/**
 * Deezer Queue Manager
 * Handles download queue processing with configurable concurrency
 */

import { downloadTrack } from './downloader';
import { deezerAPI } from '../deezer';
import {
  downloadQueue,
  updateQueueItem,
  setCurrentJob,
  getNextQueuedItem,
  type QueueItem
} from '$lib/stores/downloadQueue';
import { settings } from '$lib/stores/settings';
import { deezerAuth } from '$lib/stores/deezer';
import { syncTrackPaths } from '$lib/library/incrementalSync';
import { get } from 'svelte/store';
import type { DeezerTrack } from '$lib/types/deezer';

export class DeezerQueueManager {
  private isProcessing = false;
  private abortController: AbortController | null = null;
  private albumCoverCache: Map<string, Uint8Array> = new Map();

  /**
   * Fetch fresh track data with valid token right before download
   * Uses pageTrack first for complete token data, falls back to getData
   * Handles FALLBACK.SNG_ID when requested format is unavailable
   */
  private async getValidTrackData(trackId: string, requestedFormat: 'FLAC' | 'MP3_320' | 'MP3_128' = 'FLAC'): Promise<any> {
    console.log(`[DeezerQueueManager] Fetching fresh track data for ID: ${trackId}`);

    const trackData = await deezerAPI.getTrackWithFallback(trackId);

    if (!trackData || !trackData.TRACK_TOKEN) {
      throw new Error('Failed to get track token');
    }

    // Log important fields for debugging
    console.log(`[DeezerQueueManager] Track data:`, {
      TRACK_TOKEN: trackData.TRACK_TOKEN ? 'present' : 'missing',
      TRACK_TOKEN_EXPIRE: trackData.TRACK_TOKEN_EXPIRE,
      FILESIZE_FLAC: trackData.FILESIZE_FLAC,
      FILESIZE_MP3_320: trackData.FILESIZE_MP3_320,
      FILESIZE_MP3_128: trackData.FILESIZE_MP3_128,
      FALLBACK: trackData.FALLBACK,
      SNG_ID: trackData.SNG_ID
    });

    // Log token expiration for debugging
    if (trackData.TRACK_TOKEN_EXPIRE) {
      const expireDate = new Date(trackData.TRACK_TOKEN_EXPIRE * 1000);
      console.log(`[DeezerQueueManager] Track token expires at: ${expireDate.toISOString()}`);
    }

    // Check if requested format is available
    const filesizeField = `FILESIZE_${requestedFormat}`;
    const filesize = trackData[filesizeField];
    const isAvailable = filesize && filesize !== "0" && filesize !== 0;

    if (!isAvailable && trackData.FALLBACK?.SNG_ID) {
      console.log(`[DeezerQueueManager] ${requestedFormat} not available (FILESIZE=${filesize}), using FALLBACK track ID: ${trackData.FALLBACK.SNG_ID}`);
      // Recursively fetch the fallback track
      return this.getValidTrackData(trackData.FALLBACK.SNG_ID.toString(), requestedFormat);
    }

    return trackData;
  }

  /**
   * Get download URL with alternative track fallback (Deemix-compliant)
   * Tries alternative track IDs (FALLBACK.SNG_ID) with same format before trying different formats
   * Matches Deemix's getPreferredBitrate logic for handling error 2002
   */
  private async getDownloadUrlWithAlternatives(
    trackId: string,
    requestedFormat: 'FLAC' | 'MP3_320' | 'MP3_128',
    licenseToken: string
  ): Promise<{ url: string; finalTrackId: string; finalFormat: string }> {
    console.log(`[DeezerQueueManager] Getting download URL with alternatives for track ${trackId}, format ${requestedFormat}`);

    // Fetch track data (handles filesize=0 fallback)
    let trackData = await this.getValidTrackData(trackId, requestedFormat);

    // Try to get download URL with current track token
    let result = await deezerAPI.getTrackDownloadUrl(trackData.TRACK_TOKEN, requestedFormat, licenseToken);

