quantrs2_core/

real_time_compilation.rs

//! Real-Time Quantum Compilation
//!
//! Just-in-time compilation of quantum gates during execution with
//! adaptive optimization and hardware-specific targeting.

use crate::error::QuantRS2Error;
use crate::gate::GateOp;
use crate::qubit::QubitId;
use scirs2_core::ndarray::Array2;
use scirs2_core::Complex64;
use std::collections::HashMap;
use std::sync::{Arc, Mutex, RwLock};
use std::time::{Duration, Instant};
use tokio::sync::oneshot;
use uuid::Uuid;

fn generate_uuid() -> Uuid {
    Uuid::new_v4()
}

/// Real-time quantum compiler
#[derive(Debug)]
pub struct RealTimeQuantumCompiler {
    pub compiler_id: Uuid,
    pub compilation_cache: Arc<RwLock<CompilationCache>>,
    pub hardware_targets: Vec<Arc<dyn HardwareTarget>>,
    pub optimization_pipeline: OptimizationPipeline,
    pub compilation_queue: Arc<Mutex<Vec<CompilationTask>>>,
    pub active_compilations: Arc<Mutex<HashMap<Uuid, CompilationContext>>>,
    pub performance_monitor: PerformanceMonitor,
}

/// Hardware target abstraction
pub trait HardwareTarget: Send + Sync + std::fmt::Debug {
    fn target_name(&self) -> &str;
    fn native_gates(&self) -> Vec<String>;
    fn qubit_connectivity(&self) -> Vec<(usize, usize)>;
    fn gate_fidelities(&self) -> HashMap<String, f64>;
    fn gate_times(&self) -> HashMap<String, Duration>;
    fn coherence_times(&self) -> Vec<Duration>;
    fn compile_gate(
        &self,
        gate: &dyn GateOp,
        context: &CompilationContext,
    ) -> Result<CompiledGate, QuantRS2Error>;
    fn optimize_circuit(
        &self,
        circuit: &[CompiledGate],
    ) -> Result<Vec<CompiledGate>, QuantRS2Error>;
}

#[derive(Debug)]
pub struct CompilationTask {
    pub task_id: Uuid,
    pub gate: Box<dyn GateOp>,
    pub target_hardware: String,
    pub optimization_level: OptimizationLevel,
    pub deadline: Option<Instant>,
    pub priority: CompilationPriority,
    pub response_channel: Option<oneshot::Sender<Result<CompiledGate, QuantRS2Error>>>,
}

#[derive(Debug, Clone)]
pub struct CompilationContext {
    pub target_hardware: String,
    pub qubit_mapping: HashMap<QubitId, usize>,
    pub gate_sequence: Vec<CompiledGate>,
    pub current_fidelity: f64,
    pub compilation_time: Duration,
    pub optimization_hints: Vec<OptimizationHint>,
}

#[derive(Debug, Clone)]
pub enum OptimizationLevel {
    None,
    Basic,
    Aggressive,
    Adaptive,
}

#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub enum CompilationPriority {
    Low = 0,
    Normal = 1,
    High = 2,
    Critical = 3,
}

#[derive(Debug, Clone, PartialEq)]
pub enum OptimizationHint {
    MinimizeDepth,
    MinimizeGateCount,
    MaximizeFidelity,
    OptimizeForLatency,
    PreserveTiming,
}

impl RealTimeQuantumCompiler {
    /// Create a new real-time quantum compiler
    pub fn new() -> Self {
        Self {
            compiler_id: Uuid::new_v4(),
            compilation_cache: Arc::new(RwLock::new(CompilationCache::new(10000))),
            hardware_targets: Vec::new(),
            optimization_pipeline: OptimizationPipeline::new(),
            compilation_queue: Arc::new(Mutex::new(Vec::new())),
            active_compilations: Arc::new(Mutex::new(HashMap::new())),
            performance_monitor: PerformanceMonitor::new(),
        }
    }

    /// Add a hardware target
    pub fn add_hardware_target(&mut self, target: Arc<dyn HardwareTarget>) {
        self.hardware_targets.push(target);
    }

    /// Compile a gate for real-time execution
    pub async fn compile_gate_realtime(
        &self,
        gate: Box<dyn GateOp>,
        target_hardware: String,
        optimization_level: OptimizationLevel,
        deadline: Option<Duration>,
    ) -> Result<CompiledGate, QuantRS2Error> {
        let task_id = generate_uuid();
        let start_time = Instant::now();

