dp: RenyiDPConfig::default(),
            privacy_amplification: PrivacyAmplificationConfig::default(),
            concentrated_dp: ConcentratedDPConfig::default(),
            local_dp: LocalDPConfig::default(),
        }
    }
}

/// Privacy accounting mechanisms
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum PrivacyAccountingMechanism {
    /// Traditional (ε, δ)-DP
    Traditional,
    /// Rényi Differential Privacy
    RenyiAccountant,
    /// Concentrated Differential Privacy
    ConcentratedAccountant,
    /// Privacy Loss Distribution
    PLDAccountant,
}

/// Rényi Differential Privacy configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RenyiDPConfig {
    /// Rényi parameter α
    pub alpha: f64,
    /// Privacy budget ε(α)
    pub epsilon_alpha: f64,
    /// Orders to track
    pub orders: Vec<f64>,
    /// Target delta for conversion
    pub target_delta: f64,
}

impl Default for RenyiDPConfig {
    fn default() -> Self {
        Self {
            alpha: 2.0, // α = 2 corresponds to concentrated DP
            epsilon_alpha: 1.0,
            orders: vec![
                1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0,
                11.0, 12.0, 14.0, 16.0, 20.0,
            ],
            target_delta: 1e-5,
        }
    }
}

/// Privacy amplification configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PrivacyAmplificationConfig {
    /// Enable privacy amplification by subsampling
    pub enable_subsampling: bool,
    /// Subsampling probability
    pub sampling_probability: f64,
    /// Enable privacy amplification by shuffling
    pub enable_shuffling: bool,
    /// Shuffling buffer size
    pub shuffle_buffer_size: usize,
    /// Enable privacy amplification by iteration
    pub enable_iteration_amplification: bool,
}

impl Default for PrivacyAmplificationConfig {
    fn default() -> Self {
        Self {
            enable_subsampling: true,
            sampling_probability: 0.01, // 1% sampling
            enable_shuffling: true,
            shuffle_buffer_size: 10000,
            enable_iteration_amplification: true,
        }
    }
}

/// Concentrated Differential Privacy configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ConcentratedDPConfig {
    /// Concentration parameter μ
    pub mu: f64,
    /// Privacy loss upper bound
    pub privacy_loss_bound: f64,
    /// Tail probability bound
    pub tail_bound: f64,
}

impl Default for ConcentratedDPConfig {
    fn default() -> Self {
        Self {
            mu: 0.5,
            privacy_loss_bound: 10.0,
            tail_bound: 1e-6,
        }
    }
}

/// Local Differential Privacy configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LocalDPConfig {
    /// Enable local differential privacy
    pub enabled: bool,
    /// Local privacy parameter ε_local
    pub epsilon_local: f64,
    /// Randomized response parameters
    pub randomized_response: RandomizedResponseConfig,
    /// Local hashing configuration
    pub local_hashing: LocalHashingConfig,
}

impl Default for LocalDPConfig {
    fn default() -> Self {
        Self {
            enabled: true,
            epsilon_local: 1.0,
            randomized_response: RandomizedResponseConfig::default(),
            local_hashing: LocalHashingConfig::default(),
        }
    }
}

/// Randomized response configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct RandomizedResponseConfig {
    /// Response probability for true values
    pub true_probability: f64,
    /// Response probability for false values
    pub false_probability: f64,
    /// Use optimal randomized response
    pub use_optimal: bool,
}

impl Default for RandomizedResponseConfig {
    fn default() -> Self {
        Self {
            true_probability: 0.75,
            false_probability: 0.25,
            use_optimal: true,
        }
    }
}

/// Local hashing configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LocalHashingConfig {
    /// Number of hash functions
    pub num_hash_functions: usize,
    /// Hash domain size
    pub domain_size: usize,
    /// Use consistent hashing
    pub consistent_hashing: bool,
}

impl Default for LocalHashingConfig {
    fn default() -> Self {
        Self {
            num_hash_functions: 2,
            domain_size: 1024,
            consistent_hashing: true,
        }
    }
}

/// Secure multiparty computation configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SecureMultipartyConfig {
    /// MPC protocol type
    pub protocol: MPCProtocol,
    /// Secret sharing scheme
    pub secret_sharing: SecretSharingScheme,
    /// Number of parties
    pub num_parties: usize,
    /// Security threshold
    pub threshold: usize,
    /// Communication optimization
    pub communication_optimization: CommunicationOptimization,
}

impl Default for SecureMultipartyConfig {
    fn default() -> Self {
        Self {
            protocol: MPCProtocol::SecureAggregation,
            secret_sharing: SecretSharingScheme::Shamir,
            num_parties: 100, // Typical federated learning scenario
            threshold: 67,    // 2/3 threshold
            communication_optimization: CommunicationOptimization::default(),
        }
    }
}

/// MPC protocol types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum MPCProtocol {
    /// Secure aggregation protocol
    SecureAggregation,
    /// BGW protocol
    BGW,
    /// GMW protocol
    GMW,
    /// SPDZ protocol
    SPDZ,
    /// Custom protocol
    Custom(String),
}

/// Secret sharing schemes
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum SecretSharingScheme {
    /// Shamir's secret sharing
    Shamir,
    /// Additive secret sharing
    Additive,
    /// Replicated secret sharing
    Replicated,
    /// Packed secret sharing
    Packed,
}

/// Communication optimization settings
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CommunicationOptimization {
    /// Use compression for communication
    pub enable_compression: bool,
    /// Compression algorithm
    pub compression_algorithm: CompressionAlgorithm,
    /// Batch communication rounds
    pub batch_communications: bool,
    /// Maximum batch size
    pub max_batch_size: usize,
}

impl Default for CommunicationOptimization {
    fn default() -> Self {
        Self {
            enable_compression: true,
            compression_algorithm: CompressionAlgorithm::LZ4,
            batch_communications: true,
            max_batch_size: 1000,
        }
    }
}

/// Compression algorithms
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum CompressionAlgorithm {
    /// LZ4 compression
    LZ4,
    /// ZSTD compression
    ZSTD,
    /// Brotli compression
    Brotli,
    /// Custom compression
    Custom(String),
}

