1 files changed, 133 insertions, 0 deletions
diff --git a/platform/web/js/engine/preloader.js b/platform/web/js/engine/preloader.js
new file mode 100644
index 0000000000..564c68d264
--- /dev/null
+++ b/platform/web/js/engine/preloader.js
@@ -0,0 +1,133 @@
+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'));
+	};
+};