        // Check cache first
        if let Some(cached_result) =
            self.check_cache(gate.as_ref(), &target_hardware, &optimization_level)
        {
            self.performance_monitor
                .record_cache_hit(start_time.elapsed());
            return Ok(cached_result);
        }

        // Create compilation context
        let context = CompilationContext {
            target_hardware: target_hardware.clone(),
            qubit_mapping: self.create_qubit_mapping(gate.as_ref())?,
            gate_sequence: Vec::new(),
            current_fidelity: 1.0,
            compilation_time: Duration::ZERO,
            optimization_hints: self.infer_optimization_hints(gate.as_ref(), &optimization_level),
        };

        // Register active compilation
        {
            let mut active = self.active_compilations.lock().unwrap();
            active.insert(task_id, context.clone());
        }

        // Find target hardware
        let hardware = self.find_hardware_target(&target_hardware)?;

        // Perform compilation
        let compilation_result = self
            .perform_compilation(
                gate.as_ref(),
                &hardware,
                &context,
                &optimization_level,
                deadline.map(|d| start_time + d),
            )
            .await;

        // Remove from active compilations
        {
            let mut active = self.active_compilations.lock().unwrap();
            active.remove(&task_id);
        }

        match compilation_result {
            Ok(compiled_gate) => {
                // Cache the result
                self.cache_compilation_result(
                    gate.as_ref(),
                    &target_hardware,
                    &optimization_level,
                    &compiled_gate,
                );

                // Record performance metrics
                self.performance_monitor.record_compilation_success(
                    start_time.elapsed(),
                    compiled_gate.estimated_fidelity,
                    compiled_gate.gate_sequence.len(),
                );

                Ok(compiled_gate)
            }
            Err(e) => {
                self.performance_monitor
                    .record_compilation_failure(start_time.elapsed());
                Err(e)
            }
        }
    }

    /// Check compilation cache
    fn check_cache(
        &self,
        gate: &dyn GateOp,
        target_hardware: &str,
        optimization_level: &OptimizationLevel,
    ) -> Option<CompiledGate> {
        let cache_key = self.generate_cache_key(gate, target_hardware, optimization_level);
        let cache = self.compilation_cache.read().unwrap();
        cache.get(&cache_key).cloned()
    }

    /// Cache compilation result
    fn cache_compilation_result(
        &self,
        gate: &dyn GateOp,
        target_hardware: &str,
        optimization_level: &OptimizationLevel,
        compiled_gate: &CompiledGate,
    ) {
        let cache_key = self.generate_cache_key(gate, target_hardware, optimization_level);
        let mut cache = self.compilation_cache.write().unwrap();
        cache.insert(cache_key, compiled_gate.clone());
    }

    /// Generate cache key for a compilation
    fn generate_cache_key(
        &self,
        gate: &dyn GateOp,
        target_hardware: &str,
        optimization_level: &OptimizationLevel,
    ) -> String {
        use std::collections::hash_map::DefaultHasher;
        use std::hash::{Hash, Hasher};

        let mut hasher = DefaultHasher::new();
        gate.name().hash(&mut hasher);
        gate.qubits().hash(&mut hasher);
        target_hardware.hash(&mut hasher);

        match optimization_level {
            OptimizationLevel::None => "none".hash(&mut hasher),
            OptimizationLevel::Basic => "basic".hash(&mut hasher),
            OptimizationLevel::Aggressive => "aggressive".hash(&mut hasher),
            OptimizationLevel::Adaptive => "adaptive".hash(&mut hasher),
        }

        format!("{}_{}", target_hardware, hasher.finish())
    }

    /// Create qubit mapping for gate
    fn create_qubit_mapping(
        &self,
        gate: &dyn GateOp,
    ) -> Result<HashMap<QubitId, usize>, QuantRS2Error> {
        let mut mapping = HashMap::new();
        for (index, &qubit_id) in gate.qubits().iter().enumerate() {
            mapping.insert(qubit_id, index);
        }
        Ok(mapping)
    }

