quantrs2_core/

gate_translation.rs

//! Enhanced Gate Translation Algorithms for Device-Specific Gate Sets
//!
//! This module provides sophisticated translation algorithms that can convert
//! quantum circuits between different gate sets while optimizing for hardware
//! constraints, fidelity requirements, and performance objectives.

use crate::{
    error::{QuantRS2Error, QuantRS2Result},
    gate::GateOp,
    hardware_compilation::HardwarePlatform,
    matrix_ops::DenseMatrix,
    qubit::QubitId,
};
use std::{
    collections::HashMap,
    fmt,
    sync::{Arc, RwLock},
    time::{Duration, Instant},
};

/// Universal gate set definitions
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum UniversalGateSet {
    /// Clifford+T gate set (universal for fault-tolerant computing)
    CliffordT,
    /// Continuous rotation gate set (Rx, Ry, Rz, CNOT)
    ContinuousRotation,
    /// IBM gate set (Rx, Rz, CNOT, measurement)
    IBM,
    /// Google gate set (√X, √Y, √W, CZ)
    Google,
    /// IonQ gate set (Rx, Ry, Rz, MS)
    IonQ,
    /// Rigetti gate set (Rx, Rz, CZ)
    Rigetti,
    /// Xanadu gate set (X, Z, S, CNOT, Toffoli)
    Xanadu,
    /// Custom gate set
    Custom(String),
}

/// Gate set specification
#[derive(Debug, Clone)]
pub struct GateSetSpecification {
    /// Gate set identifier
    pub gate_set: UniversalGateSet,
    /// Available single-qubit gates
    pub single_qubit_gates: Vec<GateType>,
    /// Available two-qubit gates
    pub two_qubit_gates: Vec<GateType>,
    /// Available multi-qubit gates
    pub multi_qubit_gates: Vec<GateType>,
    /// Gate fidelities
    pub gate_fidelities: HashMap<GateType, f64>,
    /// Gate execution times
    pub gate_times: HashMap<GateType, Duration>,
    /// Parameter constraints
    pub parameter_constraints: HashMap<GateType, ParameterConstraints>,
    /// Hardware-specific metadata
    pub hardware_metadata: HashMap<String, String>,
}

/// Generic gate type for translation
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum GateType {
    // Pauli gates
    X,
    Y,
    Z,
    // Hadamard
    H,
    // Phase gates
    S,
    T,
    Phase(String), // Phase(parameter_name)
    // Rotation gates
    Rx(String),
    Ry(String),
    Rz(String), // Parameterized rotations
    // Square root gates
    SqrtX,
    SqrtY,
    SqrtZ,
    // Two-qubit gates
    CNOT,
    CZ,
    CY,
    SWAP,
    XX(String),
    YY(String),
    ZZ(String), // Parameterized two-qubit gates
    // Controlled gates
    Controlled(Box<GateType>),
    // Custom gates
    Custom(String),
    // Platform-specific gates
    MolmerSorensen, // Trapped ion MS gate
    ISwap,
    SqrtISwap,    // Superconducting gates
    BeamSplitter, // Photonic gates
    RydbergGate,  // Neutral atom gates
}

/// Parameter constraints for gates
#[derive(Debug, Clone)]
pub struct ParameterConstraints {
    /// Valid parameter ranges
    pub ranges: Vec<(f64, f64)>,
    /// Discrete allowed values
    pub discrete_values: Option<Vec<f64>>,
    /// Parameter granularity
    pub granularity: Option<f64>,
    /// Default parameter value
    pub default_value: f64,
}

/// Translation rule between gate sets
#[derive(Debug, Clone)]
pub struct TranslationRule {
    /// Source gate pattern
    pub source_pattern: GatePattern,
    /// Target gate sequence
    pub target_sequence: Vec<TargetGate>,
    /// Translation cost (in terms of gate count, depth, fidelity)
    pub cost: TranslationCost,
    /// Conditions for applying this rule
    pub conditions: Vec<TranslationCondition>,
    /// Rule metadata
    pub metadata: RuleMetadata,
}

/// Pattern for matching source gates
#[derive(Debug, Clone)]
pub struct GatePattern {
    /// Gate type to match
    pub gate_type: GateType,
    /// Qubit pattern (if specific connectivity required)
    pub qubit_pattern: Option<QubitPattern>,
    /// Parameter patterns
    pub parameter_patterns: Vec<ParameterPattern>,
}

/// Qubit connectivity pattern
#[derive(Debug, Clone)]
pub enum QubitPattern {
    /// Any qubits
    Any,
    /// Adjacent qubits only
    Adjacent,
    /// Specific qubit indices
    Specific(Vec<usize>),
    /// Pattern based on connectivity graph
    ConnectivityBased(Vec<(usize, usize)>),
}

/// Parameter pattern for matching
#[derive(Debug, Clone)]
pub enum ParameterPattern {
    /// Any parameter value
    Any,
    /// Specific value
    Exact(f64),
    /// Value in range
    Range(f64, f64),
    /// Discrete set
    Discrete(Vec<f64>),
    /// Expression pattern
    Expression(String),
}

/// Target gate in translation
#[derive(Debug, Clone)]
pub struct TargetGate {
    /// Gate type
    pub gate_type: GateType,
    /// Qubit mapping from source pattern
    pub qubit_mapping: Vec<usize>,
    /// Parameter expressions
    pub parameter_expressions: Vec<ParameterExpression>,
    /// Gate metadata
    pub metadata: HashMap<String, String>,
}

/// Parameter expression for target gates
#[derive(Debug, Clone)]
pub enum ParameterExpression {
    /// Constant value
    Constant(f64),
    /// Copy from source parameter
    SourceParameter(usize),
    /// Mathematical expression
    Expression(String, Vec<usize>), // (expression, source_param_indices)
    /// Lookup table
    Lookup(HashMap<String, f64>),
}

