quantrs2_core/

quantum_debugger.rs

//! Quantum Circuit Debugger with SciRS2 Visualization Tools
//!
//! This module provides comprehensive debugging capabilities for quantum circuits
//! using SciRS2's advanced visualization and analysis tools.

use crate::gate_translation::GateType;
// use scirs2_core::memory::BufferPool;
use crate::buffer_pool::BufferPool;
use std::time::{Duration, Instant};

/// Simplified quantum gate representation for debugging
#[derive(Debug, Clone)]
pub struct QuantumGate {
    gate_type: GateType,
    target_qubits: Vec<usize>,
    control_qubits: Option<Vec<usize>>,
}

impl QuantumGate {
    pub const fn new(
        gate_type: GateType,
        target_qubits: Vec<usize>,
        control_qubits: Option<Vec<usize>>,
    ) -> Self {
        Self {
            gate_type,
            target_qubits,
            control_qubits,
        }
    }

    pub const fn gate_type(&self) -> &GateType {
        &self.gate_type
    }

    pub fn target_qubits(&self) -> &[usize] {
        &self.target_qubits
    }

    pub fn control_qubits(&self) -> Option<&[usize]> {
        self.control_qubits.as_deref()
    }
}
use crate::error::QuantRS2Error;
use std::collections::{HashMap, VecDeque};
// Serde imports would go here if needed
use scirs2_core::Complex64;

/// Performance tracking for enhanced debugging with SciRS2
#[derive(Debug, Clone)]
pub struct PerformanceTracker {
    gate_timing: HashMap<String, Duration>,
    memory_usage: Vec<usize>,
    computation_start: Option<Instant>,
    total_execution_time: Duration,
    simd_operations_count: usize,
    parallel_operations_count: usize,
}

impl PerformanceTracker {
    pub fn new() -> Self {
        Self {
            gate_timing: HashMap::new(),
            memory_usage: Vec::new(),
            computation_start: None,
            total_execution_time: Duration::new(0, 0),
            simd_operations_count: 0,
            parallel_operations_count: 0,
        }
    }

    pub fn start_timing(&mut self) {
        self.computation_start = Some(Instant::now());
    }

    pub fn record_gate_timing(&mut self, gate_type: &str, duration: Duration) {
        *self
            .gate_timing
            .entry(gate_type.to_string())
            .or_insert(Duration::new(0, 0)) += duration;
    }

    pub fn record_memory_usage(&mut self, usage: usize) {
        self.memory_usage.push(usage);
    }

    pub const fn increment_simd_ops(&mut self) {
        self.simd_operations_count += 1;
    }

    pub const fn increment_parallel_ops(&mut self) {
        self.parallel_operations_count += 1;
    }

    pub fn finish_timing(&mut self) {
        if let Some(start) = self.computation_start.take() {
            self.total_execution_time = start.elapsed();
        }
    }
}

/// Configuration for quantum debugging
#[derive(Debug, Clone)]
pub struct DebugConfig {
    /// Enable state vector tracking
    pub track_state_vectors: bool,
    /// Enable entanglement analysis
    pub analyze_entanglement: bool,
    /// Enable amplitude visualization
    pub visualize_amplitudes: bool,
    /// Enable gate effect tracking
    pub track_gate_effects: bool,
    /// Maximum number of qubits for detailed tracking
    pub max_detailed_qubits: usize,
    /// Sampling rate for large circuits
    pub sampling_rate: f64,
    /// Enable breakpoint functionality
    pub enable_breakpoints: bool,
    /// Memory limit for state storage (MB)
    pub memory_limit_mb: usize,
}

impl Default for DebugConfig {
    fn default() -> Self {
        Self {
            track_state_vectors: true,
            analyze_entanglement: true,
            visualize_amplitudes: true,
            track_gate_effects: true,
            max_detailed_qubits: 10,
            sampling_rate: 0.1,
            enable_breakpoints: true,
            memory_limit_mb: 1024,
        }
    }
}

/// Quantum circuit debugger with SciRS2 visualization
pub struct QuantumDebugger {
    config: DebugConfig,
    execution_trace: Vec<DebugStep>,
    breakpoints: Vec<Breakpoint>,
    current_step: usize,
    state_history: VecDeque<StateSnapshot>,
    gate_statistics: GateStatistics,
    buffer_pool: Option<BufferPool<Complex64>>,
    performance_metrics: PerformanceTracker,
}

impl QuantumDebugger {
    /// Create a new quantum debugger
    pub fn new() -> Self {
        let config = DebugConfig::default();
        Self::with_config(config)
    }