/// Homomorphic encryption configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HomomorphicEncryptionConfig {
    /// HE scheme type
    pub scheme: HomomorphicScheme,
    /// Security level (in bits)
    pub security_level: usize,
    /// Key generation parameters
    pub key_params: KeyGenerationParams,
    /// Optimization settings
    pub optimization: HEOptimizationConfig,
}

impl Default for HomomorphicEncryptionConfig {
    fn default() -> Self {
        Self {
            scheme: HomomorphicScheme::BFV,
            security_level: 128,
            key_params: KeyGenerationParams::default(),
            optimization: HEOptimizationConfig::default(),
        }
    }
}

/// Homomorphic encryption schemes
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum HomomorphicScheme {
    /// Brakerski-Fan-Vercauteren scheme
    BFV,
    /// Cheon-Kim-Kim-Song scheme
    CKKS,
    /// Brakerski-Gentry-Vaikuntanathan scheme
    BGV,
    /// TFHE scheme
    TFHE,
}

/// Key generation parameters
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct KeyGenerationParams {
    /// Polynomial modulus degree
    pub poly_modulus_degree: usize,
    /// Coefficient modulus
    pub coeff_modulus: Vec<u64>,
    /// Plaintext modulus
    pub plain_modulus: u64,
    /// Standard deviation for error distribution
    pub noise_standard_deviation: f64,
}

impl Default for KeyGenerationParams {
    fn default() -> Self {
        Self {
            poly_modulus_degree: 8192,
            coeff_modulus: vec![60, 40, 40, 60],
            plain_modulus: 1024,
            noise_standard_deviation: 3.2,
        }
    }
}

/// Homomorphic encryption optimization configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HEOptimizationConfig {
    /// Enable SIMD packing
    pub enable_simd_packing: bool,
    /// Relinearization strategy
    pub relinearization: RelinearizationStrategy,
    /// Rescaling optimization
    pub rescaling: RescalingOptimization,
    /// Bootstrapping configuration
    pub bootstrapping: BootstrappingConfig,
}

impl Default for HEOptimizationConfig {
    fn default() -> Self {
        Self {
            enable_simd_packing: true,
            relinearization: RelinearizationStrategy::Lazy,
            rescaling: RescalingOptimization::Automatic,
            bootstrapping: BootstrappingConfig::default(),
        }
    }
}

/// Relinearization strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum RelinearizationStrategy {
    /// Immediate relinearization
    Immediate,
    /// Lazy relinearization
    Lazy,
    /// Threshold-based relinearization
    Threshold(usize),
}

/// Rescaling optimization
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum RescalingOptimization {
    /// Manual rescaling
    Manual,
    /// Automatic rescaling
    Automatic,
    /// Optimal rescaling
    Optimal,
}

/// Bootstrapping configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BootstrappingConfig {
    /// Enable bootstrapping
    pub enabled: bool,
    /// Bootstrapping threshold
    pub threshold: f64,
    /// Bootstrapping precision
    pub precision: usize,
}

impl Default for BootstrappingConfig {
    fn default() -> Self {
        Self {
            enabled: true,
            threshold: 0.1, // 10% noise threshold
            precision: 20,
        }
    }
}

/// Zero-knowledge proof configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ZeroKnowledgeConfig {
    /// ZK proof system
    pub proof_system: ZKProofSystem,
    /// Circuit optimization
    pub circuit_optimization: CircuitOptimization,
    /// Verification settings
    pub verification: ZKVerificationConfig,
}

impl Default for ZeroKnowledgeConfig {
    fn default() -> Self {
        Self {
            proof_system: ZKProofSystem::Groth16,
            circuit_optimization: CircuitOptimization::default(),
            verification: ZKVerificationConfig::default(),
        }
    }
}

/// Zero-knowledge proof systems
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum ZKProofSystem {
    /// Groth16 zk-SNARK
    Groth16,
    /// PLONK proof system
    PLONK,
    /// Bulletproofs
    Bulletproofs,
    /// STARK proof system
    STARK,
    /// Marlin proof system
    Marlin,
}

/// Circuit optimization configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CircuitOptimization {
    /// Enable circuit minimization
    pub enable_minimization: bool,
    /// Gate optimization level
    pub gate_optimization_level: usize,
    /// Wire optimization
    pub wire_optimization: bool,
    /// Parallel circuit generation
    pub parallel_generation: bool,
}

impl Default for CircuitOptimization {
    fn default() -> Self {
        Self {
            enable_minimization: true,
            gate_optimization_level: 2,
            wire_optimization: true,
            parallel_generation: true,
        }
    }
}

/// Zero-knowledge verification configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ZKVerificationConfig {
    /// Batch verification
    pub batch_verification: bool,
    /// Verification parallelization
    pub parallel_verification: bool,
    /// Proof caching
    pub enable_proof_caching: bool,
    /// Cache size limit
    pub cache_size_limit: usize,
}

impl Default for ZKVerificationConfig {
    fn default() -> Self {
        Self {
            batch_verification: true,
            parallel_verification: true,
            enable_proof_caching: true,
            cache_size_limit: 1000,
        }
    }
}

/// Private information retrieval configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PrivateRetrievalConfig {
    /// PIR scheme type
    pub scheme: PIRScheme,
    /// Database preprocessing
    pub preprocessing: PIRPreprocessing,
    /// Communication optimization
    pub communication_optimization: PIRCommunicationConfig,
}

impl Default for PrivateRetrievalConfig {
    fn default() -> Self {
        Self {
            scheme: PIRScheme::SingleServer,
            preprocessing: PIRPreprocessing::default(),
            communication_optimization: PIRCommunicationConfig::default(),
        }
    }
}

/// PIR scheme types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum PIRScheme {
    /// Single-server PIR
    SingleServer,
    /// Multi-server PIR
    MultiServer { num_servers: usize },
    /// Symmetric PIR
    Symmetric,
    /// Hybrid PIR
    Hybrid,
}

/// PIR preprocessing configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PIRPreprocessing {
    /// Enable preprocessing
    pub enabled: bool,
    /// Preprocessing strategy
    pub strategy: PreprocessingStrategy,
    /// Update frequency
    pub update_frequency: Duration,
}

impl Default for PIRPreprocessing {
    fn default() -> Self {
        Self {
            enabled: true,
            strategy: PreprocessingStrategy::Incremental,
            update_frequency: Duration::from_secs(3600), // 1 hour
        }
    }
}

/// Preprocessing strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum PreprocessingStrategy {
    /// Full preprocessing
    Full,
    /// Incremental preprocessing
    Incremental,
    /// Lazy preprocessing
    Lazy,
}

