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1# Copyright 2013 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
5from caching_file_system import CachingFileSystem
6from local_file_system import LocalFileSystem
7from offline_file_system import OfflineFileSystem
8from subversion_file_system import SubversionFileSystem
9from third_party.json_schema_compiler.memoize import memoize
10
11
12class HostFileSystemProvider(object):
13  '''Provides host file systems ("host" meaning the file system that hosts the
14  server's source code and templates) tracking trunk, or any branch.
15
16  File system instances are memoized to maintain the in-memory caches across
17  multiple callers.
18  '''
19  def __init__(self,
20               object_store_creator,
21               max_trunk_revision=None,
22               default_trunk_instance=None,
23               offline=False,
24               constructor_for_test=None):
25    '''
26    |object_store_creator|
27      Provides caches for file systems that need one.
28    |max_trunk_revision|
29      If not None, the maximum revision that a 'trunk' file system will be
30      created at. If None, 'trunk' file systems will use HEAD.
31    |default_trunk_instance|
32      If not None, 'trunk' file systems provided by this class without a
33      specific revision will return |default_trunk_instance| instead.
34    |offline|
35      If True all provided file systems will be wrapped in an OfflineFileSystem.
36    |constructor_for_test|
37      Provides a custom constructor rather than creating SubversionFileSystems.
38    '''
39    self._object_store_creator = object_store_creator
40    self._max_trunk_revision = max_trunk_revision
41    self._default_trunk_instance = default_trunk_instance
42    self._offline = offline
43    self._constructor_for_test = constructor_for_test
44
45  @memoize
46  def GetTrunk(self, revision=None):
47    '''Gets a file system tracking 'trunk'. Use this method rather than
48    GetBranch('trunk') because the behaviour is subtly different; 'trunk' can
49    be pinned to a max revision (|max_trunk_revision| in constructor) and can
50    have its default instance overridden (|default_trunk_instance| in
51    constructor).
52
53    |revision| if non-None determines a specific revision to pin the host file
54    system at, though it will be ignored if it exceeds |max_trunk_revision|.
55    If None then |revision| will track |max_trunk_revision| if is has been
56    set, or just HEAD (which might change during server runtime!).
57    '''
58    if revision is None:
59      if self._default_trunk_instance is not None:
60        return self._default_trunk_instance
61      return self._Create('trunk', revision=self._max_trunk_revision)
62    if self._max_trunk_revision is not None:
63      revision = min(revision, self._max_trunk_revision)
64    return self._Create('trunk', revision=revision)
65
66  @memoize
67  def GetBranch(self, branch):
68    '''Gets a file system tracking |branch|, for example '1150' - anything other
69    than 'trunk', which must be constructed via the GetTrunk() method.
70
71    Note: Unlike GetTrunk this function doesn't take a |revision| argument
72    since we assume that branches hardly ever change, while trunk frequently
73    changes.
74    '''
75    assert isinstance(branch, basestring), 'Branch %s must be a string' % branch
76    assert branch != 'trunk', 'Cannot specify branch=\'trunk\', use GetTrunk()'
77    return self._Create(branch)
78
79  def _Create(self, branch, revision=None):
80    '''Creates SVN file systems (or if in a test, potentially whatever
81    |self._constructor_for_test specifies). Wraps the resulting file system in
82    an Offline file system if the offline flag is set, and finally wraps it in
83    a Caching file system.
84    '''
85    if self._constructor_for_test is not None:
86      file_system = self._constructor_for_test(branch=branch, revision=revision)
87    else:
88      file_system = SubversionFileSystem.Create(branch=branch,
89                                                revision=revision)
90    if self._offline:
91      file_system = OfflineFileSystem(file_system)
92    return CachingFileSystem(file_system, self._object_store_creator)
93
94  @staticmethod
95  def ForLocal(object_store_creator, **optargs):
96    '''Used in creating a server instance on localhost.
97    '''
98    return HostFileSystemProvider(
99        object_store_creator,
100        constructor_for_test=lambda **_: LocalFileSystem.Create(),
101        **optargs)
102
103  @staticmethod
104  def ForTest(file_system, object_store_creator, **optargs):
105    '''Used in creating a test server instance. The HostFileSystemProvider
106    returned here will always return |file_system| when its Create() method is
107    called.
108    '''
109    return HostFileSystemProvider(
110        object_store_creator,
111        constructor_for_test=lambda **_: file_system,
112        **optargs)
113