localstorage.js

/*global ig*/
ig.module(
    'plugins.persistence.localstorage'
).requires(
    'impact.game'
).defines(function () {
    'use strict';
    ig.PersistenceLocalStorage = ig.Class.extend({
        /**
         * Initialize Persistence as localStorage
         */
        init: function () {
            try {
                if (window.localStorage) {
                    ig.Persistence.instance = this;
                }
            } catch (e) {
                throw new ig.PersistenceError("Enviroment is not capable of localStorage.");
            }
        },
        /**
         * Returns true if key is set, false otherwise
         */
        isSet: function (key) {
            return (this.get(this.currentSaveSlot + key) !== 'undefined');
        },
        /**
         * Get a key's value
         */
        get: function (key, defaultValue) {
            var value = localStorage.getItem(this.currentSaveSlot + key);
            if (value !== null) {
                if (value !== 'undefined') {
                    value = JSON.parse(value);
                    return value;
                } else {
                    throw new ig.PersistenceError("The value stored for " + "'" + key + "'" + " is undefined.");
                }
            } else if (typeof defaultValue !== 'undefined') {
                return defaultValue;
            } else {
                throw new ig.PersistenceError("No value stored for " + "'" + key + "'" + ", nor default value provided.");
            }
        },
        /**
         * Set a key's value, if it doesn't exist, it also creates the key
         */
        set: function (key, value) {
            try {
                window.localStorage.setItem(this.currentSaveSlot + key, JSON.stringify(value));
            } catch (e) {
                throw new ig.PersistenceError(e.message);
            }
        },
        /**
         * Remove a key and it's value from local storage
         */
        remove: function (key) {
            if (this.isSet(this.currentSaveSlot + key)) {
                window.localStorage.removeItem(this.currentSaveSlot + key);
            } else {
                throw new ig.PersistenceError("'" + key + "'" + " is not stored as a key.");
            }
        }
    });
});

nwfilesystem.js

/*global ig, process, require*/
ig.module(
    'plugins.persistence.nwfilesystem'
).requires(
    'impact.game'
).defines(function () {
    'use strict';
    ig.PersistenceNWFileSystem = ig.Class.extend({
        /**
         * Initialize Persistence as Node-Webkit file system
         */
        init: function () {
            try {
                if (process.versions['node-webkit']) {
                    ig.Persistence.instance = this;
                    this.fs = require('fs');
                }
            } catch (e) {
                throw new ig.PersistenceError("Enviroment is not capable of accessing File System via NodeJs.");
            }
        },
        /**
         * Returns true if key is set, false otherwise
         */
        isSet: function (key) {
            var saveSlot = 'saves/save_' + this.currentSaveSlot + '.json',
                data = {};
            try {
                data = JSON.parse(this.fs.readFileSync(saveSlot, 'utf8'));
                if (data.hasOwnProperty(key)) {
                    return true;
                } else {
                    return false;
                }
            } catch (e) {
                if (e.code === 'ENOENT') {
                    return false;
                } else {
                    throw new ig.PersistenceError(e);
                }
            }
        },
        /**
         * Get a key's value
         */
        get: function (key, defaultValue) {
            var saveSlot = 'saves/save_' + this.currentSaveSlot + '.json',
                data = {};
            try {
                data = JSON.parse(this.fs.readFileSync(saveSlot, 'utf8'));
                if (data.hasOwnProperty(key)) {
                    return data[key];
                } else if (typeof defaultValue !== 'undefined') {
                    return defaultValue;
                } else {
                    throw new ig.PersistenceError("No value stored for " + "'" + key + "'" + ", nor default value provided.");
                }
            } catch (e) {
                if (e.code === 'ENOENT') {
                    return defaultValue;
                } else {
                    throw new ig.PersistenceError(e);
                }
            }
        },
        /**
         * Set a key's value, if it doesn't exist, it also creates the key
         */
        set: function (key, value) {
            var saveSlot = 'saves/save_' + this.currentSaveSlot + '.json',
                data = {};
            try {
                data = JSON.parse(this.fs.readFileSync(saveSlot, 'utf8'));
                data[key] = value;
                data = JSON.stringify(data, null, 4);
                this.fs.writeFileSync(saveSlot, data);
            } catch (e) {
                if (e.code === 'ENOENT') {
                    data[key] = value;
                    data = JSON.stringify(data, null, 4);
                    this.fs.writeFileSync(saveSlot, data);
                } else {
                    throw new ig.PersistenceError(e);
                }
            }
        },
        /**
         * Remove a key and it's value
         */
        remove: function (key) {
            if (this.isSet(key)) {
                var saveSlot = 'saves/save_' + this.currentSaveSlot + '.json',
                    data = {};
                try {
                    data = JSON.parse(this.fs.readFileSync(saveSlot, 'utf8'));
                    delete data[key];
                    data = JSON.stringify(data, null, 4);
                    this.fs.writeFileSync(saveSlot, data);
                } catch (e) {
                    if (e.code === 'ENOENT') {
                        delete data[key];
                        data = JSON.stringify(data, null, 4);
                        this.fs.writeFileSync(saveSlot, data);
                    } else {
                        throw new ig.PersistenceError(e);
                    }
                }
            } else {
                throw new ig.PersistenceError("'" + key + "'" + " is not stored as a key.");
            }
        }
    });
});

