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


class ThumbGenerator(object):
    def __init__(self, library, storage, thumb_service_url=None):
        self.library = library
        self.storage = storage
        self.thumb_service = ThumbClient(thumb_service_url) if thumb_service_url else None
        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: file-like object of the thumbnail image's data or None if no thumbnail is available
        """
        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

        # video thumbnails are handled by an external service
        if photo.format in video_mimes:
            if self.thumb_service is None:  # videos thumbs capability is disabled, show placeholder
                return

            self.make_video_thumb(photo.uuid, style_name)
            # thumbserver will eventually generate a thumb (and the exists call above will return it)
            # for now, return None to show a placeholder
            return

        fthumblocal = tempfile.NamedTemporaryFile()

        # TODO have the subprocess download the file
        # TODO thundering herd
        with tempfile.TemporaryDirectory() as tmpdir:
            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)
        # TODO fthumblocal is leaked if we don't hit this return
        return fthumblocal

    def make_video_thumb(self, photo_uuid, style_name):
        #TODO make something like ThumbServiceError so we can differentiate requests stuff from other errors without
        #having to deal with requests outside of thumb_service's module
        self.thumb_service.request_thumb(photo_uuid, style_name)