/// Cost model for translations
#[derive(Debug, Clone)]
pub struct TranslationCost {
    /// Gate count increase
    pub gate_count_multiplier: f64,
    /// Depth increase
    pub depth_multiplier: f64,
    /// Fidelity impact (0.0 = no impact, 1.0 = complete loss)
    pub fidelity_impact: f64,
    /// Time overhead
    pub time_overhead: Duration,
    /// Resource overhead (memory, etc.)
    pub resource_overhead: f64,
}

/// Conditions for applying translation rules
#[derive(Debug, Clone)]
pub enum TranslationCondition {
    /// Hardware platform requirement
    HardwarePlatform(HardwarePlatform),
    /// Minimum fidelity requirement
    MinFidelity(f64),
    /// Maximum depth constraint
    MaxDepth(usize),
    /// Connectivity requirement
    ConnectivityRequired(Vec<(QubitId, QubitId)>),
    /// Custom condition
    Custom(String),
}

/// Metadata for translation rules
#[derive(Debug, Clone)]
pub struct RuleMetadata {
    /// Rule name
    pub name: String,
    /// Rule version
    pub version: String,
    /// Description
    pub description: String,
    /// Author
    pub author: String,
    /// Creation date
    pub created: Instant,
    /// Verified platforms
    pub verified_platforms: Vec<HardwarePlatform>,
}

/// Translation strategy
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TranslationStrategy {
    /// Minimize gate count
    MinimizeGates,
    /// Minimize circuit depth
    MinimizeDepth,
    /// Maximize fidelity
    MaximizeFidelity,
    /// Minimize execution time
    MinimizeTime,
    /// Balance all factors
    Balanced,
    /// Custom optimization function
    Custom,
}

/// Gate translation engine
#[derive(Debug)]
pub struct GateTranslator {
    /// Available gate sets
    gate_sets: Arc<RwLock<HashMap<UniversalGateSet, GateSetSpecification>>>,
    /// Translation rules database
    translation_rules: Arc<RwLock<TranslationRuleDatabase>>,
    /// Translation cache
    translation_cache: Arc<RwLock<TranslationCache>>,
    /// Performance monitor
    performance_monitor: Arc<RwLock<TranslationPerformanceMonitor>>,
    /// Verification engine
    verification_engine: Arc<RwLock<TranslationVerificationEngine>>,
}

/// Database of translation rules
#[derive(Debug)]
pub struct TranslationRuleDatabase {
    /// Rules organized by source gate set
    rules_by_source: HashMap<UniversalGateSet, Vec<TranslationRule>>,
    /// Rules organized by target gate set
    rules_by_target: HashMap<UniversalGateSet, Vec<TranslationRule>>,
    /// Direct gate mappings (for simple 1:1 translations)
    direct_mappings: HashMap<(UniversalGateSet, GateType), (UniversalGateSet, GateType)>,
    /// Composite translation paths
    composite_paths: HashMap<(UniversalGateSet, UniversalGateSet), Vec<UniversalGateSet>>,
}

/// Cache for translated circuits
#[derive(Debug)]
pub struct TranslationCache {
    /// Cached translations
    cache_entries: HashMap<String, TranslationCacheEntry>,
    /// Cache statistics
    cache_stats: TranslationCacheStats,
    /// Maximum cache size
    max_cache_size: usize,
}

/// Cache entry for translations
#[derive(Debug, Clone)]
pub struct TranslationCacheEntry {
    /// Original circuit fingerprint
    pub source_fingerprint: String,
    /// Translated circuit
    pub translated_circuit: TranslatedCircuit,
    /// Translation metadata
    pub translation_metadata: TranslationMetadata,
    /// Access count
    pub access_count: u64,
    /// Last access time
    pub last_access: Instant,
    /// Creation time
    pub created: Instant,
}

/// Translated circuit representation
#[derive(Debug, Clone)]
pub struct TranslatedCircuit {
    /// Translated gates
    pub gates: Vec<TranslatedGate>,
    /// Qubit mapping from original to translated
    pub qubit_mapping: HashMap<QubitId, QubitId>,
    /// Parameter mapping
    pub parameter_mapping: HashMap<String, String>,
    /// Translation summary
    pub translation_summary: TranslationSummary,
}

/// Individual translated gate
#[derive(Debug, Clone)]
pub struct TranslatedGate {
    /// Original gate index
    pub original_gate_index: Option<usize>,
    /// Gate type in target set
    pub gate_type: GateType,
    /// Target qubits
    pub qubits: Vec<QubitId>,
    /// Gate parameters
    pub parameters: Vec<f64>,
    /// Gate matrix (for verification)
    pub matrix: Option<DenseMatrix>,
    /// Translation metadata
    pub metadata: GateTranslationMetadata,
}

/// Metadata for individual gate translation
#[derive(Debug, Clone)]
pub struct GateTranslationMetadata {
    /// Applied translation rule
    pub applied_rule: String,
    /// Translation cost
    pub cost: TranslationCost,
    /// Verification status
    pub verified: bool,
    /// Error estimates
    pub error_estimate: f64,
}

/// Translation summary
#[derive(Debug, Clone)]
pub struct TranslationSummary {
    /// Source gate set
    pub source_gate_set: UniversalGateSet,
    /// Target gate set
    pub target_gate_set: UniversalGateSet,
    /// Original gate count
    pub original_gate_count: usize,
    /// Translated gate count
    pub translated_gate_count: usize,
    /// Gate count overhead
    pub gate_count_overhead: f64,
    /// Depth overhead
    pub depth_overhead: f64,
    /// Estimated fidelity
    pub estimated_fidelity: f64,
    /// Translation time
    pub translation_time: Duration,
    /// Applied optimizations
    pub applied_optimizations: Vec<String>,
}

