const Preloader = /** @constructor */ function () { // eslint-disable-line no-unused-vars
	function getTrackedResponse(response, load_status) {
		function onloadprogress(reader, controller) {
			return reader.read().then(function (result) {
				if (load_status.done) {
					return Promise.resolve();
				}
				if (result.value) {
					controller.enqueue(result.value);
					load_status.loaded += result.value.length;
				}
				if (!result.done) {
					return onloadprogress(reader, controller);
				}
				load_status.done = true;
				return Promise.resolve();
			});
		}
		const reader = response.body.getReader();
		return new Response(new ReadableStream({
			start: function (controller) {
				onloadprogress(reader, controller).then(function () {
					controller.close();
				});
			},
		}), { headers: response.headers });
	}

	function loadFetch(file, tracker, fileSize, raw) {
		tracker[file] = {
			total: fileSize || 0,
			loaded: 0,
			done: false,
		};
		return fetch(file).then(function (response) {
			if (!response.ok) {
				return Promise.reject(new Error(`Failed loading file '${file}'`));
			}
			const tr = getTrackedResponse(response, tracker[file]);
			if (raw) {
				return Promise.resolve(tr);
			}
			return tr.arrayBuffer();
		});
	}

	function retry(func, attempts = 1) {
		function onerror(err) {
			if (attempts <= 1) {
				return Promise.reject(err);
			}
			return new Promise(function (resolve, reject) {
				setTimeout(function () {
					retry(func, attempts - 1).then(resolve).catch(reject);
				}, 1000);
			});
		}
		return func().catch(onerror);
	}

	const DOWNLOAD_ATTEMPTS_MAX = 4;
	const loadingFiles = {};
	const lastProgress = { loaded: 0, total: 0 };
	let progressFunc = null;

	const animateProgress = function () {
		let loaded = 0;
		let total = 0;
		let totalIsValid = true;
		let progressIsFinal = true;

		Object.keys(loadingFiles).forEach(function (file) {
			const stat = loadingFiles[file];
			if (!stat.done) {
				progressIsFinal = false;
			}
			if (!totalIsValid || stat.total === 0) {
				totalIsValid = false;
				total = 0;
			} else {
				total += stat.total;
			}
			loaded += stat.loaded;
		});
		if (loaded !== lastProgress.loaded || total !== lastProgress.total) {
			lastProgress.loaded = loaded;
			lastProgress.total = total;
			if (typeof progressFunc === 'function') {
				progressFunc(loaded, total);
			}
		}
		if (!progressIsFinal) {
			requestAnimationFrame(animateProgress);
		}
	};

	this.animateProgress = animateProgress;

	this.setProgressFunc = function (callback) {
		progressFunc = callback;
	};

	this.loadPromise = function (file, fileSize, raw = false) {
		return retry(loadFetch.bind(null, file, loadingFiles, fileSize, raw), DOWNLOAD_ATTEMPTS_MAX);
	};

	this.preloadedFiles = [];
	this.preload = function (pathOrBuffer, destPath, fileSize) {
		let buffer = null;
		if (typeof pathOrBuffer === 'string') {
			const me = this;
			return this.loadPromise(pathOrBuffer, fileSize).then(function (buf) {
				me.preloadedFiles.push({
					path: destPath || pathOrBuffer,
					buffer: buf,
				});
				return Promise.resolve();
			});
		} else if (pathOrBuffer instanceof ArrayBuffer) {
			buffer = new Uint8Array(pathOrBuffer);
		} else if (ArrayBuffer.isView(pathOrBuffer)) {
			buffer = new Uint8Array(pathOrBuffer.buffer);
		}
		if (buffer) {
			this.preloadedFiles.push({
				path: destPath,
				buffer: pathOrBuffer,
			});
			return Promise.resolve();
		}
		return Promise.reject(new Error('Invalid object for preloading'));
	};
};

/**
 * An object used to configure the Engine instance based on godot export options, and to override those in custom HTML
 * templates if needed.
 *
 * @header Engine configuration
 * @summary The Engine configuration object. This is just a typedef, create it like a regular object, e.g.:
 *
 * ``const MyConfig = { executable: 'godot', unloadAfterInit: false }``
 *
 * @typedef {Object} EngineConfig
 */
const EngineConfig = {}; // eslint-disable-line no-unused-vars

