package dht

import (
	"database/sql"
	"fmt"
	"log"
	"net"
	"sync"
	"time"

	"git.sovbit.dev/enki/torrentGateway/internal/config"
)

// APINodeInfo represents a DHT node for API compatibility
type APINodeInfo struct {
	IP   string
	Port int
}

// DHTBootstrap manages DHT bootstrap functionality and persistence
type DHTBootstrap struct {
	node       *DHT
	gateway    Gateway
	knownNodes map[string]time.Time // nodeID -> last seen
	torrents   map[string]bool       // announced torrents
	db         *sql.DB
	config     *config.DHTConfig
	mutex      sync.RWMutex
	startTime  time.Time
}

// Gateway interface for DHT integration
type Gateway interface {
	GetPublicURL() string
	GetDHTPort() int
	GetDatabase() *sql.DB
	GetAllTorrentHashes() []string
}

// NodeInfo represents a DHT node with reputation
type NodeInfo struct {
	NodeID     string    `json:"node_id"`
	IP         string    `json:"ip"`
	Port       int       `json:"port"`
	LastSeen   time.Time `json:"last_seen"`
	Reputation int       `json:"reputation"`
}

// TorrentAnnounce represents a DHT torrent announcement
type TorrentAnnounce struct {
	InfoHash     string    `json:"info_hash"`
	Port         int       `json:"port"`
	LastAnnounce time.Time `json:"last_announce"`
	PeerCount    int       `json:"peer_count"`
}

// NewDHTBootstrap creates a new DHT bootstrap manager
func NewDHTBootstrap(node *DHT, gateway Gateway, config *config.DHTConfig) *DHTBootstrap {
	return &DHTBootstrap{
		node:       node,
		gateway:    gateway,
		knownNodes: make(map[string]time.Time),
		torrents:   make(map[string]bool),
		db:         gateway.GetDatabase(),
		config:     config,
		startTime:  time.Now(),
	}
}

// Initialize sets up DHT bootstrap functionality
func (d *DHTBootstrap) Initialize() error {
	log.Printf("Initializing DHT bootstrap functionality")

	// Initialize database tables
	if err := d.initializeTables(); err != nil {
		return fmt.Errorf("failed to initialize DHT tables: %w", err)
	}

	// Load persisted data
	if err := d.loadPersistedData(); err != nil {
		log.Printf("Warning: Failed to load persisted DHT data: %v", err)
	}

	// Add self as bootstrap node if configured
	if d.config.BootstrapSelf {
		if err := d.addSelfAsBootstrap(); err != nil {
			log.Printf("Warning: Failed to add self as bootstrap: %v", err)
		}
	}

	// Add default bootstrap nodes
	d.addDefaultBootstrapNodes()

	// Start announce loop for existing torrents
	go d.announceLoop()

	// Start routing table maintenance
	go d.maintainRoutingTable()

	// Start node discovery
	go d.nodeDiscoveryLoop()

	log.Printf("DHT bootstrap initialized successfully")
	return nil
}

// initializeTables creates DHT-related database tables
func (d *DHTBootstrap) initializeTables() error {
	tables := []string{
		`CREATE TABLE IF NOT EXISTS dht_announces (
			info_hash TEXT PRIMARY KEY,
			port INTEGER NOT NULL,
			last_announce TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
			peer_count INTEGER DEFAULT 0,
			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
		)`,
		`CREATE TABLE IF NOT EXISTS dht_nodes (
			node_id TEXT PRIMARY KEY,
			ip TEXT NOT NULL,
			port INTEGER NOT NULL,
			last_seen TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
			reputation INTEGER DEFAULT 0,
			first_seen TIMESTAMP DEFAULT CURRENT_TIMESTAMP
		)`,
		`CREATE INDEX IF NOT EXISTS idx_dht_announces_last_announce ON dht_announces(last_announce)`,
		`CREATE INDEX IF NOT EXISTS idx_dht_nodes_last_seen ON dht_nodes(last_seen)`,
		`CREATE INDEX IF NOT EXISTS idx_dht_nodes_reputation ON dht_nodes(reputation)`,
	}

	for _, query := range tables {
		if _, err := d.db.Exec(query); err != nil {
			return fmt.Errorf("failed to create table: %w", err)
		}
	}

