hyperswarm 0.1.0

//! Peer information and priority tracking

use std::{
    collections::HashSet,
    net::SocketAddr,
    time::{Duration, Instant},
};

use dht_rpc::IdBytes;

/// Minimum connection time before resetting attempt counter (15 seconds)
const MIN_CONNECTION_TIME: Duration = Duration::from_secs(15);

/// Connection lifecycle state
#[derive(Debug, Clone, Default)]
pub enum ConnectionState {
    /// Not doing anything
    #[default]
    Idle,
    /// In the connection queue
    Queued,
    /// Waiting in retry timer
    Waiting,
    /// Currently attempting to connect
    Connecting,
    /// Active connection established
    Connected { since: Instant },
}

impl ConnectionState {
    pub fn is_idle(&self) -> bool {
        matches!(self, Self::Idle)
    }

    pub fn is_queued(&self) -> bool {
        matches!(self, Self::Queued)
    }

    pub fn is_waiting(&self) -> bool {
        matches!(self, Self::Waiting)
    }

    pub fn is_connecting(&self) -> bool {
        matches!(self, Self::Connecting)
    }

    pub fn is_connected(&self) -> bool {
        matches!(self, Self::Connected { .. })
    }

    /// Check if peer is busy (queued, waiting, or connecting)
    pub fn is_busy(&self) -> bool {
        matches!(self, Self::Queued | Self::Waiting | Self::Connecting)
    }
}

/// How we learned about this peer
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub enum PeerOrigin {
    /// Found via DHT lookup (we initiate connection)
    #[default]
    Discovered,
    /// Added explicitly via join_peer
    Explicit,
    /// They connected to us
    Incoming,
}

impl PeerOrigin {
    /// Whether we are the client (initiator) for this peer
    pub fn is_client(&self) -> bool {
        matches!(self, Self::Discovered | Self::Explicit)
    }

    /// Whether this is an explicit peer (added via join_peer)
    pub fn is_explicit(&self) -> bool {
        matches!(self, Self::Explicit)
    }
}

/// Trust level based on connection history
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub enum TrustLevel {
    /// Never successfully connected
    #[default]
    Unknown,
    /// Had at least one successful connection
    Proven,
    /// Blocked due to firewall or too many failures
    Banned,
}

impl TrustLevel {
    pub fn is_proven(&self) -> bool {
        matches!(self, Self::Proven)
    }

    pub fn is_banned(&self) -> bool {
        matches!(self, Self::Banned)
    }
}

/// Priority levels for peer connection attempts
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
#[repr(u8)]
pub enum Priority {
    /// Lowest priority - many failed attempts or stale peer
    VeryLow = 0,
    /// Low priority - several failed attempts
    Low = 1,
    /// Normal priority - default for new peers
    #[default]
    Normal = 2,
    /// High priority - few failed attempts
    High = 3,
    /// Highest priority - proven peer with recent success
    VeryHigh = 4,
}

/// Information about a discovered peer
#[derive(Debug)]
pub struct PeerInfo {
    /// The peer's public key
    pub public_key: IdBytes,

    /// Known relay addresses for this peer
    pub relay_addresses: Vec<SocketAddr>,

    /// Whether to attempt reconnection on disconnect
    pub reconnecting: bool,

    /// Trust level based on connection history
    pub trust: TrustLevel,

    /// Number of failed connection attempts
    pub attempts: u32,

    /// Current priority level
    pub priority: Priority,

    /// Connection lifecycle state
    pub state: ConnectionState,

    /// How we learned about this peer
    pub origin: PeerOrigin,

    /// Topics this peer is associated with
    pub topics: HashSet<IdBytes>,
}

impl PeerInfo {
    /// Create a new PeerInfo for a peer
    pub fn new(public_key: IdBytes) -> Self {
        Self {
            public_key,
            relay_addresses: Vec::new(),
            reconnecting: true,
            trust: TrustLevel::Unknown,
            attempts: 0,
            priority: Priority::Normal,
            state: ConnectionState::Idle,
            origin: PeerOrigin::Discovered,
            topics: HashSet::new(),
        }
    }

    /// Called when a connection is successfully established
    pub fn connected(&mut self) {
        self.state = ConnectionState::Connected {
            since: Instant::now(),
        };
        self.trust = TrustLevel::Proven;
        self.update_priority();
    }

    /// Called when a connection is closed
    pub fn disconnected(&mut self) {
        // Only increment attempts if connection was short-lived
        if let ConnectionState::Connected { since } = self.state {
            if since.elapsed() < MIN_CONNECTION_TIME {
                self.attempts = self.attempts.saturating_add(1);
            } else {
                // Long-lived connection - reset attempts
                self.attempts = 0;
            }
        } else {
            // Never connected - increment attempts
            self.attempts = self.attempts.saturating_add(1);
        }
        self.state = ConnectionState::Idle;
        self.update_priority();
    }

    /// Add relay addresses if they are new (merge with existing)
    pub fn add_relay_addresses(&mut self, relay_addresses: Vec<SocketAddr>) -> &mut Self {
        for addr in relay_addresses {
            if !self.relay_addresses.contains(&addr) {
                self.relay_addresses.push(addr);
            }
        }
        self
    }

