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

/**
 * Get list of available playlists (subdirectories in data folder).
 * Also includes a special "default" playlist if there are audio files in the root data directory.
 * @returns {Array<{id: string, name: string, trackCount: number}>}
 */
export function getAvailablePlaylists() {
  try {
    const entries = fs.readdirSync(DATA_DIR, { withFileTypes: true });
    const playlists = [];

    // Check for files in root directory (legacy/default playlist)
    const rootFiles = entries.filter(
      (e) => e.isFile() && /\.(mp3|wav|m4a|ogg|opus)$/i.test(e.name)
    );
    if (rootFiles.length > 0) {
      playlists.push({
        id: 'default',
        name: 'Default (Root Folder)',
        trackCount: rootFiles.length,
      });
    }

    // Check subdirectories for playlists
    const subdirs = entries.filter((e) => e.isDirectory());
    for (const dir of subdirs) {
      const dirPath = path.join(DATA_DIR, dir.name);
      const dirFiles = fs.readdirSync(dirPath).filter((f) => /\.(mp3|wav|m4a|ogg|opus)$/i.test(f));
      if (dirFiles.length > 0) {
        playlists.push({
          id: dir.name,
          name: dir.name,
          trackCount: dirFiles.length,
        });
      }
    }

    return playlists;
  } catch (error) {
    console.error('Error reading playlists:', error);
    return [];
  }
}

/**
 * Load a deck of tracks from a specific playlist.
 * @param {string} [playlistId='default'] - The playlist ID to load from
 * @returns {Promise<Array>} Shuffled array of track objects
 */
export async function loadDeck(playlistId = 'default') {
  // Load the years index for this specific playlist
  const years = loadYearsIndex(playlistId);

  // Determine the directory to load from
  const targetDir = playlistId === 'default' ? DATA_DIR : path.join(DATA_DIR, playlistId);

  // Validate that the directory exists
  if (!fs.existsSync(targetDir)) {
    console.error(`Playlist directory not found: ${targetDir}`);
    return [];
  }

  const files = fs.readdirSync(targetDir).filter((f) => /\.(mp3|wav|m4a|ogg|opus)$/i.test(f));

  if (files.length === 0) {
    console.warn(`No audio files found in playlist: ${playlistId}`);
    return [];
  }

  // Process files in batches to avoid "too many open files" error
  const BATCH_SIZE = 50; // Process 50 files at a time
  const tracks = [];

  for (let i = 0; i < files.length; i += BATCH_SIZE) {
    const batch = files.slice(i, i + BATCH_SIZE);
    const batchTracks = await Promise.all(
      batch.map(async (f) => {
        const fp = path.join(targetDir, f);
        // For file paths, we need to include the playlist subdirectory if not default
        const relativeFile = playlistId === 'default' ? f : path.join(playlistId, f);

        // Get metadata from JSON first (priority), then from audio file as fallback
        const jsonMeta = years[f];
        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 (err) {
            // Log error but continue processing
            console.warn(`Failed to parse metadata for ${f}:`, err.message);
          }
        }

        return { id: f, file: relativeFile, title, artist, year };
      })
    );
    tracks.push(...batchTracks);
  }

  console.log(`Loaded ${tracks.length} tracks from playlist: ${playlistId}`);
  return shuffle(tracks);
}