import logging
import os
import asyncio
from contextlib import AsyncExitStack
from typing import Any, Callable, Optional

logger = logging.getLogger(__name__)


def get_mcp_start_timeout() -> float:
    """Return the startup timeout for optional MCP servers."""
    try:
        return float(os.getenv("MCP_START_TIMEOUT_SECONDS", "5"))
    except ValueError:
        return 5.0


async def enter_optional_mcp(
    stack: AsyncExitStack,
    factory: Callable[[], Any],
    server_name: str,
):
    """Try to start an MCP server and degrade gracefully if it is unavailable."""
    try:
        server = factory()
        timeout = get_mcp_start_timeout()
        if timeout <= 0:
            return await stack.enter_async_context(server)
        return await asyncio.wait_for(stack.enter_async_context(server), timeout=timeout)
    except asyncio.TimeoutError:
        logger.warning("%s startup timed out; continuing without it", server_name)
        return None
    except Exception as exc:
        logger.warning("%s unavailable; continuing without it: %s", server_name, exc)
        return None


def connected_mcp_servers(*servers: Optional[Any]) -> list[Any]:
    """Return only successfully connected MCP servers."""
    return [server for server in servers if server is not None]