chrome/common/extensions/docs/server2/commit_tracker.py

   1 # Copyright 2014 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 import collections
   6 import datetime
   7
   8 from object_store_creator import ObjectStoreCreator
   9 from future import Future
  10
  11
  12 # The maximum number of commit IDs to retain in a named commit's history deque.
  13 _MAX_COMMIT_HISTORY_LENGTH = 50
  14
  15
  16 class CachedCommit(object):
  17   '''Object type which is stored for each entry in a named commit's history.
  18   |datetime| is used as a timestamp for when the commit cache was completed,
  19   and is only meant to provide a loose ordering of commits for administrative
  20   servlets to display.'''
  21   def __init__(self, commit_id, datetime):
  22     self.commit_id = commit_id
  23     self.datetime = datetime
  24
  25
  26 class CommitTracker(object):
  27   '''Utility class for managing and querying the storage of various named commit
  28   IDs.'''
  29   def __init__(self, object_store_creator):
  30     # The object stores should never be created empty since the sole purpose of
  31     # this tracker is to persist named commit data across requests.
  32     self._store = object_store_creator.Create(CommitTracker, start_empty=False)
  33     self._history_store = object_store_creator.Create(CommitTracker,
  34         category='history', start_empty=False)
  35
  36   def Get(self, key):
  37     return self._store.Get(key)
  38
  39   def Set(self, key, commit):
  40     return (self._store.Set(key, commit)
  41       .Then(lambda _: self._UpdateHistory(key, commit)))
  42
  43   def GetHistory(self, key):
  44     '''Fetches the commit ID history for a named commit. If the commit has no
  45     history, this will return an empty collection.'''
  46     return (self._history_store.Get(key)
  47         .Then(lambda history: () if history is None else history))
  48
  49   def _UpdateHistory(self, key, commit):
  50     '''Appends a commit ID to a named commit's tracked history.'''
  51     def create_or_amend_history(history):
  52       if history is None:
  53         history = collections.deque([], maxlen=50)
  54       history.append(CachedCommit(commit, datetime.datetime.now()))
  55       return self._history_store.Set(key, history)
  56     return self._history_store.Get(key).Then(create_or_amend_history)