    /// Infer optimization hints from gate and level
    fn infer_optimization_hints(
        &self,
        gate: &dyn GateOp,
        level: &OptimizationLevel,
    ) -> Vec<OptimizationHint> {
        let mut hints = Vec::new();

        match level {
            OptimizationLevel::None => {}
            OptimizationLevel::Basic => {
                hints.push(OptimizationHint::MinimizeGateCount);
            }
            OptimizationLevel::Aggressive => {
                hints.push(OptimizationHint::MinimizeDepth);
                hints.push(OptimizationHint::MaximizeFidelity);
            }
            OptimizationLevel::Adaptive => {
                // Adaptive hints based on gate type
                if gate.qubits().len() > 2 {
                    hints.push(OptimizationHint::MinimizeDepth);
                } else {
                    hints.push(OptimizationHint::MaximizeFidelity);
                }
            }
        }

        hints
    }

    /// Find hardware target by name
    fn find_hardware_target(
        &self,
        target_name: &str,
    ) -> Result<Arc<dyn HardwareTarget>, QuantRS2Error> {
        self.hardware_targets
            .iter()
            .find(|target| target.target_name() == target_name)
            .cloned()
            .ok_or_else(|| QuantRS2Error::HardwareTargetNotFound(target_name.to_string()))
    }

    /// Perform the actual compilation
    async fn perform_compilation(
        &self,
        gate: &dyn GateOp,
        hardware: &Arc<dyn HardwareTarget>,
        context: &CompilationContext,
        optimization_level: &OptimizationLevel,
        deadline: Option<Instant>,
    ) -> Result<CompiledGate, QuantRS2Error> {
        let start_time = Instant::now();

        // Check deadline
        if let Some(deadline) = deadline {
            if Instant::now() > deadline {
                return Err(QuantRS2Error::CompilationTimeout(
                    "Deadline exceeded before compilation".to_string(),
                ));
            }
        }

        // Step 1: Initial compilation
        let mut compiled_gate = hardware.compile_gate(gate, context)?;

        // Step 2: Apply optimizations based on level
        match optimization_level {
            OptimizationLevel::None => {
                // No optimization
            }
            OptimizationLevel::Basic => {
                compiled_gate =
                    self.apply_basic_optimizations(compiled_gate, hardware, deadline)?;
            }
            OptimizationLevel::Aggressive => {
                compiled_gate = self
                    .apply_aggressive_optimizations(compiled_gate, hardware, deadline)
                    .await?;
            }
            OptimizationLevel::Adaptive => {
                compiled_gate = self
                    .apply_adaptive_optimizations(compiled_gate, hardware, context, deadline)
                    .await?;
            }
        }

        // Step 3: Final validation and timing estimation
        compiled_gate.compilation_time = start_time.elapsed();
        compiled_gate.estimated_execution_time =
            self.estimate_execution_time(&compiled_gate, hardware);

        Ok(compiled_gate)
    }

    /// Apply basic optimizations
    fn apply_basic_optimizations(
        &self,
        mut compiled_gate: CompiledGate,
        _hardware: &Arc<dyn HardwareTarget>,
        deadline: Option<Instant>,
    ) -> Result<CompiledGate, QuantRS2Error> {
        // Basic gate fusion
        compiled_gate.gate_sequence = self.fuse_adjacent_gates(&compiled_gate.gate_sequence)?;

        // Remove redundant gates
        compiled_gate.gate_sequence = self.remove_redundant_gates(&compiled_gate.gate_sequence)?;

        // Check deadline
        if let Some(deadline) = deadline {
            if Instant::now() > deadline {
                return Err(QuantRS2Error::CompilationTimeout(
                    "Deadline exceeded during basic optimization".to_string(),
                ));
            }
        }

        Ok(compiled_gate)
    }

    /// Apply aggressive optimizations
    async fn apply_aggressive_optimizations(
        &self,
        mut compiled_gate: CompiledGate,
        hardware: &Arc<dyn HardwareTarget>,
        deadline: Option<Instant>,
    ) -> Result<CompiledGate, QuantRS2Error> {
        // Start with basic optimizations
        compiled_gate = self.apply_basic_optimizations(compiled_gate, hardware, deadline)?;

        // Advanced circuit optimizations
        compiled_gate.gate_sequence = self.optimize_circuit_depth(&compiled_gate.gate_sequence)?;
        compiled_gate.gate_sequence =
            self.optimize_for_hardware_connectivity(&compiled_gate.gate_sequence, hardware)?;

