import asyncio
import logging

import httpx
from contextlib import AsyncExitStack
from mcp import Client, MCPError
from mcp.client.streamable_http import streamable_http_client

from common.as_type import _extract_text, _looks_like_not_found

logger = logging.getLogger("youtrack_mcp")
logger.setLevel(logging.DEBUG)

class IssueNotFound(Exception):
    """Raised when a YouTrack issue doesn't exist or isn't accessible."""

class YouTrackMCPClient:
    """Wraps an MCP connection to YouTrack, owning the lifecycle in a dedicated task."""

    def __init__(self, endpoint_url: str, token: str, proxy: str | None = None):
        self.endpoint_url = endpoint_url
        self.token = token
        self.proxy = proxy
        self._client = None
        self._lifecycle_task = None
        self._ready = asyncio.Event()
        self._stop = asyncio.Event()

    async def _run(self):
        """Single task that owns the entire MCP client lifecycle."""
        async with AsyncExitStack() as stack:
            http = await stack.enter_async_context(
                httpx.AsyncClient(
                    headers={"Authorization": f"Bearer {self.token}"},
                    proxy=self.proxy,
                    timeout=httpx.Timeout(30.0, connect=10.0, read=300.0),
                    follow_redirects=True,
                )
            )
            transport = streamable_http_client(
                self.endpoint_url,
                http_client=http,
            )
            self._client = await stack.enter_async_context(Client(transport))
            self._ready.set()
            await self._stop.wait()  # keep the context alive

    async def connect(self):
        """Start the lifecycle task and wait until the client is ready."""
        self._lifecycle_task = asyncio.create_task(self._run())
        await self._ready.wait()
        return self

    async def close(self):
        """Signal the lifecycle task to exit and wait for it to finish."""
        if self._lifecycle_task is None:
            return
        self._stop.set()
        await self._lifecycle_task
        self._lifecycle_task = None

    async def call_tool(self, name: str, arguments: dict):
        logger.debug("MCP CALL: %s with %s", name, arguments)
        result = await self._call_tool_or_raise(name, arguments)
        logger.debug("MCP RAW RESULT: %s", repr(result)[:500])
        return result.structured_content or result.content

    async def _call_tool_or_raise(self, name: str, arguments: dict):
        try:
            result = await self._client.call_tool(name, arguments)
            logger.debug("call RESULT: %s", result)
        except MCPError as e:
            # Drill into cause chain for HTTP status
            cause = e.__cause__
            while cause:
                if isinstance(cause, httpx.HTTPStatusError):
                    if cause.response.status_code == 404:
                        raise IssueNotFound(f"{arguments} not found") from e
                    raise
                cause = cause.__cause__
            raise

        # MCP-level error flag
        if getattr(result, "is_error", False):
            text = _extract_text(result)
            if _looks_like_not_found(text):
                raise IssueNotFound(text)
            raise RuntimeError(f"MCP tool {name} failed: {text}")

        return result