"""Utilities for selecting preview media from Civitai image metadata."""

from __future__ import annotations

from typing import Any, Mapping, Optional, Sequence, Tuple

from .constants import NSFW_LEVELS

PreviewMedia = Mapping[str, object]
VALID_MATURE_BLUR_LEVELS = ("PG13", "R", "X", "XXX")


def _extract_nsfw_level(entry: Mapping[str, object]) -> int:
    """Return a normalized NSFW level value for the supplied media entry."""

    value = entry.get("nsfwLevel", 0)
    try:
        return int(value)  # type: ignore[return-value]
    except (TypeError, ValueError):
        return 0


def resolve_mature_threshold(settings: Mapping[str, Any] | None) -> int:
    """Resolve the configured mature blur threshold from settings.

    Allowed values are ``PG13``, ``R``, ``X``, and ``XXX``. Any invalid or
    missing value falls back to ``R``.
    """

    if not isinstance(settings, Mapping):
        return NSFW_LEVELS.get("R", 4)

    raw_level = settings.get("mature_blur_level", "R")
    normalized = str(raw_level).strip().upper()
    if normalized not in VALID_MATURE_BLUR_LEVELS:
        normalized = "R"
    return NSFW_LEVELS.get(normalized, NSFW_LEVELS.get("R", 4))


def select_preview_media(
    images: Sequence[Mapping[str, object]] | None,
    *,
    blur_mature_content: bool,
    mature_threshold: int | None = None,
) -> Tuple[Optional[PreviewMedia], int]:
    """Select the most appropriate preview media entry.

    When ``blur_mature_content`` is enabled we first try to return the first media
    item with an ``nsfwLevel`` lower than the configured mature threshold
    (defaults to :pydata:`NSFW_LEVELS["R"]`). If none are available we return
    the media entry with the lowest NSFW level. When the setting is disabled we
    simply return the first entry.
    """

    if not images:
        return None, 0

    candidates = [item for item in images if isinstance(item, Mapping)]
    if not candidates:
        return None, 0

    selected = candidates[0]
    selected_level = _extract_nsfw_level(selected)

    if not blur_mature_content:
        return selected, selected_level

    safe_threshold = (
        mature_threshold if isinstance(mature_threshold, int) else NSFW_LEVELS.get("R", 4)
    )
    for candidate in candidates:
        level = _extract_nsfw_level(candidate)
        if level < safe_threshold:
            return candidate, level

    for candidate in candidates[1:]:
        level = _extract_nsfw_level(candidate)
        if level < selected_level:
            selected = candidate
            selected_level = level

    return selected, selected_level


__all__ = ["resolve_mature_threshold", "select_preview_media", "VALID_MATURE_BLUR_LEVELS"]