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# Copyright 2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
from typing import Dict
from twisted.web.resource import Resource
from synapse.http.server import UnrecognizedRequestResource
logger = logging.getLogger(__name__)
def create_resource_tree(
desired_tree: Dict[str, Resource], root_resource: Resource
) -> Resource:
"""Create the resource tree for this homeserver.
This in unduly complicated because Twisted does not support putting
child resources more than 1 level deep at a time.
Args:
desired_tree: Dict from desired paths to desired resources.
root_resource: The root resource to add the tree to.
Returns:
The ``root_resource`` with a tree of child resources added to it.
"""
# ideally we'd just use getChild and putChild but getChild doesn't work
# unless you give it a Request object IN ADDITION to the name :/ So
# instead, we'll store a copy of this mapping so we can actually add
# extra resources to existing nodes. See self._resource_id for the key.
resource_mappings: Dict[str, Resource] = {}
for full_path_str, res in desired_tree.items():
# twisted requires all resources to be bytes
full_path = full_path_str.encode("utf-8")
logger.info("Attaching %s to path %s", res, full_path)
last_resource = root_resource
for path_seg in full_path.split(b"/")[1:-1]:
if path_seg not in last_resource.listNames():
# resource doesn't exist, so make a "dummy resource"
child_resource: Resource = UnrecognizedRequestResource()
last_resource.putChild(path_seg, child_resource)
res_id = _resource_id(last_resource, path_seg)
resource_mappings[res_id] = child_resource
last_resource = child_resource
else:
# we have an existing Resource, use that instead.
res_id = _resource_id(last_resource, path_seg)
last_resource = resource_mappings[res_id]
# ===========================
# now attach the actual desired resource
last_path_seg = full_path.split(b"/")[-1]
# if there is already a resource here, thieve its children and
# replace it
res_id = _resource_id(last_resource, last_path_seg)
if res_id in resource_mappings:
# there is a dummy resource at this path already, which needs
# to be replaced with the desired resource.
existing_dummy_resource = resource_mappings[res_id]
for child_name in existing_dummy_resource.listNames():
child_res_id = _resource_id(existing_dummy_resource, child_name)
child_resource = resource_mappings[child_res_id]
# steal the children
res.putChild(child_name, child_resource)
# finally, insert the desired resource in the right place
last_resource.putChild(last_path_seg, res)
res_id = _resource_id(last_resource, last_path_seg)
resource_mappings[res_id] = res
return root_resource
def _resource_id(resource: Resource, path_seg: bytes) -> str:
"""Construct an arbitrary resource ID so you can retrieve the mapping
later.
If you want to represent resource A putChild resource B with path C,
the mapping should looks like _resource_id(A,C) = B.
Args:
resource: The *parent* Resourceb
path_seg: The name of the child Resource to be attached.
Returns:
A unique string which can be a key to the child Resource.
"""
return "%s-%r" % (resource, path_seg)
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