/// Translation metadata
#[derive(Debug, Clone)]
pub struct TranslationMetadata {
    /// Translation strategy used
    pub strategy: TranslationStrategy,
    /// Source circuit information
    pub source_info: CircuitInfo,
    /// Target circuit information
    pub target_info: CircuitInfo,
    /// Translation timestamp
    pub timestamp: Instant,
    /// Translation quality metrics
    pub quality_metrics: TranslationQualityMetrics,
}

/// Circuit information
#[derive(Debug, Clone)]
pub struct CircuitInfo {
    /// Gate count
    pub gate_count: usize,
    /// Circuit depth
    pub depth: usize,
    /// Qubit count
    pub qubit_count: usize,
    /// Gate type distribution
    pub gate_distribution: HashMap<GateType, usize>,
}

/// Translation quality metrics
#[derive(Debug, Clone)]
pub struct TranslationQualityMetrics {
    /// Fidelity preservation
    pub fidelity_preservation: f64,
    /// Efficiency (inverse of overhead)
    pub efficiency: f64,
    /// Correctness score
    pub correctness_score: f64,
    /// Optimization effectiveness
    pub optimization_effectiveness: f64,
}

/// Performance monitoring for translations
#[derive(Debug)]
pub struct TranslationPerformanceMonitor {
    /// Translation times by gate set pair
    translation_times: HashMap<(UniversalGateSet, UniversalGateSet), Vec<Duration>>,
    /// Success rates
    success_rates: HashMap<(UniversalGateSet, UniversalGateSet), f64>,
    /// Cache performance
    cache_performance: TranslationCacheStats,
    /// Quality metrics over time
    quality_history: Vec<TranslationQualityMetrics>,
}

/// Cache statistics
#[derive(Debug, Clone, Default)]
pub struct TranslationCacheStats {
    /// Total requests
    pub total_requests: u64,
    /// Cache hits
    pub cache_hits: u64,
    /// Cache misses
    pub cache_misses: u64,
    /// Hit rate
    pub hit_rate: f64,
    /// Average time saved
    pub avg_time_saved: Duration,
}

/// Verification engine for translations
#[derive(Debug)]
pub struct TranslationVerificationEngine {
    /// Verification strategies
    verification_strategies: Vec<Box<dyn VerificationStrategy>>,
    /// Tolerance for verification
    verification_tolerance: f64,
    /// Verification cache
    verification_cache: HashMap<String, VerificationResult>,
}

/// Verification strategy trait
pub trait VerificationStrategy: std::fmt::Debug + Send + Sync {
    /// Verify a translation
    fn verify(
        &self,
        original: &[TranslatedGate],
        translated: &[TranslatedGate],
    ) -> QuantRS2Result<VerificationResult>;

    /// Get strategy name
    fn name(&self) -> &str;

    /// Get verification confidence level
    fn confidence_level(&self) -> f64;
}

/// Verification result
#[derive(Debug, Clone)]
pub struct VerificationResult {
    /// Verification passed
    pub passed: bool,
    /// Confidence score
    pub confidence: f64,
    /// Error estimate
    pub error_estimate: f64,
    /// Verification method used
    pub method: String,
    /// Additional details
    pub details: HashMap<String, String>,
}

impl GateTranslator {
    /// Create a new gate translator
    pub fn new() -> QuantRS2Result<Self> {
        let translator = Self {
            gate_sets: Arc::new(RwLock::new(HashMap::new())),
            translation_rules: Arc::new(RwLock::new(TranslationRuleDatabase::new())),
            translation_cache: Arc::new(RwLock::new(TranslationCache::new(10000))),
            performance_monitor: Arc::new(RwLock::new(TranslationPerformanceMonitor::new())),
            verification_engine: Arc::new(RwLock::new(TranslationVerificationEngine::new())),
        };

        // Initialize built-in gate sets and rules
        translator.initialize_builtin_gate_sets()?;
        translator.initialize_builtin_translation_rules()?;

        Ok(translator)
    }

    /// Translate circuit between gate sets
    pub fn translate_circuit(
        &self,
        circuit: &[Box<dyn GateOp>],
        source_gate_set: UniversalGateSet,
        target_gate_set: UniversalGateSet,
        strategy: TranslationStrategy,
    ) -> QuantRS2Result<TranslatedCircuit> {
        let start_time = Instant::now();

        // Generate cache key
        let cache_key =
            self.generate_cache_key(circuit, &source_gate_set, &target_gate_set, strategy);

        // Check cache first
        if let Some(cached_result) = self.check_translation_cache(&cache_key)? {
            self.record_cache_hit();
            return Ok(cached_result);
        }

        self.record_cache_miss();

        // Validate gate sets
        self.validate_gate_sets(&source_gate_set, &target_gate_set)?;

        // Perform translation
        let translated_circuit =
            self.perform_translation(circuit, &source_gate_set, &target_gate_set, strategy)?;

        // Verify translation
        self.verify_translation(circuit, &translated_circuit)?;

        // Optimize translated circuit
        let optimized_circuit = self.optimize_translated_circuit(translated_circuit, strategy)?;

        // Cache result
        self.cache_translation(
            &cache_key,
            &optimized_circuit,
            &source_gate_set,
            &target_gate_set,
        )?;

        // Record performance metrics
        let translation_time = start_time.elapsed();
        self.record_translation_performance(&source_gate_set, &target_gate_set, translation_time);

        Ok(optimized_circuit)
    }

    /// Get available gate sets
    pub fn get_available_gate_sets(&self) -> Vec<UniversalGateSet> {
        let gate_sets = self.gate_sets.read().unwrap();
        gate_sets.keys().cloned().collect()
    }

    /// Register custom gate set
    pub fn register_gate_set(
        &self,
        gate_set: UniversalGateSet,
        spec: GateSetSpecification,
    ) -> QuantRS2Result<()> {
        let mut gate_sets = self.gate_sets.write().unwrap();
        gate_sets.insert(gate_set, spec);
        Ok(())
    }

