import fs from 'fs';
import nodePath from 'node:path';
import { finished } from 'stream/promises';

import type { SongMeta, ServerCreds } from './services/jellyfin.ts';
import { getSongFileBuffer } from './services/jellyfin.ts';

const QUEUE: (() => Promise<void>)[] = [];
let downloadCount = 0;
const DOWNLOAD_LIMIT = 10;

export const downloadSongs = async (
  creds: ServerCreds,
  songs: SongMeta[],
  path: string,
) => {
  const promises = songs.map(s => getSongDownloader(creds, s, path));
  QUEUE.push(...promises);
  processQueue();
  await Promise.all(promises);
};

const getSongDownloader =
  (creds: ServerCreds, song: SongMeta, path: string) => async () => {
    const extension = song.Path.split('.').pop();
    const filePath = nodePath.join(path, `${song.Id}.${extension}`);
    try {
      const write = fs.createWriteStream(filePath, {
        flags: 'wx',
      });
      console.log('Downloading: ', filePath);
      const download = await getSongFileBuffer(creds, song.Id);
      await finished(download.pipe(write));
    } catch (err: any) {
      if (err?.code !== 'EEXIST') {
        throw err;
      }
      console.log('File already exists, skipping: ', filePath);
    }
  };

const processQueue = () => {
  if (downloadCount < DOWNLOAD_LIMIT && QUEUE.length) {
    downloadCount++;
    const next = QUEUE.shift();
    next &&
      next().then(() => {
        downloadCount--;
        processQueue();
      });
    processQueue();
  }
};