dcrouter/test/suite/smtpclient_error-handling/test.cerr-03.network-failures.ts

import { tap, expect } from '@git.zone/tstest/tapbundle';
import { startTestServer, stopTestServer, type ITestServer } from '../../helpers/server.loader.js';
import { createSmtpClient } from '../../../ts/mail/delivery/smtpclient/index.js';
import type { SmtpClient } from '../../../ts/mail/delivery/smtpclient/smtp-client.js';
import { Email } from '../../../ts/mail/core/classes.email.js';
import * as net from 'net';

let testServer: ITestServer;

tap.test('setup - start SMTP server for network failure tests', async () => {
  testServer = await startTestServer({
    port: 2554,
    tlsEnabled: false,
    authRequired: false
  });
  
  expect(testServer.port).toEqual(2554);
});

tap.test('CERR-03: Network Failures - should handle connection refused', async () => {
  let errorCaught = false;
  const startTime = Date.now();
  
  try {
    // Try to connect to a port that's not listening
    const client = createSmtpClient({
      host: 'localhost',
      port: 9876, // Non-listening port
      secure: false,
      connectionTimeout: 3000,
      debug: true
    });
    
    await client.verify();
  } catch (error: any) {
    errorCaught = true;
    const duration = Date.now() - startTime;
    
    expect(error).toBeInstanceOf(Error);
    expect(error.message).toContain('ECONNREFUSED');
    console.log(`✅ Connection refused handled in ${duration}ms`);
  }
  
  expect(errorCaught).toBeTrue();
});

tap.test('CERR-03: Network Failures - should handle DNS resolution failure', async () => {
  let dnsError = false;
  
  try {
    const client = createSmtpClient({
      host: 'non.existent.domain.that.should.not.resolve.example',
      port: 25,
      secure: false,
      connectionTimeout: 5000,
      debug: true
    });
    
    await client.verify();
  } catch (error: any) {
    dnsError = true;
    expect(error).toBeInstanceOf(Error);
    console.log('✅ DNS resolution failure handled:', error.code);
  }
  
  expect(dnsError).toBeTrue();
});

tap.test('CERR-03: Network Failures - should handle connection drop during handshake', async () => {
  // Create a server that drops connections immediately
  const dropServer = net.createServer((socket) => {
    // Drop connection after accepting
    socket.destroy();
  });
  
  await new Promise<void>((resolve) => {
    dropServer.listen(2555, () => resolve());
  });
  
  let dropError = false;
  
  try {
    const client = createSmtpClient({
      host: 'localhost',
      port: 2555,
      secure: false,
      connectionTimeout: 5000
    });
    
    await client.verify();
  } catch (error: any) {
    dropError = true;
    expect(error).toBeInstanceOf(Error);
    console.log('✅ Connection drop during handshake handled');
  }
  
  expect(dropError).toBeTrue();
  
  dropServer.close();
  await new Promise(resolve => setTimeout(resolve, 100));
});

tap.test('CERR-03: Network Failures - should handle connection drop during data transfer', async () => {
  const client = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    connectionTimeout: 5000,
    socketTimeout: 10000
  });
  
  // Establish connection first
  await client.verify();
  
  // For this test, we simulate network issues by attempting
  // to send after server issues might occur
  const email = new Email({
    from: 'sender@example.com',
    to: 'recipient@example.com',
    subject: 'Network Failure Test',
    text: 'Testing network failure recovery'
  });
  
  try {
    const result = await client.sendMail(email);
    expect(result.success).toBeTrue();
    console.log('✅ Email sent successfully (no network failure simulated)');
  } catch (error) {
    console.log('✅ Network failure handled during data transfer');
  }
  
  await client.close();
});

tap.test('CERR-03: Network Failures - should retry on transient network errors', async () => {
  let attemptCount = 0;
  
  // Create a server that fails first attempt
  const retryServer = net.createServer((socket) => {
    attemptCount++;
    if (attemptCount === 1) {
      // First attempt: drop connection
      socket.destroy();
    } else {
      // Second attempt: normal SMTP
      socket.write('220 Retry server ready\r\n');
      
      socket.on('data', (data) => {
        const command = data.toString().trim();
        if (command.startsWith('EHLO') || command.startsWith('HELO')) {
          socket.write('250 OK\r\n');
        } else if (command === 'QUIT') {
          socket.write('221 Bye\r\n');
          socket.end();
        }
      });
    }
  });
  
  await new Promise<void>((resolve) => {
    retryServer.listen(2556, () => resolve());
  });
  
  const client = createSmtpClient({
    host: 'localhost',
    port: 2556,
    secure: false,
    connectionTimeout: 5000
  });
  
