text: # Copyright 2015 Jonathan Provost.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  import exifread
  
  from calbum.core.model import Media, string_to_datetime
  
  
  class ExifPicture(Media):
      file_extensions = ()
  
      timestamp_tags = (
          'Image DateTime',
          'EXIF DateTimeOriginal',
          'EXIF DateTimeDigitized',
          'DateTime'
      )
  
      def exif(self):
          if not hasattr(self, '_exif'):
              with open(self.path()) as f:
                  self._exif = exifread.process_file(f)
          return self._exif
  
      def timestamp(self):
          """
          Return the creation timestamp of the media as defined in the EXIF
          metadata ('Image DateTime', 'EXIF DateTimeOriginal',
          'EXIF DateTimeDigitized', 'DateTime')
          :rtype: datetime
          """
          exif = self.exif()
  
          d = next((
              string_to_datetime(str(exif[tag]), self.time_zone)
              for tag in self.timestamp_tags if tag in exif), None)
          if d and (d.tzinfo is None or d.tzinfo.utcoffset(d) is None):
              d = d.replace(tzinfo=self.time_zone)
  
          return d or super(ExifPicture, self).timestamp()
  
      def location(self):
          raise NotImplemented()
  
  
  class JpegPicture(ExifPicture):
      file_extensions = ('.jpeg', '.jpg')
  
  
  class TiffPicture(ExifPicture):
      file_extensions = ('.tiff', '.tif')
  