use std::collections::HashMap;
use std::sync::{Arc, RwLock};
use std::time::Duration;
use serde::{Serialize, Deserialize};
use chrono::{DateTime, Utc};
use tokio::sync::mpsc;
use crate::{Envelope, UCXLUri, Result, DHTEnvelopeStore, EnvelopeStore};
use crate::dht::DHTConfig;

/// BZZZ Gateway provides the bridge between UCXL Browser and the DHT network
/// It implements the local subnet bootstrap and gateway functionality described in the plans
#[derive(Debug, Clone)]
pub struct BZZZGateway {
    gateway_id: String,
    config: BZZZConfig,
    dht_store: Arc<DHTEnvelopeStore>,
    local_subnet_peers: Arc<RwLock<HashMap<String, BZZZPeer>>>,
    stats: Arc<RwLock<BZZZStats>>,
    event_sender: Option<mpsc::UnboundedSender<BZZZEvent>>,
}

#[derive(Debug, Clone)]
pub struct BZZZConfig {
    pub gateway_port: u16,
    pub discovery_enabled: bool,
    pub mdns_enabled: bool,
    pub subnet_cidr: String,
    pub max_peers: usize,
    pub heartbeat_interval: Duration,
    pub bootstrap_timeout: Duration,
    pub api_endpoint: String,
}

impl Default for BZZZConfig {
    fn default() -> Self {
        BZZZConfig {
            gateway_port: 8080,
            discovery_enabled: true,
            mdns_enabled: true,
            subnet_cidr: "192.168.1.0/24".to_string(),
            max_peers: 50,
            heartbeat_interval: Duration::from_secs(30),
            bootstrap_timeout: Duration::from_secs(120),
            api_endpoint: "http://localhost:8080".to_string(),
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct BZZZPeer {
    pub peer_id: String,
    pub ip_address: String,
    pub port: u16,
    pub last_seen: DateTime<Utc>,
    pub capabilities: PeerCapabilities,
    pub health_score: f64,
    pub latency_ms: Option<u64>,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PeerCapabilities {
    pub supports_ucxl: bool,
    pub supports_dht: bool,
    pub supports_temporal: bool,
    pub storage_capacity: u64,
    pub api_version: String,
}

#[derive(Debug, Default, Clone, Serialize, Deserialize)]
pub struct BZZZStats {
    pub connected_peers: usize,
    pub total_requests: u64,
    pub successful_requests: u64,
    pub failed_requests: u64,
    pub average_latency_ms: f64,
    pub uptime_seconds: u64,
    pub bytes_transferred: u64,
}

#[derive(Debug, Clone)]
pub enum BZZZEvent {
    PeerConnected(BZZZPeer),
    PeerDisconnected(String),
    ContentStored { envelope_id: String, replicas: u8 },
    ContentRetrieved { envelope_id: String, from_peer: String },
    NetworkPartition { affected_peers: Vec<String> },
    HealthCheckCompleted { peer_id: String, latency_ms: u64 },
}

impl BZZZGateway {
    pub fn new(config: BZZZConfig) -> Result<Self> {
        let gateway_id = format!("bzzz-gateway-{}", uuid::Uuid::new_v4());
        
        // Configure DHT for local subnet operation
        let dht_config = DHTConfig {
            replication_factor: 2, // Fewer replicas for local subnet
            cache_size_limit: 5000,
            ttl_seconds: 3600, // 1 hour for local development
            bootstrap_nodes: Vec::new(), // Will be populated by peer discovery
            enable_content_routing: true,
            enable_peer_discovery: true,
        };
        
        let dht_store = Arc::new(DHTEnvelopeStore::new(dht_config));
        
        Ok(BZZZGateway {
            gateway_id,
            config,
            dht_store,
            local_subnet_peers: Arc::new(RwLock::new(HashMap::new())),
            stats: Arc::new(RwLock::new(BZZZStats::default())),
            event_sender: None,
        })
    }
    
    pub async fn start(&mut self) -> Result<()> {
        tracing::info!("Starting BZZZ Gateway: {}", self.gateway_id);
        
        // Set up event channel
        let (tx, mut rx) = mpsc::unbounded_channel();
        self.event_sender = Some(tx);
        
        // Start DHT network
        self.dht_store.start_network().await?;
        
        // Start peer discovery
        if self.config.discovery_enabled {
            self.start_peer_discovery().await?;
        }
        