        // Fidelity optimization
        compiled_gate = self.optimize_for_fidelity(compiled_gate, hardware)?;

        // Check deadline
        if let Some(deadline) = deadline {
            if Instant::now() > deadline {
                return Err(QuantRS2Error::CompilationTimeout(
                    "Deadline exceeded during aggressive optimization".to_string(),
                ));
            }
        }

        Ok(compiled_gate)
    }

    /// Apply adaptive optimizations based on context
    async fn apply_adaptive_optimizations(
        &self,
        mut compiled_gate: CompiledGate,
        hardware: &Arc<dyn HardwareTarget>,
        context: &CompilationContext,
        deadline: Option<Instant>,
    ) -> Result<CompiledGate, QuantRS2Error> {
        // Analyze current performance metrics
        let current_metrics = self.performance_monitor.get_current_metrics();

        // Decide optimization strategy based on metrics and hints
        if current_metrics.average_compilation_time > Duration::from_millis(100) {
            // Fast compilation path
            compiled_gate = self.apply_basic_optimizations(compiled_gate, hardware, deadline)?;
        } else if context
            .optimization_hints
            .contains(&OptimizationHint::MaximizeFidelity)
        {
            // Fidelity-focused optimization
            compiled_gate = self.optimize_for_fidelity(compiled_gate, hardware)?;
        } else {
            // Balanced optimization
            compiled_gate = self
                .apply_aggressive_optimizations(compiled_gate, hardware, deadline)
                .await?;
        }

        Ok(compiled_gate)
    }

    /// Fuse adjacent gates where possible
    fn fuse_adjacent_gates(&self, gates: &[NativeGate]) -> Result<Vec<NativeGate>, QuantRS2Error> {
        let mut fused_gates = Vec::new();
        let mut i = 0;

        while i < gates.len() {
            let current_gate = &gates[i];

            // Look for fusable adjacent gate
            if i + 1 < gates.len() {
                let next_gate = &gates[i + 1];

                if self.can_fuse_gates(current_gate, next_gate) {
                    // Fuse the gates
                    let fused_gate = self.fuse_two_gates(current_gate, next_gate)?;
                    fused_gates.push(fused_gate);
                    i += 2; // Skip next gate as it's been fused
                    continue;
                }
            }

            // No fusion possible, add gate as-is
            fused_gates.push(current_gate.clone());
            i += 1;
        }

        Ok(fused_gates)
    }

    /// Check if two gates can be fused
    fn can_fuse_gates(&self, gate1: &NativeGate, gate2: &NativeGate) -> bool {
        // Simple fusion rules - can be extended
        match (&gate1.gate_type, &gate2.gate_type) {
            (NativeGateType::RZ(_), NativeGateType::RZ(_)) => {
                // RZ gates on same qubit can be fused
                gate1.target_qubits == gate2.target_qubits
            }
            (NativeGateType::RX(_), NativeGateType::RX(_)) => {
                gate1.target_qubits == gate2.target_qubits
            }
            (NativeGateType::RY(_), NativeGateType::RY(_)) => {
                gate1.target_qubits == gate2.target_qubits
            }
            _ => false,
        }
    }

    /// Fuse two compatible gates
    fn fuse_two_gates(
        &self,
        gate1: &NativeGate,
        gate2: &NativeGate,
    ) -> Result<NativeGate, QuantRS2Error> {
        match (&gate1.gate_type, &gate2.gate_type) {
            (NativeGateType::RZ(angle1), NativeGateType::RZ(angle2)) => Ok(NativeGate {
                gate_type: NativeGateType::RZ(angle1 + angle2),
                target_qubits: gate1.target_qubits.clone(),
                execution_time: gate1.execution_time + gate2.execution_time,
                fidelity: gate1.fidelity * gate2.fidelity,
            }),
            (NativeGateType::RX(angle1), NativeGateType::RX(angle2)) => Ok(NativeGate {
                gate_type: NativeGateType::RX(angle1 + angle2),
                target_qubits: gate1.target_qubits.clone(),
                execution_time: gate1.execution_time + gate2.execution_time,
                fidelity: gate1.fidelity * gate2.fidelity,
            }),
            (NativeGateType::RY(angle1), NativeGateType::RY(angle2)) => Ok(NativeGate {
                gate_type: NativeGateType::RY(angle1 + angle2),
                target_qubits: gate1.target_qubits.clone(),
                execution_time: gate1.execution_time + gate2.execution_time,
                fidelity: gate1.fidelity * gate2.fidelity,
            }),
            _ => Err(QuantRS2Error::GateFusionError(
                "Cannot fuse incompatible gates".to_string(),
            )),
        }
    }