	log.Printf("DHT database tables initialized")
	return nil
}

// loadPersistedData loads DHT state from database
func (d *DHTBootstrap) loadPersistedData() error {
	// Load announced torrents
	rows, err := d.db.Query(`
		SELECT info_hash, port FROM dht_announces 
		WHERE last_announce > datetime('now', '-1 day')
	`)
	if err != nil {
		return err
	}
	defer rows.Close()

	count := 0
	for rows.Next() {
		var infoHash string
		var port int
		if err := rows.Scan(&infoHash, &port); err != nil {
			continue
		}
		d.torrents[infoHash] = true
		count++
	}

	// Load known DHT nodes
	nodeRows, err := d.db.Query(`
		SELECT node_id, ip, port, last_seen FROM dht_nodes 
		WHERE last_seen > datetime('now', '-6 hours')
		ORDER BY reputation DESC, last_seen DESC
		LIMIT 1000
	`)
	if err != nil {
		return err
	}
	defer nodeRows.Close()

	nodeCount := 0
	for nodeRows.Next() {
		var nodeID, ip string
		var port int
		var lastSeen time.Time
		if err := nodeRows.Scan(&nodeID, &ip, &port, &lastSeen); err != nil {
			continue
		}
		d.knownNodes[nodeID] = lastSeen
		nodeCount++
	}

	log.Printf("Loaded %d announced torrents and %d known DHT nodes", count, nodeCount)
	return nil
}

// addSelfAsBootstrap adds the gateway as a bootstrap node
func (d *DHTBootstrap) addSelfAsBootstrap() error {
	publicURL := d.gateway.GetPublicURL()
	dhtPort := d.gateway.GetDHTPort()

	// Parse the public URL to get the hostname
	selfAddr := fmt.Sprintf("%s:%d", extractHostname(publicURL), dhtPort)
	
	// Add to bootstrap nodes list
	d.config.BootstrapNodes = append([]string{selfAddr}, d.config.BootstrapNodes...)
	
	log.Printf("Added self as DHT bootstrap node: %s", selfAddr)
	return nil
}

// addDefaultBootstrapNodes adds well-known DHT bootstrap nodes
func (d *DHTBootstrap) addDefaultBootstrapNodes() {
	defaultNodes := []string{
		"router.bittorrent.com:6881",
		"dht.transmissionbt.com:6881",
		"router.utorrent.com:6881",
		"dht.libtorrent.org:25401",
	}

	// Add default nodes if not already in config
	for _, node := range defaultNodes {
		found := false
		for _, existing := range d.config.BootstrapNodes {
			if existing == node {
				found = true
				break
			}
		}
		if !found {
			d.config.BootstrapNodes = append(d.config.BootstrapNodes, node)
		}
	}

	log.Printf("DHT bootstrap nodes: %v", d.config.BootstrapNodes)
}

// announceLoop periodically announces all tracked torrents
func (d *DHTBootstrap) announceLoop() {
	if d.config.AnnounceInterval <= 0 {
		log.Printf("DHT announce loop disabled (interval <= 0)")
		return
	}

	ticker := time.NewTicker(d.config.AnnounceInterval)
	defer ticker.Stop()

	log.Printf("Starting DHT announce loop (interval: %v)", d.config.AnnounceInterval)

	for {
		select {
		case <-ticker.C:
			d.announceAllTorrents()
		}
	}
}

// announceAllTorrents announces all known torrents to DHT
func (d *DHTBootstrap) announceAllTorrents() {
	d.mutex.RLock()
	torrents := make([]string, 0, len(d.torrents))
	for infoHash := range d.torrents {
		torrents = append(torrents, infoHash)
	}
	d.mutex.RUnlock()

	// Also get torrents from gateway storage
	gatewayTorrents := d.gateway.GetAllTorrentHashes()
	
	// Merge lists
	allTorrents := make(map[string]bool)
	for _, infoHash := range torrents {
		allTorrents[infoHash] = true
	}
	for _, infoHash := range gatewayTorrents {
		allTorrents[infoHash] = true
	}

