geutebruck/geutebruck-api/specs/001-flutter-app/constitution.md

Flutter App Constitution

Purpose

This document establishes the foundational principles and standards for developing the Geutebruck API Flutter mobile application. These guidelines ensure code quality, maintainability, and exceptional user experience.

Core Principles

1. Code Quality

• Clean Code: Follow Flutter and Dart style guides (effective_dart)
• Modularity: Organize code into reusable widgets and services
• Separation of Concerns: Implement clear boundaries between UI, business logic, and data layers
• DRY Principle: Avoid code duplication through proper abstraction
• SOLID Principles: Apply object-oriented design principles where appropriate

2. Architecture

• Pattern: Use BLoC (Business Logic Component) pattern for state management
  • Separates presentation from business logic
  • Testable and predictable state management
  • Reactive programming with streams
• Layered Architecture:
  • Presentation Layer: Widgets and UI components
  • Business Logic Layer: BLoCs and Cubits
  • Data Layer: Repositories and data sources
  • Domain Layer: Models and business entities

3. Testing Standards

• Test Coverage: Minimum 80% code coverage
• Test Types:
  • Unit Tests: All business logic, repositories, and utilities
  • Widget Tests: All custom widgets and screens
  • Integration Tests: Critical user flows
• Test-Driven Development (TDD): Write tests before implementation where feasible
• Mocking: Use mockito for dependency injection in tests

4. User Experience

• Material Design 3: Follow Material Design guidelines for consistency
• Responsive Design: Support multiple screen sizes (phones, tablets)
• Accessibility: Support screen readers, proper contrast ratios, semantic labels
• Performance:
  • App startup time < 3 seconds
  • List scrolling at 60 FPS
  • Image loading with progressive rendering
  • Efficient API calls with caching
• Offline-First: Cache data locally, sync when online
• Error Handling: Graceful error messages with retry options

5. Security

• Secure Storage: Use flutter_secure_storage for sensitive data (JWT tokens, passwords)
• HTTPS Only: All API communication over TLS
• Token Management: Automatic token refresh before expiration
• Input Validation: Sanitize all user inputs
• No Hardcoded Secrets: Use environment variables and configuration files

6. API Integration

• REST Client: Use dio package for HTTP requests
• Error Handling: Standardized error parsing and user-friendly messages
• Retry Logic: Automatic retry with exponential backoff for failed requests
• Request Cancellation: Cancel pending requests on screen navigation
• Response Caching: Implement caching strategy for frequently accessed data

7. Code Organization

lib/
├── core/
│   ├── constants/
│   ├── errors/
│   ├── network/
│   └── utils/
├── data/
│   ├── models/
│   ├── repositories/
│   └── data_sources/
├── domain/
│   ├── entities/
│   └── repositories/
├── presentation/
│   ├── blocs/
│   ├── screens/
│   └── widgets/
└── main.dart

8. Dependency Management

• Minimal Dependencies: Only add well-maintained, popular packages
• Version Locking: Use exact versions in pubspec.yaml
• Regular Updates: Review and update dependencies monthly
• Null Safety: Enforce sound null safety

9. Documentation

• Code Comments: Document complex logic and non-obvious decisions
• API Documentation: Generate documentation using dartdoc
• README: Comprehensive setup and running instructions
• Change Log: Document all changes in CHANGELOG.md

10. Version Control

• Git Flow: Use feature branches with descriptive names
• Commit Messages: Follow conventional commits format
• Pull Requests: Require code review before merging
• CI/CD: Automated testing and deployment pipelines

Governance

Technical Decisions

• Architecture changes require team consensus
• New dependencies require justification and approval
• Breaking changes require migration plan

Code Review Standards

• All code must be reviewed before merging
• Reviewers check for:
  • Adherence to principles
  • Test coverage
  • Code clarity and documentation
  • Performance implications

Performance Budgets

• App size: < 50MB
• Memory usage: < 200MB during normal operation
• Network requests: Batched and optimized
• Battery consumption: Minimal background activity

Exceptions

Exceptions to these principles require:

1. Clear justification
2. Documentation of trade-offs
3. Approval from technical lead
4. Technical debt tracking