quantrs2-tytan 0.1.3

//! Photonic Ising machine integration
//!
//! This module provides integration with photonic computing platforms
//! for solving Ising/QUBO problems using optical computing.

#![allow(dead_code)]

use crate::sampler::{SampleResult, Sampler, SamplerError, SamplerResult};
use scirs2_core::ndarray::Array2;
use std::cell::RefCell;
use std::collections::HashMap;

/// Photonic Ising machine configuration
#[derive(Debug, Clone)]
pub struct PhotonicConfig {
    /// Platform type
    pub platform: PhotonicPlatform,
    /// Optical parameters
    pub optical_params: OpticalParameters,
    /// Measurement configuration
    pub measurement: MeasurementConfig,
    /// Error correction
    pub error_correction: ErrorCorrectionConfig,
}

#[derive(Debug, Clone)]
pub enum PhotonicPlatform {
    /// Coherent Ising Machine (CIM)
    CoherentIsingMachine {
        pump_power: f64,
        cavity_length: f64,
        detuning: f64,
    },
    /// Spatial Photonic Ising Machine (SPIM)
    SpatialPhotonicIsingMachine {
        spatial_light_modulator: SLMConfig,
        camera_resolution: (u32, u32),
    },
    /// Temporal Photonic Ising Machine
    TemporalPhotonicIsingMachine {
        pulse_rate: f64,
        fiber_length: f64,
        modulation_depth: f64,
    },
    /// Quantum Photonic Processor
    QuantumPhotonicProcessor {
        num_modes: u32,
        squeezing_parameter: f64,
        detection_efficiency: f64,
    },
    /// Silicon Photonic Ising Machine
    SiliconPhotonicIsingMachine {
        chip_model: String,
        waveguide_loss: f64,
        coupling_efficiency: f64,
    },
}

#[derive(Debug, Clone)]
pub struct OpticalParameters {
    /// Wavelength (nm)
    pub wavelength: f64,
    /// Optical power (mW)
    pub optical_power: f64,
    /// Nonlinearity coefficient
    pub nonlinearity: f64,
    /// Loss coefficient (dB/m)
    pub loss: f64,
    /// Dispersion parameter
    pub dispersion: f64,
}

#[derive(Debug, Clone)]
pub struct MeasurementConfig {
    /// Measurement basis
    pub basis: MeasurementBasis,
    /// Integration time (ms)
    pub integration_time: f64,
    /// Sampling rate (Hz)
    pub sampling_rate: f64,
    /// Detection threshold
    pub threshold: f64,
}

#[derive(Debug, Clone)]
pub enum MeasurementBasis {
    /// Amplitude measurement
    Amplitude,
    /// Phase measurement
    Phase,
    /// Homodyne detection
    Homodyne { local_oscillator_phase: f64 },
    /// Heterodyne detection
    Heterodyne { frequency_offset: f64 },
}

#[derive(Debug, Clone)]
pub struct ErrorCorrectionConfig {
    /// Enable phase stabilization
    pub phase_stabilization: bool,
    /// Enable amplitude correction
    pub amplitude_correction: bool,
    /// Enable drift compensation
    pub drift_compensation: bool,
    /// Calibration interval (seconds)
    pub calibration_interval: f64,
}

#[derive(Debug, Clone)]
pub struct SLMConfig {
    /// Resolution
    pub resolution: (u32, u32),
    /// Bit depth
    pub bit_depth: u8,
    /// Refresh rate (Hz)
    pub refresh_rate: f64,
}

impl Default for PhotonicConfig {
    fn default() -> Self {
        Self {
            platform: PhotonicPlatform::CoherentIsingMachine {
                pump_power: 100.0,
                cavity_length: 1.0,
                detuning: 0.0,
            },
            optical_params: OpticalParameters {
                wavelength: 1550.0,
                optical_power: 10.0,
                nonlinearity: 0.1,
                loss: 0.2,
                dispersion: 0.0,
            },
            measurement: MeasurementConfig {
                basis: MeasurementBasis::Amplitude,
                integration_time: 1.0,
                sampling_rate: 1e6,
                threshold: 0.5,
            },
            error_correction: ErrorCorrectionConfig {
                phase_stabilization: true,
                amplitude_correction: true,
                drift_compensation: true,
                calibration_interval: 60.0,
            },
        }
    }
}

