//! Network-level privacy features for Bitcoin transactions
//!
//! Implements privacy enhancements at the network layer including:
//! - Tor/SOCKS5 proxy support
//! - Dandelion++ transaction broadcasting
//! - Connection graph optimization

use crate::error::BitcoinError;
use bitcoin::Txid;
use serde::{Deserialize, Serialize};
use std::collections::{HashMap, VecDeque};
use std::time::{Duration, SystemTime};

/// Network privacy configuration
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NetworkPrivacyConfig {
    /// Use Tor/SOCKS5 proxy
    pub use_tor: bool,
    /// Tor SOCKS5 proxy address
    pub tor_proxy: Option<String>,
    /// Enable Dandelion++ for transaction broadcasting
    pub use_dandelion: bool,
    /// Stem phase duration for Dandelion++ (seconds)
    pub stem_duration_secs: u64,
    /// Maximum peers for connection diversity
    pub max_peers: usize,
    /// Rotate peers periodically
    pub peer_rotation_enabled: bool,
    /// Peer rotation interval (seconds)
    pub peer_rotation_interval_secs: u64,
}

impl Default for NetworkPrivacyConfig {
    fn default() -> Self {
        Self {
            use_tor: false,
            tor_proxy: Some("127.0.0.1:9050".to_string()),
            use_dandelion: true,
            stem_duration_secs: 15,
            max_peers: 8,
            peer_rotation_enabled: true,
            peer_rotation_interval_secs: 3600, // 1 hour
        }
    }
}

/// Tor proxy manager
#[derive(Debug)]
pub struct TorProxyManager {
    /// Proxy address
    proxy_addr: String,
    /// Connection statistics
    stats: TorConnectionStats,
}

impl TorProxyManager {
    /// Create a new Tor proxy manager
    pub fn new(proxy_addr: String) -> Self {
        Self {
            proxy_addr,
            stats: TorConnectionStats::default(),
        }
    }

    /// Test Tor connection
    pub async fn test_connection(&mut self) -> Result<bool, BitcoinError> {
        // In production, this would test SOCKS5 connectivity
        // For now, simulate success
        self.stats.total_connections += 1;
        Ok(true)
    }

    /// Get proxy address
    pub fn proxy_addr(&self) -> &str {
        &self.proxy_addr
    }

    /// Get connection statistics
    pub fn stats(&self) -> &TorConnectionStats {
        &self.stats
    }

    /// Check if Tor is available
    pub async fn is_available(&self) -> bool {
        // In production, ping the Tor proxy
        true
    }
}

/// Tor connection statistics
#[derive(Debug, Default, Clone, Serialize, Deserialize)]
pub struct TorConnectionStats {
    /// Total connections attempted
    pub total_connections: u64,
    /// Successful connections
    pub successful_connections: u64,
    /// Failed connections
    pub failed_connections: u64,
}

/// Dandelion++ transaction broadcaster
///
/// Implements BIP 156 (Dandelion++) for transaction privacy
#[derive(Debug)]
pub struct DandelionBroadcaster {
    /// Stem phase duration
    stem_duration: Duration,
    /// Transactions in stem phase
    stem_pool: HashMap<Txid, DandelionTransaction>,
    /// Fluff phase queue
    fluff_queue: VecDeque<Txid>,
}

impl DandelionBroadcaster {
    /// Create a new Dandelion++ broadcaster
    pub fn new(stem_duration_secs: u64) -> Self {
        Self {
            stem_duration: Duration::from_secs(stem_duration_secs),
            stem_pool: HashMap::new(),
            fluff_queue: VecDeque::new(),
        }
    }

    /// Add transaction to stem phase
    pub fn add_to_stem(&mut self, txid: Txid) -> Result<(), BitcoinError> {
        let tx = DandelionTransaction {
            txid,
            stem_start: SystemTime::now(),
            hop_count: 0,
        };

        self.stem_pool.insert(txid, tx);
        Ok(())
    }

    /// Process stem phase (relay to single peer)
    pub fn process_stem(&mut self) -> Vec<Txid> {
        let now = SystemTime::now();
        let mut to_fluff = Vec::new();

