mediagoblin/workbench.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011 Free Software Foundation, Inc
   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 shutil
  19 import tempfile
  20
  21
  22 DEFAULT_WORKBENCH_DIR = os.path.join(
  23     tempfile.gettempdir(), u'mgoblin_workbench')
  24
  25
  26 # Exception(s)
  27 # ------------
  28
  29 class WorkbenchOutsideScope(Exception):
  30     """
  31     Raised when a workbench is outside a WorkbenchManager scope.
  32     """
  33     pass
  34
  35
  36 # Actual workbench stuff
  37 # ----------------------
  38
  39 class Workbench(object):
  40     """
  41     Represent the directory for the workbench
  42     """
  43     def __init__(self, dir):
  44         self.dir = dir
  45
  46     def __unicode__(self):
  47         return unicode(self.dir)
  48     def __str__(self):
  49         return str(self.dir)
  50     def __repr__(self):
  51         return repr(self.dir)
  52
  53     def joinpath(self, *args):
  54         return os.path.join(self.dir, *args)
  55
  56     def localized_file(self, storage, filepath,
  57                        filename_if_copying=None,
  58                        keep_extension_if_copying=True):
  59         """
  60         Possibly localize the file from this storage system (for read-only
  61         purposes, modifications should be written to a new file.).
  62
  63         If the file is already local, just return the absolute filename of that
  64         local file.  Otherwise, copy the file locally to the workbench, and
  65         return the absolute path of the new file.
  66
  67         If it is copying locally, we might want to require a filename like
  68         "source.jpg" to ensure that we won't conflict with other filenames in
  69         our workbench... if that's the case, make sure filename_if_copying is
  70         set to something like 'source.jpg'.  Relatedly, if you set
  71         keep_extension_if_copying, you don't have to set an extension on
  72         filename_if_copying yourself, it'll be set for you (assuming such an
  73         extension can be extacted from the filename in the filepath).
  74
  75         Returns:
  76           localized_filename
  77
  78         Examples:
  79           >>> wb_manager.localized_file(
  80           ...     '/our/workbench/subdir', local_storage,
  81           ...     ['path', 'to', 'foobar.jpg'])
  82           u'/local/storage/path/to/foobar.jpg'
  83
  84           >>> wb_manager.localized_file(
  85           ...     '/our/workbench/subdir', remote_storage,
  86           ...     ['path', 'to', 'foobar.jpg'])
  87           '/our/workbench/subdir/foobar.jpg'
  88
  89           >>> wb_manager.localized_file(
  90           ...     '/our/workbench/subdir', remote_storage,
  91           ...     ['path', 'to', 'foobar.jpg'], 'source.jpeg', False)
  92           '/our/workbench/subdir/foobar.jpeg'
  93
  94           >>> wb_manager.localized_file(
  95           ...     '/our/workbench/subdir', remote_storage,
  96           ...     ['path', 'to', 'foobar.jpg'], 'source', True)
  97           '/our/workbench/subdir/foobar.jpg'
  98         """
  99         if storage.local_storage:
 100             return storage.get_local_path(filepath)
 101         else:
 102             if filename_if_copying is None:
 103                 dest_filename = filepath[-1]
 104             else:
 105                 orig_filename, orig_ext = os.path.splitext(filepath[-1])
 106                 if keep_extension_if_copying and orig_ext:
 107                     dest_filename = filename_if_copying + orig_ext
 108                 else:
 109                     dest_filename = filename_if_copying
 110
 111             full_dest_filename = os.path.join(
 112                 self.dir, dest_filename)
 113
 114             # copy it over
 115             storage.copy_locally(
 116                 filepath, full_dest_filename)
 117
 118             return full_dest_filename
 119
 120
 121 class WorkbenchManager(object):
 122     """
 123     A system for generating and destroying workbenches.
 124
 125     Workbenches are actually just subdirectories of a temporary storage space
 126     for during the processing stage.
 127     """
 128
 129     def __init__(self, base_workbench_dir):
 130         self.base_workbench_dir = os.path.abspath(base_workbench_dir)
 131         if not os.path.exists(self.base_workbench_dir):
 132             os.makedirs(self.base_workbench_dir)
 133
 134     def create_workbench(self):
 135         """
 136         Create and return the path to a new workbench (directory).
 137         """
 138         return Workbench(tempfile.mkdtemp(dir=self.base_workbench_dir))
 139
 140     def destroy_workbench(self, workbench):
 141         """
 142         Destroy this workbench!  Deletes the directory and all its contents!
 143
 144         Makes sure the workbench actually belongs to this manager though.
 145         """
 146         # just in case
 147         workbench = os.path.abspath(workbench.dir)
 148
 149         if not workbench.startswith(self.base_workbench_dir):
 150             raise WorkbenchOutsideScope(
 151                 "Can't destroy workbench outside the base workbench dir")
 152
 153         shutil.rmtree(workbench)