shark/src/lib/services/spotify/playlistDownloader.ts

/**
 * Download Spotify playlist - converts tracks to Deezer via ISRC, adds to queue, and creates m3u8 file
 *
 * Uses a persistent SQLite cache for Spotify→Deezer conversions so that only
 * new/uncached tracks require API calls. For a 200-track playlist where 3
 * tracks were added, this reduces API calls from ~400 to ~6.
 */

import { addToQueue } from '$lib/stores/downloadQueue';
import { trackExists } from '$lib/services/deezer/downloader';
import { writeM3U8, makeRelativePath, type M3U8Track } from '$lib/library/m3u8';
import { generateTrackPath } from '$lib/services/deezer/paths';
import { settings } from '$lib/stores/settings';
import { deezerAuth } from '$lib/stores/deezer';
import { deezerAPI } from '$lib/services/deezer';
import { setInfo, setSuccess, setWarning } from '$lib/stores/status';
import { get } from 'svelte/store';
import { mkdir } from '@tauri-apps/plugin-fs';
import { convertSpotifyTrackToDeezer, type SpotifyTrackInput } from './converter';
import { getCachedConversions, cacheConversion } from '$lib/library/spotify-database';
import type { DeezerTrack } from '$lib/types/deezer';

export interface SpotifyPlaylistTrack {
  id: number | string;
  track_id: string;
  name: string;
  artist_name: string;
  album_name: string;
  duration_ms: number;
  isrc?: string | null;
}

/**
 * Download a Spotify playlist by converting tracks to Deezer equivalents.
 * Cached conversions are reused — only uncached tracks hit the Deezer API.
 */
export async function downloadSpotifyPlaylist(
  playlistName: string,
  spotifyTracks: SpotifyPlaylistTrack[],
  playlistsFolder: string,
  musicFolder: string
): Promise<{
  m3u8Path: string;
  stats: {
    total: number;
    queued: number;
    skipped: number;
    failed: number;
    cached: number;
  };
}> {
  const appSettings = get(settings);
  const authState = get(deezerAuth);

  if (!authState.loggedIn || !authState.arl) {
    throw new Error('Deezer authentication required for downloads');
  }

  deezerAPI.setArl(authState.arl);

  console.log(`[SpotifyPlaylistDownloader] Starting download for playlist: ${playlistName}`);
  console.log(`[SpotifyPlaylistDownloader] Tracks: ${spotifyTracks.length}`);

  try {
    await mkdir(playlistsFolder, { recursive: true });
  } catch (error) {
    // Folder might already exist
  }

  // --- Look up cached conversions in bulk ---
  const spotifyIds = spotifyTracks.map((t) => t.track_id);
  const cachedConversions = await getCachedConversions(spotifyIds);

  const cachedCount = cachedConversions.size;
  const uncachedCount = spotifyTracks.length - cachedCount;
  console.log(
    `[SpotifyPlaylistDownloader] Cache: ${cachedCount} cached, ${uncachedCount} need conversion`
  );

  let queuedCount = 0;
  let skippedCount = 0;
  let failedCount = 0;

  const successfulTracks: Array<{
    deezerTrack: DeezerTrack;
    spotifyTrack: SpotifyPlaylistTrack;
  }> = [];

  for (const spotifyTrack of spotifyTracks) {
    try {
      let deezerTrack: DeezerTrack;

      // --- Check cache first ---
      const cached = cachedConversions.get(spotifyTrack.track_id);

      if (cached) {
        // Use cached conversion — zero API calls
        deezerTrack = JSON.parse(cached.deezer_track_json) as DeezerTrack;
      } else {
        // Convert via API (ISRC → metadata fallback)
        const conversionInput: SpotifyTrackInput = {
          id: spotifyTrack.track_id,
          name: spotifyTrack.name,
          artists: [spotifyTrack.artist_name],
          album: spotifyTrack.album_name,
          duration_ms: spotifyTrack.duration_ms,
          isrc: spotifyTrack.isrc
        };

        const conversionResult = await convertSpotifyTrackToDeezer(conversionInput);

        if (!conversionResult.success || !conversionResult.deezerTrack) {
          console.warn(
            `[SpotifyPlaylistDownloader] Failed to convert: ${spotifyTrack.name} - ${conversionResult.error}`
          );
          failedCount++;
          continue;
        }

        const deezerPublicTrack = conversionResult.deezerTrack;