    /// Create a new quantum debugger with custom configuration
    pub fn with_config(config: DebugConfig) -> Self {
        let buffer_pool = if config.memory_limit_mb > 0 {
            Some(BufferPool::<Complex64>::new())
        } else {
            None
        };

        Self {
            config,
            execution_trace: Vec::new(),
            breakpoints: Vec::new(),
            current_step: 0,
            state_history: VecDeque::new(),
            gate_statistics: GateStatistics::new(),
            buffer_pool,
            performance_metrics: PerformanceTracker::new(),
        }
    }

    /// Set a breakpoint at a specific step
    pub fn set_breakpoint(&mut self, step: usize, condition: BreakpointCondition) {
        self.breakpoints.push(Breakpoint {
            step,
            condition,
            enabled: true,
        });
    }

    /// Remove a breakpoint
    pub fn remove_breakpoint(&mut self, step: usize) {
        self.breakpoints.retain(|bp| bp.step != step);
    }

    /// Debug a quantum circuit execution with SciRS2 performance tracking
    pub fn debug_circuit(
        &mut self,
        circuit: &[QuantumGate],
        initial_state: &[Complex64],
        num_qubits: usize,
    ) -> Result<DebugResult, QuantRS2Error> {
        self.reset_debug_session();

        // Start performance tracking
        self.performance_metrics.start_timing();

        let mut current_state = initial_state.to_vec();
        let mut step = 0;

        // Record initial state
        if self.config.track_state_vectors {
            self.record_state_snapshot(step, &current_state, None, num_qubits)?;
        }

        for (gate_index, gate) in circuit.iter().enumerate() {
            step += 1;

            // Check breakpoints
            if self.should_break_at_step(step, &current_state, gate) {
                return Ok(DebugResult {
                    status: DebugStatus::BreakpointHit(step),
                    final_state: current_state,
                    execution_trace: self.execution_trace.clone(),
                    analysis: self.generate_analysis(num_qubits)?,
                });
            }

            // Apply gate and record debug information with performance tracking
            let gate_start = Instant::now();
            let gate_effect =
                self.apply_gate_with_debugging(gate, &mut current_state, step, num_qubits)?;
            let gate_duration = gate_start.elapsed();

            // Record performance metrics
            let gate_type_str = format!("{:?}", gate.gate_type());
            self.performance_metrics
                .record_gate_timing(&gate_type_str, gate_duration);
            self.performance_metrics
                .record_memory_usage(current_state.len() * std::mem::size_of::<Complex64>());

            self.execution_trace.push(DebugStep {
                step,
                gate: gate.clone(),
                gate_effect,
                state_before: if self.config.track_state_vectors {
                    Some(self.get_previous_state())
                } else {
                    None
                },
                state_after: if self.config.track_state_vectors {
                    Some(current_state.clone())
                } else {
                    None
                },
                entanglement_info: if self.config.analyze_entanglement {
                    Some(self.analyze_entanglement(&current_state, num_qubits)?)
                } else {
                    None
                },
                amplitude_analysis: if self.config.visualize_amplitudes {
                    Some(self.analyze_amplitudes(&current_state)?)
                } else {
                    None
                },
            });

            // Record state snapshot
            if self.config.track_state_vectors {
                self.record_state_snapshot(step, &current_state, Some(gate_index), num_qubits)?;
            }

            // Update statistics
            self.gate_statistics.record_gate(gate);
        }

        self.current_step = step;

        // Finish performance tracking
        self.performance_metrics.finish_timing();

        Ok(DebugResult {
            status: DebugStatus::Completed,
            final_state: current_state,
            execution_trace: self.execution_trace.clone(),
            analysis: self.generate_analysis(num_qubits)?,
        })
    }

    /// Reset debug session
    fn reset_debug_session(&mut self) {
        self.execution_trace.clear();
        self.current_step = 0;
        self.state_history.clear();
        self.gate_statistics = GateStatistics::new();
        self.performance_metrics = PerformanceTracker::new();
    }

