mediagoblin/media_types/__init__.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011, 2012 MediaGoblin contributors.  See AUTHORS.
   3 #
   4 # This program is free software: you can redistribute it and/or modify
   5 # it under the terms of the GNU Affero General Public License as published by
   6 # the Free Software Foundation, either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Affero General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Affero General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 import os
  18 import sys
  19 import logging
  20 import tempfile
  21
  22 from mediagoblin import mg_globals
  23 from mediagoblin.tools.translate import lazy_pass_to_ugettext as _
  24
  25 _log = logging.getLogger(__name__)
  26
  27 class FileTypeNotSupported(Exception):
  28     pass
  29
  30 class InvalidFileType(Exception):
  31     pass
  32
  33
  34 def sniff_media(media):
  35     '''
  36     Iterate through the enabled media types and find those suited
  37     for a certain file.
  38     '''
  39
  40     try:
  41         return get_media_type_and_manager(media.filename)
  42     except FileTypeNotSupported:
  43         _log.info('No media handler found by file extension. Doing it the expensive way...')
  44         # Create a temporary file for sniffers suchs as GStreamer-based
  45         # Audio video
  46         media_file = tempfile.NamedTemporaryFile()
  47         media_file.write(media.file.read())
  48         media.file.seek(0)
  49
  50         for media_type, manager in get_media_managers():
  51             _log.info('Sniffing {0}'.format(media_type))
  52             if manager['sniff_handler'](media_file, media=media):
  53                 _log.info('{0} accepts the file'.format(media_type))
  54                 return media_type, manager
  55             else:
  56                 _log.debug('{0} did not accept the file'.format(media_type))
  57
  58     raise FileTypeNotSupported(
  59         # TODO: Provide information on which file types are supported
  60         _(u'Sorry, I don\'t support that file type :('))
  61
  62
  63 def get_media_types():
  64     """
  65     Generator, yields the available media types
  66     """
  67     for media_type in mg_globals.app_config['media_types']:
  68         yield media_type
  69
  70
  71 def get_media_managers():
  72     '''
  73     Generator, yields all enabled media managers
  74     '''
  75     for media_type in get_media_types():
  76         __import__(media_type)
  77
  78         yield media_type, sys.modules[media_type].MEDIA_MANAGER
  79
  80
  81 def get_media_manager(_media_type):
  82     '''
  83     Get the MEDIA_MANAGER based on a media type string
  84
  85     Example::
  86         get_media_type('mediagoblin.media_types.image')
  87     '''
  88     if not _media_type:
  89         return False
  90
  91     for media_type, manager in get_media_managers():
  92         if media_type in _media_type:
  93             return manager
  94
  95     # Nope?  Then raise an error
  96     raise FileTypeNotSupported(
  97         "MediaManager not in enabled types.  Check media_types in config?")
  98
  99
 100 def get_media_type_and_manager(filename):
 101     '''
 102     Try to find the media type based on the file name, extension
 103     specifically. This is used as a speedup, the sniffing functionality
 104     then falls back on more in-depth bitsniffing of the source file.
 105     '''
 106     if filename.find('.') > 0:
 107         # Get the file extension
 108         ext = os.path.splitext(filename)[1].lower()
 109
 110         for media_type, manager in get_media_managers():
 111             # Omit the dot from the extension and match it against
 112             # the media manager
 113             if ext[1:] in manager['accepted_extensions']:
 114                 return media_type, manager
 115     else:
 116         _log.info('File {0} has no file extension, let\'s hope the sniffers get it.'.format(
 117             filename))
 118
 119     raise FileTypeNotSupported(
 120         _(u'Sorry, I don\'t support that file type :('))