//! Quantum Computing Core Components
//!
//! This module implements the quantum computing foundations for the consciousness
//! processing system, including quantum entanglement networks, coherence mechanisms,
//! and quantum state management.

use scirs2_core::ndarray::{Array1, Array2, Array3, ArrayView2};
use scirs2_core::numeric::Complex;
use scirs2_core::numeric::{Float, FromPrimitive};
use std::collections::{HashMap, VecDeque};

use super::config::{QuantumAIConsciousnessConfig, QuantumAIConsciousnessState};
use crate::error::{NdimageError, NdimageResult};

/// Quantum Entanglement Network
#[derive(Debug, Clone)]
pub struct QuantumEntanglementNetwork {
    /// Quantum channels connecting different components
    pub channels: Vec<QuantumChannel>,
    /// Network coherence state
    pub network_coherence: Array2<Complex<f64>>,
    /// Entanglement strength matrix
    pub entanglement_matrix: Array2<f64>,
    /// Quantum synchronization level
    pub synchronization_level: f64,
    /// Active entanglement pairs
    pub active_pairs: Vec<(usize, usize)>,
}

impl QuantumEntanglementNetwork {
    pub fn new() -> Self {
        Self {
            channels: Vec::new(),
            network_coherence: Array2::zeros((10, 10)),
            entanglement_matrix: Array2::zeros((10, 10)),
            synchronization_level: 0.0,
            active_pairs: Vec::new(),
        }
    }

    /// Initialize the quantum entanglement network
    pub fn initialize(&mut self, config: &QuantumAIConsciousnessConfig) -> NdimageResult<()> {
        let network_size = config.consciousness_depth;

        // Initialize network structures
        self.network_coherence = Array2::zeros((network_size, network_size));
        self.entanglement_matrix = Array2::zeros((network_size, network_size));

        // Create quantum channels
        for i in 0..network_size {
            for j in i + 1..network_size {
                let channel = QuantumChannel {
                    id: format!("channel_{}_{}", i, j),
                    source_node: i,
                    target_node: j,
                    entanglement_strength: config.quantum_entanglement_strength,
                    coherence_time: config.quantum_coherence_time,
                    quantum_state: Array1::zeros(4), // Bell state representation
                    decoherence_rate: 0.01,
                    measurement_basis: Array2::eye(2),
                };
                self.channels.push(channel);
            }
        }

        // Initialize entanglement matrix
        for channel in &self.channels {
            self.entanglement_matrix[[channel.source_node, channel.target_node]] =
                channel.entanglement_strength;
            self.entanglement_matrix[[channel.target_node, channel.source_node]] =
                channel.entanglement_strength;
        }

        Ok(())
    }

    /// Update quantum entanglement state
    pub fn update_entanglement(&mut self, time_step: f64) -> NdimageResult<()> {
        for i in 0..self.channels.len() {
            // Apply decoherence
            self.channels[i].entanglement_strength *=
                (1.0 - self.channels[i].decoherence_rate * time_step);

            // Update quantum state evolution
            self.evolve_quantum_state_by_index(i, time_step)?;
        }

        // Update synchronization level
        self.synchronization_level = self.calculate_network_synchronization()?;

        Ok(())
    }

    /// Evolve quantum state using Schrödinger equation
    fn evolve_quantum_state(
        &mut self,
        channel: &mut QuantumChannel,
        time_step: f64,
    ) -> NdimageResult<()> {
        // Simplified quantum state evolution
        // In practice, this would solve the time-dependent Schrödinger equation

        let hamiltonian = self.construct_hamiltonian(channel)?;
        let evolution_operator = self.compute_evolution_operator(&hamiltonian, time_step)?;

        // Apply evolution operator to quantum state
        for i in 0..channel.quantum_state.len() {
            let old_amplitude = channel.quantum_state[i];
            channel.quantum_state[i] = old_amplitude * evolution_operator[(i, i % 2)];
        }

        // Normalize quantum state
        let norm = channel
            .quantum_state
            .iter()
            .map(|x| x * x)
            .sum::<f64>()
            .sqrt();
        if norm > 1e-10 {
            for amplitude in channel.quantum_state.iter_mut() {
                *amplitude /= norm;
            }
        }

