from __future__ import annotations

from dataclasses import dataclass
import os

from dotenv import load_dotenv


@dataclass(frozen=True)
class Config:
    bot_token: str
    chat_id: int | None
    db_path: str
    verify_window_seconds: int
    thanks_ttl_seconds: int


def _get_int(name: str, default: int) -> int:
    raw = os.getenv(name)
    if raw is None or raw.strip() == "":
        return default
    return int(raw)


def load_config() -> Config:
    load_dotenv()

    bot_token = (os.getenv("BOT_TOKEN") or "").strip()
    if not bot_token:
        raise RuntimeError("BOT_TOKEN is required (set it in .env)")

    chat_id_raw = (os.getenv("CHAT_ID") or "").strip()
    chat_id = int(chat_id_raw) if chat_id_raw else None

    db_path = (os.getenv("DB_PATH") or "./bot.sqlite3").strip()
    verify_window_seconds = _get_int("VERIFY_WINDOW_SECONDS", 60)
    thanks_ttl_seconds = _get_int("THANKS_TTL_SECONDS", 60)

    return Config(
        bot_token=bot_token,
        chat_id=chat_id,
        db_path=db_path,
        verify_window_seconds=verify_window_seconds,
        thanks_ttl_seconds=thanks_ttl_seconds,
    )