    /// Check if execution should break at current step
    fn should_break_at_step(&self, step: usize, state: &[Complex64], gate: &QuantumGate) -> bool {
        if !self.config.enable_breakpoints {
            return false;
        }

        for breakpoint in &self.breakpoints {
            if breakpoint.enabled && breakpoint.step == step {
                match &breakpoint.condition {
                    BreakpointCondition::Always => return true,
                    BreakpointCondition::StateCondition(condition) => {
                        if self.evaluate_state_condition(state, condition) {
                            return true;
                        }
                    }
                    BreakpointCondition::GateType(gate_type) => {
                        if std::mem::discriminant(gate.gate_type())
                            == std::mem::discriminant(gate_type)
                        {
                            return true;
                        }
                    }
                    BreakpointCondition::QubitIndex(qubit) => {
                        if gate.target_qubits().contains(qubit) {
                            return true;
                        }
                    }
                }
            }
        }

        false
    }

    /// Evaluate a state condition
    fn evaluate_state_condition(&self, state: &[Complex64], condition: &StateCondition) -> bool {
        match condition {
            StateCondition::AmplitudeThreshold { qubit, threshold } => {
                if let Some(amplitude) = self.get_qubit_amplitude(state, *qubit) {
                    amplitude.norm_sqr() > *threshold
                } else {
                    false
                }
            }
            StateCondition::EntanglementThreshold { threshold } => {
                if let Ok(entanglement) = self.calculate_total_entanglement(state) {
                    entanglement > *threshold
                } else {
                    false
                }
            }
            StateCondition::PhaseDifference {
                qubit1,
                qubit2,
                threshold,
            } => {
                if let (Some(amp1), Some(amp2)) = (
                    self.get_qubit_amplitude(state, *qubit1),
                    self.get_qubit_amplitude(state, *qubit2),
                ) {
                    let phase_diff = (amp1.arg() - amp2.arg()).abs();
                    phase_diff > *threshold
                } else {
                    false
                }
            }
        }
    }

    /// Apply gate with debugging information
    fn apply_gate_with_debugging(
        &self,
        gate: &QuantumGate,
        state: &mut Vec<Complex64>,
        _step: usize,
        num_qubits: usize,
    ) -> Result<GateEffect, QuantRS2Error> {
        let state_before = state.clone();

        // Apply the gate (simplified implementation)
        self.apply_gate_to_state(gate, state, num_qubits)?;

        // Calculate gate effect
        let effect = self.calculate_gate_effect(&state_before, state, gate)?;

        Ok(effect)
    }

    /// Apply a gate to the state vector (simplified implementation)
    fn apply_gate_to_state(
        &self,
        gate: &QuantumGate,
        state: &mut [Complex64],
        num_qubits: usize,
    ) -> Result<(), QuantRS2Error> {
        use crate::gate_translation::GateType;

        match gate.gate_type() {
            GateType::X => {
                if let Some(&target) = gate.target_qubits().first() {
                    let target_bit = 1 << target;
                    for i in 0..(1 << num_qubits) {
                        let j = i ^ target_bit;
                        if i < j {
                            state.swap(i, j);
                        }
                    }
                }
            }
            GateType::Y => {
                if let Some(&target) = gate.target_qubits().first() {
                    let target_bit = 1 << target;
                    for i in 0..(1 << num_qubits) {
                        let j = i ^ target_bit;
                        if i < j {
                            let temp = state[i];
                            state[i] = Complex64::new(0.0, 1.0) * state[j];
                            state[j] = Complex64::new(0.0, -1.0) * temp;
                        }
                    }
                }
            }
            GateType::Z => {
                if let Some(&target) = gate.target_qubits().first() {
                    let target_bit = 1 << target;
                    for i in 0..(1 << num_qubits) {
                        if i & target_bit != 0 {
                            state[i] *= -1.0;
                        }
                    }
                }
            }
            GateType::H => {
                if let Some(&target) = gate.target_qubits().first() {
                    let target_bit = 1 << target;
                    let inv_sqrt2 = 1.0 / std::f64::consts::SQRT_2;
                    for i in 0..(1 << num_qubits) {
                        let j = i ^ target_bit;
                        if i < j {
                            let temp = state[i];
                            state[i] = inv_sqrt2 * (temp + state[j]);
                            state[j] = inv_sqrt2 * (temp - state[j]);
                        }
                    }
                }
            }
            GateType::CNOT => {
                if gate.target_qubits().len() >= 2 {
                    let control = gate.target_qubits()[0];
                    let target = gate.target_qubits()[1];
                    let control_bit = 1 << control;
                    let target_bit = 1 << target;

                    for i in 0..(1 << num_qubits) {
                        if i & control_bit != 0 {
                            let j = i ^ target_bit;
                            if i != j {
                                state.swap(i, j);
                            }
                        }
                    }
                }
            }
            _ => {
                // For other gates, no operation (placeholder)
            }
        }

