"""Load/save the soundboard configuration as JSON.

Pure/headless: no audio or GUI imports, so it is fully unit-testable. Reads are
defensive — a missing or corrupt file yields a valid default config rather than crashing.
"""

from __future__ import annotations

import json
import os
from typing import Any

DEFAULT_CONFIG: dict[str, Any] = {
    "output_device": None,  # substring of the device name, e.g. "CABLE Input"
    "volume": 80,            # 0-100 (UI scale)
    "buttons": [],           # list of {"id", "label", "file_path"}
}


def default_config() -> dict[str, Any]:
    """A fresh deep copy of the default config."""
    return json.loads(json.dumps(DEFAULT_CONFIG))


def _coerce(raw: Any) -> dict[str, Any]:
    """Merge a parsed object onto the defaults, dropping anything malformed."""
    cfg = default_config()
    if not isinstance(raw, dict):
        return cfg

    if isinstance(raw.get("output_device"), str):
        cfg["output_device"] = raw["output_device"]

    vol = raw.get("volume")
    if isinstance(vol, (int, float)):
        cfg["volume"] = int(max(0, min(100, vol)))

    buttons = []
    if isinstance(raw.get("buttons"), list):
        for b in raw["buttons"]:
            if not isinstance(b, dict):
                continue
            bid = b.get("id")
            label = b.get("label")
            path = b.get("file_path")
            if isinstance(bid, str) and isinstance(label, str) and isinstance(path, str):
                buttons.append({"id": bid, "label": label, "file_path": path})
    cfg["buttons"] = buttons
    return cfg


def load_config(path: str) -> dict[str, Any]:
    """Load config from ``path``; return a valid default if missing or corrupt."""
    if not os.path.exists(path):
        return default_config()
    try:
        with open(path, "r", encoding="utf-8") as fh:
            raw = json.load(fh)
    except (OSError, ValueError):
        return default_config()
    return _coerce(raw)


def save_config(path: str, config: dict[str, Any]) -> None:
    """Atomically write config to ``path`` (write temp + replace)."""
    config = _coerce(config)
    directory = os.path.dirname(os.path.abspath(path))
    os.makedirs(directory, exist_ok=True)
    tmp = path + ".tmp"
    with open(tmp, "w", encoding="utf-8") as fh:
        json.dump(config, fh, indent=2)
    os.replace(tmp, path)