# 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