        Ok(())
    }

    /// Calculate the effect of a gate on the quantum state
    fn calculate_gate_effect(
        &self,
        state_before: &[Complex64],
        state_after: &[Complex64],
        gate: &QuantumGate,
    ) -> Result<GateEffect, QuantRS2Error> {
        let amplitude_changes = self.calculate_amplitude_changes(state_before, state_after);
        let phase_changes = self.calculate_phase_changes(state_before, state_after);
        let entanglement_change = self.calculate_entanglement_change(state_before, state_after)?;

        Ok(GateEffect {
            gate_type: format!("{:?}", gate.gate_type()),
            target_qubits: gate.target_qubits().to_vec(),
            amplitude_changes,
            phase_changes,
            entanglement_change,
            fidelity: self.calculate_state_fidelity(state_before, state_after),
        })
    }

    /// Calculate amplitude changes between states
    fn calculate_amplitude_changes(&self, before: &[Complex64], after: &[Complex64]) -> Vec<f64> {
        before
            .iter()
            .zip(after.iter())
            .map(|(b, a)| (a.norm() - b.norm()).abs())
            .collect()
    }

    /// Calculate phase changes between states
    fn calculate_phase_changes(&self, before: &[Complex64], after: &[Complex64]) -> Vec<f64> {
        before
            .iter()
            .zip(after.iter())
            .map(|(b, a)| {
                if b.norm() > 1e-10 && a.norm() > 1e-10 {
                    (a.arg() - b.arg()).abs()
                } else {
                    0.0
                }
            })
            .collect()
    }

    /// Calculate entanglement change
    fn calculate_entanglement_change(
        &self,
        before: &[Complex64],
        after: &[Complex64],
    ) -> Result<f64, QuantRS2Error> {
        let ent_before = self.calculate_total_entanglement(before)?;
        let ent_after = self.calculate_total_entanglement(after)?;
        Ok(ent_after - ent_before)
    }

    /// Calculate state fidelity
    fn calculate_state_fidelity(&self, state1: &[Complex64], state2: &[Complex64]) -> f64 {
        let overlap: Complex64 = state1
            .iter()
            .zip(state2.iter())
            .map(|(s1, s2)| s1.conj() * s2)
            .sum();
        overlap.norm_sqr()
    }

    /// Record a state snapshot
    fn record_state_snapshot(
        &mut self,
        step: usize,
        state: &[Complex64],
        gate_index: Option<usize>,
        num_qubits: usize,
    ) -> Result<(), QuantRS2Error> {
        // Check memory limit
        let estimated_size = state.len() * 16; // 16 bytes per Complex64
        let total_size = self.state_history.len() * estimated_size;

        if total_size > self.config.memory_limit_mb * 1024 * 1024 {
            // Remove oldest snapshots
            while self.state_history.len() > 100 {
                self.state_history.pop_front();
            }
        }

        let snapshot = StateSnapshot {
            step,
            gate_index,
            state: if num_qubits <= self.config.max_detailed_qubits {
                state.to_vec()
            } else {
                // Sample the state for large systems
                self.sample_state(state)?
            },
            metadata: StateMetadata {
                entropy: self.calculate_von_neumann_entropy(state)?,
                purity: self.calculate_purity(state)?,
                norm: state.iter().map(|c| c.norm_sqr()).sum::<f64>().sqrt(),
            },
        };

        self.state_history.push_back(snapshot);
        Ok(())
    }

    /// Sample state for large quantum systems
    fn sample_state(&self, state: &[Complex64]) -> Result<Vec<Complex64>, QuantRS2Error> {
        let sample_size = (state.len() as f64 * self.config.sampling_rate).ceil() as usize;
        let step = state.len() / sample_size;

        Ok(state.iter().step_by(step.max(1)).copied().collect())
    }

    /// Get previous state from history
    fn get_previous_state(&self) -> Vec<Complex64> {
        self.state_history
            .back()
            .map(|snapshot| snapshot.state.clone())
            .unwrap_or_default()
    }

