"""Asset loading helpers for backgrounds and character sprites."""

from __future__ import annotations

from pathlib import Path
from typing import Iterable

from PIL import Image


class AssetNotFoundError(FileNotFoundError):
    """Raised when an asset cannot be resolved from the project folders."""


class AssetManager:
    def __init__(self, project_root: str | Path) -> None:
        self.project_root = Path(project_root).resolve()
        self.characters_dir = self.project_root / "characters"
        self.backgrounds_dir = self.project_root / "backgrounds"

    def load_background(self, asset: str | Path) -> Image.Image:
        path = self.resolve(asset, (self.backgrounds_dir, self.project_root))
        return Image.open(path).convert("RGBA")

    def load_character(self, asset: str | Path) -> Image.Image:
        path = self.resolve(asset, (self.characters_dir, self.project_root))
        image = Image.open(path).convert("RGBA")
        return self._crop_alpha(image)

    def resolve(self, asset: str | Path, roots: Iterable[Path]) -> Path:
        asset_path = Path(asset)
        if asset_path.is_absolute() and asset_path.exists():
            return asset_path

        candidates: list[Path] = []
        for root in roots:
            candidates.append(root / asset_path)
            if asset_path.suffix:
                continue
            candidates.extend(sorted(root.glob(f"{asset_path.name}.*")))

        for candidate in candidates:
            if candidate.exists() and candidate.is_file():
                return candidate.resolve()

        searched = ", ".join(str(root) for root in roots)
        raise AssetNotFoundError(f"Could not find asset {asset!r} in {searched}.")

    @staticmethod
    def _crop_alpha(image: Image.Image) -> Image.Image:
        bbox = image.getbbox()
        if bbox is None:
            return image
        return image.crop(bbox)