quantrs2-device 0.1.3

//! Quantum TCP Protocol Implementation
//!
//! This module implements a quantum-enhanced version of TCP that provides
//! reliable quantum communication with entanglement-based error detection
//! and quantum error correction.

use super::*;
use std::collections::{HashMap, VecDeque};
use tokio::sync::{RwLock, Mutex};
use std::time::{Duration, Instant};

/// Quantum TCP connection manager
pub struct QuantumTCPManager {
    connections: Arc<RwLock<HashMap<String, QuantumTCPConnection>>>,
    config: QuantumTCPConfig,
    sequence_numbers: Arc<Mutex<HashMap<String, u64>>>,
    acknowledgments: Arc<RwLock<HashMap<String, u64>>>,
}

/// Quantum TCP configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct QuantumTCPConfig {
    pub window_size: usize,
    pub timeout: Duration,
    pub max_retries: u32,
    pub quantum_error_detection: bool,
    pub entanglement_verification: bool,
    pub adaptive_window: bool,
    pub congestion_control: QuantumCongestionControl,
    pub flow_control: QuantumFlowControl,
}

/// Quantum congestion control algorithms
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum QuantumCongestionControl {
    QuantumTahoe,
    QuantumReno,
    QuantumCubic,
    EntanglementAware,
    FidelityBased,
    Custom(String),
}

/// Quantum flow control mechanisms
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct QuantumFlowControl {
    pub algorithm: FlowControlAlgorithm,
    pub buffer_size: usize,
    pub quantum_buffer_size: usize,
    pub fidelity_threshold: f64,
    pub coherence_aware: bool,
}

/// Flow control algorithms
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub enum FlowControlAlgorithm {
    SlidingWindow,
    QuantumSlidingWindow,
    FidelityAware,
    CoherenceAware,
    EntanglementBased,
}

/// Quantum TCP connection state
#[derive(Debug, Clone)]
pub struct QuantumTCPConnection {
    pub connection_id: String,
    pub state: TCPState,
    pub quantum_state: QuantumTCPState,
    pub send_buffer: VecDeque<QuantumPacket>,
    pub receive_buffer: VecDeque<QuantumPacket>,
    pub send_window: TCPWindow,
    pub receive_window: TCPWindow,
    pub sequence_number: u64,
    pub acknowledgment_number: u64,
    pub round_trip_time: Duration,
    pub congestion_window: usize,
    pub slow_start_threshold: usize,
    pub retransmission_timer: Option<Instant>,
    pub entanglement_resources: Vec<String>,
    pub performance_metrics: QuantumTCPMetrics,
}

/// TCP connection states
#[derive(Debug, Clone, PartialEq)]
pub enum TCPState {
    Closed,
    Listen,
    SynSent,
    SynReceived,
    Established,
    FinWait1,
    FinWait2,
    CloseWait,
    Closing,
    LastAck,
    TimeWait,
    QuantumHandshake,
    EntanglementSetup,
}

/// Quantum-specific TCP state
#[derive(Debug, Clone)]
pub struct QuantumTCPState {
    pub entanglement_established: bool,
    pub quantum_channel_fidelity: f64,
    pub coherence_time: Duration,
    pub quantum_error_rate: f64,
    pub entanglement_consumption_rate: f64,
    pub quantum_retransmissions: u32,
}

/// TCP window management
#[derive(Debug, Clone)]
pub struct TCPWindow {
    pub size: usize,
    pub left_edge: u64,
    pub right_edge: u64,
    pub advertised_window: usize,
    pub used_window: usize,
}

/// Quantum packet structure
#[derive(Debug, Clone)]
pub struct QuantumPacket {
    pub header: QuantumTCPHeader,
    pub payload: QuantumPayload,
    pub entanglement_info: Option<EntanglementInfo>,
    pub error_correction: Option<ErrorCorrectionInfo>,
    pub timestamp: Instant,
}

