"""Shared configuration constants for the application."""

from __future__ import annotations

import contextlib
from pathlib import Path
from typing import Any, Callable

try:  # Python 3.11 and above
    import tomllib  # type: ignore[attr-defined]
except ModuleNotFoundError:  # pragma: no cover - fallback for <3.11
    with contextlib.suppress(ModuleNotFoundError):
        import tomli as tomllib  # type: ignore[assignment]
    if "tomllib" not in globals():
        tomllib = None  # type: ignore[assignment]

PREVIEW_MAX_SIZE = (900, 660)

BASE_DIR = Path(__file__).resolve().parents[2]
IMAGES_DIR = BASE_DIR / "images"
CONFIG_FILE = BASE_DIR / "config.toml"

_DEFAULTS_BASE = {
    "hue_min": 250.0,
    "hue_max": 310.0,
    "sat_min": 15.0,
    "val_min": 15.0,
    "val_max": 100.0,
    "alpha": 120,
}

_DEFAULT_TYPES: dict[str, Callable[[Any], Any]] = {
    "hue_min": float,
    "hue_max": float,
    "sat_min": float,
    "val_min": float,
    "val_max": float,
    "alpha": int,
}


def _load_default_overrides() -> dict[str, Any]:
    """Load default slider overrides from config.toml if available."""
    if tomllib is None or not CONFIG_FILE.exists():
        return {}
    decode_error = getattr(tomllib, "TOMLDecodeError", ValueError)  # type: ignore[attr-defined]
    try:
        with CONFIG_FILE.open("rb") as handle:
            data = tomllib.load(handle)
    except (OSError, AttributeError, decode_error, TypeError):  # type: ignore[arg-type]
        return {}
    settings = data.get("defaults")
    if not isinstance(settings, dict):
        return {}
    overrides: dict[str, Any] = {}
    for key, caster in _DEFAULT_TYPES.items():
        if key not in settings:
            continue
        try:
            overrides[key] = caster(settings[key])
        except (TypeError, ValueError):
            continue
    return overrides


DEFAULTS = {**_DEFAULTS_BASE, **_load_default_overrides()}