/**
 * @struct
 * @constructor
 * @ignore
 */
const InternalConfig = function (initConfig) { // eslint-disable-line no-unused-vars
	const cfg = /** @lends {InternalConfig.prototype} */ {
		/**
		 * Whether the unload the engine automatically after the instance is initialized.
		 *
		 * @memberof EngineConfig
		 * @default
		 * @type {boolean}
		 */
		unloadAfterInit: true,
		/**
		 * The HTML DOM Canvas object to use.
		 *
		 * By default, the first canvas element in the document will be used is none is specified.
		 *
		 * @memberof EngineConfig
		 * @default
		 * @type {?HTMLCanvasElement}
		 */
		canvas: null,
		/**
		 * The name of the WASM file without the extension. (Set by Godot Editor export process).
		 *
		 * @memberof EngineConfig
		 * @default
		 * @type {string}
		 */
		executable: '',
		/**
		 * An alternative name for the game pck to load. The executable name is used otherwise.
		 *
		 * @memberof EngineConfig
		 * @default
		 * @type {?string}
		 */
		mainPack: null,
		/**
		 * Specify a language code to select the proper localization for the game.
		 *
		 * The browser locale will be used if none is specified. See complete list of
		 * :ref:`supported locales <doc_locales>`.
		 *
		 * @memberof EngineConfig
		 * @type {?string}
		 * @default
		 */
		locale: null,
		/**
		 * The canvas resize policy determines how the canvas should be resized by Godot.
		 *
		 * ``0`` means Godot won't do any resizing. This is useful if you want to control the canvas size from
		 * javascript code in your template.
		 *
		 * ``1`` means Godot will resize the canvas on start, and when changing window size via engine functions.
		 *
		 * ``2`` means Godot will adapt the canvas size to match the whole browser window.
		 *
		 * @memberof EngineConfig
		 * @type {number}
		 * @default
		 */
		canvasResizePolicy: 2,
		/**
		 * The arguments to be passed as command line arguments on startup.
		 *
		 * See :ref:`command line tutorial <doc_command_line_tutorial>`.
		 *
		 * **Note**: :js:meth:`startGame <Engine.prototype.startGame>` will always add the ``--main-pack`` argument.
		 *
		 * @memberof EngineConfig
		 * @type {Array<string>}
		 * @default
		 */
		args: [],
		/**
		 * When enabled, the game canvas will automatically grab the focus when the engine starts.
		 *
		 * @memberof EngineConfig
		 * @type {boolean}
		 * @default
		 */
		focusCanvas: true,
		/**
		 * When enabled, this will turn on experimental virtual keyboard support on mobile.
		 *
		 * @memberof EngineConfig
		 * @type {boolean}
		 * @default
		 */
		experimentalVK: false,
		/**
		 * The progressive web app service worker to install.
		 * @memberof EngineConfig
		 * @default
		 * @type {string}
		 */
		serviceWorker: '',
		/**
		 * @ignore
		 * @type {Array.<string>}
		 */
		persistentPaths: ['/userfs'],
		/**
		 * @ignore
		 * @type {boolean}
		 */
		persistentDrops: false,
		/**
		 * @ignore
		 * @type {Array.<string>}
		 */
		gdnativeLibs: [],
		/**
		 * @ignore
		 * @type {Array.<string>}
		 */
		fileSizes: [],
		/**
		 * A callback function for handling Godot's ``OS.execute`` calls.
		 *
		 * This is for example used in the Web Editor template to switch between project manager and editor, and for running the game.
		 *
		 * @callback EngineConfig.onExecute
		 * @param {string} path The path that Godot's wants executed.
		 * @param {Array.<string>} args The arguments of the "command" to execute.
		 */
		/**
		 * @ignore
		 * @type {?function(string, Array.<string>)}
		 */
		onExecute: null,
		/**
		 * A callback function for being notified when the Godot instance quits.
		 *
		 * **Note**: This function will not be called if the engine crashes or become unresponsive.
		 *
		 * @callback EngineConfig.onExit
		 * @param {number} status_code The status code returned by Godot on exit.
		 */
		/**
		 * @ignore
		 * @type {?function(number)}
		 */
		onExit: null,
		/**
		 * A callback function for displaying download progress.
		 *
		 * The function is called once per frame while downloading files, so the usage of ``requestAnimationFrame()``
		 * is not necessary.
		 *
		 * If the callback function receives a total amount of bytes as 0, this means that it is impossible to calculate.
		 * Possible reasons include:
		 *
		 * -  Files are delivered with server-side chunked compression
		 * -  Files are delivered with server-side compression on Chromium
		 * -  Not all file downloads have started yet (usually on servers without multi-threading)
		 *
		 * @callback EngineConfig.onProgress
		 * @param {number} current The current amount of downloaded bytes so far.
		 * @param {number} total The total amount of bytes to be downloaded.
		 */
		/**
		 * @ignore
		 * @type {?function(number, number)}
		 */
		onProgress: null,
		/**
		 * A callback function for handling the standard output stream. This method should usually only be used in debug pages.
		 *
		 * By default, ``console.log()`` is used.
		 *
		 * @callback EngineConfig.onPrint
		 * @param {...*} [var_args] A variadic number of arguments to be printed.
		 */
		/**
		 * @ignore
		 * @type {?function(...*)}
		 */
		onPrint: function () {
			console.log.apply(console, Array.from(arguments)); // eslint-disable-line no-console
		},
		/**
		 * A callback function for handling the standard error stream. This method should usually only be used in debug pages.
		 *
		 * By default, ``console.error()`` is used.
		 *
		 * @callback EngineConfig.onPrintError
		 * @param {...*} [var_args] A variadic number of arguments to be printed as errors.
		*/
		/**
		 * @ignore
		 * @type {?function(...*)}
		 */
		onPrintError: function (var_args) {
			console.error.apply(console, Array.from(arguments)); // eslint-disable-line no-console
		},
	};

