mediagoblin/processing/__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 logging
  18 import os
  19
  20 from mediagoblin.db.util import atomic_update
  21 from mediagoblin import mg_globals as mgg
  22
  23 from mediagoblin.tools.translate import lazy_pass_to_ugettext as _
  24
  25 _log = logging.getLogger(__name__)
  26
  27
  28 class ProgressCallback(object):
  29     def __init__(self, entry):
  30         self.entry = entry
  31
  32     def __call__(self, progress):
  33         if progress:
  34             self.entry.transcoding_progress = progress
  35             self.entry.save()
  36
  37
  38 def create_pub_filepath(entry, filename):
  39     return mgg.public_store.get_unique_filepath(
  40             ['media_entries',
  41              unicode(entry.id),
  42              filename])
  43
  44
  45 class FilenameBuilder(object):
  46     """Easily slice and dice filenames.
  47
  48     Initialize this class with an original file path, then use the fill()
  49     method to create new filenames based on the original.
  50
  51     """
  52     MAX_FILENAME_LENGTH = 255  # VFAT's maximum filename length
  53
  54     def __init__(self, path):
  55         """Initialize a builder from an original file path."""
  56         self.dirpath, self.basename = os.path.split(path)
  57         self.basename, self.ext = os.path.splitext(self.basename)
  58         self.ext = self.ext.lower()
  59
  60     def fill(self, fmtstr):
  61         """Build a new filename based on the original.
  62
  63         The fmtstr argument can include the following:
  64         {basename} -- the original basename, with the extension removed
  65         {ext} -- the original extension, always lowercase
  66
  67         If necessary, {basename} will be truncated so the filename does not
  68         exceed this class' MAX_FILENAME_LENGTH in length.
  69
  70         """
  71         basename_len = (self.MAX_FILENAME_LENGTH -
  72                         len(fmtstr.format(basename='', ext=self.ext)))
  73         return fmtstr.format(basename=self.basename[:basename_len],
  74                              ext=self.ext)
  75
  76
  77 def mark_entry_failed(entry_id, exc):
  78     """
  79     Mark a media entry as having failed in its conversion.
  80
  81     Uses the exception that was raised to mark more information.  If
  82     the exception is a derivative of BaseProcessingFail then we can
  83     store extra information that can be useful for users telling them
  84     why their media failed to process.
  85
  86     Args:
  87      - entry_id: The id of the media entry
  88
  89     """
  90     # Was this a BaseProcessingFail?  In other words, was this a
  91     # type of error that we know how to handle?
  92     if isinstance(exc, BaseProcessingFail):
  93         # Looks like yes, so record information about that failure and any
  94         # metadata the user might have supplied.
  95         atomic_update(mgg.database.MediaEntry,
  96             {'id': entry_id},
  97             {u'state': u'failed',
  98              u'fail_error': unicode(exc.exception_path),
  99              u'fail_metadata': exc.metadata})
 100     else:
 101         _log.warn("No idea what happened here, but it failed: %r", exc)
 102         # Looks like no, so just mark it as failed and don't record a
 103         # failure_error (we'll assume it wasn't handled) and don't record
 104         # metadata (in fact overwrite it if somehow it had previous info
 105         # here)
 106         atomic_update(mgg.database.MediaEntry,
 107             {'id': entry_id},
 108             {u'state': u'failed',
 109              u'fail_error': None,
 110              u'fail_metadata': {}})
 111
 112
 113 class BaseProcessingFail(Exception):
 114     """
 115     Base exception that all other processing failure messages should
 116     subclass from.
 117
 118     You shouldn't call this itself; instead you should subclass it
 119     and provid the exception_path and general_message applicable to
 120     this error.
 121     """
 122     general_message = u''
 123
 124     @property
 125     def exception_path(self):
 126         return u"%s:%s" % (
 127             self.__class__.__module__, self.__class__.__name__)
 128
 129     def __init__(self, **metadata):
 130         self.metadata = metadata or {}
 131
 132
 133 class BadMediaFail(BaseProcessingFail):
 134     """
 135     Error that should be raised when an inappropriate file was given
 136     for the media type specified.
 137     """
 138     general_message = _(u'Invalid file given for media type.')