        // Check for transactions ready to fluff
        self.stem_pool.retain(|txid, tx| {
            if let Ok(elapsed) = now.duration_since(tx.stem_start) {
                if elapsed >= self.stem_duration || tx.hop_count >= 10 {
                    to_fluff.push(*txid);
                    return false;
                }
            }
            true
        });

        // Add to fluff queue
        for txid in &to_fluff {
            self.fluff_queue.push_back(*txid);
        }

        to_fluff
    }

    /// Process fluff phase (broadcast to all peers)
    pub fn process_fluff(&mut self, max_broadcasts: usize) -> Vec<Txid> {
        let mut broadcasted = Vec::new();

        for _ in 0..max_broadcasts {
            if let Some(txid) = self.fluff_queue.pop_front() {
                broadcasted.push(txid);
            } else {
                break;
            }
        }

        broadcasted
    }

    /// Increment hop count for a transaction
    pub fn increment_hop(&mut self, txid: &Txid) -> Result<(), BitcoinError> {
        if let Some(tx) = self.stem_pool.get_mut(txid) {
            tx.hop_count += 1;
            Ok(())
        } else {
            Err(BitcoinError::InvalidAddress(
                "Transaction not in stem pool".to_string(),
            ))
        }
    }

    /// Get stem pool size
    pub fn stem_pool_size(&self) -> usize {
        self.stem_pool.len()
    }

    /// Get fluff queue size
    pub fn fluff_queue_size(&self) -> usize {
        self.fluff_queue.len()
    }

    /// Get statistics
    pub fn stats(&self) -> DandelionStats {
        DandelionStats {
            stem_pool_size: self.stem_pool.len(),
            fluff_queue_size: self.fluff_queue.len(),
            total_processed: self.stem_pool.len() + self.fluff_queue.len(),
        }
    }
}

/// Transaction in Dandelion++ stem phase
#[derive(Debug, Clone)]
struct DandelionTransaction {
    #[allow(dead_code)]
    txid: Txid,
    stem_start: SystemTime,
    hop_count: u32,
}

/// Dandelion++ statistics
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct DandelionStats {
    /// Transactions in stem phase
    pub stem_pool_size: usize,
    /// Transactions in fluff queue
    pub fluff_queue_size: usize,
    /// Total transactions processed
    pub total_processed: usize,
}

/// Peer connection manager for privacy
#[derive(Debug)]
pub struct PrivatePeerManager {
    /// Active peers
    peers: HashMap<String, PeerConnection>,
    /// Maximum number of peers
    max_peers: usize,
    /// Peer rotation enabled
    rotation_enabled: bool,
    /// Rotation interval
    rotation_interval: Duration,
    /// Last rotation time
    last_rotation: SystemTime,
}

impl PrivatePeerManager {
    /// Create a new private peer manager
    pub fn new(max_peers: usize, rotation_interval_secs: u64) -> Self {
        Self {
            peers: HashMap::new(),
            max_peers,
            rotation_enabled: true,
            rotation_interval: Duration::from_secs(rotation_interval_secs),
            last_rotation: SystemTime::now(),
        }
    }

    /// Add a peer connection
    pub fn add_peer(&mut self, peer_id: String, peer: PeerConnection) -> Result<(), BitcoinError> {
        if self.peers.len() >= self.max_peers {
            return Err(BitcoinError::InvalidAddress(
                "Maximum peers reached".to_string(),
            ));
        }

        self.peers.insert(peer_id, peer);
        Ok(())
    }

    /// Remove a peer
    pub fn remove_peer(&mut self, peer_id: &str) -> Option<PeerConnection> {
        self.peers.remove(peer_id)
    }

    /// Check if peer rotation is needed
    pub fn should_rotate(&self) -> bool {
        if !self.rotation_enabled {
            return false;
        }

        if let Ok(elapsed) = SystemTime::now().duration_since(self.last_rotation) {
            elapsed >= self.rotation_interval
        } else {
            false
        }
    }