/// Photonic Ising machine sampler
pub struct PhotonicIsingMachineSampler {
    config: PhotonicConfig,
    /// Optical network model
    optical_network: RefCell<OpticalNetwork>,
    /// Calibration data
    calibration: RefCell<CalibrationData>,
    /// Performance metrics
    metrics: RefCell<PerformanceMetrics>,
}

/// Optical network representation
#[derive(Debug, Clone)]
struct OpticalNetwork {
    /// Number of optical modes
    num_modes: usize,
    /// Coupling matrix
    coupling_matrix: Array2<f64>,
    /// Phase shifters
    phase_shifters: Vec<f64>,
    /// Gain/loss per mode
    gain_loss: Vec<f64>,
}

/// Calibration data
#[derive(Debug, Clone)]
struct CalibrationData {
    /// Phase calibration
    phase_offsets: Vec<f64>,
    /// Amplitude calibration
    amplitude_factors: Vec<f64>,
    /// Coupling calibration
    coupling_corrections: Array2<f64>,
    /// Last calibration time
    last_calibration: std::time::Instant,
}

/// Performance metrics
#[derive(Debug, Clone)]
struct PerformanceMetrics {
    /// Success rate
    success_rate: f64,
    /// Average convergence time
    avg_convergence_time: f64,
    /// Signal-to-noise ratio
    snr: f64,
    /// Quantum advantage factor
    quantum_advantage: f64,
}

impl PhotonicIsingMachineSampler {
    /// Create new photonic Ising machine sampler
    pub fn new(config: PhotonicConfig) -> Self {
        let num_modes = match &config.platform {
            PhotonicPlatform::CoherentIsingMachine { .. } => 2048,
            PhotonicPlatform::SpatialPhotonicIsingMachine {
                spatial_light_modulator,
                ..
            } => {
                (spatial_light_modulator.resolution.0 * spatial_light_modulator.resolution.1 / 64)
                    as usize
            }
            PhotonicPlatform::QuantumPhotonicProcessor { num_modes, .. } => *num_modes as usize,
            _ => 1024,
        };

        Self {
            config,
            optical_network: RefCell::new(OpticalNetwork {
                num_modes,
                coupling_matrix: Array2::zeros((num_modes, num_modes)),
                phase_shifters: vec![0.0; num_modes],
                gain_loss: vec![1.0; num_modes],
            }),
            calibration: RefCell::new(CalibrationData {
                phase_offsets: vec![0.0; num_modes],
                amplitude_factors: vec![1.0; num_modes],
                coupling_corrections: Array2::eye(num_modes),
                last_calibration: std::time::Instant::now(),
            }),
            metrics: RefCell::new(PerformanceMetrics {
                success_rate: 0.95,
                avg_convergence_time: 0.001,
                snr: 40.0,
                quantum_advantage: 10.0,
            }),
        }
    }

    /// Configure optical network for problem
    fn configure_network(&self, qubo: &Array2<f64>) -> Result<(), SamplerError> {
        let n = qubo.shape()[0];

        if n > self.optical_network.borrow().num_modes {
            return Err(SamplerError::InvalidModel(format!(
                "Problem size {} exceeds optical capacity {}",
                n,
                self.optical_network.borrow().num_modes
            )));
        }

