(function(root, factory) {

	if (root === null) {
		throw new Error('Google-maps package can be used only in browser');
	}

	if (typeof define === 'function' && define.amd) {
		define(factory);
	} else if (typeof exports === 'object') {
		module.exports = factory();
	} else {
		root.GoogleMapsLoader = factory();
	}

})(typeof window !== 'undefined' ? window : null, function() {


	'use strict';


	var googleVersion = '3.31';

	var script = null;

	var google = null;

	var loading = false;

	var callbacks = [];

	var onLoadEvents = [];

	var originalCreateLoaderMethod = null;


	var GoogleMapsLoader = {};


	GoogleMapsLoader.URL = 'https://maps.googleapis.com/maps/api/js';

	GoogleMapsLoader.KEY = null;

	GoogleMapsLoader.LIBRARIES = [];

	GoogleMapsLoader.CLIENT = null;

	GoogleMapsLoader.CHANNEL = null;

	GoogleMapsLoader.LANGUAGE = null;

	GoogleMapsLoader.REGION = null;

	GoogleMapsLoader.VERSION = googleVersion;

	GoogleMapsLoader.WINDOW_CALLBACK_NAME = '__google_maps_api_provider_initializator__';


	GoogleMapsLoader._googleMockApiObject = {};


	GoogleMapsLoader.load = function(fn) {
		if (google === null) {
			if (loading === true) {
				if (fn) {
					callbacks.push(fn);
				}
			} else {
				loading = true;

				window[GoogleMapsLoader.WINDOW_CALLBACK_NAME] = function() {
					ready(fn);
				};

				GoogleMapsLoader.createLoader();
			}
		} else if (fn) {
			fn(google);
		}
	};


	GoogleMapsLoader.createLoader = function() {
		script = document.createElement('script');
		script.type = 'text/javascript';
		script.src = GoogleMapsLoader.createUrl();

		document.body.appendChild(script);
	};


	GoogleMapsLoader.isLoaded = function() {
		return google !== null;
	};


	GoogleMapsLoader.createUrl = function() {
		var url = GoogleMapsLoader.URL;

		url += '?callback=' + GoogleMapsLoader.WINDOW_CALLBACK_NAME;

		if (GoogleMapsLoader.KEY) {
			url += '&key=' + GoogleMapsLoader.KEY;
		}

		if (GoogleMapsLoader.LIBRARIES.length > 0) {
			url += '&libraries=' + GoogleMapsLoader.LIBRARIES.join(',');
		}

		if (GoogleMapsLoader.CLIENT) {
			url += '&client=' + GoogleMapsLoader.CLIENT;
		}

		if (GoogleMapsLoader.CHANNEL) {
			url += '&channel=' + GoogleMapsLoader.CHANNEL;
		}

		if (GoogleMapsLoader.LANGUAGE) {
			url += '&language=' + GoogleMapsLoader.LANGUAGE;
		}

		if (GoogleMapsLoader.REGION) {
			url += '&region=' + GoogleMapsLoader.REGION;
		}

		if (GoogleMapsLoader.VERSION) {
			url += '&v=' + GoogleMapsLoader.VERSION;
		}

		return url;
	};


	GoogleMapsLoader.release = function(fn) {
		var release = function() {
			GoogleMapsLoader.KEY = null;
			GoogleMapsLoader.LIBRARIES = [];
			GoogleMapsLoader.CLIENT = null;
			GoogleMapsLoader.CHANNEL = null;
			GoogleMapsLoader.LANGUAGE = null;
			GoogleMapsLoader.REGION = null;
			GoogleMapsLoader.VERSION = googleVersion;

			google = null;
			loading = false;
			callbacks = [];
			onLoadEvents = [];

			if (typeof window.google !== 'undefined') {
				delete window.google;
			}

			if (typeof window[GoogleMapsLoader.WINDOW_CALLBACK_NAME] !== 'undefined') {
				delete window[GoogleMapsLoader.WINDOW_CALLBACK_NAME];
			}

			if (originalCreateLoaderMethod !== null) {
				GoogleMapsLoader.createLoader = originalCreateLoaderMethod;
				originalCreateLoaderMethod = null;
			}

			if (script !== null) {
				script.parentElement.removeChild(script);
				script = null;
			}

			if (fn) {
				fn();
			}
		};

		if (loading) {
			GoogleMapsLoader.load(function() {
				release();
			});
		} else {
			release();
		}
	};


	GoogleMapsLoader.onLoad = function(fn) {
		onLoadEvents.push(fn);
	};


	GoogleMapsLoader.makeMock = function() {
		originalCreateLoaderMethod = GoogleMapsLoader.createLoader;

		GoogleMapsLoader.createLoader = function() {
			window.google = GoogleMapsLoader._googleMockApiObject;
			window[GoogleMapsLoader.WINDOW_CALLBACK_NAME]();
		};
	};


	var ready = function(fn) {
		var i;

		loading = false;

		if (google === null) {
			google = window.google;
		}

		for (i = 0; i < onLoadEvents.length; i++) {
			onLoadEvents[i](google);
		}

		if (fn) {
			fn(google);
		}

		for (i = 0; i < callbacks.length; i++) {
			callbacks[i](google);
		}

		callbacks = [];
	};


	return GoogleMapsLoader;

});