courseworx/docs/05-Development-Guidelines.md

# CourseWorx Development Guidelines

## 📋 Document Information
- **Version**: 1.0.0
- **Last Updated**: 2024-12-19
- **Author**: AI Assistant
- **Status**: Draft - Ready for Review

## 🎯 Development Philosophy

CourseWorx development follows these core principles:
- **Quality First**: Code quality over speed
- **Test-Driven Development**: Write tests before implementation
- **Documentation**: Every change must be documented
- **Impact Analysis**: Understand system impact before changes
- **Code Reviews**: All changes require peer review

## 🔄 Development Workflow

### 1. Feature Development Process
```
1. Issue Creation → GitHub Issue with proper template
2. Impact Analysis → Understand affected components/APIs
3. Design Review → Architecture and approach validation
4. Branch Creation → Feature branch from main
5. Implementation → Code with tests
6. Testing → Unit, integration, and manual testing
7. Documentation → Update relevant docs
8. Code Review → Peer review process
9. Merge → After approval and testing
10. Deployment → Staged deployment with monitoring
```

### 2. Branch Strategy
```
main (production-ready)
├── develop (integration branch)
│   ├── feature/user-management
│   ├── feature/course-creation
│   └── bugfix/login-validation
├── hotfix/critical-security-fix
└── release/v1.1.0
```

### 3. Commit Message Format
```
type(scope): brief description

Detailed explanation of the change

- What was changed
- Why it was changed
- Any breaking changes
- Related issue numbers

Examples:
feat(auth): add password reset functionality
fix(courses): resolve duplicate course creation bug
docs(api): update authentication endpoint documentation
refactor(components): split CourseContent into smaller components
```

## 🧪 Testing Strategy

### 1. Testing Pyramid
```
E2E Tests (5%)
├── Critical user journeys
├── Authentication flows
└── Course creation/enrollment

Integration Tests (25%)
├── API endpoint testing
├── Database integration
└── Component integration

Unit Tests (70%)
├── Component logic
├── Utility functions
├── API service methods
└── Business logic
```

### 2. Testing Requirements
- **New Features**: 80% code coverage minimum
- **Bug Fixes**: Add regression tests
- **Refactoring**: Maintain existing test coverage
- **API Changes**: Update contract tests

### 3. Testing Tools
```
Frontend Testing:
├── Jest (Test runner)
├── React Testing Library (Component testing)
├── MSW (API mocking)
└── Cypress (E2E testing)

Backend Testing:
├── Jest (Test runner)
├── Supertest (API testing)
├── Factory-bot (Test data)
└── Test database (Isolated testing)
```

## 📝 Code Standards

### 1. JavaScript/React Standards
```javascript
// Use functional components with hooks
const UserList = ({ users, onUserSelect }) => {
  const [selectedUser, setSelectedUser] = useState(null);
  
  // Use descriptive variable names
  const activeUsers = users.filter(user => user.isActive);
  
  // Extract complex logic to custom hooks
  const { loading, error, refetch } = useUserData();
  
  // Use early returns to reduce nesting
  if (loading) return <LoadingSpinner />;
  if (error) return <ErrorMessage error={error} />;
  
  return (
    <div className="user-list">
      {activeUsers.map(user => (
        <UserCard 
          key={user.id} 
          user={user} 
          onSelect={onUserSelect}
        />
      ))}
    </div>
  );
};
```

### 2. Component Guidelines
- **Single Responsibility**: One purpose per component
- **Max 300 lines**: Split larger components
- **Props Interface**: Define clear prop types
- **Error Boundaries**: Handle component errors gracefully

### 3. API Development Standards
```javascript
// Controller structure
const createUser = async (req, res) => {
  try {
    // 1. Input validation
    const validationErrors = validationResult(req);
    if (!validationErrors.isEmpty()) {
      return res.status(400).json({
        error: 'Validation Error',
        details: validationErrors.array()
      });
    }
    
    // 2. Business logic
    const userData = req.body;
    const user = await UserService.createUser(userData);
    
    // 3. Success response
    res.status(201).json({
      message: 'User created successfully',
      data: user
    });
  } catch (error) {
    // 4. Error handling
    console.error('User creation error:', error);
    res.status(500).json({
      error: 'Internal Server Error',
      message: 'Failed to create user'
    });
  }
};
```

## 🗂️ File Organization

### 1. Frontend Structure
```
frontend/src/
├── components/
│   ├── common/           # Reusable components
│   ├── forms/            # Form components
│   └── ui/               # UI elements
├── pages/
│   ├── auth/             # Authentication pages
│   ├── courses/          # Course-related pages
│   └── admin/            # Admin pages
├── hooks/                # Custom hooks
├── services/             # API services
├── utils/                # Utility functions
├── constants/            # Application constants
└── types/                # TypeScript types (future)
```

### 2. Backend Structure
```
backend/
├── controllers/          # Route handlers
├── services/             # Business logic
├── models/               # Database models
├── middleware/           # Express middleware
├── routes/               # Route definitions
├── utils/                # Utility functions
├── validators/           # Input validation
└── tests/                # Test files
```

## 🔒 Security Guidelines

### 1. Input Validation
- **Server-side validation**: Always validate on backend
- **Client-side validation**: For UX only, not security
- **Sanitization**: Clean all user inputs
- **SQL Injection**: Use parameterized queries (Sequelize ORM)