persistence.js

/*global ig*/
ig.module(
    'plugins.persistence'
).requires(
    'impact.game',
    'plugins.persistence.nwfilesystem',
    'plugins.persistence.localstorage'
).defines(function () {
    'use strict';
    ig.PersistenceError = function (message) {
        this.name = "PersistenceError";
        this.message = message;
    };
    ig.PersistenceError.prototype = Error.prototype;
    ig.Persistence = ig.Class.extend({
        currentSaveSlot: 0,
        /**
         * Create a static instance of this class
         */
        staticInstantiate: function (i) {
            this.alias('persistence');
            // for demostration purposes I'll create a ig.config object that contains the configuration we will be using
            ig.config = {};
            ig.config.persist = 'NodeWebkitFileSystem';
            switch (ig.config.persist) {
            case 'localStorage':
                ig.Persistence.inject(ig.PersistenceLocalStorage.prototype);
                break;
            case 'NodeWebkitFileSystem':
                ig.Persistence.inject(ig.PersistenceNWFileSystem.prototype);
                break;
            default:
                throw new ig.PersistenceError("No persistence enviroment defined.");
            }
            return ig.Persistence.instance || null;
        },
        /**
         * Sets an alias that can be used to access this singleton
         */
        alias: function (name) {
            Object.defineProperty(ig, name, {
                value: this,
                writable: false,
                enumerable: true,
                configurable: false
            });
        },
        /**
         * Set current save slot
         */
        setSaveSlot: function (slot) {
            this.currentSaveSlot = slot;
        },
        /**
         * Get current save slot
         */
        getCurrentSaveSlot: function () {
            return this.currentSaveSlot;
        },
        /**
         * Get a key's value as a Integer
         */
        getInt: function (key, defaultValue) {
            return parseInt(this.get(key, defaultValue), null);
        },
        /**
         * Get a key's value as a Float
         */
        getFloat: function (key, defaultValue) {
            return parseFloat(this.get(key, defaultValue));
        },
        /**
         * Get a key's value as a Boleean
         */
        getBool: function (key, defaultValue) {
            var value = this.get(key, defaultValue);
            switch (value.toString()) {
            case 'true':
                return true;
            case 'false':
                return false;
            default:
                throw new ig.PersistenceError("Value set for " + "'" + key + "'" + " is not boolean.");
            }
        },
        /**
         * Set a key's value if it's value is higher than the current persisted value
         */
        setHigher: function (key, value) {
            if (value > this.getFloat(key)) {
                this.set(key, value);
            }
        },
        /**
         * Set a key's value if it's value is lower than the current persisted value
         */
        setLower: function (key, value) {
            if (value < this.getFloat(key)) {
                this.set(key, value);
            }
        }
    });
    return new ig.Persistence();
});