dcrouter/ts/mail/delivery/smtp/utils/helpers.ts

/**
 * SMTP Helper Functions
 * Provides utility functions for SMTP server implementation
 */

import * as plugins from '../../../../plugins.js';
import { SMTP_DEFAULTS } from '../constants.js';
import type { ISmtpSession, ISmtpServerOptions } from '../../interfaces.js';

/**
 * Formats a multi-line SMTP response according to RFC 5321
 * @param code - Response code
 * @param lines - Response lines
 * @returns Formatted SMTP response
 */
export function formatMultilineResponse(code: number, lines: string[]): string {
  if (!lines || lines.length === 0) {
    return `${code} `;
  }
  
  if (lines.length === 1) {
    return `${code} ${lines[0]}`;
  }
  
  let response = '';
  for (let i = 0; i < lines.length - 1; i++) {
    response += `${code}-${lines[i]}${SMTP_DEFAULTS.CRLF}`;
  }
  response += `${code} ${lines[lines.length - 1]}`;
  
  return response;
}

/**
 * Generates a unique session ID
 * @returns Unique session ID
 */
export function generateSessionId(): string {
  return `${Date.now()}-${Math.floor(Math.random() * 10000)}`;
}

/**
 * Safely parses an integer from string with a default value
 * @param value - String value to parse
 * @param defaultValue - Default value if parsing fails
 * @returns Parsed integer or default value
 */
export function safeParseInt(value: string | undefined, defaultValue: number): number {
  if (!value) {
    return defaultValue;
  }
  
  const parsed = parseInt(value, 10);
  return isNaN(parsed) ? defaultValue : parsed;
}

/**
 * Safely gets the socket details
 * @param socket - Socket to get details from
 * @returns Socket details object
 */
export function getSocketDetails(socket: plugins.net.Socket | plugins.tls.TLSSocket): {
  remoteAddress: string;
  remotePort: number;
  remoteFamily: string;
  localAddress: string;
  localPort: number;
  encrypted: boolean;
} {
  return {
    remoteAddress: socket.remoteAddress || 'unknown',
    remotePort: socket.remotePort || 0,
    remoteFamily: socket.remoteFamily || 'unknown',
    localAddress: socket.localAddress || 'unknown',
    localPort: socket.localPort || 0,
    encrypted: socket instanceof plugins.tls.TLSSocket
  };
}

/**
 * Gets TLS details if socket is TLS
 * @param socket - Socket to get TLS details from
 * @returns TLS details or undefined if not TLS
 */
export function getTlsDetails(socket: plugins.net.Socket | plugins.tls.TLSSocket): {
  protocol?: string;
  cipher?: string;
  authorized?: boolean;
} | undefined {
  if (!(socket instanceof plugins.tls.TLSSocket)) {
    return undefined;
  }
  
  return {
    protocol: socket.getProtocol(),
    cipher: socket.getCipher()?.name,
    authorized: socket.authorized
  };
}

/**
 * Merges default options with provided options
 * @param options - User provided options
 * @returns Merged options with defaults
 */
export function mergeWithDefaults(options: Partial<ISmtpServerOptions>): ISmtpServerOptions {
  return {
    port: options.port || SMTP_DEFAULTS.SMTP_PORT,
    key: options.key || '',
    cert: options.cert || '',
    hostname: options.hostname || SMTP_DEFAULTS.HOSTNAME,
    host: options.host,
    securePort: options.securePort,
    ca: options.ca,
    maxSize: options.size || SMTP_DEFAULTS.MAX_MESSAGE_SIZE,
    maxConnections: options.maxConnections || SMTP_DEFAULTS.MAX_CONNECTIONS,
    socketTimeout: options.socketTimeout || SMTP_DEFAULTS.SOCKET_TIMEOUT,
    connectionTimeout: options.connectionTimeout || SMTP_DEFAULTS.CONNECTION_TIMEOUT,
    cleanupInterval: options.cleanupInterval || SMTP_DEFAULTS.CLEANUP_INTERVAL,
    maxRecipients: options.maxRecipients || SMTP_DEFAULTS.MAX_RECIPIENTS,
    size: options.size || SMTP_DEFAULTS.MAX_MESSAGE_SIZE,
    dataTimeout: options.dataTimeout || SMTP_DEFAULTS.DATA_TIMEOUT,
    auth: options.auth,
  };
}

/**
 * Creates a text response formatter for the SMTP server
 * @param socket - Socket to send responses to
 * @returns Function to send formatted response
 */
export function createResponseFormatter(socket: plugins.net.Socket | plugins.tls.TLSSocket): (response: string) => void {
  return (response: string): void => {
    try {
      socket.write(`${response}${SMTP_DEFAULTS.CRLF}`);
      console.log(`→ ${response}`);
    } catch (error) {
      console.error(`Error sending response: ${error instanceof Error ? error.message : String(error)}`);
      socket.destroy();
    }
  };
}

/**
 * Extracts SMTP command name from a command line
 * @param commandLine - Full command line
 * @returns Command name in uppercase
 */
export function extractCommandName(commandLine: string): string {
  const parts = commandLine.trim().split(' ');
  return parts[0].toUpperCase();
}

/**
 * Extracts SMTP command arguments from a command line
 * @param commandLine - Full command line
 * @returns Arguments string
 */
export function extractCommandArgs(commandLine: string): string {
  const firstSpace = commandLine.indexOf(' ');
  if (firstSpace === -1) {
    return '';
  }
  
  return commandLine.substring(firstSpace + 1).trim();
}

/**
 * Sanitizes data for logging (hides sensitive info)
 * @param data - Data to sanitize
 * @returns Sanitized data
 */
export function sanitizeForLogging(data: any): any {
  if (!data) {
    return data;
  }
  
  if (typeof data !== 'object') {
    return data;
  }
  
  const result: any = Array.isArray(data) ? [] : {};
  
  for (const key in data) {
    if (Object.prototype.hasOwnProperty.call(data, key)) {
      // Sanitize sensitive fields
      if (key.toLowerCase().includes('password') ||
          key.toLowerCase().includes('token') ||
          key.toLowerCase().includes('secret') ||
          key.toLowerCase().includes('credential')) {
        result[key] = '********';
      } else if (typeof data[key] === 'object' && data[key] !== null) {
        result[key] = sanitizeForLogging(data[key]);
      } else {
        result[key] = data[key];
      }
    }
  }
  
  return result;
}