        // Fetch full track data from GW API
        const deezerTrackId = deezerPublicTrack.id.toString();
        const deezerFullTrack = await deezerAPI.getTrack(deezerTrackId);

        if (!deezerFullTrack || !deezerFullTrack.SNG_ID) {
          console.warn(
            `[SpotifyPlaylistDownloader] Could not fetch full Deezer track data for ID: ${deezerTrackId}`
          );
          failedCount++;
          continue;
        }

        deezerTrack = {
          id: parseInt(deezerFullTrack.SNG_ID, 10),
          title: deezerFullTrack.SNG_TITLE,
          artist: deezerFullTrack.ART_NAME,
          artistId: parseInt(deezerFullTrack.ART_ID, 10),
          artists: [deezerFullTrack.ART_NAME],
          album: deezerFullTrack.ALB_TITLE,
          albumId: parseInt(deezerFullTrack.ALB_ID, 10),
          albumArtist: deezerFullTrack.ART_NAME,
          albumArtistId: parseInt(deezerFullTrack.ART_ID, 10),
          trackNumber:
            typeof deezerFullTrack.TRACK_NUMBER === 'number'
              ? deezerFullTrack.TRACK_NUMBER
              : parseInt(deezerFullTrack.TRACK_NUMBER, 10),
          discNumber:
            typeof deezerFullTrack.DISK_NUMBER === 'number'
              ? deezerFullTrack.DISK_NUMBER
              : parseInt(deezerFullTrack.DISK_NUMBER, 10),
          duration:
            typeof deezerFullTrack.DURATION === 'number'
              ? deezerFullTrack.DURATION
              : parseInt(deezerFullTrack.DURATION, 10),
          explicit: deezerFullTrack.EXPLICIT_LYRICS === 1,
          md5Origin: deezerFullTrack.MD5_ORIGIN,
          mediaVersion: deezerFullTrack.MEDIA_VERSION,
          trackToken: deezerFullTrack.TRACK_TOKEN
        };

        // Cache the conversion for future runs
        await cacheConversion(
          spotifyTrack.track_id,
          deezerTrack.id,
          JSON.stringify(deezerTrack),
          conversionResult.matchMethod || 'unknown'
        );

        console.log(
          `[SpotifyPlaylistDownloader] Converted & cached: ${deezerTrack.title} (via ${conversionResult.matchMethod})`
        );
      }

      // Check if track already exists locally
      if (!appSettings.deezerOverwrite && appSettings.musicFolder) {
        const exists = await trackExists(deezerTrack, appSettings.musicFolder, appSettings.deezerFormat);
        if (exists) {
          skippedCount++;
          successfulTracks.push({ deezerTrack, spotifyTrack });
          continue;
        }
      }

      // Queue track for download
      await addToQueue({
        source: 'deezer',
        type: 'track',
        title: deezerTrack.title,
        artist: deezerTrack.artist,
        totalTracks: 1,
        downloadObject: deezerTrack
      });

      queuedCount++;
      successfulTracks.push({ deezerTrack, spotifyTrack });
    } catch (error) {
      console.error(`[SpotifyPlaylistDownloader] Error processing track ${spotifyTrack.name}:`, error);
      failedCount++;
    }
  }

  console.log(
    `[SpotifyPlaylistDownloader] Queued ${queuedCount}, skipped ${skippedCount}, failed ${failedCount}, cached ${cachedCount}`
  );

  // Show queue status message
  if (queuedCount > 0) {
    const parts = [`Queued ${queuedCount} track${queuedCount !== 1 ? 's' : ''}`];
    if (skippedCount > 0) parts.push(`${skippedCount} skipped`);
    if (failedCount > 0) parts.push(`${failedCount} not found`);
    if (cachedCount > 0) parts.push(`${cachedCount} from cache`);
    setInfo(parts.join(', '));
  } else if (skippedCount > 0) {
    setWarning(`All ${skippedCount} tracks already exist`);
  } else if (failedCount > 0) {
    setWarning(`Could not find ${failedCount} tracks on Deezer`);
  }

  // Generate m3u8 file
  const m3u8Tracks: M3U8Track[] = successfulTracks.map(({ deezerTrack }) => {
    const paths = generateTrackPath(deezerTrack, musicFolder, appSettings.deezerFormat, false);
    const absolutePath = `${paths.filepath}/${paths.filename}`;
    const relativePath = makeRelativePath(absolutePath, playlistsFolder);

    return {
      duration: deezerTrack.duration,
      artist: deezerTrack.artist,
      title: deezerTrack.title,
      path: relativePath
    };
  });

  const m3u8Path = await writeM3U8(playlistName, m3u8Tracks, playlistsFolder);

  console.log(`[SpotifyPlaylistDownloader] Playlist saved to: ${m3u8Path}`);
  setSuccess(`Playlist created: ${playlistName} (${successfulTracks.length} tracks)`);

  return {
    m3u8Path,
    stats: {
      total: spotifyTracks.length,
      queued: queuedCount,
      skipped: skippedCount,
      failed: failedCount,
      cached: cachedCount
    }
  };
}