feat: Migrate Eclipse Store AFS NIO module to .NET Core

[hadv]

Overview

This PR migrates the Eclipse Store AFS NIO (New I/O) module from Java to .NET Core, providing local file system storage capabilities for NebulaStore.

Changes

Core Implementation

• ✅ Ported all 7 Java source files from Eclipse Store NIO module to C#
• ✅ Implemented NioFileSystem for local file system operations
• ✅ Implemented NioConnector for AFS integration
• ✅ Added comprehensive test suite with 23 passing tests
• ✅ Added detailed README with usage examples and documentation

Key Components

1. NioPathResolver - Path resolution with home directory expansion
2. NioFileWrapper - Thread-safe file stream management with automatic positioning
3. NioIoHandler - Core I/O operations (read, write, copy, move, truncate, etc.)
4. NioConnector - Full IBlobStoreConnector implementation for AFS integration
5. NioReadableFile - Read-only file access wrapper
6. NioWritableFile - Read-write file access wrapper

Files Added

afs/nio/
├── NebulaStore.Afs.Nio.csproj
├── README.md
├── src/
│   ├── INioFileWrapper.cs
│   ├── INioItemWrapper.cs
│   ├── NioConnector.cs
│   ├── NioFileSystem.cs
│   ├── NioFileWrapperBase.cs
│   ├── NioIoHandler.cs
│   ├── NioPathResolver.cs
│   ├── NioReadableFile.cs
│   └── NioWritableFile.cs
└── test/
    ├── NebulaStore.Afs.Nio.Tests.csproj
    ├── NioConnectorTests.cs
    └── NioFileSystemTests.cs

Java to .NET Mappings

Java	.NET
FileChannel	FileStream
Path (Java NIO)	string (file system path)
OpenOption	FileMode, FileAccess, FileShare
ByteBuffer	byte[]
synchronized blocks	lock statements

Testing

• ✅ All 23 unit tests passing
• ✅ NIO project builds successfully
• ✅ Test project builds successfully
• ✅ Entire solution builds successfully

Test Coverage

NioFileSystemTests (10 tests):

• File system creation with default/custom protocols
• Path resolution (home directory, regular paths)
• File wrapping (readable, writable)
• File conversion (readable ↔ writable)
• Read/write operations

NioConnectorTests (13 tests):

• Directory and file creation
• File existence checks
• Read/write operations (full and partial)
• File deletion
• File listing (files and directories)
• File move and copy operations
• Multi-chunk writes

Features

• Local File System Access: Direct access using .NET's System.IO
• Thread-Safe Operations: All operations use proper synchronization
• File Stream Management: Automatic positioning and lifecycle management
• Path Resolution: Home directory expansion and platform-specific paths
• AFS Integration: Full IBlobStoreConnector implementation
• Comprehensive Error Handling: Proper exceptions for all error cases

Documentation

The afs/nio/README.md includes:

• Architecture overview and class hierarchy
• Usage examples and code snippets
• Integration with EmbeddedStorage
• Advanced file operations
• Performance considerations
• Best practices
• Comparison with other AFS backends

Build Status

✅ Build succeeded with 0 errors
✅ All 23 tests passed
✅ Solution builds successfully

Related

• Original Eclipse Store NIO module: https://github.com/eclipse-store/store/tree/main/afs/nio
• Follows the same module structure and design patterns as Eclipse Store

Checklist

• Code compiles without errors
• All tests pass
• Documentation added (README.md)
• Follows existing code style and patterns
• Added to solution file
• No breaking changes to existing code

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Pull Request opened by Augment Code with guidance from the PR author