LINO API (GraphQL) - Complete Implementation

[konard]

🎉 Complete Implementation

This pull request successfully implements a GraphQL-style API that uses LINO instead of JSON, as requested in issue #34.

📋 Issue Reference

Fixes #34

✨ Features Implemented

🌐 LINO GraphQL API Server

• HTTP Server: Full ASP.NET Core-based server with GraphQL endpoint
• LINO Notation: Uses LINO syntax instead of JSON for queries and responses
• GraphQL Compatibility: Supports GraphQL-style query structure translated to LINO
• Web Playground: Built-in web interface for testing queries at http://localhost:5000/

🔧 New CLI Commands

# Start GraphQL API server
clink serve --port 5000 --trace

# Traditional query execution (backward compatible)  
clink query '() ((1 1))' --changes --after

📡 API Endpoints

• POST /graphql - Main GraphQL endpoint accepting LINO queries
• GET /graphql?query=... - GraphQL GET queries
• GET / - Interactive web playground
• GET /schema - Schema introspection in LINO format

🔍 Query Examples

# Query all links with specific fields
curl -X POST http://localhost:5000/graphql \
  -H "Content-Type: text/plain" \
  -d "(query (links (id source target)))"

# Query specific link  
curl -X POST http://localhost:5000/graphql \
  -d "(query (link (id: 1) (id source target)))"

# Schema introspection
curl -X POST http://localhost:5000/graphql \
  -d "(query (__schema))"

📊 Response Format

Responses use LINO notation:

(response (data (links ((id: 1) (source: 1) (target: 1)) ((id: 2) (source: 2) (target: 2)))))

🏗️ Technical Implementation

Core Components

• LinoGraphQLProcessor: Query parsing and execution engine
• LinoGraphQLServer: HTTP server with routing and middleware
• Updated Program.cs: New command structure with serve subcommand
• Comprehensive Tests: Unit tests covering all GraphQL functionality

Architecture Highlights

• Backward Compatibility: Existing CLI functionality unchanged
• Schema Support: Built-in schema introspection and type definitions
• Error Handling: Proper error responses in LINO format
• Tracing: Optional verbose logging for debugging
• Content Negotiation: Supports both LINO and JSON responses based on Accept header

🧪 Testing

• Unit tests for GraphQL processor functionality
• Integration tests for server endpoints
• Playground interface for manual testing
• All existing CLI tests continue to pass

📦 Version Update

• Updated version to 2.3.0 for this major feature addition

🚀 Usage

1. Start the server:

   clink serve --port 5000

2. Open web playground: Navigate to http://localhost:5000/

3. Test queries: Try example queries like (query (links (id source target)))

4. Use programmatically: Send HTTP requests to /graphql endpoint

This implementation successfully bridges GraphQL concepts with LINO notation, providing a unique API that leverages the power of link-based data structures while maintaining GraphQL's flexible query capabilities.

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