qcomm-core 0.1.0

//! BLE Mesh Transport (BitChat Compatible)
//!
//! Implements Bluetooth Low Energy mesh networking for peer-to-peer
//! communication without internet connectivity.

use super::{Transport, TransportCapability, TransportMessage, MessageMetadata};
use crate::{Error, Result};
use async_trait::async_trait;
use std::collections::VecDeque;
use std::sync::Arc;
use tokio::sync::Mutex;

/// BLE service UUID for BitChat compatibility
pub const BITCHAT_SERVICE_UUID: &str = "00001800-0000-1000-8000-00805f9b34fb";

/// BLE characteristic UUID for messages
pub const MESSAGE_CHARACTERISTIC_UUID: &str = "00002a00-0000-1000-8000-00805f9b34fb";

/// Maximum BLE message size (MTU limitation)
pub const MAX_BLE_MESSAGE_SIZE: usize = 512;

/// Maximum hops for mesh routing
pub const MAX_HOP_COUNT: u8 = 10;

/// Default TTL for messages
pub const DEFAULT_TTL: u8 = 5;

/// BLE peer information
#[derive(Debug, Clone)]
pub struct BlePeer {
    /// Device address
    pub address: String,
    /// Device name (if advertised)
    pub name: Option<String>,
    /// Signal strength (RSSI)
    pub rssi: i16,
    /// Last seen timestamp
    pub last_seen: u64,
    /// Supports PQC
    pub supports_pqc: bool,
}

/// BLE mesh transport
pub struct BleTransport {
    /// Connected state
    connected: bool,
    /// Known peers
    peers: Arc<Mutex<Vec<BlePeer>>>,
    /// Message queue
    incoming: Arc<Mutex<VecDeque<TransportMessage>>>,
    /// Pending outgoing messages
    outgoing: Arc<Mutex<VecDeque<TransportMessage>>>,
    /// Our device address
    device_address: String,
}

impl BleTransport {
    /// Create a new BLE transport
    pub fn new() -> Self {
        Self {
            connected: false,
            peers: Arc::new(Mutex::new(Vec::new())),
            incoming: Arc::new(Mutex::new(VecDeque::new())),
            outgoing: Arc::new(Mutex::new(VecDeque::new())),
            device_address: Self::generate_device_address(),
        }
    }

    /// Generate a random device address
    fn generate_device_address() -> String {
        use rand::Rng;
        let mut rng = rand::thread_rng();
        format!(
            "{:02X}:{:02X}:{:02X}:{:02X}:{:02X}:{:02X}",
            rng.gen::<u8>(),
            rng.gen::<u8>(),
            rng.gen::<u8>(),
            rng.gen::<u8>(),
            rng.gen::<u8>(),
            rng.gen::<u8>()
        )
    }

    /// Get known peers
    pub async fn peers(&self) -> Vec<BlePeer> {
        self.peers.lock().await.clone()
    }

    /// Start BLE scanning for peers
    pub async fn start_scanning(&self) -> Result<()> {
        if !self.connected {
            return Err(Error::Ble("Not connected".into()));
        }

        // In production, would use btleplug for actual scanning
        // For now, this is a placeholder
        tracing::info!("Started BLE scanning for BitChat peers");
        Ok(())
    }

    /// Stop BLE scanning
    pub async fn stop_scanning(&self) -> Result<()> {
        tracing::info!("Stopped BLE scanning");
        Ok(())
    }

    /// Start advertising as a BitChat peer
    pub async fn start_advertising(&self) -> Result<()> {
        if !self.connected {
            return Err(Error::Ble("Not connected".into()));
        }

        // In production, would set up GATT server
        tracing::info!("Started BLE advertising as BitChat peer");
        Ok(())
    }

    /// Route message through mesh
    async fn route_message(&self, message: &TransportMessage) -> Result<()> {
        let metadata = match &message.metadata {
            MessageMetadata::Ble { hop_count, ttl } => (*hop_count, *ttl),
            _ => (0, DEFAULT_TTL),
        };

        let (hop_count, ttl) = metadata;

        // Check TTL
        if hop_count >= MAX_HOP_COUNT || ttl == 0 {
            return Err(Error::Ble("Message TTL expired".into()));
        }

