hub/podcast.js

// Podcasts from Podgrab (https://github.com/akhilrex/podgrab). The hub talks to Podgrab's own web API on the person's behalf, so the
// Podgrab password (PODGRAB_PASSWORD, user "podgrab") stays on the server and the browser only ever talks to the hub.
const fs = require('fs'), path = require('path');
const users = require('./users');
const prog = require('./progress')('podcast-progress.json'); // where each person got to in each episode
const BASE = (process.env.PODCAST_URL || 'https://podcast.necloud.us/').replace(/\/$/, '');
const AUTH = process.env.PODGRAB_PASSWORD ? 'Basic ' + Buffer.from('podgrab:' + process.env.PODGRAB_PASSWORD).toString('base64') : '';

// Only these Podgrab calls are passed through: [method, path pattern]. Podgrab's page routes and its settings, backup and OPML routes are not.
const ALLOWED = [
  ['GET', /^\/podcasts$/], ['POST', /^\/podcasts$/],
  ['GET', /^\/podcasts\/[\w-]+$/], ['DELETE', /^\/podcasts\/[\w-]+$/],
  ['GET', /^\/podcasts\/[\w-]+\/(items|image|download|pause|unpause)$/], ['DELETE', /^\/podcasts\/[\w-]+\/items$/],
  ['GET', /^\/podcastitems$/], ['GET', /^\/podcastitems\/[\w-]+$/], ['PATCH', /^\/podcastitems\/[\w-]+$/],
  ['GET', /^\/podcastitems\/[\w-]+\/(image|file|markPlayed|markUnplayed|bookmark|unbookmark|download|delete)$/],
];

// Podgrab holds every show in one shared library; which of them are on a person's own list is kept here, per person. A new person starts with an empty
// list (the admin starts with everything already in Podgrab). Taking a show off your list leaves Podgrab alone unless nobody else follows it.
const subsFile = uid => path.join(users.dirOf(uid), 'podcast-subs.json');
const subsRead = uid => { try { const j = JSON.parse(fs.readFileSync(subsFile(uid), 'utf8')); return Array.isArray(j) ? j : null; } catch { return null; } };
const subsWrite = (uid, ids) => { const f = subsFile(uid), tmp = f + '.tmp'; fs.writeFileSync(tmp, JSON.stringify([...new Set(ids)]), { mode: 0o600 }); fs.renameSync(tmp, f); };
const idOf = o => o && (o.ID !== undefined ? o.ID : o.id);
async function podgrab(p, init = {}) {
  const r = await fetch(BASE + p, { ...init, headers: { accept: 'application/json', ...(AUTH ? { authorization: AUTH } : {}), ...init.headers }, redirect: 'manual', signal: AbortSignal.timeout(20000) });
  return r;
}
async function mySubs(me) {
  const have = subsRead(me.id); if (have) return have;
  let ids = [];
  if (me.role === 'admin') { try { const l = await (await podgrab('/podcasts')).json(); ids = (Array.isArray(l) ? l : []).map(idOf).filter(Boolean); } catch { return []; } }
  subsWrite(me.id, ids); return ids;
}
const json = (res, code, o) => { res.writeHead(code, { 'content-type': 'application/json', 'cache-control': 'no-store' }); res.end(JSON.stringify(o)); };
const enabled = () => !!BASE;