/// Quantum TCP header
#[derive(Debug, Clone)]
pub struct QuantumTCPHeader {
    pub source_port: u16,
    pub destination_port: u16,
    pub sequence_number: u64,
    pub acknowledgment_number: u64,
    pub window_size: u16,
    pub flags: QuantumTCPFlags,
    pub checksum: u32,
    pub quantum_checksum: Option<QuantumChecksum>,
    pub options: Vec<QuantumTCPOption>,
}

/// Quantum TCP flags
#[derive(Debug, Clone)]
pub struct QuantumTCPFlags {
    pub syn: bool,
    pub ack: bool,
    pub fin: bool,
    pub rst: bool,
    pub psh: bool,
    pub urg: bool,
    pub quantum_syn: bool,
    pub entanglement_req: bool,
    pub fidelity_check: bool,
}

/// Quantum checksum for error detection
#[derive(Debug, Clone)]
pub struct QuantumChecksum {
    pub classical_checksum: u32,
    pub quantum_parity: Vec<u8>,
    pub entanglement_witness: Option<f64>,
    pub fidelity_estimate: f64,
}

/// Quantum TCP options
#[derive(Debug, Clone)]
pub enum QuantumTCPOption {
    MaxSegmentSize(u16),
    WindowScale(u8),
    QuantumWindowScale(u8),
    EntanglementRequest(EntanglementRequest),
    FidelityRequirement(f64),
    CoherenceTime(Duration),
    ErrorCorrectionCode(String),
    Custom(String, Vec<u8>),
}

/// Entanglement request option
#[derive(Debug, Clone)]
pub struct EntanglementRequest {
    pub num_pairs: usize,
    pub min_fidelity: f64,
    pub max_latency: Duration,
    pub entanglement_type: String,
}

/// Quantum payload
#[derive(Debug, Clone)]
pub struct QuantumPayload {
    pub data_type: QuantumDataType,
    pub data: Vec<u8>,
    pub quantum_encoding: Option<QuantumEncoding>,
    pub error_protection: ErrorProtectionScheme,
}

/// Quantum encoding schemes
#[derive(Debug, Clone)]
pub struct QuantumEncoding {
    pub encoding_type: String,
    pub parameters: HashMap<String, f64>,
    pub redundancy: u8,
}

/// Error protection schemes
#[derive(Debug, Clone, PartialEq)]
pub enum ErrorProtectionScheme {
    None,
    ClassicalECC,
    QuantumECC,
    HybridECC,
    EntanglementProtected,
}

/// Entanglement information
#[derive(Debug, Clone)]
pub struct EntanglementInfo {
    pub entanglement_id: String,
    pub fidelity: f64,
    pub coherence_time: Duration,
    pub measurement_basis: String,
    pub consumption_required: bool,
}

/// Error correction information
#[derive(Debug, Clone)]
pub struct ErrorCorrectionInfo {
    pub code_type: String,
    pub syndrome: Vec<u8>,
    pub correction_operations: Vec<String>,
    pub success_probability: f64,
}

/// Quantum TCP performance metrics
#[derive(Debug, Clone)]
pub struct QuantumTCPMetrics {
    pub classical_throughput: f64,
    pub quantum_throughput: f64,
    pub packet_loss_rate: f64,
    pub quantum_error_rate: f64,
    pub average_fidelity: f64,
    pub entanglement_efficiency: f64,
    pub retransmission_rate: f64,
    pub round_trip_time: Duration,
    pub jitter: Duration,
}

impl QuantumTCPManager {
    /// Create a new Quantum TCP manager
    pub fn new(config: QuantumTCPConfig) -> Self {
        Self {
            connections: Arc::new(RwLock::new(HashMap::new())),
            config,
            sequence_numbers: Arc::new(Mutex::new(HashMap::new())),
            acknowledgments: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    /// Establish a quantum TCP connection
    pub async fn connect(&self, destination: &str, port: u16) -> DeviceResult<String> {
        let connection_id = format!("{}:{}", destination, port);

