Implement network interface with TCP server and Python client library

[Copilot]

This PR implements a complete network interface for the JHAZ Database System, enabling programmatic access through TCP connections with a JSON-based protocol and Python client library.

Problem Statement

The database system previously only supported command-line interface access, limiting its usability for programmatic integration and web applications. There was no way to access the database remotely or integrate it into other applications.

Solution Overview

Implemented a dual-interface architecture that preserves the existing CLI while adding comprehensive network capabilities:

• Network Server: TCP server (./bin/db-server) listening on port 9000 with JSON protocol
• Python Client Library: Complete client library with connection management and SQL parsing
• Protocol Design: Length-framed JSON messages for reliable communication
• Security Integration: Same authentication system as CLI maintained over network

Key Changes

1. Build System Enhancement

• Modified Makefile to generate separate binaries:
  • bin/db-cli - Interactive command-line interface (existing functionality)
  • bin/db-server - Network server with JSON API (new functionality)
• Fixed compilation issues with conflicting main() functions
• Standardized port configuration to use port 9000 consistently

2. Network Protocol Implementation

• Enhanced src/network.c with proper JSON protocol handling:
  • 4-byte length prefix + JSON payload for reliable message framing
  • JSON command parsing and conversion to existing SQL text format
  • Proper error handling and response formatting
• Updated protocol flow to eliminate welcome messages that conflicted with client expectations
• Integrated authentication to maintain security over network connections

3. Python Client Library

• Enhanced python_client/client/parser.py with support for standard SQL transactions:
  • Added BEGIN, COMMIT, ROLLBACK command parsing
  • Added LOGIN command support for authentication
  • Comprehensive SQL command coverage (SELECT, INSERT, UPDATE, DELETE, CREATE, etc.)
• Connection management with proper timeout handling and error recovery
• Transaction support with automatic rollback on connection failure

4. Command Translation System

• Implemented JSON-to-SQL converter in network server:
  • Translates JSON command objects to SQL text for existing command processor
  • Maintains full compatibility with existing database engine
  • Supports all SQL operations including complex WHERE clauses and transactions

Usage Examples

Starting the Network Server

make
./bin/db-server
# Server starts on port 9000

Python Client Usage

from client.connection import Connection

with Connection('localhost', 9000) as conn:
    # Authenticate
    conn.execute('LOGIN admin admin')
    
    # Database operations
    conn.execute('CREATE DATABASE myapp')
    conn.execute('CREATE TABLE users (id INT, name STRING(50), email STRING(100))')
    
    # Transaction support
    conn.begin()
    conn.execute('INSERT INTO users VALUES (1, "Alice", "alice@example.com")')
    conn.commit()
    
    # Query data
    result = conn.execute('SELECT * FROM users')
    print(result)  # JSON response with rows

Testing and Validation

Created comprehensive test suite that validates:

• TCP connection establishment and JSON protocol
• All SQL command types (DDL, DML, transactions)
• Authentication and security enforcement
• Error handling and proper response formatting
• Concurrent client connections
• Backwards compatibility with CLI interface

Documentation

• NETWORK_INTERFACE.md: Complete API documentation and integration examples
• demo_python_client.py: Interactive demonstration script
• Updated README.md: Reflects dual interface capabilities
• Comprehensive docstrings: Full API documentation in Python client

Benefits

1. Programmatic Access: Applications can now integrate with the database via Python/JSON API
2. Web Integration: Easy integration with web frameworks (Flask, Django, FastAPI)
3. Microservices: Database can serve as a network service in distributed architectures
4. Concurrent Access: Multiple clients can connect simultaneously
5. Language Agnostic: JSON protocol allows clients in any programming language
6. Backwards Compatible: Existing CLI workflows unchanged

Architecture Impact

The implementation maintains the existing database engine unchanged while adding a network layer that translates between JSON protocol and the existing SQL text interface. This approach ensures:

• Zero impact on existing functionality
• Same security model and authentication
• Identical SQL syntax and semantics
• Full transaction support over network

The database system now provides both interactive administration (CLI) and programmatic integration (network API) capabilities, transforming it from a CLI-only tool into a full network-accessible database server.

Original prompt

Replace command line interface with a network interface so commands can be invoked through tcp and response can be returned their. Also create a python library to simply communincation between the server

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