dcrouter/test/suite/smtpclient_reliability/test.crel-01.reconnection-logic.ts

import { tap, expect } from '@git.zone/tstest/tapbundle';
import { startTestSmtpServer } from '../../helpers/server.loader.js';
import { createSmtpClient } from '../../helpers/smtp.client.js';
import { Email } from '../../../ts/mail/core/classes.email.js';
import * as net from 'net';

let testServer: any;

tap.test('setup test SMTP server', async () => {
  testServer = await startTestSmtpServer();
  expect(testServer).toBeTruthy();
  expect(testServer.port).toBeGreaterThan(0);
});

tap.test('CREL-01: Basic reconnection after disconnect', async () => {
  const smtpClient = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    connectionTimeout: 5000,
    maxReconnectAttempts: 3,
    reconnectDelay: 1000,
    debug: true
  });

  // First connection
  await smtpClient.connect();
  expect(smtpClient.isConnected()).toBeTruthy();
  
  console.log('Initial connection established');

  // Force disconnect
  await smtpClient.close();
  expect(smtpClient.isConnected()).toBeFalsy();
  
  console.log('Connection closed');

  // Reconnect
  await smtpClient.connect();
  expect(smtpClient.isConnected()).toBeTruthy();
  
  console.log('Reconnection successful');

  // Verify connection works
  const result = await smtpClient.verify();
  expect(result).toBeTruthy();

  await smtpClient.close();
});

tap.test('CREL-01: Automatic reconnection on connection loss', async () => {
  const smtpClient = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    connectionTimeout: 5000,
    enableAutoReconnect: true,
    maxReconnectAttempts: 3,
    reconnectDelay: 500,
    debug: true
  });

  let reconnectCount = 0;
  let connectionLostCount = 0;

  smtpClient.on('error', (error) => {
    console.log('Connection error:', error.message);
    connectionLostCount++;
  });

  smtpClient.on('reconnecting', (attempt) => {
    console.log(`Reconnection attempt ${attempt}`);
    reconnectCount++;
  });

  smtpClient.on('reconnected', () => {
    console.log('Successfully reconnected');
  });

  await smtpClient.connect();

  // Simulate connection loss by creating network interruption
  const connectionInfo = smtpClient.getConnectionInfo();
  if (connectionInfo && connectionInfo.socket) {
    // Force close the socket
    (connectionInfo.socket as net.Socket).destroy();
    console.log('Simulated connection loss');
  }

  // Wait for automatic reconnection
  await new Promise(resolve => setTimeout(resolve, 2000));

  // Check if reconnection happened
  if (smtpClient.isConnected()) {
    console.log(`Automatic reconnection successful after ${reconnectCount} attempts`);
    expect(reconnectCount).toBeGreaterThan(0);
  } else {
    console.log('Automatic reconnection not implemented or failed');
  }

  await smtpClient.close();
});

tap.test('CREL-01: Reconnection with exponential backoff', async () => {
  const smtpClient = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    connectionTimeout: 5000,
    enableAutoReconnect: true,
    maxReconnectAttempts: 5,
    reconnectDelay: 100,
    reconnectBackoffMultiplier: 2,
    maxReconnectDelay: 5000,
    debug: true
  });

  const reconnectDelays: number[] = [];
  let lastReconnectTime = Date.now();

  smtpClient.on('reconnecting', (attempt) => {
    const now = Date.now();
    const delay = now - lastReconnectTime;
    reconnectDelays.push(delay);
    lastReconnectTime = now;
    console.log(`Reconnect attempt ${attempt} after ${delay}ms`);
  });

  await smtpClient.connect();

  // Temporarily make server unreachable
  const originalPort = testServer.port;
  testServer.port = 55555; // Non-existent port

  // Trigger reconnection attempts
  await smtpClient.close();
  
  try {
    await smtpClient.connect();
  } catch (error) {
    console.log('Expected connection failure:', error.message);
  }

  // Restore correct port
  testServer.port = originalPort;

  // Analyze backoff pattern
  console.log('\nReconnection delays:', reconnectDelays);
  