  // Client might or might not retry depending on implementation
  try {
    await client.verify();
    console.log(`✅ Connection established after ${attemptCount} attempts`);
  } catch (error) {
    console.log(`✅ Network error handled after ${attemptCount} attempts`);
  }
  
  retryServer.close();
  await new Promise(resolve => setTimeout(resolve, 100));
});

tap.test('CERR-03: Network Failures - should handle slow network (timeout)', async () => {
  // Create a server that responds very slowly
  const slowServer = net.createServer((socket) => {
    // Wait 5 seconds before responding
    setTimeout(() => {
      socket.write('220 Slow server ready\r\n');
    }, 5000);
  });
  
  await new Promise<void>((resolve) => {
    slowServer.listen(2557, () => resolve());
  });
  
  let timeoutError = false;
  const startTime = Date.now();
  
  try {
    const client = createSmtpClient({
      host: 'localhost',
      port: 2557,
      secure: false,
      connectionTimeout: 2000 // 2 second timeout
    });
    
    await client.verify();
  } catch (error: any) {
    timeoutError = true;
    const duration = Date.now() - startTime;
    
    expect(error).toBeInstanceOf(Error);
    expect(duration).toBeLessThan(3000);
    console.log(`✅ Slow network timeout after ${duration}ms`);
  }
  
  expect(timeoutError).toBeTrue();
  
  slowServer.close();
  await new Promise(resolve => setTimeout(resolve, 100));
});

tap.test('CERR-03: Network Failures - should recover from temporary network issues', async () => {
  const client = createSmtpClient({
    host: testServer.hostname,
    port: testServer.port,
    secure: false,
    pool: true,
    maxConnections: 2,
    connectionTimeout: 5000
  });
  
  // Send first email successfully
  const email1 = new Email({
    from: 'sender@example.com',
    to: 'recipient@example.com',
    subject: 'Before Network Issue',
    text: 'First email'
  });
  
  const result1 = await client.sendMail(email1);
  expect(result1.success).toBeTrue();
  
  // Simulate network recovery by sending another email
  const email2 = new Email({
    from: 'sender@example.com',
    to: 'recipient@example.com',
    subject: 'After Network Recovery',
    text: 'Second email after recovery'
  });
  
  const result2 = await client.sendMail(email2);
  expect(result2.success).toBeTrue();
  
  console.log('✅ Recovered from simulated network issues');
  
  await client.close();
});

tap.test('CERR-03: Network Failures - should handle EHOSTUNREACH', async () => {
  let unreachableError = false;
  
  try {
    // Use an IP that should be unreachable
    const client = createSmtpClient({
      host: '192.0.2.1', // TEST-NET-1, should be unreachable
      port: 25,
      secure: false,
      connectionTimeout: 3000
    });
    
    await client.verify();
  } catch (error: any) {
    unreachableError = true;
    expect(error).toBeInstanceOf(Error);
    console.log('✅ Host unreachable error handled:', error.code);
  }
  
  expect(unreachableError).toBeTrue();
});

tap.test('CERR-03: Network Failures - should handle packet loss simulation', async () => {
  // Create a server that randomly drops data
  let packetCount = 0;
  const lossyServer = net.createServer((socket) => {
    socket.write('220 Lossy server ready\r\n');
    
    socket.on('data', (data) => {
      packetCount++;
      
      // Simulate 30% packet loss
      if (Math.random() > 0.3) {
        const command = data.toString().trim();
        if (command.startsWith('EHLO')) {
          socket.write('250 OK\r\n');
        } else if (command === 'QUIT') {
          socket.write('221 Bye\r\n');
          socket.end();
        }
      }
      // Otherwise, don't respond (simulate packet loss)
    });
  });
  
  await new Promise<void>((resolve) => {
    lossyServer.listen(2558, () => resolve());
  });
  
  const client = createSmtpClient({
    host: 'localhost',
    port: 2558,
    secure: false,
    connectionTimeout: 5000,
    socketTimeout: 2000 // Short timeout to detect loss
  });
  
  try {
    await client.verify();
    console.log('✅ Connected despite simulated packet loss');
  } catch (error) {
    console.log(`✅ Packet loss detected after ${packetCount} packets`);
  }
  
  lossyServer.close();
  await new Promise(resolve => setTimeout(resolve, 100));
});

tap.test('CERR-03: Network Failures - should provide meaningful error messages', async () => {
  const errorScenarios = [
    {
      host: 'localhost',
      port: 9999,
      expectedError: 'ECONNREFUSED'
    },
    {
      host: 'invalid.domain.test',
      port: 25,
      expectedError: 'ENOTFOUND'
    }
  ];
  
  for (const scenario of errorScenarios) {
    try {
      const client = createSmtpClient({
        host: scenario.host,
        port: scenario.port,
        secure: false,
        connectionTimeout: 3000
      });
      
      await client.verify();
    } catch (error: any) {
      expect(error.message).toBeTypeofString();
      console.log(`✅ Clear error for ${scenario.host}:${scenario.port} - ${error.code || error.message}`);
    }
  }
});

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

tap.start();