feat: add MCP support (#20716)

Co-authored-by: QuantumGhost <obelisk.reg+git@gmail.com>

api/core/mcp/mcp_client.py

@@ -0,0 +1,150 @@
+import logging
+from collections.abc import Callable
+from contextlib import AbstractContextManager, ExitStack
+from types import TracebackType
+from typing import Any, Optional, cast
+from urllib.parse import urlparse
+
+from core.mcp.client.sse_client import sse_client
+from core.mcp.client.streamable_client import streamablehttp_client
+from core.mcp.error import MCPAuthError, MCPConnectionError
+from core.mcp.session.client_session import ClientSession
+from core.mcp.types import Tool
+
+logger = logging.getLogger(__name__)
+
+
+class MCPClient:
+    def __init__(
+        self,
+        server_url: str,
+        provider_id: str,
+        tenant_id: str,
+        authed: bool = True,
+        authorization_code: Optional[str] = None,
+        for_list: bool = False,
+    ):
+        # Initialize info
+        self.provider_id = provider_id
+        self.tenant_id = tenant_id
+        self.client_type = "streamable"
+        self.server_url = server_url
+
+        # Authentication info
+        self.authed = authed
+        self.authorization_code = authorization_code
+        if authed:
+            from core.mcp.auth.auth_provider import OAuthClientProvider
+
+            self.provider = OAuthClientProvider(self.provider_id, self.tenant_id, for_list=for_list)
+            self.token = self.provider.tokens()
+
+        # Initialize session and client objects
+        self._session: Optional[ClientSession] = None
+        self._streams_context: Optional[AbstractContextManager[Any]] = None
+        self._session_context: Optional[ClientSession] = None
+        self.exit_stack = ExitStack()
+
+        # Whether the client has been initialized
+        self._initialized = False
+
+    def __enter__(self):
+        self._initialize()
+        self._initialized = True
+        return self
+
+    def __exit__(
+        self, exc_type: Optional[type], exc_value: Optional[BaseException], traceback: Optional[TracebackType]
+    ):
+        self.cleanup()
+
+    def _initialize(
+        self,
+    ):
+        """Initialize the client with fallback to SSE if streamable connection fails"""
+        connection_methods: dict[str, Callable[..., AbstractContextManager[Any]]] = {
+            "mcp": streamablehttp_client,
+            "sse": sse_client,
+        }
+
+        parsed_url = urlparse(self.server_url)
+        path = parsed_url.path
+        method_name = path.rstrip("/").split("/")[-1] if path else ""
+        try:
+            client_factory = connection_methods[method_name]
+            self.connect_server(client_factory, method_name)
+        except KeyError:
+            try:
+                self.connect_server(sse_client, "sse")
+            except MCPConnectionError:
+                self.connect_server(streamablehttp_client, "mcp")
+
+    def connect_server(
+        self, client_factory: Callable[..., AbstractContextManager[Any]], method_name: str, first_try: bool = True
+    ):
+        from core.mcp.auth.auth_flow import auth
+
+        try:
+            headers = (
+                {"Authorization": f"{self.token.token_type.capitalize()} {self.token.access_token}"}
+                if self.authed and self.token
+                else {}
+            )
+            self._streams_context = client_factory(url=self.server_url, headers=headers)
+            if self._streams_context is None:
+                raise MCPConnectionError("Failed to create connection context")
+
+            # Use exit_stack to manage context managers properly
+            if method_name == "mcp":
+                read_stream, write_stream, _ = self.exit_stack.enter_context(self._streams_context)
+                streams = (read_stream, write_stream)
+            else:  # sse_client
+                streams = self.exit_stack.enter_context(self._streams_context)
+
+            self._session_context = ClientSession(*streams)
+            self._session = self.exit_stack.enter_context(self._session_context)
+            session = cast(ClientSession, self._session)
+            session.initialize()
+            return
+
+        except MCPAuthError:
+            if not self.authed:
+                raise
+            try:
+                auth(self.provider, self.server_url, self.authorization_code)
+            except Exception as e:
+                raise ValueError(f"Failed to authenticate: {e}")
+            self.token = self.provider.tokens()
+            if first_try:
+                return self.connect_server(client_factory, method_name, first_try=False)
+
+        except MCPConnectionError:
+            raise
+
+    def list_tools(self) -> list[Tool]:
+        """Connect to an MCP server running with SSE transport"""
+        # List available tools to verify connection
+        if not self._initialized or not self._session:
+            raise ValueError("Session not initialized.")
+        response = self._session.list_tools()
+        tools = response.tools
+        return tools
+
+    def invoke_tool(self, tool_name: str, tool_args: dict):
+        """Call a tool"""
+        if not self._initialized or not self._session:
+            raise ValueError("Session not initialized.")
+        return self._session.call_tool(tool_name, tool_args)
+
+    def cleanup(self):
+        """Clean up resources"""
+        try:
+            # ExitStack will handle proper cleanup of all managed context managers
+            self.exit_stack.close()
+            self._session = None
+            self._session_context = None
+            self._streams_context = None
+            self._initialized = False
+        except Exception as e:
+            logging.exception("Error during cleanup")
+            raise ValueError(f"Error during cleanup: {e}")