add GCS support to docs server

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

Index: chrome/common/extensions/docs/server2/gcs_file_system.py
diff --git a/chrome/common/extensions/docs/server2/gcs_file_system.py b/chrome/common/extensions/docs/server2/gcs_file_system.py
new file mode 100644
index 0000000000000000000000000000000000000000..0c346136c4a8eff37d60602a7f11fb6fd1b22fcc
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+++ b/chrome/common/extensions/docs/server2/gcs_file_system.py
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+# Copyright (c) 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from third_party.cloudstorage import cloudstorage_api
+from third_party.cloudstorage import common
+from third_party.cloudstorage import errors
+
+from docs_server_utils import StringIdentity
+from file_system import FileSystem, FileNotFoundError, StatInfo
+from future import Gettable, Future
+
+import logging
+import traceback
+
+'''See gcs_file_system_provider.py for documentation on using Google Cloud
+Storage as a filesystem.
+'''
+def _ReadFile(filename):
+  try:
+    with cloudstorage_api.open(filename, 'r') as f:
+      return f.read()
+  except errors.Error:
+    raise FileNotFoundError('Read failed for %s: %s' % (filename,
+        traceback.format_exc()))
+
+def _ListDir(dir_name):
+  try:
+    files = cloudstorage_api.listbucket(dir_name)
+    return [os_path.filename for os_path in files]
+  except errors.Error:
+    raise FileNotFoundError('cloudstorage.listbucket failed for %s: %s' %
+                            (dir_name, traceback.format_exc()))
+
+def _CreateStatInfo(bucket, path):
+  bucket = '/%s' % bucket
+  full_path = '/'.join( (bucket, path.lstrip('/')) )
+  try:
+    if full_path.endswith('/'):
+      child_versions = dict()
+      version = 0
+      # Fetching stats for all files under full_path, recursively. The
+      # listbucket method uses a prefix approach to simulate hierarchy,
+      # but calling it without the "delimiter" argument searches for prefix,
+      # which means, for directories, everything beneath it.
+      for _file in cloudstorage_api.listbucket(full_path):
+        if not _file.is_dir:
+          # GCS doesn't have metadata for dirs
+          child_stat = cloudstorage_api.stat('%s' % _file.filename).st_ctime
+          filename = _file.filename[len(bucket)+1:]
+          child_versions[filename] = child_stat
+          version = max(version, child_stat)
+    else:
+      child_versions = None
+      version = cloudstorage_api.stat(full_path).st_ctime
+    return StatInfo(version, child_versions)
+  except (TypeError, errors.Error):
+    raise FileNotFoundError('cloudstorage.stat failed for %s: %s' % (path,
+                            traceback.format_exc()))
+
+
+class CloudStorageFileSystem(FileSystem):
+  '''FileSystem implementation which fetches resources from Google Cloud
+  Storage.
+  '''
+  def __init__(self, bucket, debug_access_token=None, debug_bucket_prefix=None):
+    self._bucket = bucket
+    if debug_access_token:
+      logging.debug('gcs: using debug access token: %s' % debug_access_token)
+      common.set_access_token(debug_access_token)
+    if debug_bucket_prefix:
+      logging.debug('gcs: prefixing all bucket names with %s' %
+                    debug_bucket_prefix)
+      self._bucket = debug_bucket_prefix + self._bucket
+
+  def Read(self, paths):
+    def resolve():
+      try:
+        result = {}
+        for path in paths:
+          full_path = '/%s/%s' % (self._bucket, path.lstrip('/'))
+          logging.debug('gcs: requested path %s, reading %s' %
+                        (path, full_path))
+          if path == '' or path.endswith('/'):
+            result[path] = _ListDir(full_path)
+          else:
+            result[path] = _ReadFile(full_path)
+        return result
+      except errors.AuthorizationError:
+        self._warnAboutAuthError()
+        raise
+
+    return Future(delegate=Gettable(resolve))
+
+  def Refresh(self):
+    return Future(value=())
+
+  def Stat(self, path):
+    try:
+      return _CreateStatInfo(self._bucket, path)
+    except errors.AuthorizationError:
+      self._warnAboutAuthError()
+      raise
+
+  def GetIdentity(self):
+    return '@'.join((self.__class__.__name__, StringIdentity(self._bucket)))
+
+  def __repr__(self):
+    return 'LocalFileSystem(%s)' % self._bucket
+
+  def _warnAboutAuthError(self):
+    logging.warn(('Authentication error on Cloud Storage. Check if your'
+                  ' appengine project has permissions to Read the GCS'
+                  ' buckets. If you are running a local appengine server,'
+                  ' you need to set an access_token in'
+                  ' local_debug/gcs_debug.conf.'
+                  ' Remember that this token expires in less than 10'
+                  ' minutes, so keep it updated. See'
+                  ' gcs_file_system_provider.py for instructions.'));
+    logging.debug(traceback.format_exc())