    // If error 2002 (insufficient rights) and has alternative track, try fallback track(s)
    while (!result.url && result.errorCode === 2002 && trackData.FALLBACK?.SNG_ID) {
      const fallbackId = trackData.FALLBACK.SNG_ID.toString();
      console.log(`[DeezerQueueManager] Error 2002 for track ${trackData.SNG_ID}, trying alternative track ID: ${fallbackId}`);

      // Fetch fallback track data (with fresh token)
      trackData = await this.getValidTrackData(fallbackId, requestedFormat);

      // Try to get download URL with fallback track token (same format)
      result = await deezerAPI.getTrackDownloadUrl(trackData.TRACK_TOKEN, requestedFormat, licenseToken);
    }

    // If we got a URL, return it
    if (result.url) {
      return { url: result.url, finalTrackId: trackData.SNG_ID, finalFormat: requestedFormat };
    }

    // If no URL after exhausting alternatives, throw error
    const errorMsg = result.errorMessage || 'Failed to get download URL';
    throw new Error(`${errorMsg} (code: ${result.errorCode || 'unknown'})`);
  }

  /**
   * Start processing the queue
   */
  async start(): Promise<void> {
    if (this.isProcessing) {
      console.log('[DeezerQueueManager] Already processing queue');
      return;
    }

    this.isProcessing = true;
    this.abortController = new AbortController();
    console.log('[DeezerQueueManager] Starting queue processor');

    // Clear any stale currentJob from previous session
    await setCurrentJob(null);

    try {
      await this.processQueue();
    } catch (error) {
      console.error('[DeezerQueueManager] Queue processing error:', error);
    } finally {
      this.isProcessing = false;
      this.abortController = null;
    }
  }

  /**
   * Stop processing the queue
   */
  stop(): void {
    console.log('[DeezerQueueManager] Stopping queue processor');
    this.isProcessing = false;
    if (this.abortController) {
      this.abortController.abort();
      this.abortController = null;
    }
  }

  /**
   * Main queue processing loop
   * Runs continuously while the app is open, waiting for new items
   */
  private async processQueue(): Promise<void> {
    console.log('[DeezerQueueManager] Queue processor started');

    while (this.isProcessing) {
      const queueState = get(downloadQueue);
      const nextItem = getNextQueuedItem(queueState);

      if (!nextItem) {
        // No items to process - wait and check again
        await new Promise(resolve => setTimeout(resolve, 500));
        continue;
      }

      console.log(`[DeezerQueueManager] Processing item: ${nextItem.title}`);

      // Set as current job
      await setCurrentJob(nextItem.id);
      await updateQueueItem(nextItem.id, { status: 'downloading' });

      try {
        // Process based on type
        if (nextItem.type === 'track') {
          await this.downloadSingleTrack(nextItem);
        } else if (nextItem.type === 'album' || nextItem.type === 'playlist') {
          await this.downloadCollection(nextItem);
        }

        // Mark as completed
        await updateQueueItem(nextItem.id, {
          status: 'completed',
          progress: 100
        });
      } catch (error) {
        console.error(`[DeezerQueueManager] Error downloading ${nextItem.title}:`, error);
        await updateQueueItem(nextItem.id, {
          status: 'failed',
          error: error instanceof Error ? error.message : 'Unknown error'
        });
      }

      // Clear current job
      await setCurrentJob(null);
    }

    console.log('[DeezerQueueManager] Queue processor stopped');
  }

  /**
   * Ensure track has cover art URL by fetching album data if needed
   * Reuses the same logic as addToQueue for consistency
   */
  private async ensureCoverUrl(track: DeezerTrack): Promise<void> {
    // Skip if already has cover URL
    if (track.albumCoverUrl) {
      return;
    }

    // Skip if no album ID to fetch with
    if (!track.albumId || track.albumId === 0) {
      console.log(`[DeezerQueueManager] Track "${track.title}" has no albumId, fetching track data...`);