### 2. Authentication & Authorization
- **JWT Security**: Secure token storage and transmission
- **Role-based Access**: Verify permissions on every request
- **Password Security**: bcrypt with appropriate salt rounds
- **Session Management**: Proper token expiration

### 3. File Upload Security
```javascript
// File upload validation
const validateFileUpload = (req, res, next) => {
  const allowedTypes = ['image/jpeg', 'image/png', 'application/pdf'];
  const maxSize = 10 * 1024 * 1024; // 10MB
  
  if (!allowedTypes.includes(req.file.mimetype)) {
    return res.status(400).json({ error: 'Invalid file type' });
  }
  
  if (req.file.size > maxSize) {
    return res.status(400).json({ error: 'File too large' });
  }
  
  next();
};
```

## 📊 Performance Guidelines

### 1. Frontend Performance
- **Code Splitting**: Lazy load large components
- **Image Optimization**: Compress and resize images
- **Bundle Analysis**: Monitor bundle size
- **Memoization**: Use React.memo for expensive components

### 2. Backend Performance
- **Database Queries**: Optimize with proper indexes
- **Caching**: Implement Redis for frequently accessed data
- **Connection Pooling**: Efficient database connections
- **Response Compression**: Gzip compression for API responses

### 3. Database Performance
```sql
-- Create indexes for frequently queried columns
CREATE INDEX idx_users_email ON users(email);
CREATE INDEX idx_courses_trainer_id ON courses(trainer_id);
CREATE INDEX idx_enrollments_user_course ON enrollments(user_id, course_id);

-- Optimize queries with proper JOINs
SELECT u.first_name, u.last_name, c.title
FROM users u
JOIN enrollments e ON u.id = e.user_id
JOIN courses c ON e.course_id = c.id
WHERE u.role = 'trainee' AND e.status = 'enrolled';
```

## 🐛 Error Handling

### 1. Frontend Error Handling
```javascript
// Error boundary for component errors
class ErrorBoundary extends React.Component {
  constructor(props) {
    super(props);
    this.state = { hasError: false };
  }
  
  static getDerivedStateFromError(error) {
    return { hasError: true };
  }
  
  componentDidCatch(error, errorInfo) {
    console.error('Component error:', error, errorInfo);
    // Send to error reporting service
  }
  
  render() {
    if (this.state.hasError) {
      return <ErrorFallback />;
    }
    return this.props.children;
  }
}

// API error handling
const handleApiError = (error) => {
  if (error.response?.status === 401) {
    // Redirect to login
    window.location.href = '/login';
  } else if (error.response?.status >= 500) {
    // Show generic error message
    toast.error('Server error. Please try again later.');
  } else {
    // Show specific error message
    toast.error(error.response?.data?.message || 'An error occurred');
  }
};
```

### 2. Backend Error Handling
```javascript
// Global error handler
const errorHandler = (err, req, res, next) => {
  console.error('Error:', err);
  
  // Validation errors
  if (err.name === 'ValidationError') {
    return res.status(400).json({
      error: 'Validation Error',
      message: err.message
    });
  }
  
  // Database errors
  if (err.name === 'SequelizeValidationError') {
    return res.status(400).json({
      error: 'Database Validation Error',
      details: err.errors.map(e => ({
        field: e.path,
        message: e.message
      }))
    });
  }
  
  // Default error
  res.status(500).json({
    error: 'Internal Server Error',
    message: process.env.NODE_ENV === 'development' ? err.message : 'Something went wrong'
  });
};
```

## 📚 Documentation Requirements

### 1. Code Documentation
- **Function Documentation**: JSDoc for all functions
- **Component Documentation**: Props, usage examples
- **API Documentation**: OpenAPI/Swagger specs
- **README Files**: Setup and usage instructions

### 2. Change Documentation
- **Pull Request Templates**: Standardized PR descriptions
- **Changelog**: Track all changes with semantic versioning
- **Migration Guides**: For breaking changes
- **Version.txt Updates**: Required for all changes

## 🔍 Code Review Process

### 1. Review Checklist
- [ ] Code follows style guidelines
- [ ] Tests are included and passing
- [ ] Documentation is updated
- [ ] No security vulnerabilities
- [ ] Performance impact considered
- [ ] Breaking changes documented

### 2. Review Guidelines
- **Be Constructive**: Provide helpful feedback
- **Ask Questions**: Understand the reasoning
- **Suggest Improvements**: Offer better solutions
- **Approve Quickly**: Don't block unnecessarily

## 🚀 Deployment Guidelines

### 1. Staging Deployment
- **Automated Testing**: All tests must pass
- **Manual Testing**: User acceptance testing
- **Performance Testing**: Load and stress testing
- **Security Scanning**: Automated security checks

### 2. Production Deployment
- **Blue-Green Deployment**: Zero-downtime deployments
- **Database Migrations**: Backward-compatible changes
- **Rollback Plan**: Quick rollback procedures
- **Monitoring**: Post-deployment monitoring

---

**Next Steps**:
1. Review and approve development guidelines
2. Set up development tools and templates
3. Train team on new processes
4. Implement code quality gates