	/**
	 * @ignore
	 * @struct
	 * @constructor
	 * @param {EngineConfig} opts
	 */
	function Config(opts) {
		this.update(opts);
	}

	Config.prototype = cfg;

	/**
	 * @ignore
	 * @param {EngineConfig} opts
	 */
	Config.prototype.update = function (opts) {
		const config = opts || {};
		// NOTE: We must explicitly pass the default, accessing it via
		// the key will fail due to closure compiler renames.
		function parse(key, def) {
			if (typeof (config[key]) === 'undefined') {
				return def;
			}
			return config[key];
		}
		// Module config
		this.unloadAfterInit = parse('unloadAfterInit', this.unloadAfterInit);
		this.onPrintError = parse('onPrintError', this.onPrintError);
		this.onPrint = parse('onPrint', this.onPrint);
		this.onProgress = parse('onProgress', this.onProgress);

		// Godot config
		this.canvas = parse('canvas', this.canvas);
		this.executable = parse('executable', this.executable);
		this.mainPack = parse('mainPack', this.mainPack);
		this.locale = parse('locale', this.locale);
		this.canvasResizePolicy = parse('canvasResizePolicy', this.canvasResizePolicy);
		this.persistentPaths = parse('persistentPaths', this.persistentPaths);
		this.persistentDrops = parse('persistentDrops', this.persistentDrops);
		this.experimentalVK = parse('experimentalVK', this.experimentalVK);
		this.focusCanvas = parse('focusCanvas', this.focusCanvas);
		this.serviceWorker = parse('serviceWorker', this.serviceWorker);
		this.gdnativeLibs = parse('gdnativeLibs', this.gdnativeLibs);
		this.fileSizes = parse('fileSizes', this.fileSizes);
		this.args = parse('args', this.args);
		this.onExecute = parse('onExecute', this.onExecute);
		this.onExit = parse('onExit', this.onExit);
	};