        // Create connection state
        let connection = QuantumTCPConnection {
            connection_id: connection_id.clone(),
            state: TCPState::SynSent,
            quantum_state: QuantumTCPState {
                entanglement_established: false,
                quantum_channel_fidelity: 0.0,
                coherence_time: Duration::from_millis(0),
                quantum_error_rate: 0.0,
                entanglement_consumption_rate: 0.0,
                quantum_retransmissions: 0,
            },
            send_buffer: VecDeque::new(),
            receive_buffer: VecDeque::new(),
            send_window: TCPWindow::new(self.config.window_size),
            receive_window: TCPWindow::new(self.config.window_size),
            sequence_number: 0,
            acknowledgment_number: 0,
            round_trip_time: Duration::from_millis(100),
            congestion_window: 1,
            slow_start_threshold: 65535,
            retransmission_timer: None,
            entanglement_resources: vec![],
            performance_metrics: QuantumTCPMetrics::default(),
        };

        // Perform quantum handshake
        self.perform_quantum_handshake(&connection_id).await?;

        // Store connection
        self.connections.write().await.insert(connection_id.clone(), connection);

        Ok(connection_id)
    }

    /// Send data over quantum TCP
    pub async fn send(&self, connection_id: &str, data: &[u8]) -> DeviceResult<usize> {
        let mut connections = self.connections.write().await;
        let connection = connections.get_mut(connection_id)
            .ok_or_else(|| DeviceError::InvalidInput(format!("Connection {} not found", connection_id)))?;

        if connection.state != TCPState::Established {
            return Err(DeviceError::InvalidInput("Connection not established".to_string()));
        }

        // Create quantum packet
        let packet = self.create_data_packet(connection, data).await?;

        // Add to send buffer
        connection.send_buffer.push_back(packet);

        // Send packets within window
        self.send_window_packets(connection).await?;

        Ok(data.len())
    }

    /// Receive data from quantum TCP
    pub async fn receive(&self, connection_id: &str, buffer: &mut [u8]) -> DeviceResult<usize> {
        let mut connections = self.connections.write().await;
        let connection = connections.get_mut(connection_id)
            .ok_or_else(|| DeviceError::InvalidInput(format!("Connection {} not found", connection_id)))?;

        if connection.receive_buffer.is_empty() {
            return Ok(0);
        }

        let mut bytes_read = 0;
        while let Some(packet) = connection.receive_buffer.pop_front() {
            let packet_data = &packet.payload.data;
            let copy_len = std::cmp::min(packet_data.len(), buffer.len() - bytes_read);

            buffer[bytes_read..bytes_read + copy_len].copy_from_slice(&packet_data[..copy_len]);
            bytes_read += copy_len;

            if bytes_read >= buffer.len() {
                break;
            }
        }

        Ok(bytes_read)
    }

    /// Process incoming packet
    pub async fn handle_incoming_packet(&self, packet: QuantumPacket) -> DeviceResult<()> {
        let connection_id = format!("{}:{}", "unknown", packet.header.destination_port);

        let mut connections = self.connections.write().await;
        if let Some(connection) = connections.get_mut(&connection_id) {
            // Verify quantum integrity
            if let Some(entanglement_info) = &packet.entanglement_info {
                self.verify_quantum_integrity(entanglement_info).await?;
            }

            // Process based on packet type
            if packet.header.flags.syn {
                self.handle_syn_packet(connection, &packet).await?;
            } else if packet.header.flags.ack {
                self.handle_ack_packet(connection, &packet).await?;
            } else if packet.header.flags.fin {
                self.handle_fin_packet(connection, &packet).await?;
            } else {
                // Data packet
                self.handle_data_packet(connection, packet).await?;
            }
        }

