from __future__ import annotations

import os
from dataclasses import dataclass
from pathlib import Path


def _parse_allowed_ids(raw: str) -> frozenset[int]:
    ids: set[int] = set()
    for part in raw.split(","):
        part = part.strip()
        if not part:
            continue
        try:
            ids.add(int(part))
        except ValueError:
            continue
    return frozenset(ids)


@dataclass(frozen=True)
class Settings:
    telegram_bot_token: str
    ha_api_base_url: str
    poll_interval_sec: int
    data_dir: Path
    allowed_telegram_ids: frozenset[int]

    @property
    def db_path(self) -> Path:
        return self.data_dir / "bot.db"


def load_settings() -> Settings:
    token = os.getenv("TELEGRAM_BOT_TOKEN", "").strip()
    if not token:
        raise RuntimeError("TELEGRAM_BOT_TOKEN is required")

    base_url = os.getenv("HA_API_BASE_URL", "").strip().rstrip("/")
    if not base_url:
        raise RuntimeError("HA_API_BASE_URL is required")

    poll_raw = os.getenv("POLL_INTERVAL_SEC", "30").strip()
    try:
        poll_interval = max(10, int(poll_raw))
    except ValueError:
        poll_interval = 30

    data_dir = Path(os.getenv("DATA_DIR", "./data")).resolve()
    data_dir.mkdir(parents=True, exist_ok=True)

    allowed = _parse_allowed_ids(os.getenv("ALLOWED_TELEGRAM_IDS", ""))

    return Settings(
        telegram_bot_token=token,
        ha_api_base_url=base_url,
        poll_interval_sec=poll_interval,
        data_dir=data_dir,
        allowed_telegram_ids=allowed,
    )