add basic preferences

src/Preferences.js

@@ -0,0 +1,55 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+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 {Platform} from "./client/Platform.js";
+
+export class Preferences {
+	constructor(localStorage) {
+		this._localStorage = localStorage;
+		this.clientId = null;
+		// used to differentiate web from native if a client supports both
+		this.platform = null;
+		this.homeservers = [];
+
+		const prefsStr = localStorage.getItem("preferred_client");
+		if (prefsStr) {
+			const {id, platform} = JSON.parse(prefsStr);
+			this.clientId = id;
+			this.platform = Platform[platform];
+		}
+	}
+
+	setClient(id, platform) {
+		this.clientId = id;
+		platform = Platform[platform];
+		this.platform = platform;
+		this._localStorage.setItem("preferred_client", JSON.stringify({id, platform}));
+	}
+
+	setHomeservers(homeservers) {
+
+	}
+
+	clear() {
+		this._localStorage.removeItem("preferred_client");
+		this.clientId = null;
+		this.platform = null;
+	}
+
+	get canClear() {
+		return !!this.clientId || !!this.platform; 
+	}
+}