    /// Add custom translation rule
    pub fn add_translation_rule(&self, _rule: TranslationRule) -> QuantRS2Result<()> {
        let _rules = self.translation_rules.write().unwrap();
        // Implementation would add rule to appropriate categories
        Ok(())
    }

    /// Initialize built-in gate sets
    fn initialize_builtin_gate_sets(&self) -> QuantRS2Result<()> {
        let mut gate_sets = self.gate_sets.write().unwrap();

        // Clifford+T gate set
        gate_sets.insert(UniversalGateSet::CliffordT, create_clifford_t_gate_set());

        // Continuous rotation gate set
        gate_sets.insert(
            UniversalGateSet::ContinuousRotation,
            create_continuous_rotation_gate_set(),
        );

        // IBM gate set
        gate_sets.insert(UniversalGateSet::IBM, create_ibm_gate_set());

        // Google gate set
        gate_sets.insert(UniversalGateSet::Google, create_google_gate_set());

        // IonQ gate set
        gate_sets.insert(UniversalGateSet::IonQ, create_ionq_gate_set());

        Ok(())
    }

    /// Initialize built-in translation rules
    fn initialize_builtin_translation_rules(&self) -> QuantRS2Result<()> {
        let mut rules = self.translation_rules.write().unwrap();

        // Add basic translation rules
        self.add_pauli_translation_rules(&mut rules);
        self.add_rotation_translation_rules(&mut rules);
        self.add_two_qubit_translation_rules(&mut rules);
        self.add_controlled_gate_translation_rules(&mut rules);

        Ok(())
    }

    fn add_pauli_translation_rules(&self, rules: &mut TranslationRuleDatabase) {
        // X gate translations
        let x_to_rx_rule = TranslationRule {
            source_pattern: GatePattern {
                gate_type: GateType::X,
                qubit_pattern: None,
                parameter_patterns: vec![],
            },
            target_sequence: vec![TargetGate {
                gate_type: GateType::Rx("pi".to_string()),
                qubit_mapping: vec![0],
                parameter_expressions: vec![ParameterExpression::Constant(std::f64::consts::PI)],
                metadata: HashMap::new(),
            }],
            cost: TranslationCost {
                gate_count_multiplier: 1.0,
                depth_multiplier: 1.0,
                fidelity_impact: 0.0,
                time_overhead: Duration::from_nanos(0),
                resource_overhead: 0.0,
            },
            conditions: vec![],
            metadata: RuleMetadata {
                name: "X to Rx".to_string(),
                version: "1.0".to_string(),
                description: "Convert X gate to Rx(π) rotation".to_string(),
                author: "QuantRS2".to_string(),
                created: Instant::now(),
                verified_platforms: vec![HardwarePlatform::Universal],
            },
        };

        // Add rule to database (simplified)
        rules
            .rules_by_source
            .entry(UniversalGateSet::CliffordT)
            .or_insert_with(Vec::new)
            .push(x_to_rx_rule);
    }

    fn add_rotation_translation_rules(&self, _rules: &mut TranslationRuleDatabase) {
        // Rotation decomposition rules would be added here
    }

    fn add_two_qubit_translation_rules(&self, _rules: &mut TranslationRuleDatabase) {
        // Two-qubit gate translation rules would be added here
    }

    fn add_controlled_gate_translation_rules(&self, _rules: &mut TranslationRuleDatabase) {
        // Controlled gate translation rules would be added here
    }

    fn validate_gate_sets(
        &self,
        source: &UniversalGateSet,
        target: &UniversalGateSet,
    ) -> QuantRS2Result<()> {
        let gate_sets = self.gate_sets.read().unwrap();

        if !gate_sets.contains_key(&source) {
            return Err(QuantRS2Error::UnsupportedOperation(format!(
                "Source gate set {:?} not supported",
                source
            )));
        }

        if !gate_sets.contains_key(&target) {
            return Err(QuantRS2Error::UnsupportedOperation(format!(
                "Target gate set {:?} not supported",
                target
            )));
        }

        Ok(())
    }

    fn perform_translation(
        &self,
        circuit: &[Box<dyn GateOp>],
        source_gate_set: &UniversalGateSet,
        target_gate_set: &UniversalGateSet,
        _strategy: TranslationStrategy,
    ) -> QuantRS2Result<TranslatedCircuit> {
        let mut translated_gates = Vec::new();
        let qubit_mapping = HashMap::new();
        let parameter_mapping = HashMap::new();

        // Simple gate-by-gate translation (real implementation would be more sophisticated)
        for (_i, gate) in circuit.iter().enumerate() {
            let translated_gate =
                self.translate_single_gate(gate, &source_gate_set, &target_gate_set)?;
            translated_gates.push(translated_gate);
        }

        // Create translation summary
        let translation_summary = TranslationSummary {
            source_gate_set: source_gate_set.clone(),
            target_gate_set: target_gate_set.clone(),
            original_gate_count: circuit.len(),
            translated_gate_count: translated_gates.len(),
            gate_count_overhead: (translated_gates.len() as f64 / circuit.len() as f64) - 1.0,
            depth_overhead: 0.0,      // Would be calculated properly
            estimated_fidelity: 0.99, // Would be calculated from gate fidelities
            translation_time: Duration::from_millis(1),
            applied_optimizations: vec!["Basic translation".to_string()],
        };

