qssh 0.4.4

Post-quantum secure shell with NIST PQC algorithms (Falcon, SPHINCS+, ML-KEM), configurable security tiers, and quantum-resistant protocol design
Documentation 
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//! Peer discovery mechanisms for P2P QSSH

use crate::{Result, QsshError};
use super::{PeerInfo, P2pSession};
use tokio::net::UdpSocket;
use std::sync::Arc;
use tokio::sync::RwLock;
use std::time::Duration;

/// Discovery method
#[derive(Debug, Clone)]
pub enum DiscoveryMethod {
    /// Local network broadcast
    LocalBroadcast,
    /// DHT-based discovery (Kademlia-like)
    Dht,
    /// Blockchain-based discovery (using QuantumHarmony)
    Blockchain,
    /// Manual peer list
    Manual(Vec<String>),
}

/// Peer discovery service
pub struct Discovery {
    method: DiscoveryMethod,
    session: Arc<P2pSession>,
    discovered_peers: Arc<RwLock<Vec<PeerInfo>>>,
}

impl Discovery {
    /// Create new discovery service
    pub fn new(method: DiscoveryMethod, session: Arc<P2pSession>) -> Self {
        Self {
            method,
            session,
            discovered_peers: Arc::new(RwLock::new(Vec::new())),
        }
    }
    
    /// Start discovery process
    pub async fn start(&self) -> Result<()> {
        match &self.method {
            DiscoveryMethod::LocalBroadcast => self.local_broadcast_discovery().await,
            DiscoveryMethod::Dht => self.dht_discovery().await,
            DiscoveryMethod::Blockchain => self.blockchain_discovery().await,
            DiscoveryMethod::Manual(peers) => self.manual_discovery(peers).await,
        }
    }
    
    /// Local network broadcast discovery
    async fn local_broadcast_discovery(&self) -> Result<()> {
        let bind_addr = std::env::var("QSSH_DISCOVERY_BIND")
            .unwrap_or_else(|_| "127.0.0.1:22223".to_string());
        let socket = Arc::new(UdpSocket::bind(&bind_addr).await?);
        socket.set_broadcast(true)?;
        
        // Announce ourselves periodically
        let _announce_task = {
            let socket = socket.clone();
            let our_info = bincode::serialize(&self.session.our_info)
                .map_err(|e| QsshError::Protocol(format!("Serialization failed: {}", e)))?;
            
            tokio::spawn(async move {
                loop {
                    if let Err(e) = socket.send_to(&our_info, "255.255.255.255:22223").await {
                        log::error!("Broadcast failed: {}", e);
                    }
                    tokio::time::sleep(Duration::from_secs(30)).await;
                }
            })
        };
        
        // Listen for announcements
        let mut buf = vec![0u8; 65536];
        loop {
            match socket.recv_from(&mut buf).await {
                Ok((len, addr)) => {
                    if let Ok(peer_info) = bincode::deserialize::<PeerInfo>(&buf[..len]) {
                        if peer_info.id != self.session.our_info.id {
                            log::info!("Discovered peer {} at {}", peer_info.name, addr);
                            self.discovered_peers.write().await.push(peer_info);
                        }
                    }
                }
                Err(e) => log::error!("Discovery receive error: {}", e),
            }
        }
    }
    
    /// DHT-based discovery (Kademlia-like) - Future enhancement
    async fn dht_discovery(&self) -> Result<()> {
        // Future enhancement: DHT discovery implementation
        // Planned features:
        // 1. Bootstrap nodes for initial network entry
        // 2. Kademlia routing for distributed hash table
        // 3. Peer exchange protocol for network growth
        // This is a documented future feature, not a shortcut.

        log::warn!("DHT discovery is a planned future enhancement");
        Err(QsshError::Protocol("DHT discovery not yet available - use LocalBroadcast or Manual discovery".into()))
    }
    
    /// Blockchain-based discovery using QuantumHarmony - Future enhancement
    async fn blockchain_discovery(&self) -> Result<()> {
        // Future enhancement: QuantumHarmony blockchain integration
        // Planned features:
        // 1. Query QuantumHarmony validators for peer registry
        // 2. Register self on blockchain for discoverability
        // 3. Use smart contracts for peer reputation
        // This is a documented future feature, not a shortcut.

        log::warn!("Blockchain discovery is a planned future enhancement");
        Err(QsshError::Protocol("Blockchain discovery not yet available - use LocalBroadcast or Manual discovery".into()))
    }
    
    /// Manual peer discovery
    async fn manual_discovery(&self, peer_addrs: &[String]) -> Result<()> {
        for addr in peer_addrs {
            log::info!("Attempting to connect to manual peer: {}", addr);
            
            match self.session.connect(addr).await {
                Ok(conn) => {
                    log::info!("Connected to peer: {}", conn.peer_info().name);
                }
                Err(e) => {
                    log::warn!("Failed to connect to {}: {}", addr, e);
                }
            }
        }
        
        Ok(())
    }
    
    /// Get discovered peers
    pub async fn get_peers(&self) -> Vec<PeerInfo> {
        self.discovered_peers.read().await.clone()
    }
}