Fix initialisation of matrix backend

src/backends/matrix.js

@@ -15,12 +15,21 @@
 
 import {BaseBackend} from './base';
 import * as sdk from 'matrix-js-sdk';
+import * as utils from '../utils';
 
 class MatrixBackend extends BaseBackend {
-  constructor(userId, homeServerUrl) {
+  constructor(userId) {
     super(userId);
+  }
+
+  set userId(value) {
+    if (value !== undefined) {
+      const matrixId = utils.splitMatrixId(value);
+      const homeServerUrl = 'https://' + matrixId.homeServer
 
-    this.api = sdk.createClient(homeServerUrl);
+      this.api = sdk.createClient(homeServerUrl);
+      this.userId = value;
+    }
   }
 }
 

src/utils.js

+/* Copyright 2021 Dominik George <nik@naturalnet.de>
+ *
+ * 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.
+ */
+
+/**
+ * Split a Matrix ID into local part and homeserver
+ *
+ * @param {string} matrixId
+ *
+ * @example
+ *   splitMatrixId('@foo:example.com')
+ *   // => {'localPart': 'foo', 'homeServer': 'example.com'}
+ */
+export function splitMatrixId(matrixId) {
+  if (typeof matrixId !== 'string') {
+    throw 'Passed Matrix ID must be a string';
+  } else if (matrixId.substr(0, 1) !== '@') {
+    throw 'Passed Matrix ID must begin with @';
+  } else if (matrixId.indexOf(':') < 2) {
+    throw 'Passed Matrix ID must contain : to separate local part and home server';
+  }
+
+  const localPart = matrixId.substr(1).substr(0, matrixId.indexOf(':'));
+  const homeServer = matrixId.substr(matrixId.indexOf(':') + 1);
+
+  return {
+    'localPart': localPart,
+    'homeServer': homeServer
+  }
+}