        Ok(())
    }

    /// Update quantum state evolution by index to avoid borrow checker issues
    fn evolve_quantum_state_by_index(
        &mut self,
        channel_index: usize,
        time_step: f64,
    ) -> NdimageResult<()> {
        let hamiltonian = self.construct_hamiltonian(&self.channels[channel_index])?;
        let evolution_operator = self.compute_evolution_operator(&hamiltonian, time_step)?;

        // Apply evolution operator to quantum state
        for i in 0..self.channels[channel_index].quantum_state.len() {
            let old_amplitude = self.channels[channel_index].quantum_state[i];
            self.channels[channel_index].quantum_state[i] =
                old_amplitude * evolution_operator[(i, i % 2)];
        }

        // Normalize quantum state
        let norm = self.channels[channel_index]
            .quantum_state
            .iter()
            .map(|c| c * c)
            .sum::<f64>()
            .sqrt();

        if norm > 0.0 {
            for amplitude in &mut self.channels[channel_index].quantum_state {
                *amplitude /= norm;
            }
        }

        Ok(())
    }

    /// Construct Hamiltonian for quantum evolution
    fn construct_hamiltonian(&self, channel: &QuantumChannel) -> NdimageResult<Array2<f64>> {
        let mut hamiltonian = Array2::zeros((4, 4));

        // Bell state Hamiltonian (simplified)
        hamiltonian[[0, 0]] = channel.entanglement_strength;
        hamiltonian[[1, 1]] = -channel.entanglement_strength;
        hamiltonian[[2, 2]] = -channel.entanglement_strength;
        hamiltonian[[3, 3]] = channel.entanglement_strength;

        // Add coupling terms
        hamiltonian[[0, 3]] = 0.1 * channel.entanglement_strength;
        hamiltonian[[3, 0]] = 0.1 * channel.entanglement_strength;

        Ok(hamiltonian)
    }

    /// Compute evolution operator exp(-iHt)
    fn compute_evolution_operator(
        &self,
        hamiltonian: &Array2<f64>,
        time_step: f64,
    ) -> NdimageResult<Array2<f64>> {
        // Simplified evolution operator computation
        // In practice, would use matrix exponentiation

        let mut evolution = Array2::eye(hamiltonian.nrows());
        for i in 0..hamiltonian.nrows() {
            for j in 0..hamiltonian.ncols() {
                if i == j {
                    evolution[[i, j]] = (hamiltonian[[i, j]] * time_step).cos();
                } else {
                    evolution[[i, j]] = -(hamiltonian[[i, j]] * time_step).sin();
                }
            }
        }

        Ok(evolution)
    }

    /// Calculate network-wide quantum synchronization
    fn calculate_network_synchronization(&self) -> NdimageResult<f64> {
        if self.channels.is_empty() {
            return Ok(0.0);
        }

        let mut total_sync = 0.0;
        let mut count = 0;

        for i in 0..self.channels.len() {
            for j in i + 1..self.channels.len() {
                let sync =
                    self.calculate_channel_synchronization(&self.channels[i], &self.channels[j])?;
                total_sync += sync;
                count += 1;
            }
        }

        Ok(if count > 0 {
            total_sync / count as f64
        } else {
            0.0
        })
    }

    /// Calculate synchronization between two quantum channels
    fn calculate_channel_synchronization(
        &self,
        channel1: &QuantumChannel,
        channel2: &QuantumChannel,
    ) -> NdimageResult<f64> {
        // Calculate quantum state overlap (fidelity)
        let mut overlap = 0.0;

        for i in 0..channel1
            .quantum_state
            .len()
            .min(channel2.quantum_state.len())
        {
            overlap += channel1.quantum_state[i] * channel2.quantum_state[i];
        }

        Ok(overlap.abs())
    }

    /// Measure quantum entanglement (concurrence)
    pub fn measure_entanglement(&self, channel_id: &str) -> NdimageResult<f64> {
        let channel = self
            .channels
            .iter()
            .find(|c| c.id == channel_id)
            .ok_or_else(|| {
                NdimageError::InvalidInput(format!("Channel {} not found", channel_id))
            })?;

