dgbuilder/red/settings.js

/**
 * Copyright 2014 IBM Corp.
 *
 * 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.
 **/

var when = require("when");

var assert = require("assert");

var userSettings = null;
var globalSettings = null;
var storage = null;

var persistentSettings = {
    init: function(settings) {
        userSettings = settings;
        
        for (var i in settings) {
            if (settings.hasOwnProperty(i)) {
                (function() {
                    var j = i;
                    persistentSettings.__defineGetter__(j,function() { return userSettings[j]; });
                    persistentSettings.__defineSetter__(j,function() { throw new Error("Property '"+i+"' is read-only"); });
                })();
            }
        }
        globalSettings = null;
    },
    load: function(_storage) {
        storage = _storage;
        return storage.getSettings().then(function(_settings) {
            globalSettings = _settings;
        });
    },
    get: function(prop) {
        if (userSettings.hasOwnProperty(prop)) {
            return userSettings[prop];
        }
        if (globalSettings === null) {
            throw new Error("Settings not available");
        }
        return globalSettings[prop];
    },
    
    set: function(prop,value) {
        if (userSettings.hasOwnProperty(prop)) {
            throw new Error("Property '"+prop+"' is read-only");
        }
        if (globalSettings === null) {
            throw new Error("Settings not available");
        }
        var current = globalSettings[prop];
        globalSettings[prop] = value;
        try {
            assert.deepEqual(current,value);
            return when.resolve();
        } catch(err) {
            return storage.saveSettings(globalSettings);
        }
    },
    
    available: function() {
        return (globalSettings !== null);
    },
    
    reset: function() {
        userSettings = null;
        globalSettings = null;
        storage = null;
    }
}

module.exports = persistentSettings;