email-amazon/email-worker-nodejs/delivery.ts

/**
 * SMTP / email delivery with nodemailer pooled transport
 *
 * Replaces both Python's SMTPPool and EmailDelivery classes.
 * nodemailer handles connection pooling, keepalive, and reconnection natively.
 *
 * Removed: LMTP delivery path (never used in production).
 */

import { createTransport, type Transporter } from 'nodemailer';
import { config } from '../config.js';
import { log } from '../logger.js';

// ---------------------------------------------------------------------------
// Permanent error detection
// ---------------------------------------------------------------------------
const PERMANENT_INDICATORS = [
  '550', '551', '553',
  'mailbox not found', 'user unknown', 'no such user',
  'recipient rejected', 'does not exist', 'invalid recipient',
  'unknown user',
];

function isPermanentRecipientError(errorMsg: string): boolean {
  const lower = errorMsg.toLowerCase();
  return PERMANENT_INDICATORS.some((ind) => lower.includes(ind));
}

// ---------------------------------------------------------------------------
// Delivery class
// ---------------------------------------------------------------------------
export class EmailDelivery {
  private transport: Transporter;

  constructor() {
    this.transport = createTransport({
      host: config.smtpHost,
      port: config.smtpPort,
      secure: config.smtpUseTls,
      pool: true,
      maxConnections: config.smtpPoolSize,
      maxMessages: Infinity, // reuse connections indefinitely
      tls: { rejectUnauthorized: false },
      ...(config.smtpUser && config.smtpPass
        ? { auth: { user: config.smtpUser, pass: config.smtpPass } }
        : {}),
    });

    log(
      `📡 SMTP pool initialized → ${config.smtpHost}:${config.smtpPort} ` +
        `(max ${config.smtpPoolSize} connections)`,
    );
  }

  /**
   * Send raw email to ONE recipient via the local DMS.
   *
   * Returns: [success, errorMessage?, isPermanent]
   */
  async sendToRecipient(
    fromAddr: string,
    recipient: string,
    rawMessage: Buffer,
    workerName: string,
    maxRetries = 2,
  ): Promise<[boolean, string | null, boolean]> {
    let lastError: string | null = null;

    for (let attempt = 0; attempt <= maxRetries; attempt++) {
      try {
        await this.transport.sendMail({
          envelope: { from: fromAddr, to: [recipient] },
          raw: rawMessage,
        });

        log(`  ✓ ${recipient}: Delivered (SMTP)`, 'SUCCESS', workerName);
        return [true, null, false];
      } catch (err: any) {
        const errorMsg = err.message ?? String(err);
        const responseCode = err.responseCode ?? 0;

        // Check for permanent errors (5xx)
        if (
          responseCode >= 550 ||
          isPermanentRecipientError(errorMsg)
        ) {
          log(
            `  ✗ ${recipient}: ${errorMsg} (permanent)`,
            'ERROR',
            workerName,
          );
          return [false, errorMsg, true];
        }

        // Connection-level errors → retry
        if (
          err.code === 'ECONNRESET' ||
          err.code === 'ECONNREFUSED' ||
          err.code === 'ETIMEDOUT' ||
          errorMsg.toLowerCase().includes('disconnect') ||
          errorMsg.toLowerCase().includes('closed') ||
          errorMsg.toLowerCase().includes('connection')
        ) {
          log(
            `  ⚠ ${recipient}: Connection error, retrying... ` +
              `(attempt ${attempt + 1}/${maxRetries + 1})`,
            'WARNING',
            workerName,
          );
          lastError = errorMsg;
          await sleep(300);
          continue;
        }

        // Other SMTP errors
        const isPerm = isPermanentRecipientError(errorMsg);
        log(
          `  ✗ ${recipient}: ${errorMsg} (${isPerm ? 'permanent' : 'temporary'})`,
          'ERROR',
          workerName,
        );
        return [false, errorMsg, isPerm];
      }
    }

    // All retries exhausted
    log(
      `  ✗ ${recipient}: All retries failed - ${lastError}`,
      'ERROR',
      workerName,
    );
    return [false, lastError ?? 'Connection failed after retries', false];
  }

  /** Verify the transport is reachable (used during startup). */
  async verify(): Promise<boolean> {
    try {
      await this.transport.verify();
      return true;
    } catch {
      return false;
    }
  }

  /** Close all pooled connections. */
  close(): void {
    this.transport.close();
  }
}

// ---------------------------------------------------------------------------
function sleep(ms: number): Promise<void> {
  return new Promise((r) => setTimeout(r, ms));
}