dcrouter/test/suite/edge-cases/test.very-small-email.ts

import { tap, expect } from '@git.zone/tapbundle';
import * as net from 'net';
import { startTestServer, stopTestServer, type ITestServer } from '../../helpers/server.loader.js';

const TEST_PORT = 30034;
const TEST_TIMEOUT = 30000;

tap.test('Very Small Email - should handle minimal email with single character body', async (tools) => {
  const done = tools.defer();
  
  // Start test server
  const testServer = await startTestServer({ port: TEST_PORT });
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Get banner
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send EHLO
    socket.write('EHLO testhost\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Send MAIL FROM
    socket.write('MAIL FROM:<sender@example.com>\r\n');
    const mailResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(mailResponse).toInclude('250');
    
    // Send RCPT TO
    socket.write('RCPT TO:<recipient@example.com>\r\n');
    const rcptResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(rcptResponse).toInclude('250');
    
    // Send DATA
    socket.write('DATA\r\n');
    const dataResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(dataResponse).toInclude('354');
    
    // Send minimal email - just required headers and single character body
    const minimalEmail = 'From: sender@example.com\r\nTo: recipient@example.com\r\nSubject: \r\n\r\nX\r\n.\r\n';
    socket.write(minimalEmail);
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    expect(finalResponse).toInclude('250');
    console.log(`Minimal email (${minimalEmail.length} bytes) processed successfully`);
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    await stopTestServer(testServer);
    done.resolve();
  }
});

tap.test('Very Small Email - should handle email with empty body', async (tools) => {
  const done = tools.defer();
  
  // Start test server
  const testServer = await startTestServer({ port: TEST_PORT });
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Get banner
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send EHLO
    socket.write('EHLO testhost\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Complete envelope
    socket.write('MAIL FROM:<sender@example.com>\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('RCPT TO:<recipient@example.com>\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('DATA\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send email with empty body
    const emptyBodyEmail = 'From: sender@example.com\r\nTo: recipient@example.com\r\n\r\n.\r\n';
    socket.write(emptyBodyEmail);
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    expect(finalResponse).toInclude('250');
    console.log('Email with empty body processed successfully');
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    await stopTestServer(testServer);
    done.resolve();
  }
});

tap.test('Very Small Email - should handle email with minimal headers only', async (tools) => {
  const done = tools.defer();
  
  // Start test server
  const testServer = await startTestServer({ port: TEST_PORT });
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Get banner and send EHLO
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('EHLO testhost\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Complete envelope
    socket.write('MAIL FROM:<a@b.c>\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('RCPT TO:<x@y.z>\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('DATA\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send absolutely minimal valid email
    const minimalHeaders = 'From: a@b.c\r\n\r\n.\r\n';
    socket.write(minimalHeaders);
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    expect(finalResponse).toInclude('250');
    console.log(`Ultra-minimal email (${minimalHeaders.length} bytes) processed`);
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    await stopTestServer(testServer);
    done.resolve();
  }
});

tap.test('Very Small Email - should handle single dot line correctly', async (tools) => {
  const done = tools.defer();
  
  // Start test server
  const testServer = await startTestServer({ port: TEST_PORT });
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Setup connection
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('EHLO testhost\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Complete envelope
    socket.write('MAIL FROM:<sender@example.com>\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('RCPT TO:<recipient@example.com>\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('DATA\r\n');
    const dataResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(dataResponse).toInclude('354');
    
    // Test edge case: just the terminating dot
    socket.write('.\r\n');
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Server should accept this as an email with no headers or body
    expect(finalResponse).toMatch(/^[2-5]\d{2}/);
    console.log('Single dot terminator handled:', finalResponse.trim());
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    await stopTestServer(testServer);
    done.resolve();
  }
});

tap.test('Very Small Email - should handle email with empty subject', async (tools) => {
  const done = tools.defer();
  
  // Start test server
  const testServer = await startTestServer({ port: TEST_PORT });
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Setup connection
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('EHLO testhost\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Complete envelope
    socket.write('MAIL FROM:<sender@example.com>\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('RCPT TO:<recipient@example.com>\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    socket.write('DATA\r\n');
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send email with empty subject line
    const emptySubjectEmail = 
      'From: sender@example.com\r\n' +
      'To: recipient@example.com\r\n' +
      'Subject: \r\n' +
      'Date: ' + new Date().toUTCString() + '\r\n' +
      '\r\n' +
      'Email with empty subject.\r\n' +
      '.\r\n';
    
    socket.write(emptySubjectEmail);
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    expect(finalResponse).toInclude('250');
    console.log('Email with empty subject processed successfully');
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    await stopTestServer(testServer);
    done.resolve();
  }
});

tap.start();