import { SimplePool, type Filter, type Event, type Relay } from 'nostr-tools'

// Simple EventEmitter implementation for browser compatibility
class EventEmitter {
  private events: { [key: string]: Function[] } = {}

  on(event: string, listener: Function): void {
    if (!this.events[event]) {
      this.events[event] = []
    }
    this.events[event].push(listener)
  }

  off(event: string, listener: Function): void {
    if (!this.events[event]) return
    const index = this.events[event].indexOf(listener)
    if (index > -1) {
      this.events[event].splice(index, 1)
    }
  }

  emit(event: string, ...args: any[]): void {
    if (!this.events[event]) return
    this.events[event].forEach(listener => listener(...args))
  }

  removeAllListeners(event?: string): void {
    if (event) {
      delete this.events[event]
    } else {
      this.events = {}
    }
  }
}

export interface RelayConfig {
  url: string
  read: boolean
  write: boolean
  priority?: number // Lower number = higher priority
}

export interface SubscriptionConfig {
  id: string
  filters: Filter[]
  relays?: string[] // If not specified, uses all connected relays
  onEvent?: (event: Event) => void
  onEose?: () => void
  onClose?: () => void
}

export interface RelayStatus {
  url: string
  connected: boolean
  lastSeen: number
  error?: string
  latency?: number
}

export class RelayHub extends EventEmitter {
  private pool: SimplePool
  private relayConfigs: Map<string, RelayConfig> = new Map()
  private connectedRelays: Map<string, Relay> = new Map()
  private subscriptions: Map<string, any> = new Map()
  public isInitialized = false
  private reconnectInterval?: NodeJS.Timeout
  private healthCheckInterval?: NodeJS.Timeout
  private mobileVisibilityHandler?: () => void

  // Connection state
  private _isConnected = false
  private _connectionAttempts = 0
  private readonly maxReconnectAttempts = 5
  private readonly reconnectDelay = 5000 // 5 seconds
  private readonly healthCheckIntervalMs = 30000 // 30 seconds

  constructor() {
    super()
    this.pool = new SimplePool()
    this.setupMobileVisibilityHandling()
  }

  get isConnected(): boolean {
    return this._isConnected
  }

  get connectedRelayCount(): number {
    // Return the actual size of connectedRelays map
    const count = this.connectedRelays.size
    console.log('🔍 connectedRelayCount getter called, returning:', count)
    return count
  }

  get totalRelayCount(): number {
    return this.relayConfigs.size
  }

  get totalSubscriptionCount(): number {
    return this.subscriptions.size
  }

  get relayStatuses(): RelayStatus[] {
    console.log('🔍 relayStatuses getter called')
    console.log('🔍 relayConfigs size:', this.relayConfigs.size)
    console.log('🔍 connectedRelays size:', this.connectedRelays.size)
    console.log('🔍 connectedRelays keys:', Array.from(this.connectedRelays.keys()))
    
    return Array.from(this.relayConfigs.values()).map(config => {
      const relay = this.connectedRelays.get(config.url)
      const isConnected = !!relay
      console.log(`🔍 Relay ${config.url}: connected=${isConnected}, relay=${relay ? 'exists' : 'null'}`)
      
      return {
        url: config.url,
        connected: isConnected,
        lastSeen: relay ? Date.now() : 0,
        error: relay ? undefined : 'Not connected',
        latency: relay ? 0 : undefined // TODO: Implement actual latency measurement
      }
    })
  }

  /**
   * Initialize the relay hub with relay configurations
   */
  async initialize(relayUrls: string[]): Promise<void> {
    if (this.isInitialized) {
      console.warn('RelayHub already initialized')
      return
    }

    // Convert URLs to relay configs
    this.relayConfigs.clear()
    relayUrls.forEach((url, index) => {
      this.relayConfigs.set(url, {
        url,
        read: true,
        write: true,
        priority: index
      })
    })

    // Start connection management
    await this.connect()
    this.startHealthCheck()
    this.isInitialized = true

    console.log(`RelayHub initialized with ${relayUrls.length} relays`)
  }

  /**
   * Connect to all configured relays
   */
  async connect(): Promise<void> {
    if (this.relayConfigs.size === 0) {
      throw new Error('No relay configurations found. Call initialize() first.')
    }

    try {
      this._connectionAttempts++
      console.log(`Connecting to ${this.relayConfigs.size} relays (attempt ${this._connectionAttempts})`)

