1# Copyright 2016 OpenMarket Ltd 2# 3# Licensed under the Apache License, Version 2.0 (the "License"); 4# you may not use this file except in compliance with the License. 5# You may obtain a copy of the License at 6# 7# http://www.apache.org/licenses/LICENSE-2.0 8# 9# Unless required by applicable law or agreed to in writing, software 10# distributed under the License is distributed on an "AS IS" BASIS, 11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12# See the License for the specific language governing permissions and 13# limitations under the License. 14 15import logging 16from typing import Dict 17 18from twisted.web.resource import NoResource, Resource 19 20logger = logging.getLogger(__name__) 21 22 23def create_resource_tree( 24 desired_tree: Dict[str, Resource], root_resource: Resource 25) -> Resource: 26 """Create the resource tree for this homeserver. 27 28 This in unduly complicated because Twisted does not support putting 29 child resources more than 1 level deep at a time. 30 31 Args: 32 desired_tree: Dict from desired paths to desired resources. 33 root_resource: The root resource to add the tree to. 34 Returns: 35 The ``root_resource`` with a tree of child resources added to it. 36 """ 37 38 # ideally we'd just use getChild and putChild but getChild doesn't work 39 # unless you give it a Request object IN ADDITION to the name :/ So 40 # instead, we'll store a copy of this mapping so we can actually add 41 # extra resources to existing nodes. See self._resource_id for the key. 42 resource_mappings: Dict[str, Resource] = {} 43 for full_path_str, res in desired_tree.items(): 44 # twisted requires all resources to be bytes 45 full_path = full_path_str.encode("utf-8") 46 47 logger.info("Attaching %s to path %s", res, full_path) 48 last_resource = root_resource 49 for path_seg in full_path.split(b"/")[1:-1]: 50 if path_seg not in last_resource.listNames(): 51 # resource doesn't exist, so make a "dummy resource" 52 child_resource: Resource = NoResource() 53 last_resource.putChild(path_seg, child_resource) 54 res_id = _resource_id(last_resource, path_seg) 55 resource_mappings[res_id] = child_resource 56 last_resource = child_resource 57 else: 58 # we have an existing Resource, use that instead. 59 res_id = _resource_id(last_resource, path_seg) 60 last_resource = resource_mappings[res_id] 61 62 # =========================== 63 # now attach the actual desired resource 64 last_path_seg = full_path.split(b"/")[-1] 65 66 # if there is already a resource here, thieve its children and 67 # replace it 68 res_id = _resource_id(last_resource, last_path_seg) 69 if res_id in resource_mappings: 70 # there is a dummy resource at this path already, which needs 71 # to be replaced with the desired resource. 72 existing_dummy_resource = resource_mappings[res_id] 73 for child_name in existing_dummy_resource.listNames(): 74 child_res_id = _resource_id(existing_dummy_resource, child_name) 75 child_resource = resource_mappings[child_res_id] 76 # steal the children 77 res.putChild(child_name, child_resource) 78 79 # finally, insert the desired resource in the right place 80 last_resource.putChild(last_path_seg, res) 81 res_id = _resource_id(last_resource, last_path_seg) 82 resource_mappings[res_id] = res 83 84 return root_resource 85 86 87def _resource_id(resource: Resource, path_seg: bytes) -> str: 88 """Construct an arbitrary resource ID so you can retrieve the mapping 89 later. 90 91 If you want to represent resource A putChild resource B with path C, 92 the mapping should looks like _resource_id(A,C) = B. 93 94 Args: 95 resource: The *parent* Resourceb 96 path_seg: The name of the child Resource to be attached. 97 Returns: 98 A unique string which can be a key to the child Resource. 99 """ 100 return "%s-%r" % (resource, path_seg) 101