    /// Remove redundant gates (identity operations)
    fn remove_redundant_gates(
        &self,
        gates: &[NativeGate],
    ) -> Result<Vec<NativeGate>, QuantRS2Error> {
        let mut filtered_gates = Vec::new();

        for gate in gates {
            if !self.is_redundant_gate(gate) {
                filtered_gates.push(gate.clone());
            }
        }

        Ok(filtered_gates)
    }

    /// Check if a gate is redundant (effectively identity)
    fn is_redundant_gate(&self, gate: &NativeGate) -> bool {
        match &gate.gate_type {
            NativeGateType::RX(angle) | NativeGateType::RY(angle) | NativeGateType::RZ(angle) => {
                // Check if angle is effectively zero (modulo 2π)
                let normalized_angle = angle % (2.0 * std::f64::consts::PI);
                normalized_angle.abs() < 1e-10
                    || (normalized_angle - 2.0 * std::f64::consts::PI).abs() < 1e-10
            }
            NativeGateType::Identity => true,
            _ => false,
        }
    }

    /// Optimize circuit depth by reordering gates
    fn optimize_circuit_depth(
        &self,
        gates: &[NativeGate],
    ) -> Result<Vec<NativeGate>, QuantRS2Error> {
        // Simple depth optimization - can be made more sophisticated
        let mut optimized_gates = gates.to_vec();

        // Sort gates to minimize depth while respecting dependencies
        optimized_gates.sort_by(|a, b| {
            // Gates operating on different qubits can be parallelized
            if !self.gates_share_qubits(a, b) {
                std::cmp::Ordering::Equal
            } else {
                // Maintain original order for dependent gates
                std::cmp::Ordering::Equal
            }
        });

        Ok(optimized_gates)
    }

    /// Check if two gates share any qubits
    fn gates_share_qubits(&self, gate1: &NativeGate, gate2: &NativeGate) -> bool {
        gate1
            .target_qubits
            .iter()
            .any(|&q1| gate2.target_qubits.contains(&q1))
    }

    /// Optimize for hardware connectivity
    fn optimize_for_hardware_connectivity(
        &self,
        gates: &[NativeGate],
        hardware: &Arc<dyn HardwareTarget>,
    ) -> Result<Vec<NativeGate>, QuantRS2Error> {
        let connectivity = hardware.qubit_connectivity();
        let mut optimized_gates = Vec::new();

        for gate in gates {
            if gate.target_qubits.len() == 2 {
                let qubit1 = gate.target_qubits[0];
                let qubit2 = gate.target_qubits[1];

                // Check if qubits are connected
                if !connectivity.contains(&(qubit1, qubit2))
                    && !connectivity.contains(&(qubit2, qubit1))
                {
                    // Need to insert SWAP gates to connect qubits
                    let swap_sequence = self.find_swap_sequence(qubit1, qubit2, &connectivity)?;
                    optimized_gates.extend(swap_sequence);
                }
            }

            optimized_gates.push(gate.clone());
        }

        Ok(optimized_gates)
    }

    /// Find SWAP sequence to connect two qubits
    fn find_swap_sequence(
        &self,
        qubit1: usize,
        qubit2: usize,
        connectivity: &[(usize, usize)],
    ) -> Result<Vec<NativeGate>, QuantRS2Error> {
        // Simplified path finding - could use Dijkstra or A*
        let mut swaps = Vec::new();

        // For now, just insert a dummy SWAP if needed
        if !connectivity.contains(&(qubit1, qubit2)) {
            swaps.push(NativeGate {
                gate_type: NativeGateType::SWAP,
                target_qubits: vec![qubit1, qubit2],
                execution_time: Duration::from_micros(1000),
                fidelity: 0.99,
            });
        }

        Ok(swaps)
    }

    /// Optimize for maximum fidelity
    fn optimize_for_fidelity(
        &self,
        mut compiled_gate: CompiledGate,
        hardware: &Arc<dyn HardwareTarget>,
    ) -> Result<CompiledGate, QuantRS2Error> {
        let gate_fidelities = hardware.gate_fidelities();