      // Connect to relays in priority order
      const sortedRelays = Array.from(this.relayConfigs.values())
        .sort((a, b) => (a.priority || 0) - (b.priority || 0))

      const connectionPromises = sortedRelays.map(async (config) => {
        try {
          const relay = await this.pool.ensureRelay(config.url)
          this.connectedRelays.set(config.url, relay)
          console.log(`Connected to relay: ${config.url}`)
          return { url: config.url, success: true }
        } catch (error) {
          console.error(`Failed to connect to relay ${config.url}:`, error)
          return { url: config.url, success: false, error }
        }
      })

      const results = await Promise.allSettled(connectionPromises)
      const successfulConnections = results.filter(
        result => result.status === 'fulfilled' && result.value.success
      )

      if (successfulConnections.length > 0) {
        this._isConnected = true
        this._connectionAttempts = 0
        this.emit('connected', successfulConnections.length)
        console.log(`Successfully connected to ${successfulConnections.length}/${this.relayConfigs.size} relays`)
      } else {
        throw new Error('Failed to connect to any relay')
      }
    } catch (error) {
      this._isConnected = false
      this.emit('connectionError', error)
      console.error('Connection failed:', error)
      
      // Schedule reconnection if we haven't exceeded max attempts
      if (this._connectionAttempts < this.maxReconnectAttempts) {
        this.scheduleReconnect()
      } else {
        this.emit('maxReconnectAttemptsReached')
        console.error('Max reconnection attempts reached')
      }
    }
  }

  /**
   * Disconnect from all relays
   */
  disconnect(): void {
    console.log('Disconnecting from all relays')
    
    // Clear intervals
    if (this.reconnectInterval) {
      clearTimeout(this.reconnectInterval)
      this.reconnectInterval = undefined
    }
    
    if (this.healthCheckInterval) {
      clearInterval(this.healthCheckInterval)
      this.healthCheckInterval = undefined
    }

    // Close all subscriptions
    this.subscriptions.forEach(sub => sub.close())
    this.subscriptions.clear()

    // Close all relay connections
    this.pool.close(Array.from(this.relayConfigs.keys()))
    this.connectedRelays.clear()
    
    this._isConnected = false
    this.emit('disconnected')
  }

  /**
   * Subscribe to events from relays
   */
  subscribe(config: SubscriptionConfig): () => void {
    if (!this.isInitialized) {
      throw new Error('RelayHub not initialized. Call initialize() first.')
    }

    if (!this._isConnected) {
      throw new Error('Not connected to any relays')
    }

    // Determine which relays to use
    const targetRelays = config.relays || Array.from(this.connectedRelays.keys())
    const availableRelays = targetRelays.filter(url => this.connectedRelays.has(url))

    if (availableRelays.length === 0) {
      throw new Error('No available relays for subscription')
    }

    console.log(`Creating subscription ${config.id} on ${availableRelays.length} relays`)

    // Create subscription using the pool
    const subscription = this.pool.subscribeMany(availableRelays, config.filters, {
      onevent: (event: Event) => {
        config.onEvent?.(event)
        this.emit('event', { subscriptionId: config.id, event, relay: 'unknown' })
      },
      oneose: () => {
        config.onEose?.()
        this.emit('eose', { subscriptionId: config.id })
      }
    })

    // Store subscription for cleanup
    this.subscriptions.set(config.id, subscription)

    // Return unsubscribe function
    return () => {
      this.unsubscribe(config.id)
    }
  }

  /**
   * Unsubscribe from a specific subscription
   */
  unsubscribe(subscriptionId: string): void {
    const subscription = this.subscriptions.get(subscriptionId)
    if (subscription) {
      subscription.close()
      this.subscriptions.delete(subscriptionId)
      console.log(`Unsubscribed from ${subscriptionId}`)
    }
  }

  /**
   * Publish an event to all connected relays
   */
  async publishEvent(event: Event): Promise<{ success: number; total: number }> {
    if (!this._isConnected) {
      throw new Error('Not connected to any relays')
    }

    const relayUrls = Array.from(this.connectedRelays.keys())
    const results = await Promise.allSettled(
      relayUrls.map(relay => this.pool.publish([relay], event))
    )

    const successful = results.filter(result => result.status === 'fulfilled').length
    const total = results.length

    console.log(`Published event ${event.id} to ${successful}/${total} relays`)
    this.emit('eventPublished', { eventId: event.id, success: successful, total })

    return { success: successful, total }
  }

  /**
   * Query events from relays (one-time fetch)
   */
  async queryEvents(filters: Filter[], relays?: string[]): Promise<Event[]> {
    if (!this._isConnected) {
      throw new Error('Not connected to any relays')
    }

    const targetRelays = relays || Array.from(this.connectedRelays.keys())
    const availableRelays = targetRelays.filter(url => this.connectedRelays.has(url))

    if (availableRelays.length === 0) {
      throw new Error('No available relays for query')
    }

    try {
      // Query each filter separately and combine results
      const allEvents: Event[] = []
      for (const filter of filters) {
        const events = await this.pool.querySync(availableRelays, filter)
        allEvents.push(...events)
      }
      console.log(`Queried ${allEvents.length} events from ${availableRelays.length} relays`)
      return allEvents
    } catch (error) {
      console.error('Query failed:', error)
      throw error
    }
  }

