# Copyright 2023 (c) Anna Schumaker.
"""A cache to hold Gdk.Textures used by cover art."""
import pathlib
import sys
from gi.repository import GLib
from gi.repository import Gdk


if "unittest" in sys.modules:
    import tempfile
    TEMP_DIR = tempfile.TemporaryDirectory(prefix="emmental-")
    CACHE_PATH = pathlib.Path(TEMP_DIR.name)
else:
    from . import gsetup
    CACHE_PATH = gsetup.CACHE_DIR

CACHE_PATH.mkdir(parents=True, exist_ok=True)


class _TextureCache(dict):
    """A custom dictionary for storing texture files."""

    def __check_update_cache(self, path: pathlib.Path) -> Gdk.Texture | None:
        if path.is_file() \
                and (cache_path := self.__get_cache_path(path)).exists() \
                and cache_path.stat().st_mtime < path.stat().st_mtime:
            self.__drop(path, cache_path)
            return self.__load_new_item(path, cache_path)

    def __drop(self, path: pathlib.Path, cache_path: pathlib.Path) -> None:
        self.pop(path, None)
        cache_path.unlink(missing_ok=True)

    def __get_cache_path(self, path: pathlib.Path) -> pathlib.Path:
        return CACHE_PATH / path.absolute().relative_to("/")

    def __load_cached_item(self, path: pathlib.Path,
                           cache_path: pathlib.Path) -> Gdk.Texture:
        texture = Gdk.Texture.new_from_filename(str(cache_path))
        self.__setitem__(path, texture)
        return texture

    def __load_new_item(self, path: pathlib.Path,
                        cache_path: pathlib.Path) -> Gdk.Texture:
        cache_path.parent.mkdir(parents=True, exist_ok=True)
        with path.open("rb") as f_path:
            bytes = f_path.read()
            with cache_path.open("wb") as f_cache:
                f_cache.write(bytes)
            texture = Gdk.Texture.new_from_bytes(GLib.Bytes.new(bytes))
            self.__setitem__(path, texture)
            return texture

    def __get_missing_item(self, path: pathlib.Path,
                           cache_path: pathlib.Path) -> Gdk.Texture:
        if cache_path.is_file():
            return self.__load_cached_item(path, cache_path)
        elif path.is_file():
            return self.__load_new_item(path, cache_path)

    def __missing__(self, path: pathlib.Path | None) -> Gdk.Texture:
        """Load a cache item from disk or add a new item entirely."""
        return self.__get_missing_item(path, self.__get_cache_path(path))

    def __getitem__(self, path: pathlib.Path | None) -> Gdk.Texture | None:
        """Get a Gdk.Texture cache item from the cache."""
        if path is not None:
            texture = self.__check_update_cache(path)
            return super().__getitem__(path) if texture is None else texture

    def drop(self, path: pathlib.Path | None) -> None:
        """Drop a single cache item from the cache."""
        self.__drop(path, self.__get_cache_path(path))


CACHE = _TextureCache()