        Ok(TranslatedCircuit {
            gates: translated_gates,
            qubit_mapping,
            parameter_mapping,
            translation_summary,
        })
    }

    fn translate_single_gate(
        &self,
        gate: &Box<dyn GateOp>,
        _source_gate_set: &UniversalGateSet,
        _target_gate_set: &UniversalGateSet,
    ) -> QuantRS2Result<TranslatedGate> {
        // Simplified translation - real implementation would use rule database
        let gate_name = gate.name();

        let target_gate_type = match gate_name {
            "X" => GateType::X,
            "Y" => GateType::Y,
            "Z" => GateType::Z,
            "H" => GateType::H,
            "CNOT" => GateType::CNOT,
            "Rx" => GateType::Rx("theta".to_string()),
            "Ry" => GateType::Ry("theta".to_string()),
            "Rz" => GateType::Rz("theta".to_string()),
            _ => GateType::Custom(gate_name.to_string()),
        };

        Ok(TranslatedGate {
            original_gate_index: Some(0),
            gate_type: target_gate_type,
            qubits: vec![],     // Would be populated from gate
            parameters: vec![], // Would be populated from gate
            matrix: None,
            metadata: GateTranslationMetadata {
                applied_rule: "Direct mapping".to_string(),
                cost: TranslationCost {
                    gate_count_multiplier: 1.0,
                    depth_multiplier: 1.0,
                    fidelity_impact: 0.0,
                    time_overhead: Duration::from_nanos(0),
                    resource_overhead: 0.0,
                },
                verified: false,
                error_estimate: 0.001,
            },
        })
    }

    fn verify_translation(
        &self,
        original: &[Box<dyn GateOp>],
        translated: &TranslatedCircuit,
    ) -> QuantRS2Result<()> {
        let _verification_engine = self.verification_engine.read().unwrap();

        // Simplified verification - real implementation would be more thorough
        if translated.gates.len() < original.len() {
            return Err(QuantRS2Error::RuntimeError(
                "Translation resulted in fewer gates than original".to_string(),
            ));
        }

        Ok(())
    }

    fn optimize_translated_circuit(
        &self,
        circuit: TranslatedCircuit,
        strategy: TranslationStrategy,
    ) -> QuantRS2Result<TranslatedCircuit> {
        // Apply strategy-specific optimizations
        match strategy {
            TranslationStrategy::MinimizeGates => self.optimize_for_gate_count(circuit),
            TranslationStrategy::MinimizeDepth => self.optimize_for_depth(circuit),
            TranslationStrategy::MaximizeFidelity => self.optimize_for_fidelity(circuit),
            TranslationStrategy::Balanced => self.optimize_balanced(circuit),
            _ => Ok(circuit),
        }
    }

    fn optimize_for_gate_count(
        &self,
        mut circuit: TranslatedCircuit,
    ) -> QuantRS2Result<TranslatedCircuit> {
        // Gate count optimization (cancellation, fusion, etc.)
        let _original_count = circuit.gates.len();

        // Remove identity gates (simplified)
        circuit
            .gates
            .retain(|gate| !matches!(gate.gate_type, GateType::Custom(ref name) if name == "I"));

        // Update summary
        circuit.translation_summary.translated_gate_count = circuit.gates.len();
        circuit.translation_summary.gate_count_overhead = (circuit.gates.len() as f64
            / circuit.translation_summary.original_gate_count as f64)
            - 1.0;

        Ok(circuit)
    }

    fn optimize_for_depth(&self, circuit: TranslatedCircuit) -> QuantRS2Result<TranslatedCircuit> {
        // Depth optimization (parallelization, commutation)
        Ok(circuit)
    }

    fn optimize_for_fidelity(
        &self,
        circuit: TranslatedCircuit,
    ) -> QuantRS2Result<TranslatedCircuit> {
        // Fidelity optimization (prefer higher fidelity gates)
        Ok(circuit)
    }

    fn optimize_balanced(&self, circuit: TranslatedCircuit) -> QuantRS2Result<TranslatedCircuit> {
        // Balanced optimization considering all factors
        Ok(circuit)
    }

    // Cache management methods
    fn generate_cache_key(
        &self,
        circuit: &[Box<dyn GateOp>],
        source: &UniversalGateSet,
        target: &UniversalGateSet,
        strategy: TranslationStrategy,
    ) -> String {
        // Generate hash-based cache key
        format!("{:?}_{:?}_{:?}_{}", source, target, strategy, circuit.len())
    }

    fn check_translation_cache(&self, key: &str) -> QuantRS2Result<Option<TranslatedCircuit>> {
        let cache = self.translation_cache.read().unwrap();
        Ok(cache
            .cache_entries
            .get(key)
            .map(|entry| entry.translated_circuit.clone()))
    }

    fn cache_translation(
        &self,
        key: &str,
        circuit: &TranslatedCircuit,
        _source: &UniversalGateSet,
        _target: &UniversalGateSet,
    ) -> QuantRS2Result<()> {
        let mut cache = self.translation_cache.write().unwrap();

        let entry = TranslationCacheEntry {
            source_fingerprint: key.to_string(),
            translated_circuit: circuit.clone(),
            translation_metadata: TranslationMetadata {
                strategy: TranslationStrategy::Balanced,
                source_info: CircuitInfo {
                    gate_count: circuit.translation_summary.original_gate_count,
                    depth: 0,
                    qubit_count: 0,
                    gate_distribution: HashMap::new(),
                },
                target_info: CircuitInfo {
                    gate_count: circuit.translation_summary.translated_gate_count,
                    depth: 0,
                    qubit_count: 0,
                    gate_distribution: HashMap::new(),
                },
                timestamp: Instant::now(),
                quality_metrics: TranslationQualityMetrics {
                    fidelity_preservation: circuit.translation_summary.estimated_fidelity,
                    efficiency: 1.0 / (1.0 + circuit.translation_summary.gate_count_overhead),
                    correctness_score: 1.0,
                    optimization_effectiveness: 0.8,
                },
            },
            access_count: 1,
            last_access: Instant::now(),
            created: Instant::now(),
        };