        // Replace low-fidelity gates with high-fidelity alternatives
        for gate in &mut compiled_gate.gate_sequence {
            if let Some(&current_fidelity) = gate_fidelities.get(&format!("{:?}", gate.gate_type)) {
                if current_fidelity < 0.95 {
                    // Try to find a better implementation
                    if let Some(alternative) =
                        self.find_high_fidelity_alternative(gate, &gate_fidelities)
                    {
                        *gate = alternative;
                    }
                }
            }
        }

        // Recalculate overall fidelity
        compiled_gate.estimated_fidelity = compiled_gate
            .gate_sequence
            .iter()
            .map(|gate| gate.fidelity)
            .product();

        Ok(compiled_gate)
    }

    /// Find high-fidelity alternative for a gate
    fn find_high_fidelity_alternative(
        &self,
        _gate: &NativeGate,
        _gate_fidelities: &HashMap<String, f64>,
    ) -> Option<NativeGate> {
        // This could implement sophisticated gate replacement strategies
        // For now, return None (no alternative found)
        None
    }

    /// Estimate execution time for compiled gate
    fn estimate_execution_time(
        &self,
        compiled_gate: &CompiledGate,
        hardware: &Arc<dyn HardwareTarget>,
    ) -> Duration {
        let gate_times = hardware.gate_times();

        compiled_gate
            .gate_sequence
            .iter()
            .map(|gate| {
                gate_times
                    .get(&format!("{:?}", gate.gate_type))
                    .copied()
                    .unwrap_or(gate.execution_time)
            })
            .sum()
    }
}

/// Compilation cache for storing compiled gates
#[derive(Debug)]
pub struct CompilationCache {
    cache: HashMap<String, CompiledGate>,
    access_order: Vec<String>,
    max_size: usize,
}

impl CompilationCache {
    pub fn new(max_size: usize) -> Self {
        Self {
            cache: HashMap::new(),
            access_order: Vec::new(),
            max_size,
        }
    }

    pub fn get(&self, key: &str) -> Option<&CompiledGate> {
        self.cache.get(key)
    }

    pub fn insert(&mut self, key: String, value: CompiledGate) {
        // Remove if already exists
        if self.cache.contains_key(&key) {
            self.access_order.retain(|k| k != &key);
        }

        // Add to cache
        self.cache.insert(key.clone(), value);
        self.access_order.push(key);

        // Evict if necessary (LRU)
        while self.cache.len() > self.max_size {
            if let Some(oldest_key) = self.access_order.first().cloned() {
                self.cache.remove(&oldest_key);
                self.access_order.remove(0);
            }
        }
    }
}

/// Optimization pipeline for quantum circuits
#[derive(Debug)]
pub struct OptimizationPipeline {
    passes: Vec<Box<dyn OptimizationPass>>,
}

pub trait OptimizationPass: Send + Sync + std::fmt::Debug {
    fn pass_name(&self) -> &str;
    fn apply(&self, gates: &[NativeGate]) -> Result<Vec<NativeGate>, QuantRS2Error>;
    fn cost_estimate(&self, gates: &[NativeGate]) -> Duration;
}

impl OptimizationPipeline {
    pub fn new() -> Self {
        Self { passes: Vec::new() }
    }

    pub fn add_pass(&mut self, pass: Box<dyn OptimizationPass>) {
        self.passes.push(pass);
    }

    pub fn run(
        &self,
        gates: &[NativeGate],
        deadline: Option<Instant>,
    ) -> Result<Vec<NativeGate>, QuantRS2Error> {
        let mut current_gates = gates.to_vec();

        for pass in &self.passes {
            // Check deadline before running pass
            if let Some(deadline) = deadline {
                let estimated_cost = pass.cost_estimate(&current_gates);
                if Instant::now() + estimated_cost > deadline {
                    break; // Skip remaining passes to meet deadline
                }
            }

            current_gates = pass.apply(&current_gates)?;
        }

        Ok(current_gates)
    }
}

/// Performance monitoring for compilation
#[derive(Debug)]
pub struct PerformanceMonitor {
    metrics: Arc<Mutex<CompilationMetrics>>,
}

