Polygon Tests Bulk Downloader

script.js

// ==UserScript==
// @name        Polygon Tests Bulk Downloader
// @match       https://polygon.codeforces.com/tests?*
// @downloadURL https://gist.githubusercontent.com/kiwiyou/bc89e3dbff247619f92a70f654d6dd1f/raw/script.js
// @grant       none
// @version     1.1
// @author      kiwiyou <[email protected]>
// ==/UserScript==

if (new URLSearchParams(location.search).get('action') === 'preview') setupUi();


function setupUi() {
	import("https://www.unpkg.com/@zip.js/zip.js@2/index.min.js").then(async ({
		ZipWriter
	}) => {
		const inputs = [...document.querySelectorAll('pre[id^="input"]')].map(
			(pre) => [pre, `${pre.id.slice('input'.length)}.in`]
		);
		const answers = [...document.querySelectorAll('pre[id^="answer"]')].map(
			(pre) => [pre, `${pre.id.slice('answer'.length)}.out`]
		);
		const all = inputs.concat(answers);
		const fetchInputs = makeFetcher(inputs);
		const fetchAnswers = makeFetcher(answers);
		const fetchAll = makeFetcher(all);

		const commandBar = document.getElementById('right');
		commandBar.append(makeDownloadButton('#download-inputs', 'inputs.zip', 'Download Inputs', fetchInputs));
		commandBar.append(makeDownloadButton('#download-answers', 'answers.zip', 'Download Answers', fetchAnswers));
		commandBar.append(makeDownloadButton('#download-all', 'all.zip', 'Download All', fetchAll));

		function makeFetcher(records) {
			let url = null;
			return async () => {
				if (url === null) {
					const zipFileStream = new TransformStream();
					const zipFileBlobPromise = new Response(zipFileStream.readable).blob();
					const zipWriter = new ZipWriter(zipFileStream.writable);
					const fetchAll = [];
					for (const [pre, filename] of records) {
						const a = pre.nextElementSibling.firstElementChild;
						fetchAll.push(
							fetch(a.href).then((response) => zipWriter.add(filename, response.body))
						);
					}
					await Promise.all(fetchAll);
					await zipWriter.close();
					url = URL.createObjectURL(await zipFileBlobPromise);
				}
				return url;
			};
		}

		function makeDownloadButton(href, filename, text, fetcher) {
			const button = document.createElement('a');
			button.href = href;
			button.download = filename;
			button.append(text);
			const firstClick = async () => {
				button.removeEventListener('click', firstClick);
				button.href = await fetcher();
				button.click();
			};
			button.addEventListener('click', firstClick);
			return button;
		}
	});
}