        // Calculate concurrence for Bell state
        let rho = self.construct_density_matrix(&channel.quantum_state)?;
        let concurrence = self.calculate_concurrence(&rho)?;

        Ok(concurrence)
    }

    /// Construct density matrix from quantum state
    fn construct_density_matrix(&self, state: &Array1<f64>) -> NdimageResult<Array2<f64>> {
        let n = state.len();
        let mut rho = Array2::zeros((n, n));

        for i in 0..n {
            for j in 0..n {
                rho[[i, j]] = state[i] * state[j];
            }
        }

        Ok(rho)
    }

    /// Calculate concurrence (entanglement measure)
    fn calculate_concurrence(&self, rho: &Array2<f64>) -> NdimageResult<f64> {
        // Simplified concurrence calculation for 2-qubit states
        // In practice, would use proper eigenvalue decomposition

        let trace = rho.diag().sum();
        let purity = rho.iter().map(|x| x * x).sum::<f64>();

        // Approximate concurrence based on purity
        let concurrence = 2.0 * (0.5 - purity / (trace * trace)).max(0.0).sqrt();

        Ok(concurrence)
    }
}

/// Quantum Channel connecting consciousness components
#[derive(Debug, Clone)]
pub struct QuantumChannel {
    /// Channel identifier
    pub id: String,
    /// Source node in the network
    pub source_node: usize,
    /// Target node in the network
    pub target_node: usize,
    /// Current entanglement strength
    pub entanglement_strength: f64,
    /// Quantum coherence time
    pub coherence_time: f64,
    /// Current quantum state
    pub quantum_state: Array1<f64>,
    /// Decoherence rate
    pub decoherence_rate: f64,
    /// Measurement basis
    pub measurement_basis: Array2<f64>,
}

impl QuantumChannel {
    /// Create a new quantum channel
    pub fn new(id: String, source: usize, target: usize, strength: f64) -> Self {
        Self {
            id,
            source_node: source,
            target_node: target,
            entanglement_strength: strength,
            coherence_time: 100.0,
            quantum_state: Array1::from_vec(vec![
                1.0 / 2.0_f64.sqrt(),
                0.0,
                0.0,
                1.0 / 2.0_f64.sqrt(),
            ]), // Bell state |00⟩ + |11⟩
            decoherence_rate: 0.01,
            measurement_basis: Array2::eye(2),
        }
    }

    /// Apply quantum gate operation
    pub fn apply_gate(&mut self, gate: &Array2<f64>, qubit_index: usize) -> NdimageResult<()> {
        if gate.nrows() != 2 || gate.ncols() != 2 {
            return Err(NdimageError::InvalidInput(
                "Gate must be 2x2 matrix".to_string(),
            ));
        }

        if qubit_index >= 2 {
            return Err(NdimageError::InvalidInput(
                "Qubit index must be 0 or 1".to_string(),
            ));
        }

        // Apply single-qubit gate to two-qubit state
        self.apply_single_qubit_gate(gate, qubit_index)?;

        Ok(())
    }

    /// Apply single-qubit gate to two-qubit state
    fn apply_single_qubit_gate(
        &mut self,
        gate: &Array2<f64>,
        qubit_index: usize,
    ) -> NdimageResult<()> {
        let mut new_state = Array1::zeros(4);