#[derive(Debug, Clone)]
pub struct CompilationMetrics {
    pub total_compilations: u64,
    pub successful_compilations: u64,
    pub cache_hits: u64,
    pub average_compilation_time: Duration,
    pub average_fidelity: f64,
    pub average_gate_count: f64,
}

impl PerformanceMonitor {
    pub fn new() -> Self {
        Self {
            metrics: Arc::new(Mutex::new(CompilationMetrics {
                total_compilations: 0,
                successful_compilations: 0,
                cache_hits: 0,
                average_compilation_time: Duration::ZERO,
                average_fidelity: 0.0,
                average_gate_count: 0.0,
            })),
        }
    }

    pub fn record_compilation_success(
        &self,
        compilation_time: Duration,
        fidelity: f64,
        gate_count: usize,
    ) {
        let mut metrics = self.metrics.lock().unwrap();
        metrics.total_compilations += 1;
        metrics.successful_compilations += 1;

        // Update running averages
        let n = metrics.successful_compilations as f64;
        metrics.average_compilation_time = Duration::from_nanos(
            ((metrics.average_compilation_time.as_nanos() as f64 * (n - 1.0)
                + compilation_time.as_nanos() as f64)
                / n) as u64,
        );
        metrics.average_fidelity = (metrics.average_fidelity * (n - 1.0) + fidelity) / n;
        metrics.average_gate_count =
            (metrics.average_gate_count * (n - 1.0) + gate_count as f64) / n;
    }

    pub fn record_compilation_failure(&self, _compilation_time: Duration) {
        let mut metrics = self.metrics.lock().unwrap();
        metrics.total_compilations += 1;
    }

    pub fn record_cache_hit(&self, _access_time: Duration) {
        let mut metrics = self.metrics.lock().unwrap();
        metrics.cache_hits += 1;
    }

    pub fn get_current_metrics(&self) -> CompilationMetrics {
        self.metrics.lock().unwrap().clone()
    }
}

/// Compiled gate representation
#[derive(Debug, Clone)]
pub struct CompiledGate {
    pub original_gate_name: String,
    pub target_hardware: String,
    pub gate_sequence: Vec<NativeGate>,
    pub estimated_fidelity: f64,
    pub compilation_time: Duration,
    pub estimated_execution_time: Duration,
    pub optimization_level: OptimizationLevel,
}

/// Native gate for specific hardware
#[derive(Debug, Clone)]
pub struct NativeGate {
    pub gate_type: NativeGateType,
    pub target_qubits: Vec<usize>,
    pub execution_time: Duration,
    pub fidelity: f64,
}

#[derive(Debug, Clone)]
pub enum NativeGateType {
    RX(f64),
    RY(f64),
    RZ(f64),
    CNOT,
    CZ,
    SWAP,
    Identity,
    Custom {
        name: String,
        matrix: Array2<Complex64>,
    },
}

/// Example superconducting hardware target
#[derive(Debug)]
pub struct SuperconductingTarget {
    pub name: String,
    pub qubit_count: usize,
    pub connectivity: Vec<(usize, usize)>,
}

impl SuperconductingTarget {
    pub fn new(name: String, qubit_count: usize) -> Self {
        // Create linear connectivity for simplicity
        let connectivity = (0..qubit_count.saturating_sub(1))
            .map(|i| (i, i + 1))
            .collect();

        Self {
            name,
            qubit_count,
            connectivity,
        }
    }
}

impl HardwareTarget for SuperconductingTarget {
    fn target_name(&self) -> &str {
        &self.name
    }

    fn native_gates(&self) -> Vec<String> {
        vec![
            "RX".to_string(),
            "RY".to_string(),
            "RZ".to_string(),
            "CNOT".to_string(),
        ]
    }

    fn qubit_connectivity(&self) -> Vec<(usize, usize)> {
        self.connectivity.clone()
    }

    fn gate_fidelities(&self) -> HashMap<String, f64> {
        let mut fidelities = HashMap::new();
        fidelities.insert("RX".to_string(), 0.999);
        fidelities.insert("RY".to_string(), 0.999);
        fidelities.insert("RZ".to_string(), 0.9995);
        fidelities.insert("CNOT".to_string(), 0.995);
        fidelities
    }

    fn gate_times(&self) -> HashMap<String, Duration> {
        let mut times = HashMap::new();
        times.insert("RX".to_string(), Duration::from_nanos(20));
        times.insert("RY".to_string(), Duration::from_nanos(20));
        times.insert("RZ".to_string(), Duration::from_nanos(0)); // Virtual Z gates
        times.insert("CNOT".to_string(), Duration::from_nanos(100));
        times
    }

    fn coherence_times(&self) -> Vec<Duration> {
        vec![Duration::from_millis(100); self.qubit_count] // T2 = 100ms
    }

    fn compile_gate(
        &self,
        gate: &dyn GateOp,
        _context: &CompilationContext,
    ) -> Result<CompiledGate, QuantRS2Error> {
        let mut native_gates = Vec::new();