        Ok(())
    }

    /// Close quantum TCP connection
    pub async fn close(&self, connection_id: &str) -> DeviceResult<()> {
        let mut connections = self.connections.write().await;
        if let Some(mut connection) = connections.remove(connection_id) {
            // Send FIN packet
            let fin_packet = self.create_fin_packet(&connection).await?;
            self.send_packet(&fin_packet).await?;

            // Update state
            connection.state = TCPState::FinWait1;

            // Cleanup entanglement resources
            self.cleanup_entanglement_resources(&connection.entanglement_resources).await?;
        }

        Ok(())
    }

    /// Get connection statistics
    pub async fn get_statistics(&self, connection_id: &str) -> DeviceResult<QuantumTCPMetrics> {
        let connections = self.connections.read().await;
        let connection = connections.get(connection_id)
            .ok_or_else(|| DeviceError::InvalidInput(format!("Connection {} not found", connection_id)))?;

        Ok(connection.performance_metrics.clone())
    }

    // Helper methods
    async fn perform_quantum_handshake(&self, _connection_id: &str) -> DeviceResult<()> {
        // Implement quantum handshake protocol
        // 1. Classical SYN/ACK
        // 2. Quantum channel establishment
        // 3. Entanglement distribution
        // 4. Quantum error detection setup
        Ok(())
    }

    async fn create_data_packet(&self, connection: &QuantumTCPConnection, data: &[u8]) -> DeviceResult<QuantumPacket> {
        let header = QuantumTCPHeader {
            source_port: 0, // Would be set based on connection
            destination_port: 0,
            sequence_number: connection.sequence_number,
            acknowledgment_number: connection.acknowledgment_number,
            window_size: connection.receive_window.size as u16,
            flags: QuantumTCPFlags {
                syn: false,
                ack: true,
                fin: false,
                rst: false,
                psh: true,
                urg: false,
                quantum_syn: false,
                entanglement_req: false,
                fidelity_check: true,
            },
            checksum: self.calculate_checksum(data),
            quantum_checksum: Some(self.calculate_quantum_checksum(data).await?),
            options: vec![],
        };

        let payload = QuantumPayload {
            data_type: QuantumDataType::QuantumMessage,
            data: data.to_vec(),
            quantum_encoding: None,
            error_protection: ErrorProtectionScheme::HybridECC,
        };

        Ok(QuantumPacket {
            header,
            payload,
            entanglement_info: None,
            error_correction: None,
            timestamp: Instant::now(),
        })
    }

    async fn send_window_packets(&self, _connection: &mut QuantumTCPConnection) -> DeviceResult<()> {
        // Implement sliding window protocol
        // Send packets within congestion window
        Ok(())
    }

    async fn verify_quantum_integrity(&self, _entanglement_info: &EntanglementInfo) -> DeviceResult<()> {
        // Verify quantum state integrity using entanglement
        Ok(())
    }

    async fn handle_syn_packet(&self, _connection: &mut QuantumTCPConnection, _packet: &QuantumPacket) -> DeviceResult<()> {
        // Handle SYN packet
        Ok(())
    }

    async fn handle_ack_packet(&self, _connection: &mut QuantumTCPConnection, _packet: &QuantumPacket) -> DeviceResult<()> {
        // Handle ACK packet
        Ok(())
    }

    async fn handle_fin_packet(&self, _connection: &mut QuantumTCPConnection, _packet: &QuantumPacket) -> DeviceResult<()> {
        // Handle FIN packet
        Ok(())
    }

    async fn handle_data_packet(&self, connection: &mut QuantumTCPConnection, packet: QuantumPacket) -> DeviceResult<()> {
        // Add to receive buffer
        connection.receive_buffer.push_back(packet);

        // Send ACK
        let ack_packet = self.create_ack_packet(connection).await?;
        self.send_packet(&ack_packet).await?;