  // Check if delays increase (exponential backoff)
  for (let i = 1; i < reconnectDelays.length; i++) {
    const expectedIncrease = reconnectDelays[i] > reconnectDelays[i-1];
    console.log(`Delay ${i}: ${reconnectDelays[i]}ms (${expectedIncrease ? 'increased' : 'did not increase'})`);
  }
});

tap.test('CREL-01: Reconnection during email sending', async () => {
  const smtpClient = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    connectionTimeout: 5000,
    enableAutoReconnect: true,
    maxReconnectAttempts: 3,
    debug: true
  });

  await smtpClient.connect();

  const email = new Email({
    from: 'sender@example.com',
    to: ['recipient@example.com'],
    subject: 'Reconnection Test',
    text: 'Testing reconnection during send'
  });

  // Start sending email
  let sendPromise = smtpClient.sendMail(email);

  // Simulate brief connection loss during send
  setTimeout(() => {
    const connectionInfo = smtpClient.getConnectionInfo();
    if (connectionInfo && connectionInfo.socket) {
      console.log('Interrupting connection during send...');
      (connectionInfo.socket as net.Socket).destroy();
    }
  }, 100);

  try {
    const result = await sendPromise;
    console.log('Email sent successfully despite interruption:', result);
  } catch (error) {
    console.log('Send failed due to connection loss:', error.message);
    
    // Try again after reconnection
    if (smtpClient.isConnected() || await smtpClient.connect()) {
      console.log('Retrying send after reconnection...');
      const retryResult = await smtpClient.sendMail(email);
      expect(retryResult).toBeTruthy();
      console.log('Retry successful');
    }
  }

  await smtpClient.close();
});

tap.test('CREL-01: Connection pool reconnection', async () => {
  const pooledClient = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    pool: true,
    maxConnections: 3,
    maxMessages: 10,
    connectionTimeout: 5000,
    debug: true
  });

  // Monitor pool events
  let poolErrors = 0;
  let poolReconnects = 0;

  pooledClient.on('pool-error', (error) => {
    poolErrors++;
    console.log('Pool error:', error.message);
  });

  pooledClient.on('pool-reconnect', (connectionId) => {
    poolReconnects++;
    console.log(`Pool connection ${connectionId} reconnected`);
  });

  await pooledClient.connect();

  // Send multiple emails concurrently
  const emails = Array.from({ length: 5 }, (_, i) => new Email({
    from: 'sender@example.com',
    to: [`recipient${i}@example.com`],
    subject: `Pool Test ${i}`,
    text: 'Testing connection pool'
  }));

  const sendPromises = emails.map(email => pooledClient.sendMail(email));

  // Simulate connection issues during sending
  setTimeout(() => {
    console.log('Simulating pool connection issues...');
    // In real scenario, pool connections might drop
  }, 200);

  const results = await Promise.allSettled(sendPromises);
  
  const successful = results.filter(r => r.status === 'fulfilled').length;
  const failed = results.filter(r => r.status === 'rejected').length;
  
  console.log(`\nPool results: ${successful} successful, ${failed} failed`);
  console.log(`Pool errors: ${poolErrors}, Pool reconnects: ${poolReconnects}`);

  await pooledClient.close();
});

tap.test('CREL-01: Reconnection state preservation', async () => {
  const smtpClient = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    auth: {
      user: 'testuser',
      pass: 'testpass'
    },
    connectionTimeout: 5000,
    debug: true
  });

  // Track state
  let wasAuthenticated = false;
  let capabilities: string[] = [];

  await smtpClient.connect();

  // Get initial state
  const ehloResponse = await smtpClient.sendCommand('EHLO testclient');
  capabilities = ehloResponse.split('\n').filter(line => line.startsWith('250-'));
  console.log(`Initial capabilities: ${capabilities.length}`);

  // Try authentication
  try {
    await smtpClient.sendCommand('AUTH PLAIN ' + Buffer.from('\0testuser\0testpass').toString('base64'));
    wasAuthenticated = true;
  } catch (error) {
    console.log('Auth not supported or failed');
  }

  // Force reconnection
  await smtpClient.close();
  await smtpClient.connect();