        // Simple compilation based on gate name
        match gate.name() {
            "X" => {
                native_gates.push(NativeGate {
                    gate_type: NativeGateType::RX(std::f64::consts::PI),
                    target_qubits: vec![0], // Simplified
                    execution_time: Duration::from_nanos(20),
                    fidelity: 0.999,
                });
            }
            "Y" => {
                native_gates.push(NativeGate {
                    gate_type: NativeGateType::RY(std::f64::consts::PI),
                    target_qubits: vec![0],
                    execution_time: Duration::from_nanos(20),
                    fidelity: 0.999,
                });
            }
            "Z" => {
                native_gates.push(NativeGate {
                    gate_type: NativeGateType::RZ(std::f64::consts::PI),
                    target_qubits: vec![0],
                    execution_time: Duration::from_nanos(0),
                    fidelity: 0.9995,
                });
            }
            "CNOT" => {
                native_gates.push(NativeGate {
                    gate_type: NativeGateType::CNOT,
                    target_qubits: vec![0, 1], // Simplified
                    execution_time: Duration::from_nanos(100),
                    fidelity: 0.995,
                });
            }
            _ => {
                return Err(QuantRS2Error::UnsupportedGate(format!(
                    "Gate {} not supported",
                    gate.name()
                )));
            }
        }

        let estimated_fidelity = native_gates.iter().map(|g| g.fidelity).product();

        Ok(CompiledGate {
            original_gate_name: gate.name().to_string(),
            target_hardware: self.name.clone(),
            gate_sequence: native_gates,
            estimated_fidelity,
            compilation_time: Duration::ZERO, // Will be filled by compiler
            estimated_execution_time: Duration::ZERO, // Will be calculated
            optimization_level: OptimizationLevel::Basic,
        })
    }

    fn optimize_circuit(
        &self,
        circuit: &[CompiledGate],
    ) -> Result<Vec<CompiledGate>, QuantRS2Error> {
        // Hardware-specific circuit optimization
        Ok(circuit.to_vec())
    }
}

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

    #[tokio::test]
    async fn test_real_time_compiler_creation() {
        let compiler = RealTimeQuantumCompiler::new();
        assert_eq!(compiler.hardware_targets.len(), 0);
    }

    #[tokio::test]
    async fn test_superconducting_target() {
        let target = SuperconductingTarget::new("test_sc".to_string(), 5);
        assert_eq!(target.target_name(), "test_sc");
        assert_eq!(target.qubit_connectivity().len(), 4); // Linear connectivity
        assert!(target.gate_fidelities().contains_key("RX"));
    }

    #[tokio::test]
    async fn test_compilation_cache() {
        let mut cache = CompilationCache::new(2);

        let compiled_gate = CompiledGate {
            original_gate_name: "X".to_string(),
            target_hardware: "test".to_string(),
            gate_sequence: Vec::new(),
            estimated_fidelity: 0.99,
            compilation_time: Duration::from_millis(1),
            estimated_execution_time: Duration::from_nanos(20),
            optimization_level: OptimizationLevel::Basic,
        };

        cache.insert("key1".to_string(), compiled_gate.clone());
        assert!(cache.get("key1").is_some());

        cache.insert("key2".to_string(), compiled_gate.clone());
        cache.insert("key3".to_string(), compiled_gate); // Should evict key1

        assert!(cache.get("key1").is_none());
        assert!(cache.get("key2").is_some());
        assert!(cache.get("key3").is_some());
    }

    #[tokio::test]
    async fn test_performance_monitor() {
        let monitor = PerformanceMonitor::new();

        monitor.record_compilation_success(Duration::from_millis(10), 0.99, 5);

        let metrics = monitor.get_current_metrics();
        assert_eq!(metrics.successful_compilations, 1);
        assert_eq!(metrics.average_fidelity, 0.99);
    }
}