/// PIR communication configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PIRCommunicationConfig {
    /// Enable communication optimization
    pub enabled: bool,
    /// Batch queries
    pub batch_queries: bool,
    /// Maximum batch size
    pub max_batch_size: usize,
    /// Query compression
    pub enable_compression: bool,
}

impl Default for PIRCommunicationConfig {
    fn default() -> Self {
        Self {
            enabled: true,
            batch_queries: true,
            max_batch_size: 100,
            enable_compression: true,
        }
    }
}

/// Federated analytics configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FederatedAnalyticsConfig {
    /// Analytics types to enable
    pub enabled_analytics: Vec<AnalyticsType>,
    /// Privacy-preserving statistics
    pub statistics: PrivateStatisticsConfig,
    /// Heavy hitters identification
    pub heavy_hitters: HeavyHittersConfig,
    /// Histograms and distributions
    pub histograms: PrivateHistogramConfig,
}

impl Default for FederatedAnalyticsConfig {
    fn default() -> Self {
        Self {
            enabled_analytics: vec![
                AnalyticsType::BasicStatistics,
                AnalyticsType::HeavyHitters,
                AnalyticsType::Histograms,
            ],
            statistics: PrivateStatisticsConfig::default(),
            heavy_hitters: HeavyHittersConfig::default(),
            histograms: PrivateHistogramConfig::default(),
        }
    }
}

/// Types of federated analytics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum AnalyticsType {
    /// Basic statistics (mean, variance, etc.)
    BasicStatistics,
    /// Heavy hitters identification
    HeavyHitters,
    /// Private histograms
    Histograms,
    /// Frequent itemsets
    FrequentItemsets,
    /// Graph analytics
    GraphAnalytics,
}

/// Private statistics configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PrivateStatisticsConfig {
    /// Statistics to compute
    pub statistics: Vec<StatisticType>,
    /// Privacy budget allocation
    pub privacy_budget_per_statistic: f64,
    /// Clipping bounds
    pub clipping_bounds: ClippingBounds,
}

impl Default for PrivateStatisticsConfig {
    fn default() -> Self {
        Self {
            statistics: vec![
                StatisticType::Mean,
                StatisticType::Variance,
                StatisticType::Quantiles(vec![0.25, 0.5, 0.75]),
            ],
            privacy_budget_per_statistic: 0.1,
            clipping_bounds: ClippingBounds::default(),
        }
    }
}

/// Types of statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum StatisticType {
    /// Mean
    Mean,
    /// Variance
    Variance,
    /// Quantiles
    Quantiles(Vec<f64>),
    /// Covariance
    Covariance,
    /// Correlation
    Correlation,
}

/// Clipping bounds for statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ClippingBounds {
    /// Lower bound
    pub lower_bound: f64,
    /// Upper bound
    pub upper_bound: f64,
    /// Adaptive bounds
    pub adaptive_bounds: bool,
}

impl Default for ClippingBounds {
    fn default() -> Self {
        Self {
            lower_bound: -10.0,
            upper_bound: 10.0,
            adaptive_bounds: true,
        }
    }
}

/// Heavy hitters configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct HeavyHittersConfig {
    /// Threshold for heavy hitters
    pub threshold: f64,
    /// Maximum number of heavy hitters
    pub max_heavy_hitters: usize,
    /// Privacy budget
    pub privacy_budget: f64,
    /// Sketching algorithm
    pub sketching_algorithm: SketchingAlgorithm,
}

impl Default for HeavyHittersConfig {
    fn default() -> Self {
        Self {
            threshold: 0.01, // 1% threshold
            max_heavy_hitters: 100,
            privacy_budget: 1.0,
            sketching_algorithm: SketchingAlgorithm::CountMin,
        }
    }
}

/// Sketching algorithms
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum SketchingAlgorithm {
    /// Count-Min sketch
    CountMin,
    /// Count sketch
    Count,
    /// HyperLogLog
    HyperLogLog,
    /// Bloom filter
    BloomFilter,
}

/// Private histogram configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PrivateHistogramConfig {
    /// Number of bins
    pub num_bins: usize,
    /// Histogram range
    pub range: (f64, f64),
    /// Privacy budget
    pub privacy_budget: f64,
    /// Histogram type
    pub histogram_type: HistogramType,
}

impl Default for PrivateHistogramConfig {
    fn default() -> Self {
        Self {
            num_bins: 100,
            range: (0.0, 1.0),
            privacy_budget: 1.0,
            histogram_type: HistogramType::Uniform,
        }
    }
}

/// Histogram types
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum HistogramType {
    /// Uniform bins
    Uniform,
    /// Adaptive bins
    Adaptive,
    /// Quantile-based bins
    Quantile,
}

/// Post-quantum cryptography configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PostQuantumConfig {
    /// Enable post-quantum cryptography
    pub enabled: bool,
    /// Key encapsulation mechanism
    pub kem: KEMAlgorithm,
    /// Digital signature scheme
    pub signature: SignatureAlgorithm,
    /// Hybrid classical-quantum security
    pub hybrid_security: bool,
}

impl Default for PostQuantumConfig {
    fn default() -> Self {
        Self {
            enabled: true,
            kem: KEMAlgorithm::Kyber,
            signature: SignatureAlgorithm::Dilithium,
            hybrid_security: true,
        }
    }
}

/// Key encapsulation mechanism algorithms
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum KEMAlgorithm {
    /// CRYSTALS-Kyber
    Kyber,
    /// NTRU
    NTRU,
    /// SABER
    SABER,
    /// FrodoKEM
    FrodoKEM,
}

/// Digital signature algorithms
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum SignatureAlgorithm {
    /// CRYSTALS-Dilithium
    Dilithium,
    /// FALCON
    FALCON,
    /// SPHINCS+
    SPHINCSPlus,
    /// Rainbow
    Rainbow,
}

/// Adaptive privacy budgeting configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct AdaptiveBudgetingConfig {
    /// Enable adaptive budgeting
    pub enabled: bool,
    /// Initial privacy budget
    pub initial_budget: f64,
    /// Budget allocation strategy
    pub allocation_strategy: BudgetAllocationStrategy,
    /// Budget renewal configuration
    pub renewal: BudgetRenewalConfig,
    /// Fairness constraints
    pub fairness_constraints: FairnessConstraints,
}

impl Default for AdaptiveBudgetingConfig {
    fn default() -> Self {
        Self {
            enabled: true,
            initial_budget: 10.0,
            allocation_strategy: BudgetAllocationStrategy::Proportional,
            renewal: BudgetRenewalConfig::default(),
            fairness_constraints: FairnessConstraints::default(),
        }
    }
}