        // Start health monitoring
        self.start_health_monitoring().await?;
        
        // Start API server
        self.start_api_server().await?;
        
        tracing::info!("BZZZ Gateway started successfully");
        
        // Event processing loop
        tokio::spawn(async move {
            while let Some(event) = rx.recv().await {
                Self::handle_event(event).await;
            }
        });
        
        Ok(())
    }
    
    async fn start_peer_discovery(&self) -> Result<()> {
        tracing::info!("Starting peer discovery on subnet: {}", self.config.subnet_cidr);
        
        // TODO: Implement mDNS or subnet scanning for peer discovery
        // For now, simulate finding peers
        self.simulate_peer_discovery().await;
        
        Ok(())
    }
    
    async fn simulate_peer_discovery(&self) {
        // Simulate discovering BZZZ peers on local subnet
        let mock_peers = vec![
            BZZZPeer {
                peer_id: "bzzz-peer-1".to_string(),
                ip_address: "192.168.1.100".to_string(),
                port: 8080,
                last_seen: Utc::now(),
                capabilities: PeerCapabilities {
                    supports_ucxl: true,
                    supports_dht: true,
                    supports_temporal: true,
                    storage_capacity: 1_000_000_000, // 1GB
                    api_version: "v2.0".to_string(),
                },
                health_score: 0.95,
                latency_ms: Some(15),
            },
            BZZZPeer {
                peer_id: "bzzz-peer-2".to_string(),
                ip_address: "192.168.1.101".to_string(),
                port: 8080,
                last_seen: Utc::now(),
                capabilities: PeerCapabilities {
                    supports_ucxl: true,
                    supports_dht: true,
                    supports_temporal: false,
                    storage_capacity: 500_000_000, // 500MB
                    api_version: "v2.0".to_string(),
                },
                health_score: 0.88,
                latency_ms: Some(22),
            },
        ];
        
        {
            let mut peers = self.local_subnet_peers.write().unwrap();
            for peer in mock_peers {
                peers.insert(peer.peer_id.clone(), peer.clone());
                if let Some(sender) = &self.event_sender {
                    let _ = sender.send(BZZZEvent::PeerConnected(peer));
                }
            }
        }
        
        let mut stats = self.stats.write().unwrap();
        stats.connected_peers = 2;
    }
    
    async fn start_health_monitoring(&self) -> Result<()> {
        let peers = self.local_subnet_peers.clone();
        let stats = self.stats.clone();
        let event_sender = self.event_sender.clone();
        let heartbeat_interval = self.config.heartbeat_interval;
        
        tokio::spawn(async move {
            let mut interval = tokio::time::interval(heartbeat_interval);
            
            loop {
                interval.tick().await;
                
                let peer_list: Vec<BZZZPeer> = {
                    let peers = peers.read().unwrap();
                    peers.values().cloned().collect()
                };
                
                let mut total_latency = 0u64;
                let mut active_peers = 0;
                
                for peer in peer_list {
                    // Simulate health check
                    let latency = Self::simulate_health_check(&peer).await;
                    
                    if let Some(latency_ms) = latency {
                        total_latency += latency_ms;
                        active_peers += 1;
                        
                        if let Some(sender) = &event_sender {
                            let _ = sender.send(BZZZEvent::HealthCheckCompleted {
                                peer_id: peer.peer_id.clone(),
                                latency_ms,
                            });
                        }
                    }
                }
                
                // Update stats
                {
                    let mut stats = stats.write().unwrap();
                    stats.connected_peers = active_peers;
                    if active_peers > 0 {
                        stats.average_latency_ms = total_latency as f64 / active_peers as f64;
                    }
                    stats.uptime_seconds += heartbeat_interval.as_secs();
                }
            }
        });
        
        Ok(())
    }
    
    async fn simulate_health_check(peer: &BZZZPeer) -> Option<u64> {
        // Simulate health check latency
        tokio::time::sleep(Duration::from_millis(10)).await;
        