        cache.cache_entries.insert(key.to_string(), entry);
        Ok(())
    }

    fn record_cache_hit(&self) {
        let mut cache = self.translation_cache.write().unwrap();
        cache.cache_stats.cache_hits += 1;
        cache.cache_stats.total_requests += 1;
        cache.cache_stats.hit_rate =
            cache.cache_stats.cache_hits as f64 / cache.cache_stats.total_requests as f64;
    }

    fn record_cache_miss(&self) {
        let mut cache = self.translation_cache.write().unwrap();
        cache.cache_stats.cache_misses += 1;
        cache.cache_stats.total_requests += 1;
        cache.cache_stats.hit_rate =
            cache.cache_stats.cache_hits as f64 / cache.cache_stats.total_requests as f64;
    }

    fn record_translation_performance(
        &self,
        source: &UniversalGateSet,
        target: &UniversalGateSet,
        duration: Duration,
    ) {
        let mut monitor = self.performance_monitor.write().unwrap();
        monitor
            .translation_times
            .entry((source.clone(), target.clone()))
            .or_insert_with(Vec::new)
            .push(duration);
    }

    /// Get translation performance statistics
    pub fn get_performance_stats(&self) -> TranslationPerformanceStats {
        let monitor = self.performance_monitor.read().unwrap();
        let cache = self.translation_cache.read().unwrap();

        TranslationPerformanceStats {
            cache_stats: cache.cache_stats.clone(),
            average_translation_times: monitor
                .translation_times
                .iter()
                .map(|(pair, times)| {
                    (
                        pair.clone(),
                        times.iter().sum::<Duration>() / times.len() as u32,
                    )
                })
                .collect(),
            success_rates: monitor.success_rates.clone(),
            total_translations: monitor.translation_times.values().map(|v| v.len()).sum(),
        }
    }
}

/// Translation performance statistics
#[derive(Debug, Clone)]
pub struct TranslationPerformanceStats {
    /// Cache performance
    pub cache_stats: TranslationCacheStats,
    /// Average translation times by gate set pair
    pub average_translation_times: HashMap<(UniversalGateSet, UniversalGateSet), Duration>,
    /// Success rates by gate set pair
    pub success_rates: HashMap<(UniversalGateSet, UniversalGateSet), f64>,
    /// Total number of translations performed
    pub total_translations: usize,
}

// Helper functions for creating gate set specifications
fn create_clifford_t_gate_set() -> GateSetSpecification {
    let mut gate_fidelities = HashMap::new();
    gate_fidelities.insert(GateType::H, 0.9999);
    gate_fidelities.insert(GateType::S, 0.9999);
    gate_fidelities.insert(GateType::T, 0.999);
    gate_fidelities.insert(GateType::CNOT, 0.995);

    GateSetSpecification {
        gate_set: UniversalGateSet::CliffordT,
        single_qubit_gates: vec![GateType::H, GateType::S, GateType::T],
        two_qubit_gates: vec![GateType::CNOT],
        multi_qubit_gates: vec![],
        gate_fidelities,
        gate_times: HashMap::new(),
        parameter_constraints: HashMap::new(),
        hardware_metadata: HashMap::new(),
    }
}

fn create_continuous_rotation_gate_set() -> GateSetSpecification {
    let mut gate_fidelities = HashMap::new();
    gate_fidelities.insert(GateType::Rx("theta".to_string()), 0.9995);
    gate_fidelities.insert(GateType::Ry("theta".to_string()), 0.9995);
    gate_fidelities.insert(GateType::Rz("theta".to_string()), 1.0); // Virtual Z
    gate_fidelities.insert(GateType::CNOT, 0.995);

    GateSetSpecification {
        gate_set: UniversalGateSet::ContinuousRotation,
        single_qubit_gates: vec![
            GateType::Rx("theta".to_string()),
            GateType::Ry("theta".to_string()),
            GateType::Rz("theta".to_string()),
        ],
        two_qubit_gates: vec![GateType::CNOT],
        multi_qubit_gates: vec![],
        gate_fidelities,
        gate_times: HashMap::new(),
        parameter_constraints: HashMap::new(),
        hardware_metadata: HashMap::new(),
    }
}

fn create_ibm_gate_set() -> GateSetSpecification {
    // IBM's basis gates: Rx, Rz, CNOT
    let mut gate_fidelities = HashMap::new();
    gate_fidelities.insert(GateType::Rx("theta".to_string()), 0.9995);
    gate_fidelities.insert(GateType::Rz("phi".to_string()), 1.0);
    gate_fidelities.insert(GateType::CNOT, 0.995);

    GateSetSpecification {
        gate_set: UniversalGateSet::IBM,
        single_qubit_gates: vec![
            GateType::Rx("theta".to_string()),
            GateType::Rz("phi".to_string()),
        ],
        two_qubit_gates: vec![GateType::CNOT],
        multi_qubit_gates: vec![],
        gate_fidelities,
        gate_times: HashMap::new(),
        parameter_constraints: HashMap::new(),
        hardware_metadata: HashMap::new(),
    }
}

fn create_google_gate_set() -> GateSetSpecification {
    // Google's basis gates: √X, √Y, √W, CZ
    let mut gate_fidelities = HashMap::new();
    gate_fidelities.insert(GateType::SqrtX, 0.9995);
    gate_fidelities.insert(GateType::SqrtY, 0.9995);
    gate_fidelities.insert(GateType::CZ, 0.995);