/// Budget allocation strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum BudgetAllocationStrategy {
    /// Uniform allocation
    Uniform,
    /// Proportional allocation
    Proportional,
    /// Utility-based allocation
    UtilityBased,
    /// Reinforcement learning
    ReinforcementLearning,
}

/// Budget renewal configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BudgetRenewalConfig {
    /// Renewal strategy
    pub strategy: RenewalStrategy,
    /// Renewal interval
    pub interval: Duration,
    /// Renewal amount
    pub amount: f64,
}

impl Default for BudgetRenewalConfig {
    fn default() -> Self {
        Self {
            strategy: RenewalStrategy::Periodic,
            interval: Duration::from_secs(3600 * 24), // Daily
            amount: 1.0,
        }
    }
}

/// Budget renewal strategies
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum RenewalStrategy {
    /// Periodic renewal
    Periodic,
    /// Demand-based renewal
    DemandBased,
    /// Performance-based renewal
    PerformanceBased,
}

/// Fairness constraints for privacy budgeting
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct FairnessConstraints {
    /// Enable fairness constraints
    pub enabled: bool,
    /// Maximum budget per client
    pub max_budget_per_client: f64,
    /// Minimum participation rate
    pub min_participation_rate: f64,
    /// Fairness metric
    pub fairness_metric: FairnessMetric,
}

impl Default for FairnessConstraints {
    fn default() -> Self {
        Self {
            enabled: true,
            max_budget_per_client: 2.0,
            min_participation_rate: 0.1, // 10% minimum
            fairness_metric: FairnessMetric::MaxMin,
        }
    }
}

/// Fairness metrics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum FairnessMetric {
    /// Max-min fairness
    MaxMin,
    /// Proportional fairness
    Proportional,
    /// Utilitarian fairness
    Utilitarian,
    /// Envy-free allocation
    EnvyFree,
}

/// Advanced privacy mechanisms engine
pub struct AdvancedPrivacyMechanisms {
    config: AdvancedPrivacyConfig,

    // Privacy engines
    differential_privacy: Arc<AdvancedDifferentialPrivacy>,
    secure_mpc: Arc<SecureMultipartyComputation>,
    homomorphic_encryption: Arc<HomomorphicEncryption>,
    zero_knowledge: Arc<ZeroKnowledgeProofs>,
    private_retrieval: Arc<PrivateInformationRetrieval>,
    federated_analytics: Arc<PrivateFederatedAnalytics>,
    post_quantum: Arc<PostQuantumCryptography>,
    adaptive_budgeting: Arc<AdaptivePrivacyBudgeting>,

    // State management
    privacy_state: Arc<RwLock<PrivacyState>>,
    performance_monitor: Arc<PrivacyPerformanceMonitor>,
    audit_log: Arc<Mutex<Vec<PrivacyAuditEntry>>>,
}

impl AdvancedPrivacyMechanisms {
    /// Create new advanced privacy mechanisms engine
    pub fn new(config: AdvancedPrivacyConfig) -> Result<Self> {
        let differential_privacy = Arc::new(AdvancedDifferentialPrivacy::new(
            config.differential_privacy.clone(),
        )?);

        let secure_mpc = Arc::new(SecureMultipartyComputation::new(config.secure_mpc.clone())?);

        let homomorphic_encryption = Arc::new(HomomorphicEncryption::new(
            config.homomorphic_encryption.clone(),
        )?);

        let zero_knowledge = Arc::new(ZeroKnowledgeProofs::new(config.zero_knowledge.clone())?);

        let private_retrieval = Arc::new(PrivateInformationRetrieval::new(
            config.private_retrieval.clone(),
        )?);

        let federated_analytics = Arc::new(PrivateFederatedAnalytics::new(
            config.federated_analytics.clone(),
        )?);

        let post_quantum = Arc::new(PostQuantumCryptography::new(config.post_quantum.clone())?);

        let adaptive_budgeting = Arc::new(AdaptivePrivacyBudgeting::new(
            config.adaptive_budgeting.clone(),
        )?);

        Ok(Self {
            config,
            differential_privacy,
            secure_mpc,
            homomorphic_encryption,
            zero_knowledge,
            private_retrieval,
            federated_analytics,
            post_quantum,
            adaptive_budgeting,
            privacy_state: Arc::new(RwLock::new(PrivacyState::new())),
            performance_monitor: Arc::new(PrivacyPerformanceMonitor::new()?),
            audit_log: Arc::new(Mutex::new(Vec::new())),
        })
    }

    /// Execute privacy-preserving federated learning round
    pub async fn execute_private_federated_round(
        &self,
        model_update: &Tensor,
        client_id: &str,
    ) -> Result<PrivateFederatedResult> {
        let start_time = Instant::now();

        // 1. Check and allocate privacy budget
        let budget_allocation = self
            .adaptive_budgeting
            .allocate_budget(client_id, &self.estimate_privacy_cost(model_update).await?)
            .await?;

        // 2. Apply differential privacy mechanisms
        let dp_update = self
            .differential_privacy
            .privatize_update(model_update, &budget_allocation.differential_privacy)
            .await?;

        // 3. Apply secure multiparty computation
        let mpc_shares = self.secure_mpc.create_secret_shares(&dp_update, client_id).await?;

        // 4. Optional homomorphic encryption
        let encrypted_shares =
            if self.config.homomorphic_encryption.scheme != HomomorphicScheme::BFV {
                Some(self.homomorphic_encryption.encrypt_shares(&mpc_shares).await?)
            } else {
                None
            };

        // 5. Generate zero-knowledge proof of correctness
        let zk_proof = self
            .zero_knowledge
            .generate_correctness_proof(model_update, &dp_update, &budget_allocation)
            .await?;

        // 6. Post-quantum security wrapper
        let pq_secured = self
            .post_quantum
            .secure_transmission(&PrivateData {
                mpc_shares,
                encrypted_shares,
                zk_proof: zk_proof.clone(),
            })
            .await?;

