GUACAMOLE-549: Add service for manipulating items within localStorage.

guacamole/src/main/webapp/app/storage/services/localStorageService.js

@@ -0,0 +1,145 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+/**
+ * Service for setting, removing, and retrieving localStorage keys. If access
+ * to localStorage is disabled, or the browser does not support localStorage,
+ * key values are temporarily stored in memory instead. If necessary, the same
+ * functionality is also available at the localStorageServiceProvider level.
+ */
+angular.module('storage').provider('localStorageService', [function localStorageServiceProvider() {
+
+    /**
+     * Reference to this provider.
+     *
+     * @type localStorageServiceProvider
+     */
+    var provider = this;
+
+    /**
+     * Internal cache of key/value pairs stored within localStorage, updated
+     * lazily as keys are retrieved, updated, or removed. If localStorage is
+     * not actually available, then this cache will be the sole storage
+     * location for these key/value pairs.
+     *
+     * @type Object.<String, String>
+     */
+    var storedItems = {};
+
+    /**
+     * Stores the given value within localStorage under the given key. If access
+     * to localStorage is not provided/implemented by the browser, the key/value
+     * pair will be stored internally (in memory) only, with the stored value
+     * remaining retrievable via getItem() until the browser tab/window is
+     * closed.
+     *
+     * @param {String} key
+     *     The arbitrary, unique key under which the value should be stored.
+     *
+     * @param {Object} value
+     *     The object to store under the given key. This may be any object that
+     *     can be serialized as JSON, and will automatically be serialized as
+     *     JSON prior to storage.
+     */
+    provider.setItem = function setItem(key, value) {
+
+        // Store given value internally
+        var data = JSON.stringify(value);
+        storedItems[key] = data;
+
+        // Additionally store value within localStorage if allowed
+        try {
+            if (window.localStorage)
+                localStorage.setItem(key, data);
+        }
+        catch (ignore) {}
+
+    };
+
+    /**
+     * Removes the item having the given key from localStorage. If access to
+     * localStorage is not provided/implemented by the browser, the item is
+     * removed solely from internal, in-memory storage. If no such item exists,
+     * this function has no effect.
+     *
+     * @param {String} key
+     *     The arbitrary, unique key of the item to remove from localStorage.
+     */
+    provider.removeItem = function removeItem(key) {
+
+        // Evict key from internal storage
+        delete storedItems[key];
+
+        // Remove key from localStorage if allowed
+        try {
+            if (window.localStorage)
+                localStorage.removeItem(key);
+        }
+        catch (ignore) {}
+
+    };
+
+    /**
+     * Retrieves the value currently stored within localStorage for the item
+     * having the given key. If access to localStorage is not
+     * provided/implemented by the browser, the item is retrieved from
+     * internal, in-memory storage. The retrieved value is automatically
+     * deserialized from JSON prior to being returned.
+     *
+     * @param {String} key
+     *     The arbitrary, unique key of the item to retrieve from localStorage.
+     *
+     * @returns {Object}
+     *     The value stored within localStorage under the given key,
+     *     automatically deserialized from JSON, or null if no such item is
+     *     present.
+     */
+    provider.getItem = function getItem(key) {
+
+        // Attempt to refresh internal storage from localStorage
+        try {
+            if (window.localStorage)
+                storedItems[key] = localStorage.getItem(key);
+        }
+        catch (ignore) {}
+
+        // Pull and parse value from internal storage, if present
+        var data = storedItems[key];
+        if (data)
+            return JSON.parse(data);
+
+        // No value defined for given key
+        return null;
+
+    };
+
+    // Factory method required by provider
+    this.$get = ['$injector', function localStorageServiceFactory($injector) {
+
+        // Pass through all get/set/remove calls to the provider
+        // implementations of the same
+        return {
+            setItem    : provider.setItem,
+            removeItem : provider.removeItem,
+            getItem    : provider.getItem
+        };
+
+    }];
+
+}]);