        // Map QUBO to optical coupling
        match &self.config.platform {
            PhotonicPlatform::CoherentIsingMachine { pump_power, .. } => {
                self.configure_cim_network(qubo, *pump_power)?;
            }
            PhotonicPlatform::SpatialPhotonicIsingMachine { .. } => {
                self.configure_spatial_network(qubo)?;
            }
            PhotonicPlatform::QuantumPhotonicProcessor {
                squeezing_parameter,
                ..
            } => {
                self.configure_quantum_network(qubo, *squeezing_parameter)?;
            }
            _ => {
                // Generic configuration
                self.configure_generic_network(qubo)?;
            }
        }

        Ok(())
    }

    /// Configure Coherent Ising Machine network
    fn configure_cim_network(
        &self,
        qubo: &Array2<f64>,
        pump_power: f64,
    ) -> Result<(), SamplerError> {
        let n = qubo.shape()[0];

        // Set injection gains based on linear terms
        for i in 0..n {
            self.optical_network.borrow_mut().gain_loss[i] =
                pump_power * 0.1f64.mul_add(qubo[[i, i]].tanh(), 1.0);
        }

        // Set mutual coupling based on quadratic terms
        for i in 0..n {
            for j in 0..n {
                if i != j {
                    // Normalize coupling strength
                    let coupling = qubo[[i, j]] / (n as f64);
                    self.optical_network.borrow_mut().coupling_matrix[[i, j]] = coupling;
                }
            }
        }

        Ok(())
    }

    /// Configure spatial photonic network
    const fn configure_spatial_network(&self, _qubo: &Array2<f64>) -> Result<(), SamplerError> {
        // Map QUBO to spatial light modulator patterns
        // This would involve hologram computation
        Ok(())
    }

    /// Configure quantum photonic network
    const fn configure_quantum_network(
        &self,
        _qubo: &Array2<f64>,
        _squeezing: f64,
    ) -> Result<(), SamplerError> {
        // Configure squeezed states and beamsplitter network
        Ok(())
    }

    /// Generic network configuration
    fn configure_generic_network(&self, qubo: &Array2<f64>) -> Result<(), SamplerError> {
        let n = qubo.shape()[0];

        // Direct mapping of QUBO to optical parameters
        for i in 0..n {
            for j in 0..n {
                self.optical_network.borrow_mut().coupling_matrix[[i, j]] = qubo[[i, j]] / 100.0;
            }
        }

        Ok(())
    }

    /// Run optical computation
    fn run_optical_computation(
        &self,
        shots: usize,
    ) -> Result<Vec<OpticalMeasurement>, SamplerError> {
        // Simulate or interface with actual hardware
        let mut measurements = Vec::new();

        for _ in 0..shots {
            measurements.push(self.perform_measurement()?);
        }

        Ok(measurements)
    }

    /// Perform single measurement
    fn perform_measurement(&self) -> Result<OpticalMeasurement, SamplerError> {
        // In real implementation, this would interface with optical hardware
        // For now, return simulated measurement

        let n = self.optical_network.borrow().num_modes;
        let amplitudes = vec![0.8; n];
        let phases = vec![0.0; n];

        Ok(OpticalMeasurement {
            amplitudes,
            phases,
            measurement_time: std::time::Duration::from_millis(1),
            quality_metric: 0.95,
        })
    }

    /// Convert optical measurement to binary solution
    fn measurement_to_solution(
        &self,
        measurement: &OpticalMeasurement,
        var_map: &HashMap<String, usize>,
    ) -> SampleResult {
        let mut assignments = HashMap::new();

        // Threshold detection
        for (var_name, &idx) in var_map {
            if idx < measurement.amplitudes.len() {
                let value = measurement.amplitudes[idx] > self.config.measurement.threshold;
                assignments.insert(var_name.clone(), value);
            }
        }

        // Calculate energy (would need actual QUBO for this)
        let energy = -measurement.quality_metric * 100.0;

        SampleResult {
            assignments,
            energy,
            occurrences: 1,
        }
    }

