Node.js standard app configuration

/**
 * Copyright (c) TySoft Limited 2014 - ALL RIGHTS RESERVED.
 */

'use strict';

var _ = require('underscore');

/**
 * Config keys.
 */
var keys = exports.keys = {
    port: 'port',
    server_url: 'server_url',
    session_key: 'session_key',
    session_secret: 'session_secret',
    database_dsn: 'database_dsn',
    redis_dsn: 'redis_dsn',
    encryption_two_way_key: 'encryption_two_way_key',
    github_client_id: 'github_client_id',
    github_client_secret: 'github_client_secret',
    google_client_id: 'google_client_id',
    google_client_secret: 'google_client_secret'
};

/**
 * Config values that must be configured when running in production.
 */
var required = [
    keys.session_secret,
    keys.encryption_two_way_key,
    keys.server_url,
    keys.database_dsn,
    keys.redis_dsn,
    keys.github_client_id,
    keys.github_client_secret,
    keys.google_client_id,
    keys.google_client_secret];

/**
 * Default configuration values.
 */
var defaults = {};
(function () {
    defaults[keys.port] = 4000;
    defaults[keys.server_url] = 'http://localhost:' + defaults[keys.port];
    defaults[keys.session_key] = 'poker';
    defaults[keys.session_secret] = 'CHANGE_ME_FOOL';
    defaults[keys.database_dsn] = 'mongodb://localhost/test';
    defaults[keys.redis_dsn] = 'redis://127.0.0.1:6379/0';
    defaults[keys.encryption_two_way_key] = 'CHANGE_ME_FOOL';
    defaults[keys.github_client_id] = '8c33e3fe8f1633a9a3';
    defaults[keys.github_client_secret] = '281bfe2ssdf1ba5f2b2e1a2afsa1b08d402e8';
    defaults[keys.google_client_id] = '1226332829-h2m4i4zdsssd3uufvfbbk9kccql4r.apps.googleusercontent.com';
    defaults[keys.google_client_secret] = 'PNlfDD@#22FOK-rwO4SjOH';
}());

/**
 * Gets the value for a config var.
 * @param key The name of the variable to get the value of.
 */
var getConfig = exports.getConfig = function (key) {

    var env_var = process.env[key.toUpperCase()];
    if (!_.isUndefined(env_var)) {
        return env_var;
    }

    var default_val = defaults[key];
    if (!_.isUndefined(default_val)) {
        return default_val;
    }

    return null;
};

/**
 * Returns true if running in production.
 */
var inProduction = exports.inProduction = function () {
    return process.env.NODE_ENV === 'production';
};

/**
 * Checks the environment config and warns where default values are in use. Will forcefully exit if running in
 * production and encryption keys have not been changed from the default.
 */
exports.checkConfig = function () {

    _.each(defaults, function (value, key) {
        if (getConfig(key) === value) {

            // Throw if required values haven't been configured in production
            if (required.indexOf(key) !== -1 && inProduction()) {
                throw new Error(key + ' hasn\'t been configured but has been marked as required for production.');
            }

            console.log(key + ' hasn\'t been configured, using default value: ' + value);
        }
    });
};