"""Persist the settings an administrator edits in the UI.

config.py holds the defaults, but anything changed at runtime has to survive a
restart — otherwise editing the brand or the transcode ladder appears to work and
is silently reverted the next time the backend starts. Writes are atomic (temp
file + replace) so a crash mid-save cannot leave a half-written file that fails
to parse on boot.
"""

import json
from pathlib import Path

from config import settings

STORE_PATH = Path(__file__).resolve().parent.parent / "settings.json"

# Settings the UI may change, with the attribute they map to on Settings.
_MANAGED = (
    "brand_name",
    "brand_tagline",
    "brand_logo_url",
    "load_balance_strategy",
    "multicast_enabled",
    "transcode_profiles",
    "qualities",
)


def load_settings() -> None:
    """Apply saved overrides on top of the config defaults. Never raises."""
    if not STORE_PATH.exists():
        return
    try:
        saved = json.loads(STORE_PATH.read_text(encoding="utf-8"))
    except (OSError, json.JSONDecodeError):
        # A corrupt file must not stop the server from booting; the defaults from
        # config.py are still usable.
        return
    if not isinstance(saved, dict):
        return
    for key, value in saved.items():
        # Only known keys, so a stale or hand-edited file cannot inject arbitrary
        # attributes onto the settings object.
        if key in _MANAGED and value is not None:
            setattr(settings, key, value)


def save_settings() -> None:
    payload = {key: getattr(settings, key) for key in _MANAGED}
    temporary = STORE_PATH.with_suffix(".json.tmp")
    temporary.write_text(
        json.dumps(payload, ensure_ascii=False, indent=2),
        encoding="utf-8",
    )
    temporary.replace(STORE_PATH)