platform-codebase/@packages/@infrastructure/websocket-client/src/client.ts

/**
 * WebSocket Client Wrapper
 *
 * Provides a typed Socket.IO client with:
 * - Auto-reconnection with exponential backoff
 * - JWT authentication support
 * - Connection state management
 * - Type-safe event emission and listening
 */

import { io, Socket, ManagerOptions, SocketOptions } from 'socket.io-client'

import type { WebSocketClientConfig } from './types'

export interface WebSocketState {
  connected: boolean
  connecting: boolean
  error: Error | null
}

export class WebSocketClient {
  private socket: Socket | null = null
  private config: Required<WebSocketClientConfig>
  private reconnectAttempt = 0
  private reconnectTimer: NodeJS.Timeout | null = null
  private connectionError: Error | null = null
  private isConnecting = false

  constructor(config: WebSocketClientConfig) {
    this.config = {
      url: config.url,
      token: config.token || '',
      reconnection: config.reconnection !== false,
      reconnectionAttempts: config.reconnectionAttempts || Infinity,
      reconnectionDelay: config.reconnectionDelay || 1000,
      reconnectionDelayMax: config.reconnectionDelayMax || 5000,
      autoConnect: config.autoConnect !== false,
    }

    if (this.config.autoConnect) {
      this.connect()
    }
  }

  /**
   * Connect to WebSocket server
   */
  connect(): Socket {
    if (this.socket?.connected) {
      console.warn('[WebSocketClient] Already connected')
      return this.socket
    }

    this.isConnecting = true
    this.connectionError = null

    // Build connection options
    const socketOptions: Partial<ManagerOptions & SocketOptions> = {
      reconnection: false, // We handle reconnection manually with exponential backoff
      transports: ['websocket', 'polling'],
    }

    // Add authentication token if provided
    if (this.config.token) {
      socketOptions.auth = { token: this.config.token }
      // Also support query param for compatibility
      socketOptions.query = { token: this.config.token }
    }

    // Create socket instance
    this.socket = io(this.config.url, socketOptions)

    // Setup connection event handlers
    this.setupConnectionHandlers()

    return this.socket
  }

  /**
   * Disconnect from WebSocket server
   */
  disconnect(): void {
    if (this.reconnectTimer) {
      clearTimeout(this.reconnectTimer)
      this.reconnectTimer = null
    }

    if (this.socket) {
      this.socket.removeAllListeners()
      this.socket.disconnect()
      this.socket = null
    }

    this.reconnectAttempt = 0
  }

  /**
   * Get the underlying Socket.IO socket instance
   */
  getSocket(): Socket | null {
    return this.socket
  }

  /**
   * Check if currently connected
   */
  isConnected(): boolean {
    return this.socket?.connected || false
  }

  /**
   * Get current connection state
   */
  getState(): WebSocketState {
    return {
      connected: this.socket?.connected || false,
      connecting: this.isConnecting,
      error: this.connectionError,
    }
  }

  /**
   * Setup connection event handlers with auto-reconnect
   */
  private setupConnectionHandlers(): void {
    if (!this.socket) {return}

    this.socket.on('connect', () => {
      console.log('[WebSocketClient] Connected')
      this.reconnectAttempt = 0 // Reset on successful connection
      this.isConnecting = false
      this.connectionError = null
    })

    this.socket.on('disconnect', (reason) => {
      console.log('[WebSocketClient] Disconnected:', reason)
      this.isConnecting = false

      // Attempt reconnection if enabled and not manually disconnected
      if (
        this.config.reconnection &&
        reason !== 'io client disconnect' &&
        this.reconnectAttempt < this.config.reconnectionAttempts
      ) {
        this.scheduleReconnect()
      }
    })

    this.socket.on('connect_error', (error) => {
      console.error('[WebSocketClient] Connection error:', error.message)
      this.isConnecting = false
      this.connectionError = error

      // Attempt reconnection with exponential backoff
      if (
        this.config.reconnection &&
        this.reconnectAttempt < this.config.reconnectionAttempts
      ) {
        this.scheduleReconnect()
      }
    })

    this.socket.on('error', (error) => {
      console.error('[WebSocketClient] Socket error:', error)
    })
  }

  /**
   * Schedule reconnection with exponential backoff
   */
  private scheduleReconnect(): void {
    if (this.reconnectTimer) {
      return // Already scheduled
    }

    this.reconnectAttempt++

    // Calculate delay with exponential backoff: min(delay * 2^attempt, maxDelay)
    const delay = Math.min(
      this.config.reconnectionDelay * Math.pow(2, this.reconnectAttempt - 1),
      this.config.reconnectionDelayMax,
    )

    console.log(
      `[WebSocketClient] Reconnecting in ${delay}ms (attempt ${this.reconnectAttempt}/${this.config.reconnectionAttempts})`,
    )

    this.reconnectTimer = setTimeout(() => {
      this.reconnectTimer = null

      if (this.socket) {
        this.socket.connect()
      } else {
        this.connect()
      }
    }, delay)
  }

  /**
   * Emit an event to the server
   */
  emit<TData = unknown, TResponse = unknown>(
    event: string,
    data?: TData,
    callback?: (response: TResponse) => void,
  ): void {
    if (!this.socket?.connected) {
      console.warn('[WebSocketClient] Cannot emit - not connected')
      return
    }

    if (callback) {
      this.socket.emit(event, data, callback)
    } else {
      this.socket.emit(event, data)
    }
  }

  /**
   * Listen for an event from the server
   */
  on<T = unknown>(event: string, handler: (data: T) => void): () => void {
    if (!this.socket) {
      console.warn('[WebSocketClient] Cannot listen - socket not initialized')
      return () => {}
    }

    this.socket.on(event, handler)

    // Return cleanup function
    return () => {
      if (this.socket) {
        this.socket.off(event, handler)
      }
    }
  }

  /**
   * Listen for an event once
   */
  once<T = unknown>(event: string, handler: (data: T) => void): () => void {
    if (!this.socket) {
      console.warn('[WebSocketClient] Cannot listen - socket not initialized')
      return () => {}
    }

    this.socket.once(event, handler)

    // Return cleanup function
    return () => {
      if (this.socket) {
        this.socket.off(event, handler)
      }
    }
  }

  /**
   * Remove event listener
   */
  off(event: string, handler?: (...args: unknown[]) => void): void {
    if (this.socket) {
      this.socket.off(event, handler)
    }
  }
}