GUAC-278: Migrate to GuacamoleSessionStorage which uses localStorage only if available.

guacamole/src/main/webapp/scripts/session.js

@@ -21,96 +21,140 @@
  */
 
 /**
- * Maintains state across multiple Guacamole pages via HTML5 Web Storage.
- * @constructor
+ * Global storage for Guacamole pages. 
  */
-function GuacamoleSessionState() {
+GuacamoleSessionStorage = (opener && opener.GuacamoleSessionStorage) || new (function() {
 
     /**
-     * Reference to this GuacamoleSessionState.
+     * The contents of storage, as a JSON string containing name/value pairs as
+     * properties.
+     * 
      * @private
+     * @type String
      */
-    var guac_state = this;
+    var stored_json = "{}";
 
     /**
-     * The last read state object.
-     * @private
+     * Called whenever an item value changes.
+     *
+     * @callback onchange
+     * @param {String} name The name of the item changed.
+     * @param value The new item value.
      */
-    var state = localStorage.getItem("GUACAMOLE_STATE") || {};
 
     /**
-     * Reloads the internal state, sending onchange events for all changed,
-     * deleted, or new properties.
+     * All attached listeners.
+     * 
+     * @type onchange[]
      */
-    this.reload = function() {
+    var listeners = [];
 
-        // Pull current state
-        var new_state = JSON.parse(localStorage.getItem("GUACAMOLE_STATE") || "{}");
-        
-        // Assign new state
-        var old_state = state;
-        state = new_state;
+    /**
+     * Notifies all listeners that an item has changed.
+     * 
+     * @param {String} name The name of the item that changed.
+     * @param value The new item value.
+     */
+    function __notify_changed(name, value) {
+        for (var i=0; i<listeners.length; i++)
+            listeners[i](name, value);
+    }
 
-        // Check if any values are different
-        for (var name in new_state) {
-
-            // If value changed, call handler
-            var old = old_state[name];
-            if (old != new_state[name]) {
-
-                // Call change handler
-                if (guac_state.onchange)
-                    guac_state.onchange(state, new_state, name);
+    /**
+     * Returns the value stored within the item having the given name.
+     * 
+     * @param {String} name The name of the item to read.
+     * @param [value] The default value, if any.
+     * @return The value of the given item.
+     */
+    this.getItem = function(name, value) {
 
+        // Attempt to read JSON from localStorage, default to local variable
+        var json = stored_json;
+        if (localStorage) {
+            try {
+                json = localStorage.getItem("GUACAMOLE_STATE") || "{}";
             }
+            catch (ignore) {}
+        }
 
+        var obj = JSON.parse(json);
+        if (obj[name] !== undefined)
+            return obj[name];
+
+        return value;
+
+    };
+
+    /**
+     * Sets the item having the given name to the given value.
+     * 
+     * @param {String} name The name of the item to change.
+     * @param [value] An arbitrary value.
+     */
+    this.setItem = function(name, value) {
+
+        // Attempt to read JSON from localStorage, default to local variable
+        var json = stored_json;
+        if (localStorage) {
+            try {
+                json = localStorage.getItem("GUACAMOLE_STATE") || "{}";
+            }
+            catch (ignore) {}
+        }
+
+        // Modify object property        
+        var obj = JSON.parse(json);
+        var old = obj[name];
+        obj[name] = value;
+
+        // Notify of change
+        if (old !== value)
+            __notify_changed(name, value);
+
+        // Attempt to set JSON within localStorage, default to local variable
+        stored_json = JSON.stringify(obj);
+        if (localStorage) {
+            try {
+                localStorage.setItem("GUACAMOLE_STATE", stored_json);
+            }
+            catch (ignore) {}
         }
 
     };
 
-    /**
-     * Sets the given property to the given value.
-     * 
-     * @param {String} name The name of the property to change.
-     * @param [value] An arbitrary value.
-     */
-    this.setProperty = function(name, value) {
-        state[name] = value;
-        localStorage.setItem("GUACAMOLE_STATE", JSON.stringify(state));
-    };
-
-    /**
-     * Returns the value stored under the property having the given name.
-     * 
-     * @param {String} name The name of the property to read.
-     * @param value The default value, if any.
-     * @return The value of the given property.
-     */
-    this.getProperty = function(name, value) {
-
-        var current = state[name];
-        if (current === undefined)
-            return value;
-
-        return current;
-    };
-
-    /**
-     * Event which is fired whenever a property value is changed externally.
-     * 
-     * @event
-     * @param old_state An object whose properties' values are the old values
-     *                  of this GuacamoleSessionState.
-     * @param new_state An object whose properties' values are the new values
-     *                  of this GuacamoleSessionState.
-     * @param {String} name The name of the property that is being changed.
-     */
-    this.onchange = null;
-
     // Reload when modified
-    window.addEventListener("storage", guac_state.reload, false);
+    window.addEventListener("storage", function reload() {
 
-    // Initial load
-    guac_state.reload();
+        // Pull current state
+        var new_json = localStorage.getItem("GUACAMOLE_STATE") || "{}";
+        
+        var new_state = JSON.parse(new_json);
+        var old_state = JSON.parse(stored_json);
 
-}
+        // Check if any values are different
+        for (var name in new_state) {
+
+            // If value changed, notify
+            var old = old_state[name];
+            if (old !== new_state[name])
+                __notify_changed(name, new_state[name]);
+
+        }
+
+        stored_json = new_json;
+
+    }, false);
+
+    /**
+     * Ensures that the given function will be called for each change in
+     * item value. The function must accept a single argument which will be
+     * the name of the item changed.
+     * 
+     * @param {onchange} onchange The function to call when an item changes.
+     */
+    this.addChangeListener = function(onchange) {
+        listeners.push(onchange);
+    };
+
+})();