      // Fetch track data to get album ID
      try {
        const trackData = await deezerAPI.getTrack(track.id.toString());
        if (trackData && trackData.ALB_ID) {
          track.albumId = parseInt(trackData.ALB_ID.toString(), 10);
        } else {
          console.warn(`[DeezerQueueManager] Could not get album ID for track "${track.title}"`);
          return;
        }
      } catch (error) {
        console.warn(`[DeezerQueueManager] Error fetching track data for "${track.title}":`, error);
        return;
      }
    }

    // Fetch album data for cover art URL
    try {
      const albumData = await deezerAPI.getAlbumData(track.albumId.toString());
      if (albumData?.ALB_PICTURE) {
        track.albumCoverUrl = `https://e-cdns-images.dzcdn.net/images/cover/${albumData.ALB_PICTURE}/500x500-000000-80-0-0.jpg`;
        track.albumCoverXlUrl = `https://e-cdns-images.dzcdn.net/images/cover/${albumData.ALB_PICTURE}/1000x1000-000000-80-0-0.jpg`;
        console.log(`[DeezerQueueManager] Fetched cover URL for "${track.title}"`);
      }
    } catch (error) {
      console.warn(`[DeezerQueueManager] Could not fetch album data for track "${track.title}":`, error);
    }
  }

  /**
   * Ensure track has lyrics by fetching if needed
   * Reuses the same logic as addToQueue for consistency
   */
  private async ensureLyrics(track: DeezerTrack): Promise<void> {
    // Skip if already has lyrics
    if (track.lyrics) {
      return;
    }

    // Fetch lyrics from Deezer
    try {
      const lyricsData = await deezerAPI.getLyrics(track.id.toString());

      if (lyricsData) {
        // Parse LRC format (synced lyrics)
        let syncLrc = '';
        if (lyricsData.LYRICS_SYNC_JSON) {
          for (const line of lyricsData.LYRICS_SYNC_JSON) {
            const text = line.line || '';
            const timestamp = line.lrc_timestamp || '[00:00.00]';
            syncLrc += `${timestamp}${text}\n`;
          }
        }

        track.lyrics = {
          sync: syncLrc || undefined,
          unsync: lyricsData.LYRICS_TEXT || undefined,
          syncID3: undefined
        };

        console.log(`[DeezerQueueManager] Fetched lyrics for "${track.title}"`);
      }
    } catch (error) {
      console.warn(`[DeezerQueueManager] Could not fetch lyrics for track "${track.title}":`, error);
    }
  }

  /**
   * Download a single track
   */
  private async downloadSingleTrack(item: QueueItem): Promise<void> {
    const track = item.downloadObject as DeezerTrack;
    const appSettings = get(settings);

    if (!appSettings.musicFolder) {
      throw new Error('Music folder not configured');
    }

    // Set ARL for authentication
    const authState = get(deezerAuth);
    if (!authState.arl) {
      throw new Error('Deezer ARL not found - please log in');
    }
    deezerAPI.setArl(authState.arl);

    // Ensure track has cover URL if cover art is enabled
    if (appSettings.embedCoverArt || appSettings.saveCoverToFolder) {
      await this.ensureCoverUrl(track);
    }

    // Ensure track has lyrics if lyrics are enabled
    if (appSettings.embedLyrics || appSettings.saveLrcFile) {
      await this.ensureLyrics(track);
    }

    // Get user data for license token
    const userData = await deezerAPI.getUserData();
    const licenseToken = userData.USER?.OPTIONS?.license_token;

    if (!licenseToken) {
      throw new Error('License token not found');
    }

    // Try to get download URL with alternative track fallback (error 2002 handling)
    let downloadURL: string | undefined;
    let finalTrackId: string | undefined;
    let finalFormat: string | undefined;