    /// Perform peer rotation
    pub fn rotate_peers(&mut self) -> usize {
        let to_rotate = self.peers.len() / 4; // Rotate 25% of peers

        let mut rotated = 0;
        let peer_ids: Vec<_> = self.peers.keys().cloned().collect();

        for peer_id in peer_ids.iter().take(to_rotate) {
            self.peers.remove(peer_id);
            rotated += 1;
        }

        self.last_rotation = SystemTime::now();
        rotated
    }

    /// Get peer count
    pub fn peer_count(&self) -> usize {
        self.peers.len()
    }

    /// Get all peer IDs
    pub fn peer_ids(&self) -> Vec<String> {
        self.peers.keys().cloned().collect()
    }
}

/// Peer connection information
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PeerConnection {
    /// Peer address
    pub address: String,
    /// Connection established time
    pub connected_since: u64,
    /// Is this connection over Tor
    pub uses_tor: bool,
}

/// Network privacy manager
#[derive(Debug)]
pub struct NetworkPrivacyManager {
    /// Configuration
    #[allow(dead_code)]
    config: NetworkPrivacyConfig,
    /// Tor proxy manager
    tor_manager: Option<TorProxyManager>,
    /// Dandelion++ broadcaster
    dandelion: Option<DandelionBroadcaster>,
    /// Peer manager
    peer_manager: PrivatePeerManager,
}

impl NetworkPrivacyManager {
    /// Create a new network privacy manager
    pub fn new(config: NetworkPrivacyConfig) -> Self {
        let tor_manager = if config.use_tor {
            config.tor_proxy.clone().map(TorProxyManager::new)
        } else {
            None
        };

        let dandelion = if config.use_dandelion {
            Some(DandelionBroadcaster::new(config.stem_duration_secs))
        } else {
            None
        };

        let peer_manager =
            PrivatePeerManager::new(config.max_peers, config.peer_rotation_interval_secs);

        Self {
            config,
            tor_manager,
            dandelion,
            peer_manager,
        }
    }

    /// Broadcast transaction with privacy
    pub fn broadcast_transaction(&mut self, txid: Txid) -> Result<(), BitcoinError> {
        if let Some(dandelion) = &mut self.dandelion {
            dandelion.add_to_stem(txid)?;
        }
        // Otherwise, broadcast directly
        Ok(())
    }

    /// Process pending broadcasts
    pub fn process_broadcasts(&mut self) -> BroadcastResult {
        let mut result = BroadcastResult {
            stem_relayed: Vec::new(),
            fluff_broadcasted: Vec::new(),
        };

        if let Some(dandelion) = &mut self.dandelion {
            result.stem_relayed = dandelion.process_stem();
            result.fluff_broadcasted = dandelion.process_fluff(10);
        }

        result
    }

    /// Get Tor manager
    pub fn tor_manager(&self) -> Option<&TorProxyManager> {
        self.tor_manager.as_ref()
    }

    /// Get Dandelion++ stats
    pub fn dandelion_stats(&self) -> Option<DandelionStats> {
        self.dandelion.as_ref().map(|d| d.stats())
    }

    /// Get peer manager
    pub fn peer_manager(&self) -> &PrivatePeerManager {
        &self.peer_manager
    }

    /// Get mutable peer manager
    pub fn peer_manager_mut(&mut self) -> &mut PrivatePeerManager {
        &mut self.peer_manager
    }
}

/// Broadcast result
#[derive(Debug, Clone)]
pub struct BroadcastResult {
    /// Transactions relayed in stem phase
    pub stem_relayed: Vec<Txid>,
    /// Transactions broadcasted in fluff phase
    pub fluff_broadcasted: Vec<Txid>,
}

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

    #[tokio::test]
    async fn test_tor_manager_creation() {
        let manager = TorProxyManager::new("127.0.0.1:9050".to_string());
        assert_eq!(manager.proxy_addr(), "127.0.0.1:9050");
    }

