import asyncio
from typing import Any, Dict, Union

import aiohttp

from ..api import DEFAULT_USER_AGENT
from ..common_utils import queue_fetch_task

__all__ = ['AIOHttpMixin', 'LazySession']


class LazySession:
    def __init__(self):
        self._session = None

    async def get_session(self):
        session = self._session
        if session is None:
            self._session = session = aiohttp.ClientSession()
        return session

    async def close(self):
        session = self._session
        if session is not None:
            await session.close()


class AIOHttpMixin:
    def __init__(
        self,
        session: Union[aiohttp.ClientSession, LazySession],
        user_agent=None,
        per_request_timeout=10,
    ):
        self._session = session
        self.user_agent = user_agent or DEFAULT_USER_AGENT
        self.per_request_timeout = per_request_timeout
        self.__results: Dict[Any, Any] = {}
        self.__result_events: Dict[Any, asyncio.Event] = {}
        super().__init__()

    async def get_session(self) -> aiohttp.ClientSession:
        session = self._session
        if isinstance(session, LazySession):
            return await session.get_session()
        else:
            return session

    def get_results(self):
        return {
            v for v in self.__results.values() if not isinstance(v, Exception)
        }

    def _iter_results(self):
        for k, v in self.__results.items():
            if not isinstance(v, Exception):
                yield k, v

    async def _post_fetch_task(self, tag, async_fun):
        return await queue_fetch_task(
            self.__results, self.__result_events, tag, async_fun
        )