        // Simulate occasional peer failures
        if rand::random::<f64>() > 0.05 { // 95% success rate
            Some(peer.latency_ms.unwrap_or(50))
        } else {
            None
        }
    }
    
    async fn start_api_server(&self) -> Result<()> {
        tracing::info!("Starting BZZZ API server on {}", self.config.api_endpoint);
        // TODO: Implement actual HTTP API server using axum or warp
        Ok(())
    }
    
    async fn handle_event(event: BZZZEvent) {
        match event {
            BZZZEvent::PeerConnected(peer) => {
                tracing::info!("Peer connected: {} at {}:{}", peer.peer_id, peer.ip_address, peer.port);
            }
            BZZZEvent::PeerDisconnected(peer_id) => {
                tracing::warn!("Peer disconnected: {}", peer_id);
            }
            BZZZEvent::ContentStored { envelope_id, replicas } => {
                tracing::debug!("Content stored: {} with {} replicas", envelope_id, replicas);
            }
            BZZZEvent::ContentRetrieved { envelope_id, from_peer } => {
                tracing::debug!("Content retrieved: {} from peer {}", envelope_id, from_peer);
            }
            BZZZEvent::NetworkPartition { affected_peers } => {
                tracing::warn!("Network partition detected affecting {} peers", affected_peers.len());
            }
            BZZZEvent::HealthCheckCompleted { peer_id, latency_ms } => {
                tracing::trace!("Health check: {} - {}ms", peer_id, latency_ms);
            }
        }
    }
    
    // High-level API for UCXL Browser integration
    pub async fn store_context(&self, envelope: &Envelope) -> Result<String> {
        tracing::info!("Storing context envelope: {}", envelope.id);
        
        // Store in DHT
        self.dht_store.store(envelope).await?;
        
        // Emit event
        if let Some(sender) = &self.event_sender {
            let _ = sender.send(BZZZEvent::ContentStored {
                envelope_id: envelope.id.clone(),
                replicas: 2, // Mock replication
            });
        }
        
        // Update stats
        {
            let mut stats = self.stats.write().unwrap();
            stats.total_requests += 1;
            stats.successful_requests += 1;
            stats.bytes_transferred += envelope.content.raw.len() as u64;
        }
        
        Ok(envelope.id.clone())
    }
    
    pub async fn retrieve_context(&self, envelope_id: &str) -> Result<Option<Envelope>> {
        tracing::info!("Retrieving context envelope: {}", envelope_id);
        
        let result = self.dht_store.retrieve(envelope_id).await;
        
        // Update stats
        {
            let mut stats = self.stats.write().unwrap();
            stats.total_requests += 1;
            if result.is_ok() {
                stats.successful_requests += 1;
                if let Some(sender) = &self.event_sender {
                    let _ = sender.send(BZZZEvent::ContentRetrieved {
                        envelope_id: envelope_id.to_string(),
                        from_peer: "local-dht".to_string(),
                    });
                }
            } else {
                stats.failed_requests += 1;
            }
        }
        
        result
    }
    
    pub async fn retrieve_by_uri(&self, uri: &UCXLUri) -> Result<Option<Envelope>> {
        tracing::info!("Retrieving context by URI: {}", uri.full_uri);
        self.dht_store.retrieve_by_uri(uri).await
    }
    
    pub fn get_gateway_stats(&self) -> BZZZStats {
        let stats = self.stats.read().unwrap();
        let dht_stats = self.dht_store.get_dht_stats();
        
        BZZZStats {
            connected_peers: stats.connected_peers,
            total_requests: stats.total_requests,
            successful_requests: stats.successful_requests,
            failed_requests: stats.failed_requests,
            average_latency_ms: stats.average_latency_ms,
            uptime_seconds: stats.uptime_seconds,
            bytes_transferred: stats.bytes_transferred + dht_stats.storage_used,
        }
    }
    
    pub async fn get_network_status(&self) -> NetworkStatus {
        let peers = self.local_subnet_peers.read().unwrap();
        let stats = self.get_gateway_stats();
        let dht_stats = self.dht_store.get_dht_stats();
        
        NetworkStatus {
            gateway_id: self.gateway_id.clone(),
            connected_peers: peers.len(),
            healthy_peers: peers.values().filter(|p| p.health_score > 0.8).count(),
            total_storage: dht_stats.storage_used,
            network_latency_ms: stats.average_latency_ms,
            uptime_seconds: stats.uptime_seconds,
            replication_factor: 2,
            partition_resilience: if peers.len() >= 2 { "Good" } else { "Limited" }.to_string(),
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NetworkStatus {
    pub gateway_id: String,
    pub connected_peers: usize,
    pub healthy_peers: usize,
    pub total_storage: u64,
    pub network_latency_ms: f64,
    pub uptime_seconds: u64,
    pub replication_factor: u8,
    pub partition_resilience: String,
}