    /// Analyze entanglement in the quantum state
    fn analyze_entanglement(
        &self,
        state: &[Complex64],
        num_qubits: usize,
    ) -> Result<EntanglementAnalysis, QuantRS2Error> {
        let total_entanglement = self.calculate_total_entanglement(state)?;
        let pairwise_entanglement = self.calculate_pairwise_entanglement(state, num_qubits)?;
        let entanglement_spectrum = self.calculate_entanglement_spectrum(state, num_qubits)?;
        let max_entangled_pair = self.find_max_entangled_pair(&pairwise_entanglement);

        Ok(EntanglementAnalysis {
            total_entanglement,
            pairwise_entanglement,
            entanglement_spectrum,
            max_entangled_pair,
        })
    }

    /// Calculate total entanglement (simplified von Neumann entropy)
    fn calculate_total_entanglement(&self, state: &[Complex64]) -> Result<f64, QuantRS2Error> {
        // Simplified calculation - in practice, this would use reduced density matrices
        let probabilities: Vec<f64> = state.iter().map(|c| c.norm_sqr()).collect();
        let entropy = -probabilities
            .iter()
            .filter(|&&p| p > 1e-15)
            .map(|&p| p * p.log2())
            .sum::<f64>();
        Ok(entropy)
    }

    /// Calculate pairwise entanglement between qubits
    fn calculate_pairwise_entanglement(
        &self,
        state: &[Complex64],
        num_qubits: usize,
    ) -> Result<HashMap<(usize, usize), f64>, QuantRS2Error> {
        let mut pairwise = HashMap::new();

        // Simplified pairwise entanglement calculation
        for i in 0..num_qubits {
            for j in (i + 1)..num_qubits {
                let entanglement =
                    self.calculate_bipartite_entanglement(state, i, j, num_qubits)?;
                pairwise.insert((i, j), entanglement);
            }
        }

        Ok(pairwise)
    }

    /// Calculate bipartite entanglement between two qubits
    fn calculate_bipartite_entanglement(
        &self,
        state: &[Complex64],
        qubit1: usize,
        qubit2: usize,
        num_qubits: usize,
    ) -> Result<f64, QuantRS2Error> {
        // Simplified calculation - would use partial trace in practice
        let mut correlation = 0.0;

        for i in 0..(1 << num_qubits) {
            let bit1 = (i >> qubit1) & 1;
            let bit2 = (i >> qubit2) & 1;

            if bit1 == bit2 {
                correlation += state[i].norm_sqr();
            } else {
                correlation -= state[i].norm_sqr();
            }
        }

        Ok(correlation.abs())
    }

    /// Calculate entanglement spectrum
    fn calculate_entanglement_spectrum(
        &self,
        state: &[Complex64],
        _num_qubits: usize,
    ) -> Result<Vec<f64>, QuantRS2Error> {
        // Simplified entanglement spectrum
        let mut spectrum: Vec<f64> = state.iter().map(|c| c.norm_sqr()).collect();
        spectrum.sort_by(|a, b| b.partial_cmp(a).unwrap_or(std::cmp::Ordering::Equal));
        Ok(spectrum)
    }

    /// Find the pair of qubits with maximum entanglement
    fn find_max_entangled_pair(
        &self,
        pairwise: &HashMap<(usize, usize), f64>,
    ) -> Option<(usize, usize)> {
        pairwise
            .iter()
            .max_by(|(_, v1), (_, v2)| v1.partial_cmp(v2).unwrap_or(std::cmp::Ordering::Equal))
            .map(|(pair, _)| *pair)
    }

    /// Analyze amplitude distribution
    fn analyze_amplitudes(&self, state: &[Complex64]) -> Result<AmplitudeAnalysis, QuantRS2Error> {
        let amplitudes: Vec<f64> = state.iter().map(|c| c.norm()).collect();
        let phases: Vec<f64> = state.iter().map(|c| c.arg()).collect();

        let max_amplitude_index = amplitudes
            .iter()
            .enumerate()
            .max_by(|(_, a), (_, b)| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal))
            .map_or(0, |(i, _)| i);

        let mean_amplitude = amplitudes.iter().sum::<f64>() / amplitudes.len() as f64;
        let amplitude_variance = amplitudes
            .iter()
            .map(|a| (a - mean_amplitude).powi(2))
            .sum::<f64>()
            / amplitudes.len() as f64;

        let significant_states = self.find_significant_states(&amplitudes);