async function handle(req, res) {
  const u = new URL(req.url, 'http://x'), p = u.pathname.slice('/api/podcast'.length) || '/';
  if (p === '/discover') { // find new shows in Apple's free podcast directory (the search words go to Apple; nothing else does)
    const q = (u.searchParams.get('q') || '').trim().slice(0, 100);
    if (q.length < 2) return json(res, 200, []);
    try {
      const r = await fetch('https://itunes.apple.com/search?' + new URLSearchParams({ media: 'podcast', limit: '15', term: q }), { signal: AbortSignal.timeout(10000) });
      if (!r.ok) throw new Error('status ' + r.status);
      const out = ((await r.json()).results || []).filter(x => /^https?:\/\//i.test(x.feedUrl || '')).map(x => ({ title: x.collectionName, author: x.artistName, feedUrl: x.feedUrl, image: x.artworkUrl100 }));
      return json(res, 200, out);
    } catch { return json(res, 502, { error: 'The podcast directory did not answer' }); }
  }
  if (p === '/progress') {
    if (req.method === 'GET') return json(res, 200, prog.load());
    if (req.method !== 'POST') return json(res, 405, { error: 'Method not allowed' });
    const chunks = []; let n = 0; for await (const c of req) { n += c.length; if (n > 1e6) return json(res, 413, { error: 'Too large' }); chunks.push(c); }
    let body; try { body = JSON.parse(Buffer.concat(chunks).toString('utf8') || '{}'); } catch { return json(res, 400, { error: 'Bad request' }); }
    return json(res, 200, prog.merge(body));
  }
  if (!BASE) return json(res, 503, { error: 'Podcasts are not set up on this server' });
  if (p === '/status') return json(res, 200, { ok: true, host: new URL(BASE).host });
  if (!ALLOWED.some(([m, re]) => m === req.method && re.test(p))) return json(res, 404, { error: 'Not found' });
  const me = users.current(), mine = await mySubs(me);
  let m;
  try {
    if (req.method === 'GET' && p === '/podcasts') { // only the shows on this person's list
      const r = await podgrab('/podcasts' + u.search); const l = await r.json();
      return json(res, r.status, Array.isArray(l) ? l.filter(x => mine.includes(idOf(x))) : l);
    }
    if (req.method === 'POST' && p === '/podcasts') { // add to Podgrab (if it is not there yet) and to this person's list
      const chunks = []; let n = 0; for await (const c of req) { n += c.length; if (n > 1e5) return json(res, 413, { error: 'Too large' }); chunks.push(c); }
      let url = ''; try { url = String(JSON.parse(Buffer.concat(chunks).toString('utf8')).url || '').trim(); } catch {}
      if (!/^https?:\/\//i.test(url)) return json(res, 400, { error: 'Enter a feed address starting with http' });
      const r = await podgrab('/podcasts', { method: 'POST', headers: { 'content-type': 'application/json' }, body: JSON.stringify({ url }) });
      let added = null; if (r.status === 200) { try { added = await r.json(); } catch {} }
      let id = idOf(added);
      if (!id) { // Podgrab already had it (409), or did not say which: find it by its feed address
        const l = await (await podgrab('/podcasts')).json(); const norm = x => String(x || '').replace(/\/+$/, '').toLowerCase();
        const hit = (Array.isArray(l) ? l : []).find(x => norm(x.URL || x.url) === norm(url)); id = idOf(hit); added = hit;
        if (!id) return json(res, r.status === 200 ? 502 : r.status, { error: 'Podgrab could not add that feed' });
      }
      subsWrite(me.id, [...mine, id]); return json(res, 200, added || { ID: id });
    }
    if (req.method === 'DELETE' && (m = /^\/podcasts\/([\w-]+)$/.exec(p))) { // off this person's list; out of Podgrab only when nobody else follows it
      subsWrite(me.id, mine.filter(x => x !== m[1]));
      const others = users.all().some(x => x.id !== me.id && (subsRead(x.id) || []).includes(m[1]));
      if (!others) await podgrab(p, { method: 'DELETE' }).catch(() => {});
      return json(res, 200, { ok: true, removed: !others });
    }
    if ((m = /^\/podcasts\/([\w-]+)(\/|$)/.exec(p)) && !mine.includes(m[1])) return json(res, 404, { error: 'That podcast is not on your list' });
  } catch (e) { return json(res, 502, { error: 'Podgrab did not answer' + (e.name === 'TimeoutError' ? ' in time' : '') }); }
  const hasBody = req.method === 'POST' || req.method === 'PATCH';
  let body;
  if (hasBody) { const chunks = []; let n = 0; for await (const c of req) { n += c.length; if (n > 1e5) return json(res, 413, { error: 'Too large' }); chunks.push(c); } body = Buffer.concat(chunks); }
  const h = { accept: req.headers.accept || '*/*', 'accept-encoding': 'identity' }; // so the length Podgrab reports is the length we pass on
  if (AUTH) h.authorization = AUTH;
  if (req.headers.range) h.range = req.headers.range;
  if (hasBody) h['content-type'] = 'application/json';
  const ctl = new AbortController(), streaming = p.endsWith('/file'), t = streaming ? null : setTimeout(() => ctl.abort(), 20000); // audio may take as long as it takes
  res.on('close', () => { clearTimeout(t); ctl.abort(); });
  try {
    const up = await fetch(BASE + p + u.search, { method: req.method, headers: h, body, signal: ctl.signal, redirect: 'manual' });
    const out = { 'cache-control': p.endsWith('/image') ? 'private, max-age=86400' : 'no-store' };
    for (const k of ['content-type', 'content-length', 'content-range', 'accept-ranges']) if (up.headers.get(k)) out[k] = up.headers.get(k);
    if (up.status >= 300 && up.status < 400) { // Podgrab sends you to the original file or picture when it has no copy of its own
      const loc = up.headers.get('location');
      if (loc && /^https?:\/\//i.test(loc)) { res.writeHead(302, { location: loc, 'referrer-policy': 'no-referrer' }); return res.end(); }
      return json(res, 502, { error: 'Podgrab sent an unexpected redirect' });
    }
    res.writeHead(up.status, out);
    if (!up.body) return res.end();
    const { Readable } = require('stream');
    Readable.fromWeb(up.body).on('error', () => res.destroy()).pipe(res);
  } catch (e) {
    if (res.headersSent) return res.destroy();
    json(res, 502, { error: 'Podgrab did not answer' + (e.name === 'AbortError' ? ' in time' : '') });
  }
}

/** For transcripts: where an episode came from (its feed, its id in that feed, its file). Anyone may ask about the shows on their own list only. */
async function feedInfo(me, itemId) {
  if (!BASE || !/^[\w-]+$/.test(String(itemId))) return null;
  const f = (o, k) => { if (!o) return undefined; const hit = Object.keys(o).find(x => x.toLowerCase() === k.toLowerCase()); return hit === undefined ? undefined : o[hit]; }; // (Podgrab's field names, whatever their capitals)
  const it = await (await podgrab('/podcastitems/' + itemId)).json().catch(() => null); if (!it) return null;
  const pid = f(it, 'PodcastID') || f(it, 'podcastId'); if (!pid || !(await mySubs(me)).includes(pid)) return null;
  const sh = await (await podgrab('/podcasts/' + pid)).json().catch(() => null);
  return { guid: f(it, 'GUID') || f(it, 'guid') || '', fileUrl: f(it, 'FileURL') || f(it, 'fileUrl') || '', feedUrl: (sh && (f(sh, 'URL') || f(sh, 'url'))) || '' };
}
module.exports = { handle, enabled, feedInfo };