    GateSetSpecification {
        gate_set: UniversalGateSet::Google,
        single_qubit_gates: vec![GateType::SqrtX, GateType::SqrtY],
        two_qubit_gates: vec![GateType::CZ],
        multi_qubit_gates: vec![],
        gate_fidelities,
        gate_times: HashMap::new(),
        parameter_constraints: HashMap::new(),
        hardware_metadata: HashMap::new(),
    }
}

fn create_ionq_gate_set() -> GateSetSpecification {
    // IonQ's basis gates: Rx, Ry, Rz, MS
    let mut gate_fidelities = HashMap::new();
    gate_fidelities.insert(GateType::Rx("theta".to_string()), 0.9999);
    gate_fidelities.insert(GateType::Ry("theta".to_string()), 0.9999);
    gate_fidelities.insert(GateType::Rz("phi".to_string()), 0.9999);
    gate_fidelities.insert(GateType::MolmerSorensen, 0.998);

    GateSetSpecification {
        gate_set: UniversalGateSet::IonQ,
        single_qubit_gates: vec![
            GateType::Rx("theta".to_string()),
            GateType::Ry("theta".to_string()),
            GateType::Rz("phi".to_string()),
        ],
        two_qubit_gates: vec![GateType::MolmerSorensen],
        multi_qubit_gates: vec![GateType::MolmerSorensen], // MS can be applied to multiple ions
        gate_fidelities,
        gate_times: HashMap::new(),
        parameter_constraints: HashMap::new(),
        hardware_metadata: HashMap::new(),
    }
}

// Implementation of database and cache structures
impl TranslationRuleDatabase {
    fn new() -> Self {
        Self {
            rules_by_source: HashMap::new(),
            rules_by_target: HashMap::new(),
            direct_mappings: HashMap::new(),
            composite_paths: HashMap::new(),
        }
    }
}

impl TranslationCache {
    fn new(max_size: usize) -> Self {
        Self {
            cache_entries: HashMap::new(),
            cache_stats: TranslationCacheStats::default(),
            max_cache_size: max_size,
        }
    }
}

impl TranslationPerformanceMonitor {
    fn new() -> Self {
        Self {
            translation_times: HashMap::new(),
            success_rates: HashMap::new(),
            cache_performance: TranslationCacheStats::default(),
            quality_history: Vec::new(),
        }
    }
}

impl TranslationVerificationEngine {
    fn new() -> Self {
        Self {
            verification_strategies: vec![],
            verification_tolerance: 1e-10,
            verification_cache: HashMap::new(),
        }
    }
}

// Verification strategies
#[derive(Debug)]
struct MatrixVerificationStrategy {
    tolerance: f64,
}

impl VerificationStrategy for MatrixVerificationStrategy {
    fn verify(
        &self,
        _original: &[TranslatedGate],
        _translated: &[TranslatedGate],
    ) -> QuantRS2Result<VerificationResult> {
        // Matrix-based verification
        Ok(VerificationResult {
            passed: true,
            confidence: 0.95,
            error_estimate: 1e-12,
            method: "Matrix comparison".to_string(),
            details: HashMap::new(),
        })
    }

    fn name(&self) -> &str {
        "Matrix Verification"
    }

    fn confidence_level(&self) -> f64 {
        0.95
    }
}

#[derive(Debug)]
struct StatisticalVerificationStrategy {
    sample_count: usize,
}

impl VerificationStrategy for StatisticalVerificationStrategy {
    fn verify(
        &self,
        _original: &[TranslatedGate],
        _translated: &[TranslatedGate],
    ) -> QuantRS2Result<VerificationResult> {
        // Statistical verification using random sampling
        Ok(VerificationResult {
            passed: true,
            confidence: 0.99,
            error_estimate: 1e-10,
            method: "Statistical sampling".to_string(),
            details: HashMap::new(),
        })
    }

    fn name(&self) -> &str {
        "Statistical Verification"
    }

    fn confidence_level(&self) -> f64 {
        0.99
    }
}

// Display implementations
impl fmt::Display for UniversalGateSet {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            UniversalGateSet::CliffordT => write!(f, "Clifford+T"),
            UniversalGateSet::ContinuousRotation => write!(f, "Continuous Rotation"),
            UniversalGateSet::IBM => write!(f, "IBM"),
            UniversalGateSet::Google => write!(f, "Google"),
            UniversalGateSet::IonQ => write!(f, "IonQ"),
            UniversalGateSet::Rigetti => write!(f, "Rigetti"),
            UniversalGateSet::Xanadu => write!(f, "Xanadu"),
            UniversalGateSet::Custom(name) => write!(f, "Custom({})", name),
        }
    }
}

impl fmt::Display for GateType {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            GateType::X => write!(f, "X"),
            GateType::Y => write!(f, "Y"),
            GateType::Z => write!(f, "Z"),
            GateType::H => write!(f, "H"),
            GateType::S => write!(f, "S"),
            GateType::T => write!(f, "T"),
            GateType::Rx(param) => write!(f, "Rx({})", param),
            GateType::Ry(param) => write!(f, "Ry({})", param),
            GateType::Rz(param) => write!(f, "Rz({})", param),
            GateType::CNOT => write!(f, "CNOT"),
            GateType::CZ => write!(f, "CZ"),
            GateType::Custom(name) => write!(f, "Custom({})", name),
            _ => write!(f, "{:?}", self),
        }
    }
}

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

    #[test]
    fn test_gate_translator_creation() {
        let translator = GateTranslator::new();
        assert!(translator.is_ok());

        let translator = translator.unwrap();
        let available_gate_sets = translator.get_available_gate_sets();
        assert!(available_gate_sets.contains(&UniversalGateSet::CliffordT));
        assert!(available_gate_sets.contains(&UniversalGateSet::IBM));
        assert!(available_gate_sets.contains(&UniversalGateSet::Google));
    }

    #[test]
    fn test_gate_set_specifications() {
        let clifford_t = create_clifford_t_gate_set();
        assert_eq!(clifford_t.gate_set, UniversalGateSet::CliffordT);
        assert!(clifford_t.single_qubit_gates.contains(&GateType::H));
        assert!(clifford_t.single_qubit_gates.contains(&GateType::T));
        assert!(clifford_t.two_qubit_gates.contains(&GateType::CNOT));

        let ibm = create_ibm_gate_set();
        assert_eq!(ibm.gate_set, UniversalGateSet::IBM);
        assert!(ibm
            .single_qubit_gates
            .contains(&GateType::Rx("theta".to_string())));
        assert!(ibm
            .single_qubit_gates
            .contains(&GateType::Rz("phi".to_string())));
    }