        Ok(AmplitudeAnalysis {
            amplitudes,
            phases,
            max_amplitude_index,
            mean_amplitude,
            amplitude_variance,
            significant_states,
        })
    }

    /// Find states with significant amplitudes
    fn find_significant_states(&self, amplitudes: &[f64]) -> Vec<usize> {
        let threshold = 0.1; // 10% threshold
        amplitudes
            .iter()
            .enumerate()
            .filter(|(_, &amp)| amp > threshold)
            .map(|(i, _)| i)
            .collect()
    }

    /// Get qubit amplitude (simplified)
    fn get_qubit_amplitude(&self, state: &[Complex64], qubit: usize) -> Option<Complex64> {
        // Simplified - would calculate reduced amplitude in practice
        if qubit < 64 && (1 << qubit) < state.len() {
            Some(state[1 << qubit])
        } else {
            None
        }
    }

    /// Calculate von Neumann entropy
    fn calculate_von_neumann_entropy(&self, state: &[Complex64]) -> Result<f64, QuantRS2Error> {
        let probabilities: Vec<f64> = state.iter().map(|c| c.norm_sqr()).collect();
        let entropy = -probabilities
            .iter()
            .filter(|&&p| p > 1e-15)
            .map(|&p| p * p.log2())
            .sum::<f64>();
        Ok(entropy)
    }

    /// Calculate state purity
    fn calculate_purity(&self, state: &[Complex64]) -> Result<f64, QuantRS2Error> {
        let purity = state.iter().map(|c| c.norm_sqr().powi(2)).sum::<f64>();
        Ok(purity)
    }

    /// Generate comprehensive analysis with SciRS2 enhanced metrics
    fn generate_analysis(&self, _num_qubits: usize) -> Result<DebugAnalysis, QuantRS2Error> {
        Ok(DebugAnalysis {
            gate_statistics: self.gate_statistics.clone(),
            execution_summary: ExecutionSummary {
                total_steps: self.execution_trace.len(),
                total_gates: self.gate_statistics.total_gates(),
                circuit_depth: self.calculate_circuit_depth(),
                execution_time: self.performance_metrics.total_execution_time.as_secs_f64(),
            },
            performance_metrics: self.calculate_enhanced_performance_metrics()?,
            recommendations: self.generate_enhanced_recommendations()?,
        })
    }

    /// Calculate circuit depth
    fn calculate_circuit_depth(&self) -> usize {
        // Simplified depth calculation
        self.execution_trace.len()
    }

    /// Estimate execution time
    fn estimate_execution_time(&self) -> f64 {
        // Simplified time estimation (microseconds)
        self.execution_trace.len() as f64 * 0.1
    }

    /// Calculate enhanced performance metrics with SciRS2 features
    fn calculate_enhanced_performance_metrics(&self) -> Result<PerformanceMetrics, QuantRS2Error> {
        Ok(PerformanceMetrics {
            average_gate_fidelity: self.calculate_average_fidelity(),
            entanglement_efficiency: self.calculate_entanglement_efficiency(),
            state_overlap_preservation: self.calculate_state_overlap_preservation(),
        })
    }

    /// Legacy performance metrics calculation (kept for compatibility)
    fn calculate_performance_metrics(&self) -> Result<PerformanceMetrics, QuantRS2Error> {
        self.calculate_enhanced_performance_metrics()
    }

    /// Calculate average gate fidelity
    fn calculate_average_fidelity(&self) -> f64 {
        if self.execution_trace.is_empty() {
            return 1.0;
        }

        let total_fidelity: f64 = self
            .execution_trace
            .iter()
            .map(|step| step.gate_effect.fidelity)
            .sum();

        total_fidelity / self.execution_trace.len() as f64
    }

    /// Calculate entanglement efficiency
    const fn calculate_entanglement_efficiency(&self) -> f64 {
        // Simplified calculation
        0.85 // Placeholder
    }

    /// Calculate state overlap preservation
    const fn calculate_state_overlap_preservation(&self) -> f64 {
        // Simplified calculation
        0.92 // Placeholder
    }

    /// Generate enhanced optimization recommendations using SciRS2 analysis
    fn generate_enhanced_recommendations(&self) -> Result<Vec<String>, QuantRS2Error> {
        let mut recommendations = Vec::new();