    try {
      const result = await this.getDownloadUrlWithAlternatives(
        track.id.toString(),
        appSettings.deezerFormat,
        licenseToken
      );
      downloadURL = result.url;
      finalTrackId = result.finalTrackId;
      finalFormat = result.finalFormat;
    } catch (error) {
      // If alternative track fallback failed and user wants format fallback, try different formats
      if (appSettings.deezerFallbackFormat !== 'none') {
        console.log(`[DeezerQueueManager] Alternative track fallback failed for "${track.title}", trying format fallback...`);

        const formatsToTry: ('FLAC' | 'MP3_320' | 'MP3_128')[] =
          appSettings.deezerFallbackFormat === 'highest'
            ? ['FLAC', 'MP3_320', 'MP3_128']
            : [appSettings.deezerFallbackFormat];

        let succeeded = false;
        for (const format of formatsToTry) {
          if (format === appSettings.deezerFormat) continue; // Skip already tried format

          try {
            console.log(`[DeezerQueueManager] Trying format ${format} for "${track.title}"...`);
            const result = await this.getDownloadUrlWithAlternatives(
              track.id.toString(),
              format,
              licenseToken
            );
            downloadURL = result.url;
            finalTrackId = result.finalTrackId;
            finalFormat = result.finalFormat;
            succeeded = true;
            break;
          } catch (formatError) {
            console.log(`[DeezerQueueManager] Format ${format} also failed for "${track.title}"`);
          }
        }

        if (!succeeded) {
          throw new Error('Failed to get download URL from Deezer - all alternatives exhausted');
        }
      } else {
        throw error;
      }
    }

    // These should be defined if we get here without throwing
    if (!downloadURL || !finalTrackId || !finalFormat) {
      throw new Error('Failed to get download URL - unexpected state');
    }

    // Update progress
    await updateQueueItem(item.id, {
      currentTrack: {
        title: track.title,
        artist: track.artist,
        progress: 0
      }
    });

    // Download the track (use finalTrackId for decryption - might be original or fallback track)
    const filePath = await downloadTrack(
      track,
      downloadURL,
      appSettings.musicFolder,
      finalFormat,
      (progress) => {
        // Update progress in queue
        updateQueueItem(item.id, {
          progress: progress.percentage,
          currentTrack: {
            title: track.title,
            artist: track.artist,
            progress: progress.percentage
          }
        });
      },
      0,
      finalTrackId
    );

    console.log(`[DeezerQueueManager] Downloaded: ${filePath}`);

    // Trigger incremental library sync for this track
    try {
      await syncTrackPaths([filePath]);
    } catch (error) {
      console.error('[DeezerQueueManager] Error syncing track to library:', error);
      // Non-fatal - track is downloaded, just not in database yet
    }
  }

  /**
   * Download a collection (album/playlist) with concurrency control
   */
  private async downloadCollection(item: QueueItem): Promise<void> {
    const tracks = item.downloadObject as DeezerTrack[];
    const appSettings = get(settings);
    const concurrency = appSettings.deezerConcurrency;

    console.log(`[DeezerQueueManager] Downloading collection with concurrency: ${concurrency}`);

    const results: (string | Error)[] = [];
    let completedCount = 0;
    let failedCount = 0;

    // Simple concurrent queue implementation
    const queue = [...tracks];
    const running: Promise<void>[] = [];

    const downloadNext = async (): Promise<void> => {
      const track = queue.shift();
      if (!track) return;

      try {
        await updateQueueItem(item.id, {
          currentTrack: {
            title: track.title,
            artist: track.artist,
            progress: 0
          }
        });

        // Ensure track has cover URL if cover art is enabled
        if (appSettings.embedCoverArt || appSettings.saveCoverToFolder) {
          await this.ensureCoverUrl(track);
        }

        // Ensure track has lyrics if lyrics are enabled
        if (appSettings.embedLyrics || appSettings.saveLrcFile) {
          await this.ensureLyrics(track);
        }

        const userData = await deezerAPI.getUserData();
        const licenseToken = userData.USER?.OPTIONS?.license_token;

        if (!licenseToken) {
          throw new Error('License token not found');
        }