    #[tokio::test]
    async fn test_tor_connection_test() {
        let mut manager = TorProxyManager::new("127.0.0.1:9050".to_string());
        let result = manager.test_connection().await;
        assert!(result.is_ok());
    }

    #[test]
    fn test_dandelion_creation() {
        let broadcaster = DandelionBroadcaster::new(15);
        assert_eq!(broadcaster.stem_pool_size(), 0);
        assert_eq!(broadcaster.fluff_queue_size(), 0);
    }

    #[test]
    fn test_dandelion_add_to_stem() {
        let mut broadcaster = DandelionBroadcaster::new(15);
        let txid = Txid::all_zeros();

        broadcaster.add_to_stem(txid).unwrap();
        assert_eq!(broadcaster.stem_pool_size(), 1);
    }

    #[test]
    fn test_dandelion_process_stem() {
        let mut broadcaster = DandelionBroadcaster::new(0); // Immediate fluff
        let txid = Txid::all_zeros();

        broadcaster.add_to_stem(txid).unwrap();

        // Process should move to fluff
        std::thread::sleep(Duration::from_millis(10));
        let to_fluff = broadcaster.process_stem();

        assert!(!to_fluff.is_empty());
        assert_eq!(broadcaster.fluff_queue_size(), 1);
    }

    #[test]
    fn test_dandelion_process_fluff() {
        let mut broadcaster = DandelionBroadcaster::new(15);
        let txid = Txid::all_zeros();

        broadcaster.fluff_queue.push_back(txid);

        let broadcasted = broadcaster.process_fluff(10);
        assert_eq!(broadcasted.len(), 1);
        assert_eq!(broadcaster.fluff_queue_size(), 0);
    }

    #[test]
    fn test_peer_manager_creation() {
        let manager = PrivatePeerManager::new(8, 3600);
        assert_eq!(manager.peer_count(), 0);
        assert_eq!(manager.max_peers, 8);
    }

    #[test]
    fn test_peer_manager_add_peer() {
        let mut manager = PrivatePeerManager::new(8, 3600);
        let peer = PeerConnection {
            address: "127.0.0.1:8333".to_string(),
            connected_since: 0,
            uses_tor: false,
        };

        manager.add_peer("peer1".to_string(), peer).unwrap();
        assert_eq!(manager.peer_count(), 1);
    }

    #[test]
    fn test_peer_manager_max_peers() {
        let mut manager = PrivatePeerManager::new(2, 3600);

        for i in 0..2 {
            let peer = PeerConnection {
                address: format!("127.0.0.1:833{}", i),
                connected_since: 0,
                uses_tor: false,
            };
            manager.add_peer(format!("peer{}", i), peer).unwrap();
        }

        // Adding 3rd peer should fail
        let peer = PeerConnection {
            address: "127.0.0.1:8335".to_string(),
            connected_since: 0,
            uses_tor: false,
        };
        let result = manager.add_peer("peer3".to_string(), peer);
        assert!(result.is_err());
    }

    #[test]
    fn test_peer_manager_rotation() {
        let mut manager = PrivatePeerManager::new(8, 0); // Immediate rotation

        for i in 0..4 {
            let peer = PeerConnection {
                address: format!("127.0.0.1:833{}", i),
                connected_since: 0,
                uses_tor: false,
            };
            manager.add_peer(format!("peer{}", i), peer).unwrap();
        }

        std::thread::sleep(Duration::from_millis(10));
        let rotated = manager.rotate_peers();
        assert!(rotated > 0);
        assert!(manager.peer_count() < 4);
    }

    #[test]
    fn test_network_privacy_manager() {
        let config = NetworkPrivacyConfig::default();
        let mut manager = NetworkPrivacyManager::new(config);

        let txid = Txid::all_zeros();
        let result = manager.broadcast_transaction(txid);
        assert!(result.is_ok());
    }

    #[test]
    fn test_network_privacy_config_default() {
        let config = NetworkPrivacyConfig::default();
        assert!(config.use_dandelion);
        assert_eq!(config.max_peers, 8);
    }
}
