api/src/processing/services/soundcloud.js

import { env } from "../../config.js";
import { resolveRedirectingURL } from "../url.js";

const cachedID = {
    version: '',
    id: ''
}

async function findClientID() {
    try {
        const sc = await fetch('https://soundcloud.com/').then(r => r.text()).catch(() => {});
        const scVersion = String(sc.match(/<script>window\.__sc_version="[0-9]{10}"<\/script>/)[0].match(/[0-9]{10}/));

        if (cachedID.version === scVersion) {
            return cachedID.id;
        }

        const scripts = sc.matchAll(/<script.+src="(.+)">/g);

        let clientid;
        for (let script of scripts) {
            const url = script[1];

            if (!url?.startsWith('https://a-v2.sndcdn.com/')) {
                return;
            }

            const scrf = await fetch(url).then(r => r.text()).catch(() => {});
            const id = scrf.match(/\("client_id=[A-Za-z0-9]{32}"\)/);

            if (id && typeof id[0] === 'string') {
                clientid = id[0].match(/[A-Za-z0-9]{32}/)[0];
                break;
            }
        }
        cachedID.version = scVersion;
        cachedID.id = clientid;

        return clientid;
    } catch {}
}

const findBestForPreset = (transcodings, preset) => {
    let inferior;
    for (const entry of transcodings) {
        const protocol = entry?.format?.protocol;

        if (entry.snipped || protocol?.includes('encrypted')) {
            continue;
        }

        if (entry?.preset?.startsWith(`${preset}_`)) {
            if (protocol === 'progressive') {
                return entry;
            }

            inferior = entry;
        }
    }

    return inferior;
}

export default async function(obj) {
    const clientId = await findClientID();
    if (!clientId) return { error: "fetch.fail" };

    let link;

    if (obj.shortLink) {
        obj = {
            ...obj,
            ...await resolveRedirectingURL(
                `https://on.soundcloud.com/${obj.shortLink}`
            )
        }
    }

    if (obj.author && obj.song) {
        link = `https://soundcloud.com/${obj.author}/${obj.song}`;
        if (obj.accessKey) {
            link += `/s-${obj.accessKey}`;
        }
    }

    if (!link && obj.shortLink) return { error: "fetch.short_link" };
    if (!link) return { error: "link.unsupported" };

    const resolveURL = new URL("https://api-v2.soundcloud.com/resolve");
    resolveURL.searchParams.set("url", link);
    resolveURL.searchParams.set("client_id", clientId);

    const json = await fetch(resolveURL).then(r => r.json()).catch(() => {});
    if (!json) return { error: "fetch.fail" };

    if (json.duration > env.durationLimit * 1000) {
        return { error: "content.too_long" };
    }

    if (json.policy === "BLOCK") {
        return { error: "content.region" };
    }

    if (json.policy === "SNIP") {
        return { error: "content.paid" };
    }

    if (!json.media?.transcodings || !json.media?.transcodings.length === 0) {
        return { error: "fetch.empty" };
    }

    let bestAudio = "opus",
        selectedStream = findBestForPreset(json.media.transcodings, "opus");

    const mp3Media = findBestForPreset(json.media.transcodings, "mp3");

    // use mp3 if present if user prefers it or if opus isn't available
    if (mp3Media && (obj.format === "mp3" || !selectedStream)) {
        selectedStream = mp3Media;
        bestAudio = "mp3"
    }

    if (!selectedStream) {
        return { error: "fetch.empty" };
    }

    const fileUrl = new URL(selectedStream.url);
    fileUrl.searchParams.set("client_id", clientId);
    fileUrl.searchParams.set("track_authorization", json.track_authorization);

    const file = await fetch(fileUrl)
                     .then(async r => new URL((await r.json()).url))
                     .catch(() => {});

    if (!file) return { error: "fetch.empty" };

    const artist = json.user?.username?.trim();
    const fileMetadata = {
        title: json.title?.trim(),
        album: json.publisher_metadata?.album_title?.trim(),
        artist,
        album_artist: artist,
        composer: json.publisher_metadata?.writer_composer?.trim(),
        genre: json.genre?.trim(),
        date: json.display_date?.trim().slice(0, 10),
        copyright: json.license?.trim(),
    }

    let cover;
    if (json.artwork_url) {
        const coverUrl = json.artwork_url.replace(/-large/, "-t1080x1080");
        const testCover = await fetch(coverUrl)
            .then(r => r.status === 200)
            .catch(() => {});

        if (testCover) {
            cover = coverUrl;
        }
    }

    return {
        urls: file.toString(),
        cover,
        filenameAttributes: {
            service: "soundcloud",
            id: json.id,
            ...fileMetadata
        },
        bestAudio,
        fileMetadata,
        isHLS: file.pathname.endsWith('.m3u8'),
    }
}