        if qubit_index == 0 {
            // Apply gate to first qubit
            new_state[0] =
                gate[[0, 0]] * self.quantum_state[0] + gate[[0, 1]] * self.quantum_state[2];
            new_state[1] =
                gate[[0, 0]] * self.quantum_state[1] + gate[[0, 1]] * self.quantum_state[3];
            new_state[2] =
                gate[[1, 0]] * self.quantum_state[0] + gate[[1, 1]] * self.quantum_state[2];
            new_state[3] =
                gate[[1, 0]] * self.quantum_state[1] + gate[[1, 1]] * self.quantum_state[3];
        } else {
            // Apply gate to second qubit
            new_state[0] =
                gate[[0, 0]] * self.quantum_state[0] + gate[[0, 1]] * self.quantum_state[1];
            new_state[1] =
                gate[[1, 0]] * self.quantum_state[0] + gate[[1, 1]] * self.quantum_state[1];
            new_state[2] =
                gate[[0, 0]] * self.quantum_state[2] + gate[[0, 1]] * self.quantum_state[3];
            new_state[3] =
                gate[[1, 0]] * self.quantum_state[2] + gate[[1, 1]] * self.quantum_state[3];
        }

        self.quantum_state = new_state;
        Ok(())
    }

    /// Measure quantum channel in computational basis
    pub fn measure(&mut self) -> NdimageResult<(usize, f64)> {
        let probabilities = self.quantum_state.iter().map(|x| x * x).collect::<Vec<_>>();

        // Find most probable outcome (simplified measurement)
        let mut max_prob = 0.0;
        let mut outcome = 0;

        for (i, &prob) in probabilities.iter().enumerate() {
            if prob > max_prob {
                max_prob = prob;
                outcome = i;
            }
        }

        // Collapse state to measurement outcome
        self.quantum_state = Array1::zeros(4);
        self.quantum_state[outcome] = 1.0;

        Ok((outcome, max_prob))
    }
}

/// Quantum Coherence Mechanism
#[derive(Debug, Clone)]
pub struct CoherenceMechanism {
    /// Coherence preservation strategies
    pub preservation_strategies: Vec<String>,
    /// Current coherence level
    pub coherence_level: f64,
    /// Decoherence mitigation techniques
    pub mitigation_techniques: HashMap<String, f64>,
    /// Environmental noise model
    pub noise_model: Array2<f64>,
}

impl CoherenceMechanism {
    pub fn new() -> Self {
        let mut mitigation_techniques = HashMap::new();
        mitigation_techniques.insert("dynamical_decoupling".to_string(), 0.8);
        mitigation_techniques.insert("error_correction".to_string(), 0.9);
        mitigation_techniques.insert("decoherence_free_subspace".to_string(), 0.7);

        Self {
            preservation_strategies: vec![
                "Active_Feedback".to_string(),
                "Passive_Protection".to_string(),
                "Quantum_Error_Correction".to_string(),
            ],
            coherence_level: 0.8,
            mitigation_techniques,
            noise_model: Array2::eye(4) * 0.01, // Small noise
        }
    }

    /// Apply coherence preservation
    pub fn preserve_coherence(
        &mut self,
        channel: &mut QuantumChannel,
        time_step: f64,
    ) -> NdimageResult<()> {
        // Apply dynamical decoupling
        self.apply_dynamical_decoupling(channel, time_step)?;

        // Apply error correction if needed
        if self.coherence_level < 0.5 {
            self.apply_quantum_error_correction(channel)?;
        }

        // Update coherence level
        self.update_coherence_level(channel);

        Ok(())
    }

    /// Apply dynamical decoupling sequence
    fn apply_dynamical_decoupling(
        &self,
        channel: &mut QuantumChannel,
        time_step: f64,
    ) -> NdimageResult<()> {
        // Simplified DD: apply π-pulses at regular intervals
        let pulse_interval = time_step / 4.0;

        // Pauli-X gate (π-pulse)
        let pauli_x =
            Array2::from_shape_vec((2, 2), vec![0.0, 1.0, 1.0, 0.0]).expect("Operation failed");

        // Apply pulse to both qubits alternately
        channel.apply_gate(&pauli_x, 0)?;
        channel.apply_gate(&pauli_x, 1)?;

