import os
from collections import defaultdict
import tempfile
from shutil import copyfileobj
from contextlib import closing
from photoapp.thumb import thumb_path, image_file_style_process


class ThumbGenerator(object):
    def __init__(self, library, storage):
        self.library = library
        self.storage = storage
        self._failed_thumbs_cache = defaultdict(dict)

    def make_thumb(self, photo, style_name):
        """
        Create a thumbnail of the given photo, scaled/cropped to the given named style
        :return: local path to thumbnail file or None if creation failed or was blocked
        """
        dest = thumb_path(style_name, photo.uuid)

        if self.storage.exists(dest):
            return self.storage.open(dest, "rb")

        if photo.uuid in self._failed_thumbs_cache[style_name]:
            return None

        # if photo.width is None:  # todo better detection of images that PIL can't open
        #     return None

        # TODO have the subprocess download the file
        # TODO thundering herd
        with tempfile.TemporaryDirectory() as tmpdir:
            fthumblocal = tempfile.NamedTemporaryFile(delete=True)
            fpath = os.path.join(tmpdir, "image")
            with self.library.storage.open(photo.path, 'rb') as fsrc:
                with open(fpath, 'wb') as ftmpdest:
                    copyfileobj(fsrc, ftmpdest)

            if not image_file_style_process(fpath, fthumblocal.name, style_name, photo.orientation):
                self._failed_thumbs_cache[style_name][photo.uuid] = True  # dont retry failed generations
                return

            with closing(self.storage.open(dest, 'wb')) as fdest:
                copyfileobj(fthumblocal, fdest)

        fthumblocal.seek(0)
        return fthumblocal