Initial commit

scripts/connections.py

@@ -0,0 +1,151 @@
+"""Lightweight connection handling for MCP servers."""
+
+from abc import ABC, abstractmethod
+from contextlib import AsyncExitStack
+from typing import Any
+
+from mcp import ClientSession, StdioServerParameters
+from mcp.client.sse import sse_client
+from mcp.client.stdio import stdio_client
+from mcp.client.streamable_http import streamablehttp_client
+
+
+class MCPConnection(ABC):
+    """Base class for MCP server connections."""
+
+    def __init__(self):
+        self.session = None
+        self._stack = None
+
+    @abstractmethod
+    def _create_context(self):
+        """Create the connection context based on connection type."""
+
+    async def __aenter__(self):
+        """Initialize MCP server connection."""
+        self._stack = AsyncExitStack()
+        await self._stack.__aenter__()
+
+        try:
+            ctx = self._create_context()
+            result = await self._stack.enter_async_context(ctx)
+
+            if len(result) == 2:
+                read, write = result
+            elif len(result) == 3:
+                read, write, _ = result
+            else:
+                raise ValueError(f"Unexpected context result: {result}")
+
+            session_ctx = ClientSession(read, write)
+            self.session = await self._stack.enter_async_context(session_ctx)
+            await self.session.initialize()
+            return self
+        except BaseException:
+            await self._stack.__aexit__(None, None, None)
+            raise
+
+    async def __aexit__(self, exc_type, exc_val, exc_tb):
+        """Clean up MCP server connection resources."""
+        if self._stack:
+            await self._stack.__aexit__(exc_type, exc_val, exc_tb)
+        self.session = None
+        self._stack = None
+
+    async def list_tools(self) -> list[dict[str, Any]]:
+        """Retrieve available tools from the MCP server."""
+        response = await self.session.list_tools()
+        return [
+            {
+                "name": tool.name,
+                "description": tool.description,
+                "input_schema": tool.inputSchema,
+            }
+            for tool in response.tools
+        ]
+
+    async def call_tool(self, tool_name: str, arguments: dict[str, Any]) -> Any:
+        """Call a tool on the MCP server with provided arguments."""
+        result = await self.session.call_tool(tool_name, arguments=arguments)
+        return result.content
+
+
+class MCPConnectionStdio(MCPConnection):
+    """MCP connection using standard input/output."""
+
+    def __init__(self, command: str, args: list[str] = None, env: dict[str, str] = None):
+        super().__init__()
+        self.command = command
+        self.args = args or []
+        self.env = env
+
+    def _create_context(self):
+        return stdio_client(
+            StdioServerParameters(command=self.command, args=self.args, env=self.env)
+        )
+
+
+class MCPConnectionSSE(MCPConnection):
+    """MCP connection using Server-Sent Events."""
+
+    def __init__(self, url: str, headers: dict[str, str] = None):
+        super().__init__()
+        self.url = url
+        self.headers = headers or {}
+
+    def _create_context(self):
+        return sse_client(url=self.url, headers=self.headers)
+
+
+class MCPConnectionHTTP(MCPConnection):
+    """MCP connection using Streamable HTTP."""
+
+    def __init__(self, url: str, headers: dict[str, str] = None):
+        super().__init__()
+        self.url = url
+        self.headers = headers or {}
+
+    def _create_context(self):
+        return streamablehttp_client(url=self.url, headers=self.headers)
+
+
+def create_connection(
+    transport: str,
+    command: str = None,
+    args: list[str] = None,
+    env: dict[str, str] = None,
+    url: str = None,
+    headers: dict[str, str] = None,
+) -> MCPConnection:
+    """Factory function to create the appropriate MCP connection.
+
+    Args:
+        transport: Connection type ("stdio", "sse", or "http")
+        command: Command to run (stdio only)
+        args: Command arguments (stdio only)
+        env: Environment variables (stdio only)
+        url: Server URL (sse and http only)
+        headers: HTTP headers (sse and http only)
+
+    Returns:
+        MCPConnection instance
+    """
+    transport = transport.lower()
+
+    if transport == "stdio":
+        if not command:
+            raise ValueError("Command is required for stdio transport")
+        return MCPConnectionStdio(command=command, args=args, env=env)
+
+    elif transport == "sse":
+        if not url:
+            raise ValueError("URL is required for sse transport")
+        return MCPConnectionSSE(url=url, headers=headers)
+
+    elif transport in ["http", "streamable_http", "streamable-http"]:
+        if not url:
+            raise ValueError("URL is required for http transport")
+        return MCPConnectionHTTP(url=url, headers=headers)
+
+    else:
+        raise ValueError(f"Unsupported transport type: {transport}. Use 'stdio', 'sse', or 'http'")