	/**
	 * @ignore
	 * @param {string} loadPath
	 * @param {Response} response
	 */
	Config.prototype.getModuleConfig = function (loadPath, response) {
		let r = response;
		return {
			'print': this.onPrint,
			'printErr': this.onPrintError,
			'thisProgram': this.executable,
			'noExitRuntime': true,
			'dynamicLibraries': [`${loadPath}.side.wasm`],
			'instantiateWasm': function (imports, onSuccess) {
				function done(result) {
					onSuccess(result['instance'], result['module']);
				}
				if (typeof (WebAssembly.instantiateStreaming) !== 'undefined') {
					WebAssembly.instantiateStreaming(Promise.resolve(r), imports).then(done);
				} else {
					r.arrayBuffer().then(function (buffer) {
						WebAssembly.instantiate(buffer, imports).then(done);
					});
				}
				r = null;
				return {};
			},
			'locateFile': function (path) {
				if (path.endsWith('.worker.js')) {
					return `${loadPath}.worker.js`;
				} else if (path.endsWith('.audio.worklet.js')) {
					return `${loadPath}.audio.worklet.js`;
				} else if (path.endsWith('.js')) {
					return `${loadPath}.js`;
				} else if (path.endsWith('.side.wasm')) {
					return `${loadPath}.side.wasm`;
				} else if (path.endsWith('.wasm')) {
					return `${loadPath}.wasm`;
				}
				return path;
			},
		};
	};

	/**
	 * @ignore
	 * @param {function()} cleanup
	 */
	Config.prototype.getGodotConfig = function (cleanup) {
		// Try to find a canvas
		if (!(this.canvas instanceof HTMLCanvasElement)) {
			const nodes = document.getElementsByTagName('canvas');
			if (nodes.length && nodes[0] instanceof HTMLCanvasElement) {
				this.canvas = nodes[0];
			}
			if (!this.canvas) {
				throw new Error('No canvas found in page');
			}
		}
		// Canvas can grab focus on click, or key events won't work.
		if (this.canvas.tabIndex < 0) {
			this.canvas.tabIndex = 0;
		}

		// Browser locale, or custom one if defined.
		let locale = this.locale;
		if (!locale) {
			locale = navigator.languages ? navigator.languages[0] : navigator.language;
			locale = locale.split('.')[0];
		}
		const onExit = this.onExit;

		// Godot configuration.
		return {
			'canvas': this.canvas,
			'canvasResizePolicy': this.canvasResizePolicy,
			'locale': locale,
			'persistentDrops': this.persistentDrops,
			'virtualKeyboard': this.experimentalVK,
			'focusCanvas': this.focusCanvas,
			'onExecute': this.onExecute,
			'onExit': function (p_code) {
				cleanup(); // We always need to call the cleanup callback to free memory.
				if (typeof (onExit) === 'function') {
					onExit(p_code);
				}
			},
		};
	};
	return new Config(initConfig);
};

/**
 * Projects exported for the Web expose the :js:class:`Engine` class to the JavaScript environment, that allows
 * fine control over the engine's start-up process.
 *
 * This API is built in an asynchronous manner and requires basic understanding
 * of `Promises <https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises>`__.
 *
 * @module Engine
 * @header HTML5 shell class reference
 */
const Engine = (function () {
	const preloader = new Preloader();

	let loadPromise = null;
	let loadPath = '';
	let initPromise = null;

	/**
	 * @classdesc The ``Engine`` class provides methods for loading and starting exported projects on the Web. For default export
	 * settings, this is already part of the exported HTML page. To understand practical use of the ``Engine`` class,
	 * see :ref:`Custom HTML page for Web export <doc_customizing_html5_shell>`.
	 *
	 * @description Create a new Engine instance with the given configuration.
	 *
	 * @global
	 * @constructor
	 * @param {EngineConfig} initConfig The initial config for this instance.
	 */
	function Engine(initConfig) { // eslint-disable-line no-shadow
		this.config = new InternalConfig(initConfig);
		this.rtenv = null;
	}

	/**
	 * Load the engine from the specified base path.
	 *
	 * @param {string} basePath Base path of the engine to load.
	 * @param {number=} [size=0] The file size if known.
	 * @returns {Promise} A Promise that resolves once the engine is loaded.
	 *
	 * @function Engine.load
	 */
	Engine.load = function (basePath, size) {
		if (loadPromise == null) {
			loadPath = basePath;
			loadPromise = preloader.loadPromise(`${loadPath}.wasm`, size, true);
			requestAnimationFrame(preloader.animateProgress);
		}
		return loadPromise;
	};

