from tenacity import retry, wait_exponential, stop_after_attempt
from typing import List, Dict, Any
import asyncio
import os
import logging
from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client

# v1.1 Compliance: Transit Logging (SOC2 CC6.1)
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger("mcp_hub")

class MCPHub:
    """
    Model Context Protocol (MCP) Hub.
    Provides a unified interface for tool discovery and execution across
    multiple MCP servers (Google Search, SQL, internal tools).
    """

    def __init__(self):
        self.servers: Dict[str, StdioServerParameters] = {}
        self.registry = {'search': {'type': 'mcp', 'provider': 'google-search', 'server': 'google-search-mcp'}, 'db': {'type': 'mcp', 'provider': 'alloydb', 'server': 'postgres-mcp'}, 'legacy_crm': {'type': 'rest', 'provider': 'internal', 'status': 'deprecated'}}

    def register_server(self, name: str, command: str, args: List[str]=None):
        """Registers a local MCP server."""
        self.servers[name] = StdioServerParameters(command=command, args=args or [], env=os.environ.copy())

    async def execute_tool(self, tool_name: str, arguments: Dict[str, Any]):
        """
        Executes a tool call using the Model Context Protocol.
        """
        logger.info(f"TRANSIT_LOG: Executing tool '{tool_name}' with {len(arguments)} args.")
        if tool_name not in self.registry:
            raise ValueError(f'Tool {tool_name} not found in MCP registry.')
        config = self.registry[tool_name]
        if config['type'] == 'rest':
            print(f'⚠️  Executing legacy REST tool: {tool_name}')
            return await self._mock_legacy_exec(tool_name, arguments)
        server_name = config.get('server')
        if not server_name or server_name not in self.servers:
            print(f"ℹ️  MCP Server '{server_name}' not configured. Running in simulated mode.")
            return await self._mock_mcp_exec(tool_name, arguments)
        async with stdio_client(self.servers[server_name]) as (read, write):
            async with ClientSession(read, write) as session:
                await session.initialize()
                result = await session.call_tool(tool_name, arguments, timeout=10)
                return {'result': result.content, 'protocol': 'mcp-v1', 'server': server_name}

    async def _mock_mcp_exec(self, tool_name: str, args: Dict[str, Any]):
        await asyncio.sleep(0.2)
        return {'result': f'Simulated MCP response for {tool_name}', 'protocol': 'mcp-virtual', 'assurance': 0.95}

    async def _mock_legacy_exec(self, tool_name: str, args: Dict[str, Any]):
        await asyncio.sleep(0.5)
        return {'result': f'Legacy response for {tool_name}', 'protocol': 'rest-legacy', 'warning': 'MIGRATE_TO_MCP'}
global_mcp_hub = MCPHub()