Backend Complete: Interface Refactoring & Service Container Enhancements

Repository Interface Optimization:
- Created IBaseRepository.ts and IPaginatedRepository.ts
- Refactored all 7 repository interfaces to extend base interfaces
- Eliminated ~200 lines of redundant code (70% reduction)
- Improved type safety and maintainability

 Dependency Injection Improvements:
- Added EmailService and GameTokenService to DIContainer
- Updated CreateUserCommandHandler constructor for DI
- Updated RequestPasswordResetCommandHandler constructor for DI
- Enhanced testability and service consistency

 Environment Configuration:
- Created comprehensive .env.example with 40+ variables
- Organized into 12 logical sections (Database, Security, Email, etc.)
- Added security guidelines and best practices
- Documented all backend environment requirements

 Documentation:
- Added comprehensive codebase review
- Created refactoring summary report
- Added frontend implementation guide

Impact: Improved code quality, reduced maintenance overhead, enhanced developer experience

SerpentRace_Backend/tests/Application/Services/EmailService.test.ts

@@ -0,0 +1,224 @@
+import { EmailService, EmailOptions } from '../../../src/Application/Services/EmailService';
+import * as nodemailer from 'nodemailer';
+import * as fs from 'fs';
+
+// Mock nodemailer
+jest.mock('nodemailer');
+jest.mock('fs');
+
+// Mock logger
+jest.mock('../../../src/Application/Services/Logger', () => ({
+  logError: jest.fn(),
+  logAuth: jest.fn(),
+  logStartup: jest.fn(),
+}));
+
+describe('EmailService', () => {
+  let emailService: EmailService;
+  let mockTransporter: jest.Mocked<nodemailer.Transporter>;
+  let mockCreateTransporter: jest.MockedFunction<typeof nodemailer.createTransport>;
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+
+    // Mock nodemailer.createTransporter
+    mockTransporter = {
+      sendMail: jest.fn(),
+    } as any;
+    
+    mockCreateTransporter = nodemailer.createTransport as jest.MockedFunction<typeof nodemailer.createTransport>;
+    mockCreateTransporter.mockReturnValue(mockTransporter);
+
+    // Mock fs
+    (fs.readFileSync as jest.Mock).mockImplementation((filePath: string) => {
+      if (filePath.includes('html')) {
+        return 'HTML template: {{name}}';
+      }
+      return 'Text template: {{name}}';
+    });
+
+    (fs.existsSync as jest.Mock).mockReturnValue(true);
+
+    emailService = new EmailService();
+  });
+
+  describe('sendEmail', () => {
+    it('should send email successfully', async () => {
+      // Arrange
+      const emailOptions: EmailOptions = {
+        to: 'test@example.com',
+        subject: 'Test Subject',
+        html: '<p>Test HTML</p>',
+        text: 'Test Text',
+      };
+
+      mockTransporter.sendMail.mockResolvedValue({ messageId: 'test-id' });
+
+      // Act
+      const result = await emailService.sendEmail(emailOptions);
+
+      // Assert
+      expect(result).toBe(true);
+      expect(mockTransporter.sendMail).toHaveBeenCalledWith({
+        from: process.env.EMAIL_FROM || 'noreply@serpentrace.com',
+        to: emailOptions.to,
+        subject: emailOptions.subject,
+        html: emailOptions.html,
+        text: emailOptions.text,
+      });
+    });
+
+    it('should send email with template', async () => {
+      // Arrange
+      const emailOptions: EmailOptions = {
+        to: 'test@example.com',
+        subject: 'Test Subject',
+        template: 'verification',
+        templateData: { name: 'John', token: 'abc123' },
+      };
+
+      mockTransporter.sendMail.mockResolvedValue({ messageId: 'test-id' });
+
+      // Act
+      const result = await emailService.sendEmail(emailOptions);
+
+      // Assert
+      expect(result).toBe(true);
+      expect(mockTransporter.sendMail).toHaveBeenCalledWith({
+        from: process.env.EMAIL_FROM || 'noreply@serpentrace.com',
+        to: emailOptions.to,
+        subject: emailOptions.subject,
+        html: expect.stringContaining('John'),
+        text: expect.stringContaining('John'),
+      });
+    });
+
+    it('should handle email send failure', async () => {
+      // Arrange
+      const emailOptions: EmailOptions = {
+        to: 'test@example.com',
+        subject: 'Test Subject',
+        text: 'Test Text',
+      };
+
+      mockTransporter.sendMail.mockRejectedValue(new Error('SMTP Error'));
+
+      // Act
+      const result = await emailService.sendEmail(emailOptions);
+
+      // Assert
+      expect(result).toBe(false);
+    });
+
+    it('should handle missing template files', async () => {
+      // Arrange
+      const emailOptions: EmailOptions = {
+        to: 'test@example.com',
+        subject: 'Test Subject',
+        template: 'nonexistent',
+        templateData: { name: 'John' },
+      };
+
+      (fs.existsSync as jest.Mock).mockReturnValue(false);
+
+      // Act
+      const result = await emailService.sendEmail(emailOptions);
+
+      // Assert
+      expect(result).toBe(false);
+    });
+
+    it('should handle template processing errors', async () => {
+      // Arrange
+      const emailOptions: EmailOptions = {
+        to: 'test@example.com',
+        subject: 'Test Subject',
+        template: 'verification',
+        templateData: { name: 'John' },
+      };
+
+      (fs.readFileSync as jest.Mock).mockImplementation(() => {
+        throw new Error('File read error');
+      });
+
+      // Act
+      const result = await emailService.sendEmail(emailOptions);
+
+      // Assert
+      expect(result).toBe(false);
+    });
+
+    it('should use fallback content when template data is missing', async () => {
+      // Arrange
+      const emailOptions: EmailOptions = {
+        to: 'test@example.com',
+        subject: 'Test Subject',
+        template: 'verification',
+      };
+
+      mockTransporter.sendMail.mockResolvedValue({ messageId: 'test-id' });
+
+      // Act
+      const result = await emailService.sendEmail(emailOptions);
+
+      // Assert
+      expect(result).toBe(true);
+    });
+  });
+
+  describe('constructor', () => {
+    it('should initialize with environment variables', () => {
+      // Arrange
+      const originalEnv = process.env;
+      process.env = {
+        ...originalEnv,
+        EMAIL_HOST: 'test-smtp.com',
+        EMAIL_PORT: '465',
+        EMAIL_SECURE: 'true',
+        EMAIL_USER: 'test@example.com',
+        EMAIL_PASS: 'testpass',
+        EMAIL_FROM: 'sender@example.com',
+      };
+
+      // Act
+      const service = new EmailService();
+
+      // Assert
+      expect(mockCreateTransporter).toHaveBeenCalledWith({
+        host: 'test-smtp.com',
+        port: 465,
+        secure: true,
+        auth: {
+          user: 'test@example.com',
+          pass: 'testpass',
+        },
+      });
+
+      // Restore environment
+      process.env = originalEnv;
+    });
+
+    it('should use default values when environment variables are missing', () => {
+      // Arrange
+      const originalEnv = process.env;
+      process.env = {};
+
+      // Act
+      const service = new EmailService();
+
+      // Assert
+      expect(mockCreateTransporter).toHaveBeenCalledWith({
+        host: 'smtp.gmail.com',
+        port: 587,
+        secure: false,
+        auth: {
+          user: '',
+          pass: '',
+        },
+      });
+
+      // Restore environment
+      process.env = originalEnv;
+    });
+  });
+});