    /// Add a topic this peer is associated with
    pub fn add_topic(&mut self, topic: IdBytes) -> &mut Self {
        self.topics.insert(topic);
        self
    }

    /// Remove a topic association
    pub fn remove_topic(&mut self, topic: &IdBytes) {
        self.topics.remove(topic);
    }

    /// Ban this peer
    pub fn ban(&mut self) {
        self.trust = TrustLevel::Banned;
        self.priority = Priority::VeryLow;
    }

    /// Update the priority based on current state
    pub fn update_priority(&mut self) -> bool {
        if self.trust.is_banned() {
            self.priority = Priority::VeryLow;
            return false;
        }

        let old_priority = self.priority;
        self.priority = self.calculate_priority();

        // Return true if should be queued (priority changed or is high enough)
        self.priority != Priority::VeryLow
            && (self.priority != old_priority || !self.state.is_queued())
    }

    /// Calculate priority based on attempts and trust level
    fn calculate_priority(&self) -> Priority {
        match (self.trust.is_proven(), self.attempts) {
            // Proven peers get higher priority
            (true, 0) => Priority::VeryHigh,
            (true, 1) => Priority::VeryHigh,
            (true, 2) => Priority::High,
            (true, 3) => Priority::Normal,
            (true, _) => Priority::Low,

            // Unproven peers start lower
            (false, 0) => Priority::Normal,
            (false, 1) => Priority::High, // Give one retry at high priority
            (false, 2) => Priority::Normal,
            (false, 3) => Priority::Low,
            (false, _) => Priority::VeryLow,
        }
    }

    /// Reset state for re-discovery
    pub fn reset(&mut self) {
        if !self.trust.is_proven() {
            self.attempts = 0;
        }
        self.update_priority();
    }

    /// Check if this peer should be garbage collected
    pub fn should_gc(&self) -> bool {
        // Don't GC if busy, explicit, or has topics
        if self.state.is_busy() || self.origin.is_explicit() || !self.topics.is_empty() {
            return false;
        }

        // GC if banned or too many attempts
        self.trust.is_banned() || self.attempts > 10
    }
}

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

    #[test]
    fn test_priority_ordering() {
        assert!(Priority::VeryLow < Priority::Low);
        assert!(Priority::Low < Priority::Normal);
        assert!(Priority::Normal < Priority::High);
        assert!(Priority::High < Priority::VeryHigh);
    }

    #[test]
    fn test_new_peer_priority() {
        let info = PeerInfo::new(IdBytes::random());
        assert_eq!(info.priority, Priority::Normal);
        assert_eq!(info.trust, TrustLevel::Unknown);
        assert_eq!(info.attempts, 0);
    }

    #[test]
    fn test_connected_sets_proven() {
        let mut info = PeerInfo::new(IdBytes::random());
        assert!(!info.trust.is_proven());

        info.connected();
        assert!(info.trust.is_proven());
        assert_eq!(info.priority, Priority::VeryHigh);
    }

    #[test]
    fn test_ban_sets_very_low() {
        let mut info = PeerInfo::new(IdBytes::random());
        info.ban();

        assert!(info.trust.is_banned());
        assert_eq!(info.priority, Priority::VeryLow);
    }

    #[test]
    fn test_attempts_decrease_priority() {
        let mut info = PeerInfo::new(IdBytes::random());

        // Start at Normal
        assert_eq!(info.calculate_priority(), Priority::Normal);

        // First attempt - High (retry)
        info.attempts = 1;
        assert_eq!(info.calculate_priority(), Priority::High);

        // Second attempt - Normal
        info.attempts = 2;
        assert_eq!(info.calculate_priority(), Priority::Normal);

        // Third attempt - Low
        info.attempts = 3;
        assert_eq!(info.calculate_priority(), Priority::Low);

        // Many attempts - VeryLow
        info.attempts = 5;
        assert_eq!(info.calculate_priority(), Priority::VeryLow);
    }

    #[test]
    fn test_proven_peer_priority() {
        let mut info = PeerInfo::new(IdBytes::random());
        info.trust = TrustLevel::Proven;

        // Proven with no attempts - VeryHigh
        assert_eq!(info.calculate_priority(), Priority::VeryHigh);

        // Proven with attempts still gets better treatment
        info.attempts = 3;
        assert_eq!(info.calculate_priority(), Priority::Normal);

        info.attempts = 5;
        assert_eq!(info.calculate_priority(), Priority::Low);
    }

    #[test]
    fn test_should_gc() {
        let mut info = PeerInfo::new(IdBytes::random());

        // New peer with no topics should not be GC'd immediately
        assert!(!info.should_gc());

        // Banned peer should be GC'd
        info.ban();
        assert!(info.should_gc());

        // Reset and add topic - should not GC
        info.trust = TrustLevel::Unknown;
        info.topics.insert(IdBytes::random());
        assert!(!info.should_gc());

        // Explicit peer should not be GC'd
        info.topics.clear();
        info.origin = PeerOrigin::Explicit;
        assert!(!info.should_gc());

        // Queued peer should not be GC'd
        info.origin = PeerOrigin::Discovered;
        info.state = ConnectionState::Queued;
        assert!(!info.should_gc());
    }
}