	/**
	 * Unload the engine to free memory.
	 *
	 * This method will be called automatically depending on the configuration. See :js:attr:`unloadAfterInit`.
	 *
	 * @function Engine.unload
	 */
	Engine.unload = function () {
		loadPromise = null;
	};

	/**
	 * Check whether WebGL is available. Optionally, specify a particular version of WebGL to check for.
	 *
	 * @param {number=} [majorVersion=1] The major WebGL version to check for.
	 * @returns {boolean} If the given major version of WebGL is available.
	 * @function Engine.isWebGLAvailable
	 */
	Engine.isWebGLAvailable = function (majorVersion = 1) {
		try {
			return !!document.createElement('canvas').getContext(['webgl', 'webgl2'][majorVersion - 1]);
		} catch (e) { /* Not available */ }
		return false;
	};

	/**
	 * Safe Engine constructor, creates a new prototype for every new instance to avoid prototype pollution.
	 * @ignore
	 * @constructor
	 */
	function SafeEngine(initConfig) {
		const proto = /** @lends Engine.prototype */ {
			/**
			 * Initialize the engine instance. Optionally, pass the base path to the engine to load it,
			 * if it hasn't been loaded yet. See :js:meth:`Engine.load`.
			 *
			 * @param {string=} basePath Base path of the engine to load.
			 * @return {Promise} A ``Promise`` that resolves once the engine is loaded and initialized.
			 */
			init: function (basePath) {
				if (initPromise) {
					return initPromise;
				}
				if (loadPromise == null) {
					if (!basePath) {
						initPromise = Promise.reject(new Error('A base path must be provided when calling `init` and the engine is not loaded.'));
						return initPromise;
					}
					Engine.load(basePath, this.config.fileSizes[`${basePath}.wasm`]);
				}
				const me = this;
				function doInit(promise) {
					// Care! Promise chaining is bogus with old emscripten versions.
					// This caused a regression with the Mono build (which uses an older emscripten version).
					// Make sure to test that when refactoring.
					return new Promise(function (resolve, reject) {
						promise.then(function (response) {
							const cloned = new Response(response.clone().body, { 'headers': [['content-type', 'application/wasm']] });
							Godot(me.config.getModuleConfig(loadPath, cloned)).then(function (module) {
								const paths = me.config.persistentPaths;
								module['initFS'](paths).then(function (err) {
									me.rtenv = module;
									if (me.config.unloadAfterInit) {
										Engine.unload();
									}
									resolve();
								});
							});
						});
					});
				}
				preloader.setProgressFunc(this.config.onProgress);
				initPromise = doInit(loadPromise);
				return initPromise;
			},

			/**
			 * Load a file so it is available in the instance's file system once it runs. Must be called **before** starting the
			 * instance.
			 *
			 * If not provided, the ``path`` is derived from the URL of the loaded file.
			 *
			 * @param {string|ArrayBuffer} file The file to preload.
			 *
			 * If a ``string`` the file will be loaded from that path.
			 *
			 * If an ``ArrayBuffer`` or a view on one, the buffer will used as the content of the file.
			 *
			 * @param {string=} path Path by which the file will be accessible. Required, if ``file`` is not a string.
			 *
			 * @returns {Promise} A Promise that resolves once the file is loaded.
			 */
			preloadFile: function (file, path) {
				return preloader.preload(file, path, this.config.fileSizes[file]);
			},

			/**
			 * Start the engine instance using the given override configuration (if any).
			 * :js:meth:`startGame <Engine.prototype.startGame>` can be used in typical cases instead.
			 *
			 * This will initialize the instance if it is not initialized. For manual initialization, see :js:meth:`init <Engine.prototype.init>`.
			 * The engine must be loaded beforehand.
			 *
			 * Fails if a canvas cannot be found on the page, or not specified in the configuration.
			 *
			 * @param {EngineConfig} override An optional configuration override.
			 * @return {Promise} Promise that resolves once the engine started.
			 */
			start: function (override) {
				this.config.update(override);
				const me = this;
				return me.init().then(function () {
					if (!me.rtenv) {
						return Promise.reject(new Error('The engine must be initialized before it can be started'));
					}

					let config = {};
					try {
						config = me.config.getGodotConfig(function () {
							me.rtenv = null;
						});
					} catch (e) {
						return Promise.reject(e);
					}
					// Godot configuration.
					me.rtenv['initConfig'](config);

