OpenModLauncher-Base/lib/downloader.js

const path = require("node:path");
const fs = require("node:fs");
const fsPromises = require("node:fs/promises");

const httpsWrapper = require("./util/https.js");
const utilities = require("./util/functions.js");

let maxConcurrentDownloads = 16;
let downloadQueue = [];
let totalDownloads = 0;
let isDownloading = false;
let ongoingDownloads = 0;

function waitUntilDownloadsFinish() {
	return new Promise(async function (resolve, reject) {
		var downloadCountChecker = setInterval(function () {
			if (ongoingDownloads < 1 && downloadQueue.length < 1 && !isDownloading) {
				resolve(clearInterval(downloadCountChecker));
			}
		}, 256);
	});
}

module.exports = {
	"download_file": function (url, filePath) {
		return new Promise(async function (resolve, reject) {
			var directory = path.dirname(filePath);
			if (!(await fs.existsSync(directory))) await fsPromises.mkdir(directory, {"recursive": true});

			var writeStream = fs.createWriteStream(filePath);
			writeStream.on("finish", resolve);

			httpsWrapper.getStream(url).then(function (response) {
				response.pipe(writeStream);
			}).catch(reject);
		});
	},
	"process_queue": function (progressCB) {
		return new Promise(async function (resolve, reject) {
			totalDownloads = downloadQueue.length;
			if (downloadQueue.length > 0) isDownloading = true;

			if (progressCB) {
				progressCB(0.0, 0, downloadQueue.length, totalDownloads);
			}

			while (downloadQueue.length > 0) {
				if (ongoingDownloads < maxConcurrentDownloads) {
					setImmediate(function (downloadData) {
						module.exports.download_file(downloadData.url, downloadData.path).then(function () {
							ongoingDownloads--;
							if (downloadQueue.length < 1) {
								isDownloading = false;
							}
						}).catch(function (error) {
							ongoingDownloads--;
							downloadQueue.push(downloadData);
						});
					}, downloadQueue.shift());
					ongoingDownloads++;
					let progress = (totalDownloads - (downloadQueue.length + ongoingDownloads)) / totalDownloads;
					if (progressCB) {
						progressCB(progress, ongoingDownloads, downloadQueue.length, totalDownloads);
					}
				} else {
					await utilities.sleep(256);
				}
			}

			waitUntilDownloadsFinish().then(function () {
				if (progressCB) {
					progressCB(1.0, 0, 0, totalDownloads);
				}
				resolve();
			}).catch(reject);
		});
	},
	"download_minecraft": function (directory, meta, manifestSource, progressCB) {
		return new Promise(async function (resolve, reject) {
			let gameManifest = JSON.parse(await httpsWrapper.get(manifestSource["versions_manifest"]));

			let versionInManifest = gameManifest.versions.find(ver => ver.id == meta["version"]);

			if (!versionInManifest) {
				return reject(new Error("Minecraft version \"" + meta["version"] + "\" could not be found in given source. "));
			}

			if (!fs.existsSync(directory)) await fsPromises.mkdir(directory, {"recursive": true});

			let versionDirectory = path.join(directory, "versions", meta["version"]);

			if (!fs.existsSync(versionDirectory)) await fsPromises.mkdir(versionDirectory, {"recursive": true});
			let versionManifest = JSON.parse(await httpsWrapper.get(versionInManifest.url));
			fs.writeFileSync(path.join(versionDirectory, meta["version"] + ".json"), JSON.stringify(versionManifest, null, "\t"));

			let librariesDirectory = path.join(directory, "libraries");

			for (let l = 0; l < versionManifest.libraries.length; l++) {
				let library = versionManifest.libraries[l];

				if ("classifiers" in library.downloads) continue; // Attempt at skipping platform-specific code, hoping the game still starts.

				let libraryFilePath = path.join(librariesDirectory, ...(library.downloads.artifact.path.split("/")));

				downloadQueue.push({
					"url": library.downloads.artifact.url,
					"path": libraryFilePath
				});
			}

			let assetsDirectory = path.join(directory, "assets");

			let assetIndexesDirectory = path.join(assetsDirectory, "indexes");
			if (!fs.existsSync(assetIndexesDirectory)) await fsPromises.mkdir(assetIndexesDirectory, {"recursive": true});

			let assetIndexPath = path.join(assetIndexesDirectory, versionManifest.assetIndex.id + ".json");
			let assetIndex = JSON.parse(await httpsWrapper.get(versionManifest.assetIndex.url));
			fs.writeFileSync(assetIndexPath, JSON.stringify(assetIndex, null, "\t"));

			let assetObjectsDirectory = path.join(assetsDirectory, "objects");
			for (const assetLocation in assetIndex.objects) {
				if (assetIndex.objects.hasOwnProperty(assetLocation)) {
					let asset = assetIndex.objects[assetLocation];

					let assetPath = [
						asset.hash.substring(0, 2), asset.hash
					];

					downloadQueue.push({
						"url": manifestSource["asset_base"] + assetPath.join("/"),
						"path": path.join(assetObjectsDirectory, ...assetPath)
					});
				}
			}

			downloadQueue.push({
				"url": versionManifest.downloads.client.url,
				"path": path.join(versionDirectory, meta["version"] + ".jar")
			});

			if (!isDownloading) await module.exports.process_queue(progressCB);

			resolve(true);
		});
	}
};