        // 7. Log privacy audit entry
        self.log_privacy_operation(
            client_id,
            PrivacyOperation::FederatedRound,
            &budget_allocation,
            start_time.elapsed(),
        )
        .await?;

        // 8. Update privacy state
        self.update_privacy_state(client_id, &budget_allocation).await?;

        // Compute privacy guarantees BEFORE moving budget_allocation
        let privacy_guarantees = self.compute_privacy_guarantees(&budget_allocation).await?;

        Ok(PrivateFederatedResult {
            secured_data: pq_secured,
            zk_proof,
            budget_consumed: budget_allocation,
            execution_time: start_time.elapsed(),
            privacy_guarantees,
        })
    }

    /// Perform private federated analytics
    pub async fn compute_private_analytics(
        &self,
        data_samples: &[Tensor],
        analytics_types: &[AnalyticsType],
    ) -> Result<PrivateAnalyticsResult> {
        self.federated_analytics.compute_analytics(data_samples, analytics_types).await
    }

    /// Retrieve model updates privately
    pub async fn private_model_retrieval(
        &self,
        query_parameters: &ModelQuery,
    ) -> Result<PrivateRetrievalResult> {
        self.private_retrieval.retrieve_model_update(query_parameters).await
    }

    /// Get comprehensive privacy report
    pub async fn get_privacy_report(&self) -> Result<PrivacyReport> {
        let state = self.privacy_state.read().expect("Operation failed").clone();
        let performance_metrics = self.performance_monitor.get_metrics().await?;
        let audit_entries = self.audit_log.lock().expect("Operation failed").clone();

        Ok(PrivacyReport {
            current_state: state,
            performance_metrics,
            audit_log: audit_entries,
            recommendations: self.generate_privacy_recommendations().await?,
        })
    }

    // Private helper methods
    async fn estimate_privacy_cost(&self, _model_update: &Tensor) -> Result<PrivacyCost> {
        // Sophisticated privacy cost estimation
        Ok(PrivacyCost {
            differential_privacy_cost: 0.1,
            computational_cost: 1000, // milliseconds
            communication_cost: 1024, // bytes
        })
    }

    async fn log_privacy_operation(
        &self,
        client_id: &str,
        operation: PrivacyOperation,
        budget_allocation: &BudgetAllocation,
        execution_time: Duration,
    ) -> Result<()> {
        let entry = PrivacyAuditEntry {
            timestamp: Instant::now(),
            client_id: client_id.to_string(),
            operation,
            budget_consumed: budget_allocation.clone(),
            execution_time,
            success: true,
        };

        self.audit_log.lock().expect("Operation failed").push(entry);
        Ok(())
    }

    async fn update_privacy_state(
        &self,
        client_id: &str,
        budget_allocation: &BudgetAllocation,
    ) -> Result<()> {
        let mut state = self.privacy_state.write().expect("Operation failed");
        state.update_client_budget(client_id, budget_allocation);
        Ok(())
    }

    async fn compute_privacy_guarantees(
        &self,
        budget_allocation: &BudgetAllocation,
    ) -> Result<PrivacyGuarantees> {
        // Compute comprehensive privacy guarantees
        Ok(PrivacyGuarantees {
            epsilon: budget_allocation.differential_privacy.epsilon,
            delta: budget_allocation.differential_privacy.delta,
            renyi_alpha: budget_allocation.differential_privacy.renyi_alpha,
            security_level: 128, // bits
            quantum_resistance: self.config.post_quantum.enabled,
        })
    }

    async fn generate_privacy_recommendations(&self) -> Result<Vec<PrivacyRecommendation>> {
        // Generate intelligent privacy recommendations
        Ok(vec![PrivacyRecommendation {
            category: PrivacyRecommendationCategory::BudgetAllocation,
            priority: RecommendationPriority::High,
            description: "Consider increasing privacy budget for better utility".to_string(),
            expected_improvement: 0.15,
        }])
    }
}

// Supporting structures and placeholder implementations
// (In a real implementation, these would be fully implemented)

pub struct AdvancedDifferentialPrivacy {
    config: AdvancedDifferentialPrivacyConfig,
}

impl AdvancedDifferentialPrivacy {
    pub fn new(config: AdvancedDifferentialPrivacyConfig) -> Result<Self> {
        Ok(Self { config })
    }

    pub async fn privatize_update(
        &self,
        update: &Tensor,
        budget: &DifferentialPrivacyBudget,
    ) -> Result<Tensor> {
        // Advanced DP implementation
        let _ = (update, budget);
        Ok(Tensor::zeros(&[1, 1])?)
    }
}

// ... (Additional implementation structures would follow)

/// Privacy state management
#[derive(Debug, Clone)]
pub struct PrivacyState {
    client_budgets: HashMap<String, f64>,
    global_privacy_loss: f64,
    active_sessions: HashMap<String, Instant>,
}

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

impl PrivacyState {
    pub fn new() -> Self {
        Self {
            client_budgets: HashMap::new(),
            global_privacy_loss: 0.0,
            active_sessions: HashMap::new(),
        }
    }

    pub fn update_client_budget(&mut self, client_id: &str, allocation: &BudgetAllocation) {
        let current_budget = self.client_budgets.get(client_id).unwrap_or(&10.0);
        self.client_budgets.insert(
            client_id.to_string(),
            current_budget - allocation.total_cost(),
        );
    }
}

/// Supporting types for the advanced privacy system

#[derive(Debug, Clone)]
pub struct BudgetAllocation {
    pub differential_privacy: DifferentialPrivacyBudget,
    pub computational_budget: f64,
    pub communication_budget: f64,
}

impl BudgetAllocation {
    pub fn total_cost(&self) -> f64 {
        self.differential_privacy.epsilon
            + self.computational_budget * 0.001
            + self.communication_budget * 0.0001
    }
}

#[derive(Debug, Clone)]
pub struct DifferentialPrivacyBudget {
    pub epsilon: f64,
    pub delta: f64,
    pub renyi_alpha: f64,
}

#[derive(Debug, Clone)]
pub struct PrivacyCost {
    pub differential_privacy_cost: f64,
    pub computational_cost: u64,
    pub communication_cost: u64,
}

#[derive(Debug, Clone)]
pub struct PrivateData {
    pub mpc_shares: Vec<SecretShare>,
    pub encrypted_shares: Option<Vec<EncryptedShare>>,
    pub zk_proof: ZKProof,
}