					// Preload GDNative libraries.
					const libs = [];
					me.config.gdnativeLibs.forEach(function (lib) {
						libs.push(me.rtenv['loadDynamicLibrary'](lib, { 'loadAsync': true }));
					});
					return Promise.all(libs).then(function () {
						return new Promise(function (resolve, reject) {
							preloader.preloadedFiles.forEach(function (file) {
								me.rtenv['copyToFS'](file.path, file.buffer);
							});
							preloader.preloadedFiles.length = 0; // Clear memory
							me.rtenv['callMain'](me.config.args);
							initPromise = null;
							if (me.config.serviceWorker && 'serviceWorker' in navigator) {
								navigator.serviceWorker.register(me.config.serviceWorker);
							}
							resolve();
						});
					});
				});
			},

			/**
			 * Start the game instance using the given configuration override (if any).
			 *
			 * This will initialize the instance if it is not initialized. For manual initialization, see :js:meth:`init <Engine.prototype.init>`.
			 *
			 * This will load the engine if it is not loaded, and preload the main pck.
			 *
			 * This method expects the initial config (or the override) to have both the :js:attr:`executable` and :js:attr:`mainPack`
			 * properties set (normally done by the editor during export).
			 *
			 * @param {EngineConfig} override An optional configuration override.
			 * @return {Promise} Promise that resolves once the game started.
			 */
			startGame: function (override) {
				this.config.update(override);
				// Add main-pack argument.
				const exe = this.config.executable;
				const pack = this.config.mainPack || `${exe}.pck`;
				this.config.args = ['--main-pack', pack].concat(this.config.args);
				// Start and init with execName as loadPath if not inited.
				const me = this;
				return Promise.all([
					this.init(exe),
					this.preloadFile(pack, pack),
				]).then(function () {
					return me.start.apply(me);
				});
			},

			/**
			 * Create a file at the specified ``path`` with the passed as ``buffer`` in the instance's file system.
			 *
			 * @param {string} path The location where the file will be created.
			 * @param {ArrayBuffer} buffer The content of the file.
			 */
			copyToFS: function (path, buffer) {
				if (this.rtenv == null) {
					throw new Error('Engine must be inited before copying files');
				}
				this.rtenv['copyToFS'](path, buffer);
			},

			/**
			 * Request that the current instance quit.
			 *
			 * This is akin the user pressing the close button in the window manager, and will
			 * have no effect if the engine has crashed, or is stuck in a loop.
			 *
			 */
			requestQuit: function () {
				if (this.rtenv) {
					this.rtenv['request_quit']();
				}
			},
		};

		Engine.prototype = proto;
		// Closure compiler exported instance methods.
		Engine.prototype['init'] = Engine.prototype.init;
		Engine.prototype['preloadFile'] = Engine.prototype.preloadFile;
		Engine.prototype['start'] = Engine.prototype.start;
		Engine.prototype['startGame'] = Engine.prototype.startGame;
		Engine.prototype['copyToFS'] = Engine.prototype.copyToFS;
		Engine.prototype['requestQuit'] = Engine.prototype.requestQuit;
		// Also expose static methods as instance methods
		Engine.prototype['load'] = Engine.load;
		Engine.prototype['unload'] = Engine.unload;
		Engine.prototype['isWebGLAvailable'] = Engine.isWebGLAvailable;
		return new Engine(initConfig);
	}

	// Closure compiler exported static methods.
	SafeEngine['load'] = Engine.load;
	SafeEngine['unload'] = Engine.unload;
	SafeEngine['isWebGLAvailable'] = Engine.isWebGLAvailable;

	return SafeEngine;
}());
if (typeof window !== 'undefined') {
	window['Engine'] = Engine;
}