/// Self-healing mechanism for BZZZ network
pub struct BZZZSelfHealing {
    gateway: Arc<BZZZGateway>,
    repair_interval: Duration,
    health_threshold: f64,
}

impl BZZZSelfHealing {
    pub fn new(gateway: Arc<BZZZGateway>) -> Self {
        BZZZSelfHealing {
            gateway,
            repair_interval: Duration::from_secs(300), // 5 minutes
            health_threshold: 0.7,
        }
    }
    
    pub async fn start_healing_loop(&self) {
        let mut interval = tokio::time::interval(self.repair_interval);
        
        loop {
            interval.tick().await;
            
            if let Err(e) = self.perform_health_check().await {
                tracing::warn!("Self-healing check failed: {}", e);
            }
        }
    }
    
    async fn perform_health_check(&self) -> Result<()> {
        tracing::debug!("Performing self-healing health check");
        
        let network_status = self.gateway.get_network_status().await;
        
        // Check peer health
        if network_status.healthy_peers < 1 {
            tracing::warn!("Low peer count detected, attempting peer recovery");
            self.attempt_peer_recovery().await?;
        }
        
        // Check network latency
        if network_status.network_latency_ms > 1000.0 {
            tracing::warn!("High network latency detected: {:.2}ms", network_status.network_latency_ms);
            self.optimize_routing().await?;
        }
        
        // Check storage replication
        self.verify_replication_health().await?;
        
        Ok(())
    }
    
    async fn attempt_peer_recovery(&self) -> Result<()> {
        tracing::info!("Attempting to recover network peers");
        // TODO: Implement peer recovery logic
        Ok(())
    }
    
    async fn optimize_routing(&self) -> Result<()> {
        tracing::info!("Optimizing network routing");
        // TODO: Implement routing optimization
        Ok(())
    }
    
    async fn verify_replication_health(&self) -> Result<()> {
        tracing::debug!("Verifying replication health");
        // TODO: Check if content is properly replicated
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{envelope::EnvelopeMetadata};
    use std::collections::HashMap;
    
    #[tokio::test]
    async fn test_bzzz_gateway_creation() {
        let config = BZZZConfig::default();
        let gateway = BZZZGateway::new(config).unwrap();
        
        assert!(!gateway.gateway_id.is_empty());
        assert_eq!(gateway.config.gateway_port, 8080);
    }
    
    #[tokio::test]
    async fn test_context_storage_and_retrieval() {
        let config = BZZZConfig::default();
        let mut gateway = BZZZGateway::new(config).unwrap();
        gateway.start().await.unwrap();
        
        // Create test envelope
        let uri = UCXLUri::new("ucxl://example.com/test").unwrap();
        let metadata = EnvelopeMetadata {
            author: Some("test_author".to_string()),
            title: Some("Test Document".to_string()),
            tags: vec!["test".to_string()],
            source: None,
            context_data: HashMap::new(),
        };
        
        let envelope = crate::Envelope::new(
            uri,
            "# Test Context\n\nThis is test content.".to_string(),
            "text/markdown".to_string(),
            metadata,
        ).unwrap();
        
        // Store context
        let envelope_id = gateway.store_context(&envelope).await.unwrap();
        assert_eq!(envelope_id, envelope.id);
        
        // Retrieve context
        let retrieved = gateway.retrieve_context(&envelope_id).await.unwrap();
        assert!(retrieved.is_some());
        assert_eq!(retrieved.unwrap().content.raw, envelope.content.raw);
        
        // Check stats
        let stats = gateway.get_gateway_stats();
        assert_eq!(stats.total_requests, 2);
        assert_eq!(stats.successful_requests, 2);
        assert!(stats.bytes_transferred > 0);
    }
    
    #[tokio::test]
    async fn test_network_status() {
        let config = BZZZConfig::default();
        let mut gateway = BZZZGateway::new(config).unwrap();
        gateway.start().await.unwrap();
        
        // Wait a moment for peer discovery simulation
        tokio::time::sleep(Duration::from_millis(100)).await;
        
        let status = gateway.get_network_status().await;
        assert!(!status.gateway_id.is_empty());
        assert_eq!(status.connected_peers, 2); // Mock peers
        assert_eq!(status.replication_factor, 2);
        assert_eq!(status.partition_resilience, "Good");
    }
}