/**
 * 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,
		/**
		 * @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.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);
};