Concurrent NodeJS downloader

index.js

import fs from 'fs'

async function getMeta(url) {
    let resp = await fetch(url, { method: 'HEAD' });
    const size = parseInt(resp.headers.get('Content-Length'));
    const contentDisposition = resp.headers.get('Content-Disposition')
    const filename = contentDisposition.match(/; filename=(.+)/)[1] ?? 'Unnamed'
    return {size, filename};
}

async function createRanges(url, chunkSize) {
    const meta = await getMeta(url);
    const ranges = [];

    for (let start = 0; start < meta.size; start += chunkSize) {
        const end = Math.min(start + chunkSize - 1, meta.size - 1);
        ranges.push([start, end]);
    }
    return { meta, ranges };
}

async function fetchRange(url, start, end) {
    const headers = { 'Range': `bytes=${start}-${end}` };
    const resp = await fetch(url, { headers });
    if (!resp.ok) {
        throw new Error(`${resp.status}: ${await resp.text()}`);
    }
    const data = await resp.arrayBuffer();

    return { start, end, data };
}

function toMB(bytes) {
    return bytes / 1024 / 1024
}

async function download(url, maxWorkers = 15, chunkSize = 1024 * 1024 * 2, filename = null) {
    let { meta, ranges } = await createRanges(url, chunkSize);
    if (filename != null) {
        meta.filename = filename
    }
    const writer = fs.createWriteStream(meta.filename)
    let read = 0;
    let completedChunks = 0;

    
    for (let i = 0; i < ranges.length; i += maxWorkers) {
        const slice = ranges.slice(i, i + maxWorkers);
        const promises = slice.map((chunk) => fetchRange(url, chunk[0], chunk[1]));
        let startTime = Date.now();
        const chunks = await Promise.all(promises);
        const elapsedTime = (Date.now() - startTime) / 1000; // in seconds
        chunks.sort((a, b) => a.start - b.start);
        let phaseSize = 0
        for (const chunk of chunks) {
            phaseSize += chunk.data.byteLength
        }
        read += phaseSize
        completedChunks += slice.length;
        for (const chunk of chunks) {
            writer.write(chunk.data)
        }
        const progress = (completedChunks / ranges.length) * 100;
        const speedMbps = toMB(phaseSize) / elapsedTime;
        console.log(`${toMB(read).toFixed(0)}MB | ${progress.toFixed(1)}% | ${speedMbps.toFixed(1)}mb/s`);
    }
    return {meta}
}

await download("https://github.com/thewh1teagle/vibe/releases/download/v1.0.4/vibe_1.0.4_amd64.deb")