	// Announce each torrent
	count := 0
	port := d.gateway.GetDHTPort()
	for infoHash := range allTorrents {
		d.node.Announce(infoHash, port)
		d.updateDHTAnnounce(infoHash, port)
		count++
	}

	if count > 0 {
		log.Printf("Announced %d torrents to DHT", count)
	}
}

// AnnounceNewTorrent immediately announces a new torrent to DHT
func (d *DHTBootstrap) AnnounceNewTorrent(infoHash string, port int) {
	d.mutex.Lock()
	d.torrents[infoHash] = true
	d.mutex.Unlock()

	// Immediately announce to DHT
	d.node.Announce(infoHash, port)
	d.updateDHTAnnounce(infoHash, port)

	log.Printf("Announced new torrent to DHT: %s", infoHash[:8])
}

// updateDHTAnnounce updates announce record in database
func (d *DHTBootstrap) updateDHTAnnounce(infoHash string, port int) {
	_, err := d.db.Exec(`
		INSERT OR REPLACE INTO dht_announces (info_hash, port, last_announce, peer_count)
		VALUES (?, ?, CURRENT_TIMESTAMP, 
			COALESCE((SELECT peer_count FROM dht_announces WHERE info_hash = ?), 0))
	`, infoHash, port, infoHash)

	if err != nil {
		log.Printf("Failed to update DHT announce record: %v", err)
	}
}

// maintainRoutingTable performs routing table maintenance
func (d *DHTBootstrap) maintainRoutingTable() {
	cleanupInterval := 5 * time.Minute
	if d.config.CleanupInterval > 0 {
		cleanupInterval = d.config.CleanupInterval
	}

	ticker := time.NewTicker(cleanupInterval)
	defer ticker.Stop()

	log.Printf("Starting DHT routing table maintenance (interval: %v)", cleanupInterval)

	for range ticker.C {
		d.refreshBuckets()
		d.cleanDeadNodes()
		d.pruneOldData()
	}
}

// refreshBuckets refreshes DHT routing table buckets
func (d *DHTBootstrap) refreshBuckets() {
	// In a real implementation, this would send find_node queries
	// to refresh buckets that haven't been active
	
	stats := d.node.GetStats()
	d.mutex.Lock()
	defer d.mutex.Unlock()

	// Update node count in known nodes
	activeNodes := 0
	now := time.Now()
	cutoff := now.Add(-30 * time.Minute)

	for nodeID, lastSeen := range d.knownNodes {
		if lastSeen.After(cutoff) {
			activeNodes++
		} else {
			delete(d.knownNodes, nodeID)
		}
	}

	log.Printf("DHT bucket refresh: %d nodes in routing table, %d known nodes, %d stored items", 
		stats.NodesInTable, activeNodes, stats.StoredItems)
}

// cleanDeadNodes removes expired nodes from database
func (d *DHTBootstrap) cleanDeadNodes() {
	cutoff := time.Now().Add(-6 * time.Hour)
	
	result, err := d.db.Exec(`
		DELETE FROM dht_nodes WHERE last_seen < ?
	`, cutoff)
	
	if err != nil {
		log.Printf("Failed to clean dead DHT nodes: %v", err)
		return
	}

	if rowsAffected, _ := result.RowsAffected(); rowsAffected > 0 {
		log.Printf("Cleaned %d dead DHT nodes", rowsAffected)
	}
}

// pruneOldData removes old DHT announce data
func (d *DHTBootstrap) pruneOldData() {
	// Remove announces older than 7 days
	cutoff := time.Now().Add(-7 * 24 * time.Hour)
	
	result, err := d.db.Exec(`
		DELETE FROM dht_announces WHERE last_announce < ?
	`, cutoff)
	
	if err != nil {
		log.Printf("Failed to prune old DHT announces: %v", err)
		return
	}

	if rowsAffected, _ := result.RowsAffected(); rowsAffected > 0 {
		log.Printf("Pruned %d old DHT announces", rowsAffected)
	}
}

// nodeDiscoveryLoop discovers and tracks new DHT nodes
func (d *DHTBootstrap) nodeDiscoveryLoop() {
	ticker := time.NewTicker(10 * time.Minute)
	defer ticker.Stop()

	log.Printf("Starting DHT node discovery loop")

	for range ticker.C {
		d.discoverNewNodes()
	}
}

// discoverNewNodes attempts to discover new DHT nodes
func (d *DHTBootstrap) discoverNewNodes() {
	// In a real implementation, this would:
	// 1. Send find_node queries to known nodes
	// 2. Parse responses to discover new nodes
	// 3. Add new nodes to routing table and database

	stats := d.node.GetStats()
	log.Printf("DHT node discovery: %d nodes in routing table", stats.NodesInTable)
}

