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Architecture Overview

The Cryptographer application is built using Clean Architecture principles, ensuring a modular, testable, and maintainable codebase. This section provides an overview of the architectural design.

Project Structure

The codebase is organized following Clean Architecture with clear layer separation:

app/src/main/java/com/example/cryptographer/
├── domain/              # Business logic (no Android dependencies)
│   ├── text/            # Text encryption domain
│   └── common/          # Shared domain concepts
├── application/         # Use cases and orchestration (CQRS)
│   ├── commands/        # Command handlers
│   ├── queries/         # Query handlers
│   └── common/          # Shared application code
├── infrastructure/      # External adapters
│   ├── key/             # Key storage adapters
│   └── settings/        # Settings storage adapters
├── presentation/        # UI layer
│   ├── key/             # Key generation screen
│   ├── encryption/      # Encryption/decryption screen
│   ├── encoding/        # Encoding conversion screen
│   └── main/            # Main navigation
└── setup/               # Configuration and setup
    ├── configs/         # Theme and styling
    ├── i18n/            # Internationalization
    └── ioc/             # Dependency injection

Key Components

  • Jetpack Compose: Powers the modern declarative UI
  • Hilt: Handles dependency injection
  • Coroutines + Flow: Manages asynchronous operations and reactive streams
  • Material Design 3: Provides the design system
  • Clean Architecture: Ensures separation of concerns
  • CQRS: Separates commands and queries
  • DDD: Domain-Driven Design principles

Architecture Layers

The application follows Clean Architecture with four primary layers:

1. Domain Layer

Location: domain/

Pure business logic with no Android dependencies.

  • Entities: Text, EncryptionKey, EncryptedText
  • Value Objects: EncryptionAlgorithm, TextEncoding, ValidatedText
  • Services: AesEncryptionService, ChaCha20EncryptionService, TextService
  • Domain Events: Base domain event infrastructure

2. Application Layer

Location: application/

Orchestrates domain logic through commands and queries (CQRS pattern).

  • Commands: Key generation, encryption, decryption, encoding conversion
  • Queries: Key retrieval, settings retrieval
  • Views: Data transfer objects for presentation
  • Error Handling: Application-specific error types

3. Infrastructure Layer

Location: infrastructure/

Adapters connecting domain to external systems.

  • Key Storage: Local key persistence adapters
  • Settings Storage: User preferences and settings adapters
  • ID Generation: UUID-based ID generation

4. Presentation Layer

Location: presentation/

UI components and state management.

  • Screens: Compose UI screens
  • ViewModels: State management with StateFlow
  • Components: Reusable Compose UI components
  • Navigation: Screen navigation logic

Dependency Flow

Presentation → Application → Domain
                    ↓
               Infrastructure

Key Principles:

  • Inner layers (Domain) have no dependencies on outer layers
  • Dependencies point inward toward the domain
  • Business logic is isolated from frameworks and UI
  • Each layer has clear responsibilities

Design Patterns

CQRS (Command Query Responsibility Segregation)

Commands and queries are separated: - Commands: Modify state (generate key, encrypt text) - Queries: Read state (get keys, get settings)

MVVM (Model-View-ViewModel)

  • Model: Domain entities and business logic
  • View: Compose UI components
  • ViewModel: State management and UI logic

Dependency Injection

Using Hilt for dependency injection: - Services provided as singletons - ViewModels automatically injected - Clear dependency graph

Benefits

  1. Testability: Domain logic can be tested without Android dependencies
  2. Maintainability: Clear separation makes code easier to understand and modify
  3. Scalability: Easy to add new features without affecting existing code
  4. Flexibility: Can swap implementations (e.g., storage adapters) easily

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