"""Fetching file bytes from Telegram's CDN."""

from __future__ import annotations

from typing import Protocol, runtime_checkable

import aiohttp

from sticker_downloader.errors import FetchError


@runtime_checkable
class Fetcher(Protocol):
    """Minimal interface the downloader needs to read a file off the network."""

    async def fetch(self, url: str) -> bytes: ...


class AiohttpFetcher:
    """A :class:`Fetcher` backed by a shared :class:`aiohttp.ClientSession`."""

    def __init__(self, session: aiohttp.ClientSession) -> None:
        self._session = session

    async def fetch(self, url: str) -> bytes:
        async with self._session.get(url) as response:
            if response.status >= 400:
                raise FetchError(url, response.status, response.reason or "")
            return await response.read()