// AddKnownNode adds a newly discovered node to our knowledge base
func (d *DHTBootstrap) AddKnownNode(nodeID, ip string, port int, reputation int) {
	d.mutex.Lock()
	defer d.mutex.Unlock()

	now := time.Now()
	d.knownNodes[nodeID] = now

	// Store in database
	_, err := d.db.Exec(`
		INSERT OR REPLACE INTO dht_nodes (node_id, ip, port, last_seen, reputation)
		VALUES (?, ?, ?, ?, ?)
	`, nodeID, ip, port, now, reputation)

	if err != nil {
		log.Printf("Failed to store DHT node: %v", err)
	}
}


// GetDHTStats returns comprehensive DHT statistics
func (d *DHTBootstrap) GetDHTStats() map[string]interface{} {
	d.mutex.RLock()
	knownNodesCount := len(d.knownNodes)
	announcedTorrents := len(d.torrents)
	d.mutex.RUnlock()

	nodeStats := d.node.GetStats()

	// Get database stats
	var totalAnnounces, totalNodes int64
	d.db.QueryRow(`SELECT COUNT(*) FROM dht_announces`).Scan(&totalAnnounces)
	d.db.QueryRow(`SELECT COUNT(*) FROM dht_nodes`).Scan(&totalNodes)

	// Get recent activity
	var recentAnnounces, activeNodes int64
	d.db.QueryRow(`SELECT COUNT(*) FROM dht_announces WHERE last_announce > datetime('now', '-1 hour')`).Scan(&recentAnnounces)
	d.db.QueryRow(`SELECT COUNT(*) FROM dht_nodes WHERE last_seen > datetime('now', '-1 hour')`).Scan(&activeNodes)

	return map[string]interface{}{
		"node_id":             fmt.Sprintf("%x", d.node.nodeID),
		"routing_table_size":  nodeStats.NodesInTable,
		"active_torrents":     announcedTorrents,
		"total_announces":     totalAnnounces,
		"recent_announces":    recentAnnounces,
		"known_nodes":         knownNodesCount,
		"total_nodes":         totalNodes,
		"active_nodes":        activeNodes,
		"packets_sent":        nodeStats.PacketsSent,
		"packets_received":    nodeStats.PacketsReceived,
		"stored_items":        nodeStats.StoredItems,
		"uptime":              time.Since(d.startTime).String(),
		"bootstrap_nodes":     len(d.config.BootstrapNodes),
	}
}

// GetTorrentStats returns DHT statistics for a specific torrent
func (d *DHTBootstrap) GetTorrentStats(infoHash string) map[string]interface{} {
	var announce TorrentAnnounce
	err := d.db.QueryRow(`
		SELECT info_hash, port, last_announce, peer_count 
		FROM dht_announces 
		WHERE info_hash = ?
	`, infoHash).Scan(&announce.InfoHash, &announce.Port, &announce.LastAnnounce, &announce.PeerCount)

	if err != nil {
		return map[string]interface{}{
			"info_hash":     infoHash,
			"announced":     false,
			"last_announce": nil,
			"peer_count":    0,
		}
	}

	return map[string]interface{}{
		"info_hash":     announce.InfoHash,
		"announced":     true,
		"port":          announce.Port,
		"last_announce": announce.LastAnnounce.Format(time.RFC3339),
		"peer_count":    announce.PeerCount,
	}
}

// Stop gracefully shuts down DHT bootstrap functionality
func (d *DHTBootstrap) Stop() error {
	log.Printf("Stopping DHT bootstrap functionality")
	
	// Persist current state
	d.mutex.RLock()
	defer d.mutex.RUnlock()

	// Update final announce times
	for infoHash := range d.torrents {
		d.updateDHTAnnounce(infoHash, d.gateway.GetDHTPort())
	}

	log.Printf("DHT bootstrap stopped, persisted %d torrents", len(d.torrents))
	return nil
}