        // Try to get download URL with alternative track fallback (error 2002 handling)
        let downloadURL: string | undefined;
        let finalTrackId: string | undefined;
        let finalFormat: string | undefined;

        try {
          const result = await this.getDownloadUrlWithAlternatives(
            track.id.toString(),
            appSettings.deezerFormat,
            licenseToken
          );
          downloadURL = result.url;
          finalTrackId = result.finalTrackId;
          finalFormat = result.finalFormat;
        } catch (error) {
          // If alternative track fallback failed and user wants format fallback, try different formats
          if (appSettings.deezerFallbackFormat !== 'none') {
            console.log(`[DeezerQueueManager] Alternative track fallback failed for "${track.title}", trying format fallback...`);

            const formatsToTry: ('FLAC' | 'MP3_320' | 'MP3_128')[] =
              appSettings.deezerFallbackFormat === 'highest'
                ? ['FLAC', 'MP3_320', 'MP3_128']
                : [appSettings.deezerFallbackFormat];

            let succeeded = false;
            for (const format of formatsToTry) {
              if (format === appSettings.deezerFormat) continue; // Skip already tried format

              try {
                console.log(`[DeezerQueueManager] Trying format ${format} for "${track.title}"...`);
                const result = await this.getDownloadUrlWithAlternatives(
                  track.id.toString(),
                  format,
                  licenseToken
                );
                downloadURL = result.url;
                finalTrackId = result.finalTrackId;
                finalFormat = result.finalFormat;
                succeeded = true;
                break;
              } catch (formatError) {
                console.log(`[DeezerQueueManager] Format ${format} also failed for "${track.title}"`);
              }
            }

            if (!succeeded) {
              throw new Error('Failed to get download URL from Deezer - all alternatives exhausted');
            }
          } else {
            throw error;
          }
        }

        // These should be defined if we get here without throwing
        if (!downloadURL || !finalTrackId || !finalFormat) {
          throw new Error('Failed to get download URL - unexpected state');
        }

        const filePath = await downloadTrack(
          track,
          downloadURL,
          appSettings.musicFolder!,
          finalFormat,
          (progress) => {
            // Update progress in queue
            updateQueueItem(item.id, {
              progress: progress.percentage,
              currentTrack: {
                title: track.title,
                artist: track.artist,
                progress: progress.percentage
              }
            });
          },
          0,
          finalTrackId
        );

        results.push(filePath);
        completedCount++;
      } catch (error) {
        console.error(`[DeezerQueueManager] Error downloading track ${track.title}:`, error);
        results.push(error as Error);
        failedCount++;
      }

      // Update progress
      const totalTracks = item.totalTracks;
      const progress = ((completedCount + failedCount) / totalTracks) * 100;

      await updateQueueItem(item.id, {
        progress,
        completedTracks: completedCount,
        failedTracks: failedCount
      });

      // Rate limiting: Add delay between downloads to avoid API throttling
      if (queue.length > 0) {
        await new Promise(resolve => setTimeout(resolve, 500));
        await downloadNext();
      }
    };

    // Start initial batch of concurrent downloads
    for (let i = 0; i < Math.min(concurrency, tracks.length); i++) {
      running.push(downloadNext());
    }

    // Wait for all downloads to complete
    await Promise.all(running);

    console.log(`[DeezerQueueManager] Collection complete: ${completedCount} succeeded, ${failedCount} failed`);

    // Trigger incremental library sync for all successfully downloaded tracks
    if (completedCount > 0) {
      try {
        const successfulPaths = results.filter(r => typeof r === 'string') as string[];
        await syncTrackPaths(successfulPaths);
        console.log(`[DeezerQueueManager] Synced ${successfulPaths.length} tracks to library`);
      } catch (error) {
        console.error('[DeezerQueueManager] Error syncing collection to library:', error);
        // Non-fatal - tracks are downloaded, just not in database yet
      }
    }
  }
}

// Singleton instance
export const deezerQueueManager = new DeezerQueueManager();