#[derive(Debug, Clone)]
pub struct SecretShare {
    pub share_data: Vec<u8>,
    pub share_id: usize,
}

#[derive(Debug, Clone)]
pub struct EncryptedShare {
    pub ciphertext: Vec<u8>,
    pub public_key_id: String,
}

#[derive(Debug, Clone)]
pub struct ZKProof {
    pub proof_data: Vec<u8>,
    pub verification_key: Vec<u8>,
}

#[derive(Debug, Clone)]
pub struct PrivateFederatedResult {
    pub secured_data: PostQuantumSecuredData,
    pub zk_proof: ZKProof,
    pub budget_consumed: BudgetAllocation,
    pub execution_time: Duration,
    pub privacy_guarantees: PrivacyGuarantees,
}

#[derive(Debug, Clone)]
pub struct PostQuantumSecuredData {
    pub encrypted_payload: Vec<u8>,
    pub quantum_signature: Vec<u8>,
}

#[derive(Debug, Clone)]
pub struct PrivacyGuarantees {
    pub epsilon: f64,
    pub delta: f64,
    pub renyi_alpha: f64,
    pub security_level: usize,
    pub quantum_resistance: bool,
}

#[derive(Debug, Clone)]
pub struct PrivateAnalyticsResult {
    pub statistics: HashMap<String, f64>,
    pub privacy_cost: PrivacyCost,
    pub confidence_intervals: HashMap<String, (f64, f64)>,
}

#[derive(Debug, Clone)]
pub struct ModelQuery {
    pub model_id: String,
    pub version: u64,
    pub client_capabilities: Vec<String>,
}

#[derive(Debug, Clone)]
pub struct PrivateRetrievalResult {
    pub model_update: Option<Tensor>,
    pub privacy_cost: PrivacyCost,
    pub retrieval_time: Duration,
}

#[derive(Debug, Clone)]
pub struct PrivacyReport {
    pub current_state: PrivacyState,
    pub performance_metrics: PrivacyPerformanceMetrics,
    pub audit_log: Vec<PrivacyAuditEntry>,
    pub recommendations: Vec<PrivacyRecommendation>,
}

#[derive(Debug, Clone)]
pub struct PrivacyPerformanceMetrics {
    pub average_execution_time: Duration,
    pub throughput: f64,
    pub privacy_efficiency: f64,
    pub resource_utilization: f64,
}

#[derive(Debug, Clone)]
pub struct PrivacyAuditEntry {
    pub timestamp: Instant,
    pub client_id: String,
    pub operation: PrivacyOperation,
    pub budget_consumed: BudgetAllocation,
    pub execution_time: Duration,
    pub success: bool,
}

#[derive(Debug, Clone)]
pub enum PrivacyOperation {
    FederatedRound,
    Analytics,
    ModelRetrieval,
    BudgetAllocation,
}

#[derive(Debug, Clone)]
pub struct PrivacyRecommendation {
    pub category: PrivacyRecommendationCategory,
    pub priority: RecommendationPriority,
    pub description: String,
    pub expected_improvement: f64,
}

#[derive(Debug, Clone)]
pub enum PrivacyRecommendationCategory {
    BudgetAllocation,
    SecurityLevel,
    Performance,
    Utility,
}

// Placeholder implementations for the various privacy engines
pub struct SecureMultipartyComputation {
    config: SecureMultipartyConfig,
}

impl SecureMultipartyComputation {
    pub fn new(config: SecureMultipartyConfig) -> Result<Self> {
        Ok(Self { config })
    }

    pub async fn create_secret_shares(
        &self,
        data: &Tensor,
        client_id: &str,
    ) -> Result<Vec<SecretShare>> {
        let _ = (data, client_id);
        Ok(vec![SecretShare {
            share_data: vec![0u8; 32],
            share_id: 1,
        }])
    }
}

pub struct HomomorphicEncryption {
    config: HomomorphicEncryptionConfig,
}

impl HomomorphicEncryption {
    pub fn new(config: HomomorphicEncryptionConfig) -> Result<Self> {
        Ok(Self { config })
    }

    pub async fn encrypt_shares(&self, shares: &[SecretShare]) -> Result<Vec<EncryptedShare>> {
        let _ = shares;
        Ok(vec![EncryptedShare {
            ciphertext: vec![0u8; 64],
            public_key_id: "key1".to_string(),
        }])
    }
}

pub struct ZeroKnowledgeProofs {
    config: ZeroKnowledgeConfig,
}

impl ZeroKnowledgeProofs {
    pub fn new(config: ZeroKnowledgeConfig) -> Result<Self> {
        Ok(Self { config })
    }

    pub async fn generate_correctness_proof(
        &self,
        original: &Tensor,
        privatized: &Tensor,
        budget: &BudgetAllocation,
    ) -> Result<ZKProof> {
        let _ = (original, privatized, budget);
        Ok(ZKProof {
            proof_data: vec![0u8; 128],
            verification_key: vec![0u8; 32],
        })
    }
}

pub struct PrivateInformationRetrieval {
    config: PrivateRetrievalConfig,
}

impl PrivateInformationRetrieval {
    pub fn new(config: PrivateRetrievalConfig) -> Result<Self> {
        Ok(Self { config })
    }

    pub async fn retrieve_model_update(
        &self,
        query: &ModelQuery,
    ) -> Result<PrivateRetrievalResult> {
        let _ = query;
        Ok(PrivateRetrievalResult {
            model_update: Some(Tensor::zeros(&[1, 1])?),
            privacy_cost: PrivacyCost {
                differential_privacy_cost: 0.05,
                computational_cost: 500,
                communication_cost: 2048,
            },
            retrieval_time: Duration::from_millis(100),
        })
    }
}

pub struct PrivateFederatedAnalytics {
    config: FederatedAnalyticsConfig,
}

impl PrivateFederatedAnalytics {
    pub fn new(config: FederatedAnalyticsConfig) -> Result<Self> {
        Ok(Self { config })
    }