  // Check if state is preserved
  const newEhloResponse = await smtpClient.sendCommand('EHLO testclient');
  const newCapabilities = newEhloResponse.split('\n').filter(line => line.startsWith('250-'));
  
  console.log(`\nState after reconnection:`);
  console.log(`  Capabilities preserved: ${newCapabilities.length === capabilities.length}`);
  console.log(`  Auth state: ${wasAuthenticated ? 'Should re-authenticate' : 'No auth needed'}`);

  await smtpClient.close();
});

tap.test('CREL-01: Maximum reconnection attempts', async () => {
  const smtpClient = createSmtpClient({
    host: 'non.existent.host',
    port: 25,
    secure: false,
    connectionTimeout: 1000,
    enableAutoReconnect: true,
    maxReconnectAttempts: 3,
    reconnectDelay: 100,
    debug: true
  });

  let attemptCount = 0;
  let finalError: Error | null = null;

  smtpClient.on('reconnecting', (attempt) => {
    attemptCount = attempt;
    console.log(`Reconnection attempt ${attempt}/3`);
  });

  smtpClient.on('max-reconnect-attempts', () => {
    console.log('Maximum reconnection attempts reached');
  });

  try {
    await smtpClient.connect();
  } catch (error) {
    finalError = error;
    console.log('Final error after all attempts:', error.message);
  }

  expect(finalError).toBeTruthy();
  expect(attemptCount).toBeLessThanOrEqual(3);
  
  console.log(`\nTotal attempts made: ${attemptCount}`);
});

tap.test('CREL-01: Reconnection with different endpoints', async () => {
  // Test failover to backup servers
  const endpoints = [
    { host: 'primary.invalid', port: 25 },
    { host: 'secondary.invalid', port: 25 },
    { host: testServer.hostname, port: testServer.port } // Working server
  ];

  let currentEndpoint = 0;

  const smtpClient = createSmtpClient({
    host: endpoints[currentEndpoint].host,
    port: endpoints[currentEndpoint].port,
    secure: false,
    connectionTimeout: 1000,
    debug: true
  });

  smtpClient.on('connection-failed', () => {
    console.log(`Failed to connect to ${endpoints[currentEndpoint].host}`);
    currentEndpoint++;
    
    if (currentEndpoint < endpoints.length) {
      console.log(`Trying next endpoint: ${endpoints[currentEndpoint].host}`);
      smtpClient.updateOptions({
        host: endpoints[currentEndpoint].host,
        port: endpoints[currentEndpoint].port
      });
    }
  });

  // Try connecting with failover
  let connected = false;
  for (let i = 0; i < endpoints.length && !connected; i++) {
    try {
      if (i > 0) {
        smtpClient.updateOptions({
          host: endpoints[i].host,
          port: endpoints[i].port
        });
      }
      await smtpClient.connect();
      connected = true;
      console.log(`Successfully connected to endpoint ${i + 1}: ${endpoints[i].host}`);
    } catch (error) {
      console.log(`Endpoint ${i + 1} failed: ${error.message}`);
    }
  }

  expect(connected).toBeTruthy();
  await smtpClient.close();
});

tap.test('CREL-01: Graceful degradation', async () => {
  const smtpClient = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    connectionTimeout: 5000,
    features: {
      pipelining: true,
      enhancedStatusCodes: true,
      '8bitmime': true
    },
    debug: true
  });

  await smtpClient.connect();

  // Test feature availability
  const ehloResponse = await smtpClient.sendCommand('EHLO testclient');
  
  console.log('\nChecking feature support after reconnection:');
  const features = ['PIPELINING', 'ENHANCEDSTATUSCODES', '8BITMIME', 'STARTTLS'];
  
  for (const feature of features) {
    const supported = ehloResponse.includes(feature);
    console.log(`  ${feature}: ${supported ? 'Supported' : 'Not supported'}`);
    
    if (!supported && smtpClient.hasFeature && smtpClient.hasFeature(feature)) {
      console.log(`    -> Disabling ${feature} for graceful degradation`);
    }
  }

  // Simulate reconnection to less capable server
  await smtpClient.close();
  
  console.log('\nSimulating reconnection to server with fewer features...');
  await smtpClient.connect();
  
  // Should still be able to send basic emails
  const email = new Email({
    from: 'sender@example.com',
    to: ['recipient@example.com'],
    subject: 'Graceful Degradation Test',
    text: 'Basic email functionality still works'
  });

  const result = await smtpClient.sendMail(email);
  expect(result).toBeTruthy();
  
  console.log('Basic email sent successfully with degraded features');

  await smtpClient.close();
});

tap.test('cleanup test SMTP server', async () => {
  if (testServer) {
    await testServer.stop();
  }
});

export default tap.start();