Codex365 Downloader

A professional C# (.NET 8+) Azure Blob Storage downloader application with advanced features for reliable large file downloads.

Features

Core Functionality

• Azure Blob Storage Integration: Full support for Azure Blob Storage with multiple authentication methods
• Chunked Downloads: Configurable chunk size (default: 4MB) for efficient large file handling
• Parallel Processing: Concurrent chunk downloads using ThreadPool and Task Parallel Library
• Pausable/Resumable: Downloads can be paused and resumed at any time
• State Persistence: SQLite database tracks download progress and enables recovery after application restart

Reliability & Resilience

• Retry Logic: Exponential backoff retry policy for failed chunks using Polly
• Circuit Breaker: Network instability protection with configurable failure thresholds
• Checksum Validation: MD5 checksum verification for downloaded chunks and complete files
• Error Handling: Comprehensive error handling and logging
• Concurrent Access: Thread-safe state management for multiple simultaneous downloads

Authentication Support

• Connection String: Traditional Azure Storage connection string authentication
• Managed Identity: Azure Active Directory Managed Identity support for secure, credential-free authentication
• DefaultAzureCredential: Automatic credential discovery in Azure environments
• Public Blob Access: Direct HTTPS URLs for publicly accessible blobs (no authentication required)

User Interface

• Interactive Console: Rich console interface using Spectre.Console
• WPF GUI Application: Cross-platform graphical interface with Fluent UI design and dark theme support
• Multi-language Support: English and Georgian language support with easy language switching
• Real-time Progress: Live progress reporting with download speed and ETA
• Multiple Downloads: Manage multiple concurrent downloads
• Download Management: Start, pause, resume, cancel, and monitor downloads

Configuration

Authentication Methods

Connection String (Development/Testing)

{
  "ConnectionStrings": {
    "AzureStorage": "DefaultEndpointsProtocol=https;AccountName=myaccount;AccountKey=mykey;EndpointSuffix=core.windows.net"
  }
}

Managed Identity (Production)

{
  "AzureStorage": {
    "AccountUrl": "https://mystorageaccount.blob.core.windows.net"
  }
}

Public Blob Access (No Authentication)

For publicly accessible blobs, leave both ConnectionStrings:AzureStorage and AzureStorage:AccountUrl empty or unset:

{
  "ConnectionStrings": {
    "AzureStorage": ""
  },
  "AzureStorage": {
    "AccountUrl": ""
  }
}

Then use direct HTTPS URLs like:

• https://mystorageaccount.blob.core.windows.net/public-container/file.zip
• https://mydomain.com/files/document.pdf (if using custom domain)

Download Configuration

{
  "DownloadConfiguration": {
    "ChunkSizeBytes": 4194304,           // 4MB chunks
    "MaxParallelDownloads": 4,           // Maximum concurrent downloads
    "MaxRetryAttempts": 3,               // Retry attempts per chunk
    "RetryDelay": "00:00:01",            // Base retry delay
    "CircuitBreakerTimeout": "00:05:00", // Circuit breaker timeout
    "CircuitBreakerFailureThreshold": 5, // Failures before opening circuit
    "DatabasePath": "downloads.db"       // SQLite database path
  }
}

Usage

Console Application

dotnet run --project src/Codex365Downloader.Console

WPF GUI Application

dotnet run --project src/Codex365Downloader.WPF

The WPF GUI provides a user-friendly graphical interface with:

• Modern Fluent UI design
• Real-time progress bars and statistics
• File browser for easy location selection
• Concurrent download management
• Cross-platform support (Windows, macOS, Linux)

See WPF GUI README for detailed usage instructions.

Download Management

1. Start New Download: Enter blob URL and local file path
2. View Downloads: See all downloads with status and progress
3. Pause Download: Temporarily halt an active download
4. Resume Download: Continue a paused download from where it left off
5. Cancel Download: Stop and remove a download

Environment Variables

Set configuration via environment variables:

export ConnectionStrings__AzureStorage="your-connection-string"
export AzureStorage__AccountUrl="https://youraccount.blob.core.windows.net"
export DownloadConfiguration__ChunkSizeBytes=8388608

Architecture

Project Structure

src/
├── Codex365Downloader.Core/         # Core business logic
│   ├── Models/                      # Data models
│   ├── Interfaces/                  # Service interfaces
│   ├── Services/                    # Core services
│   ├── Data/                        # Data access layer
│   └── Extensions/                  # Dependency injection extensions
├── Codex365Downloader.Console/      # Console application
├── Codex365Downloader.WPF/          # WPF GUI application
│   ├── ViewModels/                  # MVVM ViewModels
│   ├── Views/                       # XAML Views
│   └── README.md                    # GUI-specific documentation
└── tests/
    └── Codex365Downloader.Tests/    # Unit and integration tests

Key Components

DownloadService

Main orchestrator for download operations:

• Manages download lifecycle
• Coordinates chunked downloads
• Handles parallel processing
• Implements retry logic

BlobStorageService

Azure Blob Storage integration:

• Blob size retrieval
• Chunk-based downloads
• Connection string and Managed Identity support

SqliteStateRepository

Persistent state management:

• Download metadata storage
• Chunk completion tracking
• Recovery support

CircuitBreaker

Network resilience:

• Failure threshold monitoring
• Automatic circuit opening/closing
• Protection against cascading failures

Testing

Run Unit Tests

dotnet test

Test Coverage

• Core download logic validation
• State persistence verification
• Circuit breaker functionality
• Checksum calculation accuracy

Dependencies

Core Dependencies

• Azure.Storage.Blobs: Azure Blob Storage client
• Azure.Identity: Azure authentication
• Microsoft.Data.Sqlite: SQLite data access
• Polly: Resilience and retry patterns
• Spectre.Console: Rich console interface

GUI Dependencies

• Avalonia: Cross-platform .NET UI framework
• CommunityToolkit.Mvvm: MVVM helpers and source generators

Development Dependencies

• xUnit: Testing framework
• Moq: Mocking framework

Performance Considerations

Large File Support

• Optimized for files >1GB
• Memory-efficient streaming
• Configurable chunk sizes
• Parallel processing

Network Optimization

• Concurrent chunk downloads
• Retry logic for network failures
• Circuit breaker for stability
• Progress reporting without blocking

Resource Management

• Proper disposal of streams and connections
• Semaphore-controlled concurrency
• Memory-efficient chunk processing

Security

Credential Management

• No hardcoded credentials
• Managed Identity support
• Secure credential storage
• Environment variable configuration

Data Integrity

• MD5 checksum validation
• Chunk-level verification
• File integrity checks
• Error detection and recovery

Deployment

Azure VM/Container

# Install .NET 8 Runtime
# Configure Managed Identity
# Set environment variables
dotnet Codex365Downloader.Console.dll

Docker

FROM mcr.microsoft.com/dotnet/runtime:8.0
COPY . /app
WORKDIR /app
ENTRYPOINT ["dotnet", "Codex365Downloader.Console.dll"]

Localization

The WPF GUI application supports multiple languages:

• English (en): Default language
• Georgian (ka): ქართული ენა

Using Different Languages

• Use the language selector in the top-right corner of the application
• Changes take effect immediately without restarting

Adding New Languages

See Localization Guide for detailed instructions on:

• Adding new language support
• Translating UI strings
• Testing localization

Contributing

1. Fork the repository
2. Create a feature branch
3. Add tests for new functionality
4. Ensure all tests pass
5. Submit a pull request

License

This project is licensed under the MIT License - see the LICENSE file for details.

Support

For questions, issues, or feature requests, please open an issue on GitHub.