import fs from 'fs';
import path from 'path';
import { parseFile as mmParseFile } from 'music-metadata';
import { getPlaylistDir } from './config.js';
import { loadYearsIndex } from './years.js';

/**
 * List tracks from a specific playlist
 * @param {string} [playlistId='default'] - The playlist ID to list tracks from
 * @returns {Promise<Array>} Array of track objects
 */
export async function listTracks(playlistId = 'default') {
  const years = loadYearsIndex(playlistId);
  const targetDir = getPlaylistDir(playlistId);

  const files = fs
    .readdirSync(targetDir)
    .filter((f) => /\.(mp3|wav|m4a|ogg|opus)$/i.test(f))
    .filter((f) => {
      // If both base.ext and base.opus exist, list only once (prefer .opus)
      const ext = path.extname(f).toLowerCase();
      if (ext === '.opus') return true;
      const opusTwin = f.replace(/\.[^.]+$/i, '.opus');
      return !fs.existsSync(path.join(targetDir, opusTwin));
    });
  const tracks = await Promise.all(
    files.map(async (f) => {
      // Prefer .opus for playback if exists
      const ext = path.extname(f).toLowerCase();
      const opusName = ext === '.opus' ? f : f.replace(/\.[^.]+$/i, '.opus');
      const chosen = fs.existsSync(path.join(targetDir, opusName)) ? opusName : f;
      const fp = path.join(targetDir, chosen);

      // Get metadata from JSON first (priority), then from audio file as fallback
      const jsonMeta = years[f] || years[chosen];
      let year = jsonMeta?.year ?? null;
      let title = jsonMeta?.title ?? path.parse(f).name;
      let artist = jsonMeta?.artist ?? '';

      // Only parse audio file if JSON doesn't have title or artist metadata
      // Note: year is ONLY taken from years.json, never from audio file
      if (!jsonMeta || !jsonMeta.title || !jsonMeta.artist) {
        try {
          const meta = await mmParseFile(fp, { duration: false });
          title = jsonMeta?.title || meta.common.title || title;
          artist = jsonMeta?.artist || meta.common.artist || artist;
          // year remains from years.json only - do not use meta.common.year
        } catch {}
      }

      return { id: chosen, file: chosen, title, artist, year };
    })
  );
  return tracks;
}

export function registerTracksApi(app) {
  app.get('/api/tracks', async (req, res) => {
    try {
      // Support optional playlist parameter (defaults to 'default')
      const playlistId = req.query.playlist || 'default';
      const tracks = await listTracks(playlistId);
      res.json({ tracks, playlist: playlistId });
    } catch (e) {
      res.status(500).json({ error: e.message });
    }
  });
}