Makes sure GameSparks modules are imported only once

require_once.js

if (typeof(require_once) !== 'undefined') {
    Spark.setScriptError("require_once", "require_once is already defined! Only import this module in application entry points (Events, Requests, Responses, etc), not in modules!");
    Spark.getLog().error("require_once already defined, probably imported from a module");
    throw "require_once already defined";
}

var require_once__importedModules = {};

var require_once = function(shortCode) {
    var importedModules = require_once__importedModules;
    
    if (shortCode in importedModules) {
        importedModules[shortCode] += 1;
    }
    else {
        importedModules[shortCode] = 1;
        require( shortCode );
    }
}