        // Standard recommendations
        if self.gate_statistics.two_qubit_gate_ratio() > 0.5 {
            recommendations
                .push("Consider reducing two-qubit gates to improve fidelity".to_string());
        }

        if self.calculate_circuit_depth() > 100 {
            recommendations.push("Circuit depth is high - consider parallelization".to_string());
        }

        // SciRS2-enhanced recommendations based on performance metrics
        if self.performance_metrics.simd_operations_count > 0 {
            recommendations
                .push("SIMD operations detected - good use of vectorization".to_string());
        } else {
            recommendations
                .push("Consider enabling SIMD operations for better performance".to_string());
        }

        if self.performance_metrics.parallel_operations_count > 0 {
            recommendations
                .push("Parallel operations used - optimal for multi-core systems".to_string());
        }

        // Memory usage analysis
        if let Some(max_memory) = self.performance_metrics.memory_usage.iter().max() {
            if *max_memory > 1024 * 1024 * 100 {
                // > 100MB
                recommendations.push(
                    "High memory usage detected - consider SciRS2 memory optimization".to_string(),
                );
            }
        }

        // Performance-based recommendations
        let avg_gate_time = self.performance_metrics.total_execution_time.as_nanos() as f64
            / (self.execution_trace.len() as f64 + 1.0);
        if avg_gate_time > 1000.0 {
            // > 1μs per gate
            recommendations.push("Gate execution time is high - consider optimization".to_string());
        }

        recommendations.push("Apply error mitigation techniques".to_string());
        recommendations.push("Use SciRS2 advanced quantum state management".to_string());

        Ok(recommendations)
    }

    /// Legacy recommendations method (kept for compatibility)
    fn generate_recommendations(&self) -> Result<Vec<String>, QuantRS2Error> {
        self.generate_enhanced_recommendations()
    }
}

/// Debug step information
#[derive(Debug, Clone)]
pub struct DebugStep {
    pub step: usize,
    pub gate: QuantumGate,
    pub gate_effect: GateEffect,
    pub state_before: Option<Vec<Complex64>>,
    pub state_after: Option<Vec<Complex64>>,
    pub entanglement_info: Option<EntanglementAnalysis>,
    pub amplitude_analysis: Option<AmplitudeAnalysis>,
}

/// Gate effect information
#[derive(Debug, Clone)]
pub struct GateEffect {
    pub gate_type: String,
    pub target_qubits: Vec<usize>,
    pub amplitude_changes: Vec<f64>,
    pub phase_changes: Vec<f64>,
    pub entanglement_change: f64,
    pub fidelity: f64,
}

/// Breakpoint configuration
#[derive(Debug, Clone)]
pub struct Breakpoint {
    pub step: usize,
    pub condition: BreakpointCondition,
    pub enabled: bool,
}

/// Breakpoint conditions
#[derive(Debug, Clone)]
pub enum BreakpointCondition {
    Always,
    StateCondition(StateCondition),
    GateType(GateType),
    QubitIndex(usize),
}

/// State-based breakpoint conditions
#[derive(Debug, Clone)]
pub enum StateCondition {
    AmplitudeThreshold {
        qubit: usize,
        threshold: f64,
    },
    EntanglementThreshold {
        threshold: f64,
    },
    PhaseDifference {
        qubit1: usize,
        qubit2: usize,
        threshold: f64,
    },
}

/// State snapshot for debugging
#[derive(Debug, Clone)]
pub struct StateSnapshot {
    pub step: usize,
    pub gate_index: Option<usize>,
    pub state: Vec<Complex64>,
    pub metadata: StateMetadata,
}

/// State metadata
#[derive(Debug, Clone)]
pub struct StateMetadata {
    pub entropy: f64,
    pub purity: f64,
    pub norm: f64,
}

/// Entanglement analysis results
#[derive(Debug, Clone)]
pub struct EntanglementAnalysis {
    pub total_entanglement: f64,
    pub pairwise_entanglement: HashMap<(usize, usize), f64>,
    pub entanglement_spectrum: Vec<f64>,
    pub max_entangled_pair: Option<(usize, usize)>,
}

/// Amplitude analysis results
#[derive(Debug, Clone)]
pub struct AmplitudeAnalysis {
    pub amplitudes: Vec<f64>,
    pub phases: Vec<f64>,
    pub max_amplitude_index: usize,
    pub mean_amplitude: f64,
    pub amplitude_variance: f64,
    pub significant_states: Vec<usize>,
}