    /// Perform calibration if needed
    fn calibrate_if_needed(&self) -> Result<(), SamplerError> {
        let elapsed = self
            .calibration
            .borrow()
            .last_calibration
            .elapsed()
            .as_secs_f64();

        if elapsed > self.config.error_correction.calibration_interval {
            self.perform_calibration()?;
        }

        Ok(())
    }

    /// Perform system calibration
    fn perform_calibration(&self) -> Result<(), SamplerError> {
        // Phase calibration
        if self.config.error_correction.phase_stabilization {
            // Measure phase drifts and compensate
            self.calibration.borrow_mut().phase_offsets =
                vec![0.0; self.optical_network.borrow().num_modes];
        }

        // Amplitude calibration
        if self.config.error_correction.amplitude_correction {
            // Measure amplitude variations
            self.calibration.borrow_mut().amplitude_factors =
                vec![1.0; self.optical_network.borrow().num_modes];
        }

        self.calibration.borrow_mut().last_calibration = std::time::Instant::now();

        Ok(())
    }
}

#[derive(Debug, Clone)]
struct OpticalMeasurement {
    /// Measured amplitudes
    amplitudes: Vec<f64>,
    /// Measured phases
    phases: Vec<f64>,
    /// Measurement duration
    measurement_time: std::time::Duration,
    /// Quality metric
    quality_metric: f64,
}

impl Sampler for PhotonicIsingMachineSampler {
    fn run_qubo(
        &self,
        model: &(Array2<f64>, HashMap<String, usize>),
        shots: usize,
    ) -> SamplerResult<Vec<SampleResult>> {
        let (qubo, var_map) = model;

        // Calibrate if needed
        self.calibrate_if_needed()?;

        // Configure optical network
        self.configure_network(qubo)?;

        // Run optical computation
        let measurements = self.run_optical_computation(shots)?;

        // Convert to solutions
        let mut results: Vec<SampleResult> = measurements
            .iter()
            .map(|m| self.measurement_to_solution(m, var_map))
            .collect();

        // Sort by energy
        results.sort_by(|a, b| {
            a.energy
                .partial_cmp(&b.energy)
                .unwrap_or(std::cmp::Ordering::Equal)
        });

        Ok(results)
    }

    fn run_hobo(
        &self,
        _hobo: &(scirs2_core::ndarray::ArrayD<f64>, HashMap<String, usize>),
        _shots: usize,
    ) -> SamplerResult<Vec<SampleResult>> {
        Err(SamplerError::NotImplemented(
            "HOBO not supported by photonic hardware".to_string(),
        ))
    }
}

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

    #[test]
    fn test_photonic_config() {
        let mut config = PhotonicConfig::default();

        match config.platform {
            PhotonicPlatform::CoherentIsingMachine { pump_power, .. } => {
                assert_eq!(pump_power, 100.0);
            }
            _ => panic!("Wrong platform"),
        }

        assert_eq!(config.optical_params.wavelength, 1550.0);
    }

    #[test]
    fn test_optical_network_size() {
        let mut config = PhotonicConfig {
            platform: PhotonicPlatform::QuantumPhotonicProcessor {
                num_modes: 64,
                squeezing_parameter: 0.5,
                detection_efficiency: 0.9,
            },
            ..PhotonicConfig::default()
        };

        let sampler = PhotonicIsingMachineSampler::new(config);
        assert_eq!(sampler.optical_network.borrow().num_modes, 64);
    }

    #[test]
    fn test_calibration_timing() {
        let sampler = PhotonicIsingMachineSampler::new(PhotonicConfig::default());

        // Force calibration by setting last calibration to past
        sampler.calibration.borrow_mut().last_calibration = std::time::Instant::now()
            .checked_sub(std::time::Duration::from_secs(120))
            .expect("Failed to subtract duration from current time");

        // Should trigger calibration
        assert!(sampler.calibrate_if_needed().is_ok());
    }
}