smartmta/ts/mail/delivery/smtpserver/utils/connection-wrapper.ts

/**
 * Connection Wrapper Utility
 * Wraps Deno.Conn to provide Node.js net.Socket-compatible interface
 * This allows the SMTP server to use Deno's native networking while maintaining
 * compatibility with existing Socket-based code
 */

import { EventEmitter } from '../../../../plugins.ts';

/**
 * Wraps a Deno.Conn or Deno.TlsConn to provide a Node.js Socket-compatible interface
 */
export class ConnectionWrapper extends EventEmitter {
  private conn: Deno.Conn | Deno.TlsConn;
  private _destroyed = false;
  private _reading = false;
  private _remoteAddr: Deno.NetAddr;
  private _localAddr: Deno.NetAddr;

  constructor(conn: Deno.Conn | Deno.TlsConn) {
    super();
    this.conn = conn;
    this._remoteAddr = conn.remoteAddr as Deno.NetAddr;
    this._localAddr = conn.localAddr as Deno.NetAddr;

    // Start reading from the connection
    this._reading = true;
    this._startReading();
  }

  /**
   * Get remote address (Node.js net.Socket compatible)
   */
  get remoteAddress(): string {
    return this._remoteAddr.hostname;
  }

  /**
   * Get remote port (Node.js net.Socket compatible)
   */
  get remotePort(): number {
    return this._remoteAddr.port;
  }

  /**
   * Get local address (Node.js net.Socket compatible)
   */
  get localAddress(): string {
    return this._localAddr.hostname;
  }

  /**
   * Get local port (Node.js net.Socket compatible)
   */
  get localPort(): number {
    return this._localAddr.port;
  }

  /**
   * Check if connection is destroyed
   */
  get destroyed(): boolean {
    return this._destroyed;
  }

  /**
   * Check ready state (Node.js compatible)
   */
  get readyState(): string {
    if (this._destroyed) {
      return 'closed';
    }
    return 'open';
  }

  /**
   * Check if writable (Node.js compatible)
   */
  get writable(): boolean {
    return !this._destroyed;
  }

  /**
   * Check if this is a secure (TLS) connection
   */
  get encrypted(): boolean {
    return 'handshake' in this.conn; // TlsConn has handshake property
  }

  /**
   * Write data to the connection (Node.js net.Socket compatible)
   */
  write(data: string | Uint8Array, encoding?: string | ((err?: Error) => void), callback?: (err?: Error) => void): boolean {
    // Handle overloaded signatures (encoding is optional)
    if (typeof encoding === 'function') {
      callback = encoding;
      encoding = undefined;
    }

    if (this._destroyed) {
      const error = new Error('Connection is destroyed');
      if (callback) {
        setTimeout(() => callback(error), 0);
      }
      return false;
    }

    const bytes = typeof data === 'string'
      ? new TextEncoder().encode(data)
      : data;

    // Use a promise-based approach that Node.js compatibility expects
    // Write happens async but we return true immediately (buffered)
    this.conn.write(bytes)
      .then(() => {
        if (callback) {
          callback();
        }
      })
      .catch((err) => {
        const error = err instanceof Error ? err : new Error(String(err));
        if (callback) {
          callback(error);
        } else {
          this.emit('error', error);
        }
      });

    return true;
  }

  /**
   * End the connection (Node.js net.Socket compatible)
   */
  end(data?: string | Uint8Array, encoding?: string, callback?: () => void): void {
    if (data) {
      this.write(data, encoding, () => {
        this.destroy();
        if (callback) callback();
      });
    } else {
      this.destroy();
      if (callback) callback();
    }
  }

  /**
   * Destroy the connection (Node.js net.Socket compatible)
   */
  destroy(error?: Error): void {
    if (this._destroyed) {
      return;
    }

    this._destroyed = true;
    this._reading = false;

    try {
      this.conn.close();
    } catch (closeError) {
      // Ignore close errors
    }

    if (error) {
      this.emit('error', error);
    }

    this.emit('close', !!error);
  }

  /**
   * Set TCP_NODELAY option (Node.js net.Socket compatible)
   */
  setNoDelay(noDelay: boolean = true): this {
    try {
      // @ts-ignore - Deno.Conn has setNoDelay
      if (typeof this.conn.setNoDelay === 'function') {
        // @ts-ignore
        this.conn.setNoDelay(noDelay);
      }
    } catch {
      // Ignore if not supported
    }
    return this;
  }

  /**
   * Set keep-alive option (Node.js net.Socket compatible)
   */
  setKeepAlive(enable: boolean = true, initialDelay?: number): this {
    try {
      // @ts-ignore - Deno.Conn has setKeepAlive
      if (typeof this.conn.setKeepAlive === 'function') {
        // @ts-ignore
        this.conn.setKeepAlive(enable);
      }
    } catch {
      // Ignore if not supported
    }
    return this;
  }

  /**
   * Set timeout (Node.js net.Socket compatible)
   */
  setTimeout(timeout: number, callback?: () => void): this {
    // Deno doesn't have built-in socket timeout, but we can implement it
    // For now, just accept the call without error (most timeout handling is done elsewhere)
    if (callback) {
      // If callback provided, we could set up a timer, but for now just ignore
      // The SMTP server handles timeouts at a higher level
    }
    return this;
  }

  /**
   * Pause reading from the connection
   */
  pause(): this {
    this._reading = false;
    return this;
  }

  /**
   * Resume reading from the connection
   */
  resume(): this {
    if (!this._reading && !this._destroyed) {
      this._reading = true;
      this._startReading();
    }
    return this;
  }

  /**
   * Get the underlying Deno.Conn
   */
  getDenoConn(): Deno.Conn | Deno.TlsConn {
    return this.conn;
  }

  /**
   * Replace the underlying connection (for STARTTLS upgrade)
   */
  replaceConnection(newConn: Deno.TlsConn): void {
    this.conn = newConn;
    this._remoteAddr = newConn.remoteAddr as Deno.NetAddr;
    this._localAddr = newConn.localAddr as Deno.NetAddr;

    // Restart reading from the new TLS connection
    if (!this._destroyed) {
      this._reading = true;
      this._startReading();
    }
  }

  /**
   * Internal method to read data from the connection
   */
  private async _startReading(): Promise<void> {
    if (!this._reading || this._destroyed) {
      return;
    }

    try {
      const buffer = new Uint8Array(4096);

      while (this._reading && !this._destroyed) {
        const n = await this.conn.read(buffer);

        if (n === null) {
          // EOF
          this._destroyed = true;
          this.emit('end');
          this.emit('close', false);
          break;
        }

        const data = buffer.subarray(0, n);
        this.emit('data', data);
      }
    } catch (error) {
      if (!this._destroyed) {
        this._destroyed = true;
        this.emit('error', error instanceof Error ? error : new Error(String(error)));
        this.emit('close', true);
      }
    }
  }

  /**
   * Remove all listeners (cleanup helper)
   */
  removeAllListeners(event?: string): this {
    super.removeAllListeners(event);
    return this;
  }
}