/// Gate statistics tracking
#[derive(Debug, Clone)]
pub struct GateStatistics {
    gate_counts: HashMap<String, usize>,
    total_count: usize,
}

impl GateStatistics {
    pub fn new() -> Self {
        Self {
            gate_counts: HashMap::new(),
            total_count: 0,
        }
    }

    pub fn record_gate(&mut self, gate: &QuantumGate) {
        let gate_type = format!("{:?}", gate.gate_type());
        *self.gate_counts.entry(gate_type).or_insert(0) += 1;
        self.total_count += 1;
    }

    pub const fn total_gates(&self) -> usize {
        self.total_count
    }

    pub fn two_qubit_gate_ratio(&self) -> f64 {
        let two_qubit_gates =
            *self.gate_counts.get("CNOT").unwrap_or(&0) + *self.gate_counts.get("CZ").unwrap_or(&0);
        if self.total_count > 0 {
            two_qubit_gates as f64 / self.total_count as f64
        } else {
            0.0
        }
    }
}

/// Debug result
#[derive(Debug, Clone)]
pub struct DebugResult {
    pub status: DebugStatus,
    pub final_state: Vec<Complex64>,
    pub execution_trace: Vec<DebugStep>,
    pub analysis: DebugAnalysis,
}

/// Debug status
#[derive(Debug, Clone)]
pub enum DebugStatus {
    Completed,
    BreakpointHit(usize),
    Error(String),
}

/// Debug analysis results
#[derive(Debug, Clone)]
pub struct DebugAnalysis {
    pub gate_statistics: GateStatistics,
    pub execution_summary: ExecutionSummary,
    pub performance_metrics: PerformanceMetrics,
    pub recommendations: Vec<String>,
}

/// Execution summary
#[derive(Debug, Clone)]
pub struct ExecutionSummary {
    pub total_steps: usize,
    pub total_gates: usize,
    pub circuit_depth: usize,
    pub execution_time: f64,
}

/// Performance metrics
#[derive(Debug, Clone)]
pub struct PerformanceMetrics {
    pub average_gate_fidelity: f64,
    pub entanglement_efficiency: f64,
    pub state_overlap_preservation: f64,
}

#[cfg(test)]
mod tests {
    use super::*;
    use super::{GateType, QuantumGate};

    #[test]
    fn test_debugger_creation() {
        let debugger = QuantumDebugger::new();
        assert!(debugger.config.track_state_vectors);
    }

    #[test]
    fn test_breakpoint_setting() {
        let mut debugger = QuantumDebugger::new();
        debugger.set_breakpoint(5, BreakpointCondition::Always);
        assert_eq!(debugger.breakpoints.len(), 1);
        assert_eq!(debugger.breakpoints[0].step, 5);
    }

    #[test]
    fn test_gate_statistics() {
        let mut stats = GateStatistics::new();
        let gate = QuantumGate::new(GateType::H, vec![0], None);
        stats.record_gate(&gate);
        assert_eq!(stats.total_gates(), 1);
    }

    #[test]
    fn test_simple_circuit_debugging() {
        let mut debugger = QuantumDebugger::new();
        let circuit = vec![QuantumGate::new(GateType::H, vec![0], None)];

        let initial_state = vec![Complex64::new(1.0, 0.0), Complex64::new(0.0, 0.0)];

        let result = debugger
            .debug_circuit(&circuit, &initial_state, 1)
            .expect("debug_circuit should succeed with valid input");
        assert!(matches!(result.status, DebugStatus::Completed));
        assert_eq!(result.execution_trace.len(), 1);
    }

    #[test]
    fn test_amplitude_analysis() {
        let debugger = QuantumDebugger::new();
        let state = vec![
            Complex64::new(std::f64::consts::FRAC_1_SQRT_2, 0.0),
            Complex64::new(std::f64::consts::FRAC_1_SQRT_2, 0.0),
        ];

        let analysis = debugger
            .analyze_amplitudes(&state)
            .expect("analyze_amplitudes should succeed with valid state");
        assert_eq!(analysis.amplitudes.len(), 2);
        assert!((analysis.mean_amplitude - std::f64::consts::FRAC_1_SQRT_2).abs() < 1e-4);
    }
}