  /**
   * Get a specific relay instance
   */
  getRelay(url: string): Relay | undefined {
    return this.connectedRelays.get(url)
  }

  /**
   * Check if a specific relay is connected
   */
  isRelayConnected(url: string): boolean {
    return this.connectedRelays.has(url)
  }

  /**
   * Force reconnection to all relays
   */
  async reconnect(): Promise<void> {
    console.log('Forcing reconnection to all relays')
    this.disconnect()
    await this.connect()
  }

  /**
   * Schedule automatic reconnection
   */
  private scheduleReconnect(): void {
    if (this.reconnectInterval) {
      clearTimeout(this.reconnectInterval)
    }

    this.reconnectInterval = setTimeout(async () => {
      console.log('Attempting automatic reconnection...')
      await this.connect()
    }, this.reconnectDelay)
  }

  /**
   * Start health check monitoring
   */
  private startHealthCheck(): void {
    if (this.healthCheckInterval) {
      clearInterval(this.healthCheckInterval)
    }

    this.healthCheckInterval = setInterval(() => {
      this.performHealthCheck()
    }, this.healthCheckIntervalMs)
  }

  /**
   * Perform health check on all relays
   */
  private async performHealthCheck(): Promise<void> {
    if (!this._isConnected) return

    console.log('Performing relay health check...')
    const disconnectedRelays: string[] = []

    // Check each relay connection
    for (const [url] of this.connectedRelays) {
      try {
        // Try to send a ping or check connection status
        // For now, we'll just check if the relay is still in our connected relays map
        if (!this.connectedRelays.has(url)) {
          disconnectedRelays.push(url)
        }
      } catch (error) {
        console.warn(`Health check failed for relay ${url}:`, error)
        disconnectedRelays.push(url)
      }
    }

    // Remove disconnected relays
    disconnectedRelays.forEach(url => {
      this.connectedRelays.delete(url)
      console.log(`Removed disconnected relay: ${url}`)
    })

    // Update connection status
    if (this.connectedRelays.size === 0) {
      this._isConnected = false
      this.emit('allRelaysDisconnected')
      console.warn('All relays disconnected, attempting reconnection...')
      await this.connect()
    } else if (this.connectedRelays.size < this.relayConfigs.size) {
      this.emit('partialDisconnection', {
        connected: this.connectedRelays.size,
        total: this.relayConfigs.size
      })
    }
  }

  /**
   * Setup mobile visibility handling for better WebSocket management
   */
  private setupMobileVisibilityHandling(): void {
    // Handle page visibility changes (mobile app backgrounding)
    if (typeof document !== 'undefined') {
      this.mobileVisibilityHandler = () => {
        if (document.hidden) {
          console.log('Page hidden, maintaining WebSocket connections')
          // Keep connections alive but reduce activity
        } else {
          console.log('Page visible, resuming normal WebSocket activity')
          // Resume normal activity and check connections
          this.performHealthCheck()
        }
      }

      document.addEventListener('visibilitychange', this.mobileVisibilityHandler)
    }

    // Handle online/offline events
    if (typeof window !== 'undefined') {
      window.addEventListener('online', () => {
        console.log('Network online, checking relay connections...')
        this.performHealthCheck()
      })

      window.addEventListener('offline', () => {
        console.log('Network offline, marking as disconnected...')
        this._isConnected = false
        this.emit('networkOffline')
      })
    }
  }

  /**
   * Cleanup resources
   */
  destroy(): void {
    console.log('Destroying RelayHub...')
    
    // Remove event listeners
    if (this.mobileVisibilityHandler && typeof document !== 'undefined') {
      document.removeEventListener('visibilitychange', this.mobileVisibilityHandler)
    }

    if (typeof window !== 'undefined') {
      window.removeEventListener('online', () => {})
      window.removeEventListener('offline', () => {})
    }

    // Disconnect and cleanup
    this.disconnect()
    this.removeAllListeners()
    this.isInitialized = false
  }
}

// Export singleton instance
export const relayHub = new RelayHub()