[Claude] Add unit tests and REST API server

[jbowen93]

NOTE: ALL VIBE CODED

Added unit tests and REST API server

🚀 Server Features

• Framework: Built with Axum (modern Rust async web framework)
• Port: Runs on http://127.0.0.1:3000
• CORS: Enabled for web client access
• JSON API: Full JSON request/response handling

📡 API Endpoints

1. GET /health - Health check
2. GET /orderbook - Get current bid/ask prices
3. POST /orders - Create new orders (limit, market, post_only, fill_or_kill)
4. DELETE /orders/:side/:order_id - Cancel orders
5. GET /orders/:order_id - Check order existence (placeholder)

🧪 Tested Functionality

• ✅ Creating limit orders (bid/ask)
• ✅ Order book state tracking
• ✅ Market order execution and matching
• ✅ Price-time priority matching
• ✅ Transaction logging

📁 Files Created

• src/bin/server.rs - REST API server binary
• examples/api_demo.sh - Demo script with example API calls
• API.md - Complete API documentation

🏃‍♂️ How to Run

Start the server

cargo run --bin server

Test with the demo script

./examples/api_demo.sh

Or test manually

curl -X POST http://127.0.0.1:3000/orders
-H "Content-Type: application/json"
-d '{"order_type": "limit", "side": "Bid", "price": 5000, "quantity": 100}'

The API successfully demonstrates:

• Order Creation: Different order types with proper validation
• Order Matching: Market orders executing against limit orders
• State Management: Real-time order book updates
• Transaction Logging: Complete audit trail of all operations

You now have a fully functional order book REST API that you can interact with locally!