        // Find best peer to forward to
        let peers = self.peers.lock().await;

        // In production, would implement actual mesh routing algorithm
        // (flooding, AODV, or similar)
        if peers.is_empty() {
            return Err(Error::Ble("No peers available".into()));
        }

        // Queue for transmission to all peers (flooding)
        let mut outgoing = self.outgoing.lock().await;

        let mut forwarded = message.clone();
        forwarded.metadata = MessageMetadata::Ble {
            hop_count: hop_count + 1,
            ttl: ttl - 1,
        };

        outgoing.push_back(forwarded);

        Ok(())
    }

    /// Chunk message for BLE MTU
    fn chunk_message(data: &[u8]) -> Vec<Vec<u8>> {
        data.chunks(MAX_BLE_MESSAGE_SIZE)
            .map(|c| c.to_vec())
            .collect()
    }

    /// Reassemble chunked message
    fn reassemble_message(chunks: &[Vec<u8>]) -> Vec<u8> {
        chunks.iter().flatten().copied().collect()
    }
}

impl Default for BleTransport {
    fn default() -> Self {
        Self::new()
    }
}

#[async_trait]
impl Transport for BleTransport {
    fn name(&self) -> &str {
        "BLE Mesh"
    }

    fn capabilities(&self) -> Vec<TransportCapability> {
        vec![
            TransportCapability::Send,
            TransportCapability::Receive,
            TransportCapability::PostQuantum, // We upgrade with PQC
        ]
    }

    async fn is_connected(&self) -> bool {
        self.connected
    }

    async fn connect(&mut self) -> Result<()> {
        // In production:
        // 1. Initialize BLE adapter via btleplug
        // 2. Start scanning for peers
        // 3. Set up GATT server for receiving

        #[cfg(feature = "btleplug")]
        {
            use btleplug::api::{Central, Manager as _};
            use btleplug::platform::Manager;

            let manager = Manager::new().await
                .map_err(|e| Error::Ble(e.to_string()))?;

            let adapters = manager.adapters().await
                .map_err(|e| Error::Ble(e.to_string()))?;

            if adapters.is_empty() {
                return Err(Error::Ble("No BLE adapters found".into()));
            }

            // Use first adapter
            let adapter = &adapters[0];
            adapter.start_scan(btleplug::api::ScanFilter::default()).await
                .map_err(|e| Error::Ble(e.to_string()))?;
        }

        self.connected = true;
        tracing::info!("BLE transport connected");
        Ok(())
    }

    async fn disconnect(&mut self) -> Result<()> {
        self.connected = false;
        tracing::info!("BLE transport disconnected");
        Ok(())
    }

    async fn send(&self, message: TransportMessage) -> Result<()> {
        if !self.connected {
            return Err(Error::Ble("Not connected".into()));
        }

        // Serialize message
        let data = bincode::serialize(&message)
            .map_err(|e| Error::Serialization(e.to_string()))?;

        // Check size
        if data.len() > MAX_BLE_MESSAGE_SIZE * 10 {
            return Err(Error::Ble("Message too large for BLE".into()));
        }

        // Route through mesh
        self.route_message(&message).await?;

        Ok(())
    }

    async fn receive(&mut self) -> Result<TransportMessage> {
        loop {
            if let Some(msg) = self.incoming.lock().await.pop_front() {
                return Ok(msg);
            }

            // In production, would actually wait for BLE notifications
            tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;

            if !self.connected {
                return Err(Error::Ble("Disconnected while waiting".into()));
            }
        }
    }

    async fn poll(&mut self) -> Result<Option<TransportMessage>> {
        Ok(self.incoming.lock().await.pop_front())
    }
}

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

    #[tokio::test]
    async fn test_ble_transport_creation() {
        let transport = BleTransport::new();
        assert!(!transport.is_connected().await);
        assert_eq!(transport.name(), "BLE Mesh");
    }

    #[tokio::test]
    async fn test_chunk_message() {
        let data = vec![0u8; 1500];
        let chunks = BleTransport::chunk_message(&data);
        assert_eq!(chunks.len(), 3); // 512 + 512 + 476

        let reassembled = BleTransport::reassemble_message(&chunks);
        assert_eq!(reassembled, data);
    }
}