// named-pipe-client.js
const net = require('net');
const { EventEmitter } = require('events');
const { v4: uuidv4 } = require('uuid');

/**
 * 基于命名管道的读写锁客户端
 * 提供对NamedPipeLockServer的客户端接口，允许应用程序请求和释放读写锁
 * 支持自动重连和超时机制
 */
class NamedPipeRWLock extends EventEmitter {
  /**
   * 创建NamedPipeRWLock实例
   * @param {string} resource - 要锁定的资源名称
   * @param {string} pipePath - 服务器命名管道路径
   * @param {Object} options - 配置选项
   * @param {number} options.timeout - 锁请求超时时间（毫秒），默认30000
   * @param {number} options.retryInterval - 重连间隔（毫秒），默认1000
   * @param {number} options.maxRetries - 最大重连次数，默认5
   */
  constructor(resource, pipePath = '\\\\.\\pipe\\rwlock-server', options = {}) {
    super();
    this.resource = resource;
    this.pipePath = pipePath;
    this.timeout = options.timeout || 30000;
    this.retryInterval = options.retryInterval || 1000;
    this.maxRetries = options.maxRetries || 5;
    
    this.socket = null;
    this.requestId = null;
    this.isLocked = false;
    this.lockType = null;
    this.timeoutHandle = null;
    this.retryCount = 0;
  }

  /**
   * 连接到锁服务器
   * @returns {Promise<void>} 连接成功时resolve
   */
  async connect() {
    return new Promise((resolve, reject) => {
      if (this.socket && !this.socket.destroyed) {
        resolve();
        return;
      }

      this.socket = net.createConnection(this.pipePath, () => {
        console.log(`Connected to lock server at ${this.pipePath}`);
        this.retryCount = 0;
        resolve();
      });
      
      this.socket.on('error', (error) => {
        console.error('Connection error:', error);
        reject(error);
      });
      
      this.socket.on('data', data => this.handleMessage(data));
      this.socket.on('close', () => this.handleDisconnect());
      this.socket.on('end', () => this.handleDisconnect());
    });
  }

  /**
   * 请求读锁
   * @returns {Promise<void>} 锁获取成功时resolve
   */
  async readLock() {
    return this.acquireLock('readLock');
  }

  /**
   * 请求写锁
   * @returns {Promise<void>} 锁获取成功时resolve
   */
  async writeLock() {
    return this.acquireLock('writeLock');
  }

  /**
   * 获取指定类型的锁
   * @param {string} type - 锁类型 ('readLock' 或 'writeLock')
   * @returns {Promise<void>} 锁获取成功时resolve
   */
  async acquireLock(type) {
    await this.ensureConnected();

    return new Promise((resolve, reject) => {
      if (this.isLocked) {
        reject(new Error('Lock already held'));
        return;
      }

      this.requestId = uuidv4();
      this.lockType = type;

      // 发送锁请求
      this.sendMessage({
        type,
        resource: this.resource,
        requestId: this.requestId
      });

      // 设置超时
      this.timeoutHandle = setTimeout(() => {
        this.cleanup();
        reject(new Error(`Lock acquisition timeout after ${this.timeout}ms`));
      }, this.timeout);

      // 监听锁授予事件
      const onLockGranted = (data) => {
        if (data.requestId === this.requestId) {
          this.isLocked = true;
          clearTimeout(this.timeoutHandle);
          this.removeListener('lockGranted', onLockGranted);
          resolve();
        }
      };

      this.on('lockGranted', onLockGranted);

      // 监听错误事件
      const onError = (errorData) => {
        if (errorData.requestId === this.requestId) {
          clearTimeout(this.timeoutHandle);
          this.removeListener('error', onError);
          reject(new Error(errorData.message));
        }
      };

      this.on('error', onError);
    });
  }

  /**
   * 释放当前持有的锁
   * @returns {Promise<void>}
   */
  async unlock() {
    if (!this.isLocked || !this.socket) return;

    this.sendMessage({
      type: 'unlock',
      resource: this.resource
    });

    this.cleanup();
    console.log(`Lock released for resource: ${this.resource}`);
  }

  /**
   * 处理从服务器收到的消息
   * @param {Buffer} data - 接收的数据
   */
  handleMessage(data) {
    try {
      const messages = data.toString().split('\n').filter(msg => msg.trim());
      
      for (const msg of messages) {
        const message = JSON.parse(msg);
        
        switch (message.type) {
          case 'lockGranted':
            this.emit('lockGranted', message);
            break;
          case 'error':
            this.emit('error', message);
            break;
          default:
            console.warn('Unknown message type:', message.type);
        }
      }
    } catch (error) {
      console.error('Error parsing message:', error, 'Raw data:', data.toString());
    }
  }

  /**
   * 处理与服务器的连接断开
   */
  handleDisconnect() {
    console.log('Disconnected from lock server');
    this.cleanup();
    this.socket = null;
    
    // 自动重连逻辑
    if (this.retryCount < this.maxRetries) {
      this.retryCount++;
      console.log(`Attempting to reconnect... (${this.retryCount}/${this.maxRetries})`);
      
      setTimeout(() => {
        this.ensureConnected().catch(error => {
          console.error('Reconnection failed:', error);
        });
      }, this.retryInterval);
    }
  }

  /**
   * 向服务器发送消息
   * @param {Object} message - 要发送的消息对象
   */
  sendMessage(message) {
    if (this.socket && !this.socket.destroyed) {
      try {
        this.socket.write(JSON.stringify(message) + '\n');
      } catch (error) {
        console.error('Error sending message:', error);
        this.handleDisconnect();
      }
    } else {
      console.error('Socket not connected');
      this.handleDisconnect();
    }
  }

  /**
   * 确保客户端已连接到服务器
   * @returns {Promise<void>}
   */
  async ensureConnected() {
    if (!this.socket || this.socket.destroyed) {
      await this.connect();
    }
  }

  /**
   * 清理内部状态
   */
  cleanup() {
    this.isLocked = false;
    this.lockType = null;
    this.requestId = null;
    if (this.timeoutHandle) {
      clearTimeout(this.timeoutHandle);
      this.timeoutHandle = null;
    }
  }

  /**
   * 关闭连接
   */
  close() {
    if (this.socket) {
        this.socket.removeAllListeners();

        this.socket.end();
      this.socket.destroy();
    }
    this.cleanup();
  }
}

module.exports = NamedPipeRWLock;