text: # GNU MediaGoblin -- federated, autonomous media hosting
  # Copyright (C) 2011, 2012 MediaGoblin contributors.  See AUTHORS.
  #
  # This program is free software: you can redistribute it and/or modify
  # it under the terms of the GNU Affero General Public License as published by
  # the Free Software Foundation, either version 3 of the License, or
  # (at your option) any later version.
  #
  # This program is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU Affero General Public License for more details.
  #
  # You should have received a copy of the GNU Affero General Public License
  # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  
  import logging
  import json
  
  from functools import wraps
  from werkzeug.exceptions import Forbidden
  from werkzeug.wrappers import Response
  
  from six.moves.urllib.parse import urljoin
  
  from mediagoblin import mg_globals
  from mediagoblin.tools.pluginapi import PluginManager
  from mediagoblin.storage.filestorage import BasicFileStorage
  
  _log = logging.getLogger(__name__)
  
  
  class Auth(object):
      '''
      An object with two significant methods, 'trigger' and 'run'.
  
      Using a similar object to this, plugins can register specific
      authentication logic, for example the GET param 'access_token' for OAuth.
  
      - trigger: Analyze the 'request' argument, return True if you think you
        can handle the request, otherwise return False
      - run: The authentication logic, set the request.user object to the user
        you intend to authenticate and return True, otherwise return False.
  
      If run() returns False, an HTTP 403 Forbidden error will be shown.
  
      You may also display custom errors, just raise them within the run()
      method.
      '''
      def trigger(self, request):
          raise NotImplemented()
  
      def __call__(self, request, *args, **kw):
          raise NotImplemented()
  
  def get_entry_serializable(entry, urlgen):
      '''
      Returns a serializable dict() of a MediaEntry instance.
  
      :param entry: A MediaEntry instance
      :param urlgen: An urlgen instance, can be found on the request object passed
      to views.
      '''
      return {
              'user': entry.get_uploader.username,
              'user_id': entry.get_uploader.id,
              'user_bio': entry.get_uploader.bio,
              'user_bio_html': entry.get_uploader.bio_html,
              'user_permalink': urlgen('mediagoblin.user_pages.user_home',
                  user=entry.get_uploader.username,
                  qualified=True),
              'id': entry.id,
              'created': entry.created.isoformat(),
              'title': entry.title,
              'license': entry.license,
              'description': entry.description,
              'description_html': entry.description_html,
              'media_type': entry.media_type,
              'state': entry.state,
              'permalink': entry.url_for_self(urlgen, qualified=True),
              'media_files': get_media_file_paths(entry.media_files, urlgen)}
  
  
  def get_media_file_paths(media_files, urlgen):
      '''
      Returns a dictionary of media files with `file_handle` => `qualified URL`
  
      :param media_files: dict-like object consisting of `file_handle => `listy
      filepath` pairs.
      :param urlgen: An urlgen object, usually found on request.urlgen.
      '''
      media_urls = {}
  
      for key, val in media_files.items():
          if isinstance(mg_globals.public_store, BasicFileStorage):
              # BasicFileStorage does not provide a qualified URI
              media_urls[key] = urljoin(
                      urlgen('index', qualified=True),
                      mg_globals.public_store.file_url(val))
          else:
              media_urls[key] = mg_globals.public_store.file_url(val)
  
      return media_urls
  
  
  def api_auth(controller):
      '''
      Decorator, allows plugins to register auth methods that will then be
      evaluated against the request, finally a worthy authenticator object is
      chosen and used to decide whether to grant or deny access.
      '''
      @wraps(controller)
      def wrapper(request, *args, **kw):
          auth_candidates = []
  
          for auth in PluginManager().get_hook_callables('auth'):
              if auth.trigger(request):
                  _log.debug('{0} believes it is capable of authenticating this request.'.format(auth))
                  auth_candidates.append(auth)
  
          # If we can't find any authentication methods, we should not let them
          # pass.
          if not auth_candidates:
              raise Forbidden()
  
          # For now, just select the first one in the list
          auth = auth_candidates[0]
  
          _log.debug('Using {0} to authorize request {1}'.format(
              auth, request.url))
  
          if not auth(request, *args, **kw):
              if getattr(auth, 'errors', []):
                  return json_response({
                          'status': 403,
                          'errors': auth.errors})
  
              raise Forbidden()
  
          return controller(request, *args, **kw)
  
      return wrapper
  