from __future__ import annotations

from aiohttp import BasicAuth
from aiogram.client.session.aiohttp import AiohttpSession
from decouple import config


SUPPORTED_PROXY_PROTOCOLS = {"http", "socks5"}


def build_bot_session() -> AiohttpSession | None:
    proxy_raw = config("BOT_PROXY", default="").strip()
    if not proxy_raw:
        return None

    proxy = parse_proxy_value(proxy_raw)
    return AiohttpSession(proxy=proxy)


def parse_proxy_value(proxy_raw: str) -> str | tuple[str, BasicAuth]:
    if "://" in proxy_raw:
        return proxy_raw

    parts = proxy_raw.split(":")
    if len(parts) not in {3, 5}:
        raise ValueError(
            "BOT_PROXY must be in format protocol:ip:port or protocol:ip:port:user:pass"
        )

    protocol, host, port = parts[:3]
    protocol = protocol.lower()

    if protocol not in SUPPORTED_PROXY_PROTOCOLS:
        raise ValueError(
            f"Unsupported proxy protocol '{protocol}'. Supported: http, socks5"
        )

    proxy_url = f"{protocol}://{host}:{port}"

    if len(parts) == 3:
        return proxy_url

    username, password = parts[3], parts[4]
    return proxy_url, BasicAuth(login=username, password=password)