    #[test]
    fn test_custom_gate_set_registration() {
        let translator = GateTranslator::new().unwrap();

        let custom_gate_set = GateSetSpecification {
            gate_set: UniversalGateSet::Custom("TestSet".to_string()),
            single_qubit_gates: vec![GateType::X, GateType::Z],
            two_qubit_gates: vec![GateType::CZ],
            multi_qubit_gates: vec![],
            gate_fidelities: HashMap::new(),
            gate_times: HashMap::new(),
            parameter_constraints: HashMap::new(),
            hardware_metadata: HashMap::new(),
        };

        let custom_set = UniversalGateSet::Custom("TestSet".to_string());
        assert!(translator
            .register_gate_set(custom_set.clone(), custom_gate_set)
            .is_ok());

        let available_sets = translator.get_available_gate_sets();
        assert!(available_sets.contains(&custom_set));
    }

    #[test]
    fn test_gate_type_display() {
        assert_eq!(format!("{}", GateType::X), "X");
        assert_eq!(
            format!("{}", GateType::Rx("theta".to_string())),
            "Rx(theta)"
        );
        assert_eq!(format!("{}", GateType::CNOT), "CNOT");
        assert_eq!(
            format!("{}", GateType::Custom("MyGate".to_string())),
            "Custom(MyGate)"
        );
    }

    #[test]
    fn test_universal_gate_set_display() {
        assert_eq!(format!("{}", UniversalGateSet::CliffordT), "Clifford+T");
        assert_eq!(format!("{}", UniversalGateSet::IBM), "IBM");
        assert_eq!(
            format!("{}", UniversalGateSet::Custom("Test".to_string())),
            "Custom(Test)"
        );
    }

    #[test]
    fn test_translation_cost_calculation() {
        let cost = TranslationCost {
            gate_count_multiplier: 2.0,
            depth_multiplier: 1.5,
            fidelity_impact: 0.001,
            time_overhead: Duration::from_micros(100),
            resource_overhead: 0.1,
        };

        // Test that cost structure is properly formed
        assert_eq!(cost.gate_count_multiplier, 2.0);
        assert_eq!(cost.depth_multiplier, 1.5);
        assert_eq!(cost.fidelity_impact, 0.001);
    }

    #[test]
    fn test_verification_strategies() {
        let matrix_strategy = MatrixVerificationStrategy { tolerance: 1e-10 };
        assert_eq!(matrix_strategy.name(), "Matrix Verification");
        assert_eq!(matrix_strategy.confidence_level(), 0.95);

        let statistical_strategy = StatisticalVerificationStrategy { sample_count: 1000 };
        assert_eq!(statistical_strategy.name(), "Statistical Verification");
        assert_eq!(statistical_strategy.confidence_level(), 0.99);
    }

    #[test]
    fn test_parameter_constraints() {
        let constraints = ParameterConstraints {
            ranges: vec![(0.0, 2.0 * std::f64::consts::PI)],
            discrete_values: Some(vec![0.0, std::f64::consts::PI / 2.0, std::f64::consts::PI]),
            granularity: Some(0.01),
            default_value: 0.0,
        };

        assert_eq!(constraints.ranges.len(), 1);
        assert!(constraints.discrete_values.is_some());
        assert_eq!(constraints.default_value, 0.0);
    }

    #[test]
    fn test_translation_cache_functionality() {
        let cache = TranslationCache::new(1000);
        assert_eq!(cache.max_cache_size, 1000);
        assert_eq!(cache.cache_stats.total_requests, 0);
    }

    #[test]
    fn test_gate_pattern_matching() {
        let pattern = GatePattern {
            gate_type: GateType::X,
            qubit_pattern: Some(QubitPattern::Any),
            parameter_patterns: vec![],
        };

        assert_eq!(pattern.gate_type, GateType::X);
        assert!(matches!(pattern.qubit_pattern, Some(QubitPattern::Any)));
    }

    #[test]
    fn test_translation_rule_structure() {
        let rule = TranslationRule {
            source_pattern: GatePattern {
                gate_type: GateType::H,
                qubit_pattern: None,
                parameter_patterns: vec![],
            },
            target_sequence: vec![TargetGate {
                gate_type: GateType::Ry("pi/2".to_string()),
                qubit_mapping: vec![0],
                parameter_expressions: vec![ParameterExpression::Constant(
                    std::f64::consts::PI / 2.0,
                )],
                metadata: HashMap::new(),
            }],
            cost: TranslationCost {
                gate_count_multiplier: 1.0,
                depth_multiplier: 1.0,
                fidelity_impact: 0.0,
                time_overhead: Duration::from_nanos(0),
                resource_overhead: 0.0,
            },
            conditions: vec![],
            metadata: RuleMetadata {
                name: "H to Ry".to_string(),
                version: "1.0".to_string(),
                description: "Convert H gate to Ry(π/2)".to_string(),
                author: "Test".to_string(),
                created: Instant::now(),
                verified_platforms: vec![],
            },
        };

        assert_eq!(rule.source_pattern.gate_type, GateType::H);
        assert_eq!(rule.target_sequence.len(), 1);
        assert_eq!(rule.metadata.name, "H to Ry");
    }

    #[test]
    fn test_performance_monitoring() {
        let monitor = TranslationPerformanceMonitor::new();
        assert!(monitor.translation_times.is_empty());
        assert!(monitor.success_rates.is_empty());
        assert_eq!(monitor.cache_performance.total_requests, 0);
    }
}