    pub async fn compute_analytics(
        &self,
        data: &[Tensor],
        analytics: &[AnalyticsType],
    ) -> Result<PrivateAnalyticsResult> {
        let _ = (data, analytics);
        Ok(PrivateAnalyticsResult {
            statistics: HashMap::from([("mean".to_string(), 0.5), ("variance".to_string(), 0.1)]),
            privacy_cost: PrivacyCost {
                differential_privacy_cost: 0.2,
                computational_cost: 1000,
                communication_cost: 1024,
            },
            confidence_intervals: HashMap::from([
                ("mean".to_string(), (0.45, 0.55)),
                ("variance".to_string(), (0.08, 0.12)),
            ]),
        })
    }
}

pub struct PostQuantumCryptography {
    config: PostQuantumConfig,
}

impl PostQuantumCryptography {
    pub fn new(config: PostQuantumConfig) -> Result<Self> {
        Ok(Self { config })
    }

    pub async fn secure_transmission(&self, data: &PrivateData) -> Result<PostQuantumSecuredData> {
        let _ = data;
        Ok(PostQuantumSecuredData {
            encrypted_payload: vec![0u8; 256],
            quantum_signature: vec![0u8; 64],
        })
    }
}

pub struct AdaptivePrivacyBudgeting {
    config: AdaptiveBudgetingConfig,
}

impl AdaptivePrivacyBudgeting {
    pub fn new(config: AdaptiveBudgetingConfig) -> Result<Self> {
        Ok(Self { config })
    }

    pub async fn allocate_budget(
        &self,
        client_id: &str,
        cost: &PrivacyCost,
    ) -> Result<BudgetAllocation> {
        let _ = (client_id, cost);
        Ok(BudgetAllocation {
            differential_privacy: DifferentialPrivacyBudget {
                epsilon: 0.1,
                delta: 1e-5,
                renyi_alpha: 2.0,
            },
            computational_budget: 1000.0,
            communication_budget: 1024.0,
        })
    }
}

pub struct PrivacyPerformanceMonitor;

impl PrivacyPerformanceMonitor {
    pub fn new() -> Result<Self> {
        Ok(Self)
    }

    pub async fn get_metrics(&self) -> Result<PrivacyPerformanceMetrics> {
        Ok(PrivacyPerformanceMetrics {
            average_execution_time: Duration::from_millis(500),
            throughput: 100.0,          // operations per second
            privacy_efficiency: 0.85,   // 85% efficiency
            resource_utilization: 0.70, // 70% utilization
        })
    }
}

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

    #[tokio::test]
    async fn test_advanced_privacy_mechanisms() {
        let config = AdvancedPrivacyConfig::default();
        let privacy_engine = AdvancedPrivacyMechanisms::new(config).expect("Operation failed");

        let model_update = Tensor::zeros(&[10, 10]).expect("Operation failed");

        let result = privacy_engine
            .execute_private_federated_round(&model_update, "client_001")
            .await;

        assert!(result.is_ok());
        let private_result = result.expect("Operation failed");
        assert!(private_result.execution_time < Duration::from_secs(10));
        assert!(private_result.privacy_guarantees.epsilon > 0.0);
    }

    #[test]
    fn test_privacy_config_defaults() {
        let config = AdvancedPrivacyConfig::default();
        assert!(config.differential_privacy.renyi_dp.alpha == 2.0);
        assert!(config.secure_mpc.num_parties == 100);
        assert!(config.homomorphic_encryption.security_level == 128);
        assert!(config.post_quantum.enabled);
    }

    #[test]
    fn test_budget_allocation() {
        let allocation = BudgetAllocation {
            differential_privacy: DifferentialPrivacyBudget {
                epsilon: 1.0,
                delta: 1e-5,
                renyi_alpha: 2.0,
            },
            computational_budget: 1000.0,
            communication_budget: 2000.0,
        };

        let total_cost = allocation.total_cost();
        assert!(total_cost > 0.0);
        assert!(total_cost < 10.0); // Reasonable bounds
    }

    #[test]
    fn test_renyi_dp_config_defaults() {
        let config = RenyiDPConfig::default();
        assert_eq!(config.alpha, 2.0);
        assert_eq!(config.epsilon_alpha, 1.0);
        assert_eq!(config.target_delta, 1e-5);
        assert!(!config.orders.is_empty());
        assert!(config.orders.contains(&2.0));
    }

    #[test]
    fn test_privacy_amplification_config_defaults() {
        let config = PrivacyAmplificationConfig::default();
        assert!(config.enable_subsampling);
        assert_eq!(config.sampling_probability, 0.01);
        assert!(config.enable_shuffling);
        assert_eq!(config.shuffle_buffer_size, 10000);
        assert!(config.enable_iteration_amplification);
    }

    #[test]
    fn test_concentrated_dp_config_defaults() {
        let config = ConcentratedDPConfig::default();
        assert_eq!(config.mu, 0.5);
        assert_eq!(config.privacy_loss_bound, 10.0);
        assert_eq!(config.tail_bound, 1e-6);
    }

    #[test]
    fn test_local_dp_config_defaults() {
        let config = LocalDPConfig::default();
        assert!(config.enabled);
        assert_eq!(config.epsilon_local, 1.0);
    }

    #[test]
    fn test_randomized_response_config_defaults() {
        let config = RandomizedResponseConfig::default();
        assert_eq!(config.true_probability, 0.75);
        assert_eq!(config.false_probability, 0.25);
        assert!(config.use_optimal);
    }

    #[test]
    fn test_local_hashing_config_defaults() {
        let config = LocalHashingConfig::default();
        assert_eq!(config.num_hash_functions, 2);
        assert_eq!(config.domain_size, 1024);
        assert!(config.consistent_hashing);
    }

    #[test]
    fn test_secure_multiparty_config_defaults() {
        let config = SecureMultipartyConfig::default();
        assert_eq!(config.num_parties, 100);
        assert_eq!(config.threshold, 67);
        assert!(matches!(config.protocol, MPCProtocol::SecureAggregation));
        assert!(matches!(config.secret_sharing, SecretSharingScheme::Shamir));
    }

    #[test]
    fn test_communication_optimization_defaults() {
        let config = CommunicationOptimization::default();
        assert!(config.enable_compression);
        assert!(config.batch_communications);
        assert!(config.max_batch_size > 0);
    }

    #[test]
    fn test_bootstrapping_config_defaults() {
        let config = BootstrappingConfig::default();
        assert!(config.enabled);
        assert_eq!(config.threshold, 0.1);
        assert_eq!(config.precision, 20);
    }