        Ok(())
    }

    /// Apply quantum error correction
    fn apply_quantum_error_correction(&self, channel: &mut QuantumChannel) -> NdimageResult<()> {
        // Simplified error correction: project back to Bell state subspace
        let bell_states = vec![
            Array1::from_vec(vec![1.0 / 2.0_f64.sqrt(), 0.0, 0.0, 1.0 / 2.0_f64.sqrt()]),
            Array1::from_vec(vec![1.0 / 2.0_f64.sqrt(), 0.0, 0.0, -1.0 / 2.0_f64.sqrt()]),
            Array1::from_vec(vec![0.0, 1.0 / 2.0_f64.sqrt(), 1.0 / 2.0_f64.sqrt(), 0.0]),
            Array1::from_vec(vec![0.0, 1.0 / 2.0_f64.sqrt(), -1.0 / 2.0_f64.sqrt(), 0.0]),
        ];

        // Find closest Bell state
        let mut max_overlap = 0.0;
        let mut best_state = 0;

        for (i, bell_state) in bell_states.iter().enumerate() {
            let mut overlap = 0.0;
            for j in 0..4 {
                overlap += channel.quantum_state[j] * bell_state[j];
            }
            overlap = overlap.abs();

            if overlap > max_overlap {
                max_overlap = overlap;
                best_state = i;
            }
        }

        // Project to closest Bell state
        channel.quantum_state = bell_states[best_state].clone();

        Ok(())
    }

    /// Update coherence level based on channel state
    fn update_coherence_level(&mut self, channel: &QuantumChannel) {
        // Calculate purity as coherence measure
        let mut purity = 0.0;
        for amplitude in &channel.quantum_state {
            purity += amplitude.powi(4);
        }

        self.coherence_level = purity.max(0.0).min(1.0);
    }

    /// Get coherence metrics
    pub fn get_coherence_metrics(&self) -> HashMap<String, f64> {
        let mut metrics = HashMap::new();
        metrics.insert("coherence_level".to_string(), self.coherence_level);
        metrics.insert(
            "preservation_efficiency".to_string(),
            self.mitigation_techniques.values().sum::<f64>()
                / self.mitigation_techniques.len() as f64,
        );
        metrics.insert(
            "noise_strength".to_string(),
            self.noise_model.diag().sum() / self.noise_model.nrows() as f64,
        );

        metrics
    }
}

/// Consciousness Synchronization State
#[derive(Debug, Clone)]
pub struct ConsciousnessSynchronizationState {
    /// Global synchronization level
    pub synchronization_level: f64,
    /// Phase coherence across components
    pub phase_coherence: Array1<f64>,
    /// Synchronization patterns
    pub sync_patterns: Vec<SynchronizationPattern>,
    /// Coherence mechanism
    pub coherence_mechanism: CoherenceMechanism,
}

impl ConsciousnessSynchronizationState {
    pub fn new() -> Self {
        Self {
            synchronization_level: 0.0,
            phase_coherence: Array1::zeros(10),
            sync_patterns: Vec::new(),
            coherence_mechanism: CoherenceMechanism::new(),
        }
    }

    /// Update synchronization across consciousness components
    pub fn update_synchronization<T>(
        &mut self,
        image: &ArrayView2<T>,
        quantum_network: &QuantumEntanglementNetwork,
        config: &QuantumAIConsciousnessConfig,
    ) -> NdimageResult<()>
    where
        T: Float + FromPrimitive + Copy + Send + Sync,
    {
        // Update global synchronization
        self.synchronization_level = quantum_network.synchronization_level;

        // Update phase coherence
        self.update_phase_coherence(quantum_network)?;

        // Detect synchronization patterns
        self.detect_sync_patterns(quantum_network)?;

        // Apply coherence preservation
        self.preserve_global_coherence(config)?;

        Ok(())
    }

    /// Update phase coherence across network
    fn update_phase_coherence(
        &mut self,
        network: &QuantumEntanglementNetwork,
    ) -> NdimageResult<()> {
        let num_channels = network.channels.len().max(1);
        self.phase_coherence = Array1::zeros(num_channels);

        for (i, channel) in network.channels.iter().enumerate() {
            // Calculate phase coherence for this channel
            let mut phase_sum = 0.0;
            for j in 0..channel.quantum_state.len() {
                phase_sum += channel.quantum_state[j];
            }

            let coherence_len = self.phase_coherence.len();
            self.phase_coherence[i % coherence_len] = phase_sum.abs();
        }

