const EmailService = require('../../../src/application/services/EmailService');
const nodemailer = require('nodemailer');

// Mock nodemailer
jest.mock('nodemailer');

describe('EmailService', () => {
  let emailService;
  let mockTransporter;

  beforeEach(() => {
    // Reset mocks
    jest.clearAllMocks();

    // Mock transporter
    mockTransporter = {
      sendMail: jest.fn().mockResolvedValue({
        messageId: 'test-message-id',
        response: '250 OK',
      }),
    };

    // Mock nodemailer.createTransport
    nodemailer.createTransport.mockReturnValue(mockTransporter);

    // Create EmailService instance
    emailService = new EmailService();
  });

  describe('constructor', () => {
    test('should create transporter with correct configuration', () => {
      expect(nodemailer.createTransport).toHaveBeenCalled();
      
      const config = nodemailer.createTransport.mock.calls[0][0];
      expect(config).toHaveProperty('host');
      expect(config).toHaveProperty('port');
      expect(config).toHaveProperty('auth');
      expect(config.auth).toHaveProperty('user');
      expect(config.auth).toHaveProperty('pass');
    });

    test('should initialize transporter instance', () => {
      expect(emailService.transporter).toBeDefined();
      expect(emailService.transporter).toBe(mockTransporter);
    });
  });

  describe('sendWelcomeEmail', () => {
    test('should send welcome email with correct parameters', async () => {
      const userEmail = 'test@example.com';
      const userName = 'John Doe';

      await emailService.sendWelcomeEmail(userEmail, userName);

      expect(mockTransporter.sendMail).toHaveBeenCalledTimes(1);
      
      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      expect(emailOptions.to).toBe(userEmail);
      expect(emailOptions.subject).toContain('Üdvözlünk');
      expect(emailOptions).toHaveProperty('html');
    });

    test('should include user name in email content', async () => {
      const userEmail = 'jane@example.com';
      const userName = 'Jane Smith';

      await emailService.sendWelcomeEmail(userEmail, userName);

      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      expect(emailOptions.html).toContain(userName);
    });

    test('should include user email in email content', async () => {
      const userEmail = 'contact@test.com';
      const userName = 'Test User';

      await emailService.sendWelcomeEmail(userEmail, userName);

      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      expect(emailOptions.html).toContain(userEmail);
    });

    test('should return messageId on successful send', async () => {
      const result = await emailService.sendWelcomeEmail('user@test.com', 'User');

      expect(result).toBeDefined();
      expect(result.messageId).toBe('test-message-id');
    });

    test('should use correct from address', async () => {
      await emailService.sendWelcomeEmail('recipient@test.com', 'Recipient');

      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      expect(emailOptions).toHaveProperty('from');
      expect(emailOptions.from).toBeTruthy();
    });

    test('should handle multiple recipients', async () => {
      await emailService.sendWelcomeEmail('user1@test.com', 'User 1');
      await emailService.sendWelcomeEmail('user2@test.com', 'User 2');
      await emailService.sendWelcomeEmail('user3@test.com', 'User 3');

      expect(mockTransporter.sendMail).toHaveBeenCalledTimes(3);
    });
  });

  describe('error handling', () => {
    test('should throw error when email sending fails', async () => {
      mockTransporter.sendMail.mockRejectedValue(new Error('SMTP connection failed'));

      await expect(
        emailService.sendWelcomeEmail('user@test.com', 'User')
      ).rejects.toThrow('SMTP connection failed');
    });

    test('should throw error for invalid email address', async () => {
      mockTransporter.sendMail.mockRejectedValue(new Error('Invalid recipient'));

      await expect(
        emailService.sendWelcomeEmail('invalid-email', 'User')
      ).rejects.toThrow();
    });

    test('should throw error when transporter is not configured', async () => {
      mockTransporter.sendMail.mockRejectedValue(new Error('Transporter not configured'));

      await expect(
        emailService.sendWelcomeEmail('user@test.com', 'User')
      ).rejects.toThrow('Transporter not configured');
    });
  });

  describe('template rendering', () => {
    test('should render HTML template with Handlebars', async () => {
      await emailService.sendWelcomeEmail('template@test.com', 'Template User');

      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      
      // Check that HTML is rendered (not raw Handlebars template)
      expect(emailOptions.html).not.toContain('{{userName}}');
      expect(emailOptions.html).not.toContain('{{userEmail}}');
      expect(emailOptions.html).toContain('Template User');
      expect(emailOptions.html).toContain('template@test.com');
    });

    test('should handle special characters in user name', async () => {
      const specialName = "O'Reilly & Sons <script>alert('xss')</script>";
      
      await emailService.sendWelcomeEmail('user@test.com', specialName);

      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      
      // Handlebars should escape HTML by default
      expect(emailOptions.html).toBeDefined();
    });

    test('should use correct template file path', async () => {
      await emailService.sendWelcomeEmail('user@test.com', 'User');

      // Verify that email was sent (which means template was loaded successfully)
      expect(mockTransporter.sendMail).toHaveBeenCalled();
    });
  });

  describe('real-world scenarios', () => {
    test('should send welcome email after user registration', async () => {
      const newUser = {
        email: 'newuser@example.com',
        name: 'New User',
      };

      const result = await emailService.sendWelcomeEmail(newUser.email, newUser.name);

      expect(result).toBeDefined();
      expect(mockTransporter.sendMail).toHaveBeenCalledWith(
        expect.objectContaining({
          to: newUser.email,
          html: expect.stringContaining(newUser.name),
        })
      );
    });

    test('should handle concurrent email sends', async () => {
      const users = [
        { email: 'user1@test.com', name: 'User 1' },
        { email: 'user2@test.com', name: 'User 2' },
        { email: 'user3@test.com', name: 'User 3' },
      ];

      await Promise.all(
        users.map(user => emailService.sendWelcomeEmail(user.email, user.name))
      );

      expect(mockTransporter.sendMail).toHaveBeenCalledTimes(3);
    });

    test('should work with Ethereal Email test account', async () => {
      // Simulate Ethereal Email configuration
      const etherealTransporter = {
        sendMail: jest.fn().mockResolvedValue({
          messageId: '<ethereal-id@ethereal.email>',
          response: '250 Accepted',
        }),
      };

      nodemailer.createTransport.mockReturnValue(etherealTransporter);
      const etherealEmailService = new EmailService();

      const result = await etherealEmailService.sendWelcomeEmail('test@ethereal.email', 'Test User');

      expect(result.messageId).toContain('ethereal');
      expect(etherealTransporter.sendMail).toHaveBeenCalled();
    });
  });

  describe('email content validation', () => {
    test('should include welcome message', async () => {
      await emailService.sendWelcomeEmail('user@test.com', 'User');

      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      expect(emailOptions.html.toLowerCase()).toMatch(/üdvözl|welcome/i);
    });

    test('should be HTML formatted', async () => {
      await emailService.sendWelcomeEmail('user@test.com', 'User');

      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      expect(emailOptions.html).toContain('<html');
      expect(emailOptions.html).toContain('</html>');
    });

    test('should have valid subject line', async () => {
      await emailService.sendWelcomeEmail('user@test.com', 'User');

      const emailOptions = mockTransporter.sendMail.mock.calls[0][0];
      expect(emailOptions.subject).toBeTruthy();
      expect(emailOptions.subject.length).toBeGreaterThan(0);
    });
  });
});