// Helper functions

// extractHostname extracts hostname from URL
func extractHostname(url string) string {
	// Simple URL parsing - in production use net/url
	if host, _, err := net.SplitHostPort(url); err == nil {
		return host
	}
	// Fallback for URLs without port
	return url
}

// isValidNodeID checks if a node ID is valid
func isValidNodeID(nodeID string) bool {
	return len(nodeID) == NodeIDLength*2 // hex-encoded 20 bytes
}

// ForceAnnounce manually triggers announcement of all torrents
func (d *DHTBootstrap) ForceAnnounce() map[string]interface{} {
	before := d.GetDHTStats()
	d.announceAllTorrents()
	after := d.GetDHTStats()

	return map[string]interface{}{
		"before": before,
		"after":  after,
		"action": "force_announce",
	}
}

// GetActiveBootstrapNodes returns currently active bootstrap nodes
func (d *DHTBootstrap) GetActiveBootstrapNodes() []NodeInfo {
	var activeNodes []NodeInfo
	cutoff := time.Now().Add(-1 * time.Hour)

	rows, err := d.db.Query(`
		SELECT node_id, ip, port, last_seen, reputation 
		FROM dht_nodes 
		WHERE last_seen > ? AND reputation > 0
		ORDER BY reputation DESC, last_seen DESC
		LIMIT 50
	`, cutoff)
	if err != nil {
		return activeNodes
	}
	defer rows.Close()

	for rows.Next() {
		var node NodeInfo
		if err := rows.Scan(&node.NodeID, &node.IP, &node.Port, &node.LastSeen, &node.Reputation); err != nil {
			continue
		}
		activeNodes = append(activeNodes, node)
	}

	return activeNodes
}

// GetBootstrapNodes returns nodes in API-compatible format for interface compliance
func (d *DHTBootstrap) GetBootstrapNodes() []APINodeInfo {
	var nodes []APINodeInfo

	// Add self if configured
	if d.config.BootstrapSelf {
		publicURL := d.gateway.GetPublicURL()
		selfNode := APINodeInfo{
			IP:   extractHostname(publicURL),
			Port: d.gateway.GetDHTPort(),
		}
		nodes = append(nodes, selfNode)
	}

	// Add other good nodes from database
	rows, err := d.db.Query(`
		SELECT ip, port FROM dht_nodes 
		WHERE last_seen > datetime('now', '-1 hour')
		ORDER BY reputation DESC, last_seen DESC
		LIMIT 20
	`)
	if err != nil {
		log.Printf("Failed to query DHT nodes: %v", err)
		return nodes
	}
	defer rows.Close()

	for rows.Next() {
		var node APINodeInfo
		if err := rows.Scan(&node.IP, &node.Port); err != nil {
			continue
		}
		nodes = append(nodes, node)
	}

	return nodes
}

// GetBootstrapNodesInternal returns nodes with full NodeInfo structure  
func (d *DHTBootstrap) GetBootstrapNodesInternal() []NodeInfo {
	var nodes []NodeInfo

	// Add self if configured
	if d.config.BootstrapSelf {
		publicURL := d.gateway.GetPublicURL()
		selfNode := NodeInfo{
			NodeID:     fmt.Sprintf("%x", d.node.nodeID),
			IP:         extractHostname(publicURL),
			Port:       d.gateway.GetDHTPort(),
			LastSeen:   time.Now(),
			Reputation: 100, // High reputation for self
		}
		nodes = append(nodes, selfNode)
	}

	// Add other good nodes from database
	rows, err := d.db.Query(`
		SELECT node_id, ip, port, last_seen, reputation 
		FROM dht_nodes 
		WHERE last_seen > datetime('now', '-1 hour')
		ORDER BY reputation DESC, last_seen DESC
		LIMIT 20
	`)
	if err != nil {
		log.Printf("Failed to query DHT nodes: %v", err)
		return nodes
	}
	defer rows.Close()

	for rows.Next() {
		var node NodeInfo
		if err := rows.Scan(&node.NodeID, &node.IP, &node.Port, &node.LastSeen, &node.Reputation); err != nil {
			continue
		}
		nodes = append(nodes, node)
	}

	return nodes
}