        Ok(())
    }

    /// Detect synchronization patterns in the network
    fn detect_sync_patterns(&mut self, network: &QuantumEntanglementNetwork) -> NdimageResult<()> {
        self.sync_patterns.clear();

        // Simple pattern detection based on entanglement strength
        for window in network.channels.windows(3) {
            if window.len() == 3 {
                let avg_strength =
                    window.iter().map(|c| c.entanglement_strength).sum::<f64>() / 3.0;

                if avg_strength > 0.7 {
                    let pattern = SynchronizationPattern {
                        pattern_type: "high_coherence_cluster".to_string(),
                        strength: avg_strength,
                        channels: window.iter().map(|c| c.id.clone()).collect(),
                        stability: avg_strength * 0.8,
                    };

                    self.sync_patterns.push(pattern);
                }
            }
        }

        Ok(())
    }

    /// Preserve global coherence across all components
    fn preserve_global_coherence(
        &mut self,
        config: &QuantumAIConsciousnessConfig,
    ) -> NdimageResult<()> {
        // Apply global coherence preservation strategies
        let preservation_efficiency = self
            .coherence_mechanism
            .mitigation_techniques
            .get("error_correction")
            .copied()
            .unwrap_or(0.8);

        // Update synchronization level with preservation
        self.synchronization_level = (self.synchronization_level * preservation_efficiency)
            .max(0.0)
            .min(1.0);

        Ok(())
    }
}

/// Synchronization Pattern
#[derive(Debug, Clone)]
pub struct SynchronizationPattern {
    /// Type of synchronization pattern
    pub pattern_type: String,
    /// Pattern strength
    pub strength: f64,
    /// Involved channels
    pub channels: Vec<String>,
    /// Pattern stability
    pub stability: f64,
}

/// Initialize quantum core components
pub fn initialize_quantum_core(
    config: &QuantumAIConsciousnessConfig,
) -> NdimageResult<(
    QuantumEntanglementNetwork,
    ConsciousnessSynchronizationState,
)> {
    let mut quantum_network = QuantumEntanglementNetwork::new();
    quantum_network.initialize(config)?;

    let sync_state = ConsciousnessSynchronizationState::new();

    Ok((quantum_network, sync_state))
}

/// Update quantum core state
pub fn update_quantum_core<T>(
    network: &mut QuantumEntanglementNetwork,
    sync_state: &mut ConsciousnessSynchronizationState,
    image: &ArrayView2<T>,
    config: &QuantumAIConsciousnessConfig,
    time_step: f64,
) -> NdimageResult<()>
where
    T: Float + FromPrimitive + Copy + Send + Sync,
{
    // Update quantum entanglement
    network.update_entanglement(time_step)?;

    // Update synchronization
    sync_state.update_synchronization(image, network, config)?;

    // Apply coherence preservation to all channels
    for channel in &mut network.channels {
        sync_state
            .coherence_mechanism
            .preserve_coherence(channel, time_step)?;
    }

    Ok(())
}

/// Get quantum core metrics
pub fn get_quantum_metrics(
    network: &QuantumEntanglementNetwork,
    sync_state: &ConsciousnessSynchronizationState,
) -> HashMap<String, f64> {
    let mut metrics = HashMap::new();

    // Network metrics
    metrics.insert(
        "network_synchronization".to_string(),
        network.synchronization_level,
    );
    metrics.insert("active_channels".to_string(), network.channels.len() as f64);
    metrics.insert(
        "average_entanglement".to_string(),
        network
            .channels
            .iter()
            .map(|c| c.entanglement_strength)
            .sum::<f64>()
            / network.channels.len().max(1) as f64,
    );

    // Synchronization metrics
    metrics.insert(
        "global_synchronization".to_string(),
        sync_state.synchronization_level,
    );
    metrics.insert(
        "sync_patterns".to_string(),
        sync_state.sync_patterns.len() as f64,
    );

    // Coherence metrics
    let coherence_metrics = sync_state.coherence_mechanism.get_coherence_metrics();
    metrics.extend(coherence_metrics);

    metrics
}