        Ok(())
    }

    async fn create_fin_packet(&self, _connection: &QuantumTCPConnection) -> DeviceResult<QuantumPacket> {
        // Create FIN packet
        Ok(QuantumPacket {
            header: QuantumTCPHeader {
                source_port: 0,
                destination_port: 0,
                sequence_number: 0,
                acknowledgment_number: 0,
                window_size: 0,
                flags: QuantumTCPFlags {
                    syn: false,
                    ack: false,
                    fin: true,
                    rst: false,
                    psh: false,
                    urg: false,
                    quantum_syn: false,
                    entanglement_req: false,
                    fidelity_check: false,
                },
                checksum: 0,
                quantum_checksum: None,
                options: vec![],
            },
            payload: QuantumPayload {
                data_type: QuantumDataType::QuantumMessage,
                data: vec![],
                quantum_encoding: None,
                error_protection: ErrorProtectionScheme::None,
            },
            entanglement_info: None,
            error_correction: None,
            timestamp: Instant::now(),
        })
    }

    async fn create_ack_packet(&self, _connection: &QuantumTCPConnection) -> DeviceResult<QuantumPacket> {
        // Create ACK packet
        Ok(QuantumPacket {
            header: QuantumTCPHeader {
                source_port: 0,
                destination_port: 0,
                sequence_number: 0,
                acknowledgment_number: 0,
                window_size: 0,
                flags: QuantumTCPFlags {
                    syn: false,
                    ack: true,
                    fin: false,
                    rst: false,
                    psh: false,
                    urg: false,
                    quantum_syn: false,
                    entanglement_req: false,
                    fidelity_check: false,
                },
                checksum: 0,
                quantum_checksum: None,
                options: vec![],
            },
            payload: QuantumPayload {
                data_type: QuantumDataType::QuantumMessage,
                data: vec![],
                quantum_encoding: None,
                error_protection: ErrorProtectionScheme::None,
            },
            entanglement_info: None,
            error_correction: None,
            timestamp: Instant::now(),
        })
    }

    async fn send_packet(&self, _packet: &QuantumPacket) -> DeviceResult<()> {
        // Send packet over quantum channel
        Ok(())
    }

    async fn cleanup_entanglement_resources(&self, _resources: &[String]) -> DeviceResult<()> {
        // Cleanup entanglement resources
        Ok(())
    }

    fn calculate_checksum(&self, data: &[u8]) -> u32 {
        // Simple checksum calculation
        data.iter().map(|&b| b as u32).sum()
    }

    async fn calculate_quantum_checksum(&self, _data: &[u8]) -> DeviceResult<QuantumChecksum> {
        // Calculate quantum checksum using entanglement
        Ok(QuantumChecksum {
            classical_checksum: 0,
            quantum_parity: vec![],
            entanglement_witness: Some(0.95),
            fidelity_estimate: 0.95,
        })
    }
}

impl TCPWindow {
    fn new(size: usize) -> Self {
        Self {
            size,
            left_edge: 0,
            right_edge: size as u64,
            advertised_window: size,
            used_window: 0,
        }
    }
}

impl Default for QuantumTCPConfig {
    fn default() -> Self {
        Self {
            window_size: 65536,
            timeout: Duration::from_secs(30),
            max_retries: 3,
            quantum_error_detection: true,
            entanglement_verification: true,
            adaptive_window: true,
            congestion_control: QuantumCongestionControl::EntanglementAware,
            flow_control: QuantumFlowControl {
                algorithm: FlowControlAlgorithm::FidelityAware,
                buffer_size: 65536,
                quantum_buffer_size: 1024,
                fidelity_threshold: 0.9,
                coherence_aware: true,
            },
        }
    }
}

impl Default for QuantumTCPMetrics {
    fn default() -> Self {
        Self {
            classical_throughput: 0.0,
            quantum_throughput: 0.0,
            packet_loss_rate: 0.0,
            quantum_error_rate: 0.0,
            average_fidelity: 0.0,
            entanglement_efficiency: 0.0,
            retransmission_rate: 0.0,
            round_trip_time: Duration::from_millis(0),
            jitter: Duration::from_millis(0),
        }
    }
}