backend-documentation.md

Backend Documentation

Architecture and Implementation

The backend follows a service-oriented architecture built with .NET. The key components include:

Controllers

• RESTful API endpoints organized by domain entity
• Handle HTTP requests and delegate business logic to services
• Return standardized responses

Services

• Implement business logic independent of HTTP concerns
• Interact with repositories for data access
• Handle error cases and validation

Data Access

• Repository pattern for database operations
• Entity models with navigation properties for relationships
• Uses Entity Framework Core for ORM capabilities

Storage Services

• AzureBlobStorageService for handling file uploads
• Secure access to stored files
• File metadata management

Key Design Decisions

Service Layer Pattern

• What: Business logic lives in dedicated service classes
• Why: Separation of concerns, enables unit testing
• Example: MaterialService implements operations on materials

Cloud Storage Integration

• What: Azure Blob Storage for file storage
• Why: Scalable solution for storing user-uploaded content
• Example: Methods for generating URLs and managing storage containers

Authentication

• What: JWT-based authentication
• Why: Stateless authentication suitable for API services
• Example: Token validation in request pipeline

Resource Hierarchy

• What: Resources organized hierarchically (courses contain materials, assignments)
• Why: Reflects real-world relationships and simplifies access control
• Example: Endpoints like /course/{id}/materials

Areas for Improvement

Error Handling

• Inconsistent null handling in several services
• Consider using Result pattern or nullable reference types more effectively
• Implement global exception handling middleware

Field Validation

• Add comprehensive input validation
• Use data annotations or FluentValidation for consistent validation rules
• Ensure client receives clear validation error messages

API Documentation

• Implement Swagger/OpenAPI documentation
• Document expected request/response formats
• Generate client SDKs for frontend consumption

Performance

• Add caching layer for frequently accessed data
• Optimize database queries (missing indexes, N+1 query problems)
• Consider implementing batch operations for bulk changes

Security

• Audit authorization logic
• Implement resource-based permissions
• Add rate limiting to prevent abuse

Testing

• Expand unit test coverage
• Add integration tests for API endpoints
• Implement automated testing for critical workflows