    #[test]
    fn test_zero_knowledge_config_defaults() {
        let config = ZeroKnowledgeConfig::default();
        assert!(matches!(config.proof_system, ZKProofSystem::Groth16));
        assert!(config.circuit_optimization.enable_minimization);
    }

    #[test]
    fn test_circuit_optimization_defaults() {
        let config = CircuitOptimization::default();
        assert!(config.enable_minimization);
        assert_eq!(config.gate_optimization_level, 2);
        assert!(config.wire_optimization);
        assert!(config.parallel_generation);
    }

    #[test]
    fn test_zk_verification_config_defaults() {
        let config = ZKVerificationConfig::default();
        assert!(config.batch_verification);
        assert!(config.parallel_verification);
        assert!(config.enable_proof_caching);
        assert_eq!(config.cache_size_limit, 1000);
    }

    #[test]
    fn test_private_retrieval_config_defaults() {
        let config = PrivateRetrievalConfig::default();
        assert!(matches!(config.scheme, PIRScheme::SingleServer));
        assert!(config.preprocessing.enabled);
    }

    #[test]
    fn test_pir_preprocessing_defaults() {
        let config = PIRPreprocessing::default();
        assert!(config.enabled);
        assert!(matches!(
            config.strategy,
            PreprocessingStrategy::Incremental
        ));
        assert_eq!(config.update_frequency, Duration::from_secs(3600));
    }

    #[test]
    fn test_pir_communication_config_defaults() {
        let config = PIRCommunicationConfig::default();
        assert!(config.enabled);
        assert!(config.batch_queries);
        assert_eq!(config.max_batch_size, 100);
        assert!(config.enable_compression);
    }

    #[test]
    fn test_federated_analytics_config_defaults() {
        let config = FederatedAnalyticsConfig::default();
        assert_eq!(config.enabled_analytics.len(), 3);
    }

    #[test]
    fn test_private_statistics_config_defaults() {
        let config = PrivateStatisticsConfig::default();
        assert!(!config.statistics.is_empty());
        assert_eq!(config.privacy_budget_per_statistic, 0.1);
    }

    #[test]
    fn test_post_quantum_config_defaults() {
        let config = PostQuantumConfig::default();
        assert!(config.enabled);
        assert!(matches!(config.kem, KEMAlgorithm::Kyber));
        assert!(matches!(config.signature, SignatureAlgorithm::Dilithium));
        assert!(config.hybrid_security);
    }

    #[test]
    fn test_adaptive_budgeting_config_defaults() {
        let config = AdaptiveBudgetingConfig::default();
        assert!(config.enabled);
        assert_eq!(config.initial_budget, 10.0);
        assert!(matches!(
            config.allocation_strategy,
            BudgetAllocationStrategy::Proportional
        ));
    }

    #[test]
    fn test_budget_renewal_config_defaults() {
        let config = BudgetRenewalConfig::default();
        assert!(matches!(config.strategy, RenewalStrategy::Periodic));
        assert_eq!(config.interval, Duration::from_secs(3600 * 24));
        assert_eq!(config.amount, 1.0);
    }

    #[test]
    fn test_fairness_constraints_defaults() {
        let config = FairnessConstraints::default();
        assert!(config.enabled);
        assert_eq!(config.max_budget_per_client, 2.0);
        assert_eq!(config.min_participation_rate, 0.1);
        assert!(matches!(config.fairness_metric, FairnessMetric::MaxMin));
    }

    #[test]
    fn test_privacy_state_new() {
        let state = PrivacyState::new();
        assert!(state.client_budgets.is_empty());
        assert_eq!(state.global_privacy_loss, 0.0);
        assert!(state.active_sessions.is_empty());
    }

    #[test]
    fn test_privacy_state_update_client_budget() {
        let mut state = PrivacyState::new();
        let allocation = BudgetAllocation {
            differential_privacy: DifferentialPrivacyBudget {
                epsilon: 0.5,
                delta: 1e-5,
                renyi_alpha: 2.0,
            },
            computational_budget: 100.0,
            communication_budget: 200.0,
        };
        state.update_client_budget("client1", &allocation);
        let budget = state.client_budgets.get("client1");
        assert!(budget.is_some());
    }

    #[test]
    fn test_budget_allocation_total_cost_calculation() {
        let allocation = BudgetAllocation {
            differential_privacy: DifferentialPrivacyBudget {
                epsilon: 2.0,
                delta: 1e-5,
                renyi_alpha: 3.0,
            },
            computational_budget: 0.0,
            communication_budget: 0.0,
        };
        // With zero computational and communication budgets, cost = epsilon
        assert_eq!(allocation.total_cost(), 2.0);
    }

    #[test]
    fn test_budget_allocation_components() {
        let allocation = BudgetAllocation {
            differential_privacy: DifferentialPrivacyBudget {
                epsilon: 1.0,
                delta: 1e-5,
                renyi_alpha: 2.0,
            },
            computational_budget: 500.0,
            communication_budget: 1000.0,
        };
        let cost = allocation.total_cost();
        // cost = 1.0 + 500*0.001 + 1000*0.0001 = 1.0 + 0.5 + 0.1 = 1.6
        assert!((cost - 1.6).abs() < 1e-10);
    }

    #[test]
    fn test_privacy_state_default() {
        let state = PrivacyState::default();
        assert!(state.client_budgets.is_empty());
    }

    #[test]
    fn test_privacy_state_multiple_clients() {
        let mut state = PrivacyState::new();
        let allocation = BudgetAllocation {
            differential_privacy: DifferentialPrivacyBudget {
                epsilon: 0.1,
                delta: 1e-5,
                renyi_alpha: 2.0,
            },
            computational_budget: 10.0,
            communication_budget: 20.0,
        };
        state.update_client_budget("client_a", &allocation);
        state.update_client_budget("client_b", &allocation);
        assert_eq!(state.client_budgets.len(), 2);
    }

    #[test]
    fn test_heavy_hitters_config_defaults() {
        let config = HeavyHittersConfig::default();
        assert!(config.threshold > 0.0);
        assert!(config.max_heavy_hitters > 0);
    }

    #[test]
    fn test_private_histogram_config_defaults() {
        let config = PrivateHistogramConfig::default();
        assert!(config.num_bins > 0);
    }

    #[test]
    fn test_clipping_bounds_defaults() {
        let bounds = ClippingBounds::default();
        assert!(bounds.lower_bound < bounds.upper_bound);
    }
}