"""Runtime settings store.

Configuration can come from two places: environment variables (the deploy-time
defaults) and a JSON file written by the in-app Settings page. The file, when
present, wins. ``load`` returns the effective settings; ``save`` persists the
editable subset and returns the new effective settings.
"""

from __future__ import annotations

import json
import os
from pathlib import Path

SETTINGS_FILE = Path(os.environ.get("SETTINGS_FILE", "cache/settings.json"))

FIELDS = (
    "emby_url",
    "emby_api_key",
    "navidrome_url",
    "navidrome_user",
    "navidrome_password",
    "music_root",
)


def env_defaults() -> dict:
    return {
        "emby_url": os.environ.get("EMBY_URL", "http://10.0.0.2:8096"),
        "emby_api_key": os.environ.get("EMBY_API_KEY", ""),
        "navidrome_url": os.environ.get("NAVIDROME_URL", "http://10.0.0.2:4533"),
        "navidrome_user": os.environ.get("NAVIDROME_USER", ""),
        "navidrome_password": os.environ.get("NAVIDROME_PASSWORD", ""),
        "music_root": os.environ.get("MUSIC_ROOT", r"\\Matt-htpc\d\Music"),
    }


def _read_file() -> dict:
    if not SETTINGS_FILE.exists():
        return {}
    try:
        data = json.loads(SETTINGS_FILE.read_text(encoding="utf-8"))
    except (OSError, ValueError):
        return {}
    return {k: str(v) for k, v in data.items() if k in FIELDS and v is not None}


def load() -> dict:
    """Effective settings: env defaults overlaid with the saved file."""
    values = env_defaults()
    values.update(_read_file())
    return values


def save(updates: dict) -> dict:
    """Persist the editable subset of ``updates`` and return effective settings."""
    current = _read_file()
    for key in FIELDS:
        if key in updates and updates[key] is not None:
            current[key] = str(updates[key]).strip()
    SETTINGS_FILE.parent.mkdir(parents=True, exist_ok=True)
    SETTINGS_FILE.write_text(json.dumps(current, indent=2), encoding="utf-8")
    return load()