import 'dart:io';
import 'dart:typed_data';

import 'package:path_provider/path_provider.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import '../models/song.dart';
import '../database/db_helper.dart';
import '../utils/audio_validator.dart';
import 'id3_reader.dart';
import '../services/melo_logger.dart';
import '../config/app_config.dart';

class MusikScanner {
  static final MusikScanner _instanz = MusikScanner._();
  factory MusikScanner() => _instanz;
  MusikScanner._();

  final DbHelper _db = DbHelper();
  int _neueSongs = 0;

  int get anzahlNeueSongs => _neueSongs;

  Future<bool> frageSpeicherZugriff() async {
    // App-interner Speicher (Cloud-Downloads) benötigt NIE Berechtigungen
    if (Platform.isIOS) return true;

    if (Platform.isAndroid) {
      // Android 13+: READ_MEDIA_AUDIO
      var status = await Permission.audio.status;
      if (!status.isGranted) status = await Permission.audio.request();
      if (status.isGranted) return true;

      // Fallback für Android 10 und älter
      var storageStatus = await Permission.storage.status;
      if (!storageStatus.isGranted) storageStatus = await Permission.storage.request();
      return storageStatus.isGranted;
    }

    return true;
  }

  Future<List<Song>> scanneMusikOrdner() async {
    _neueSongs = 0;
    final gefunden = <Song>[];
    final pfade = await _sammleMusikPfade();

    for (final pfad in pfade) {
      try {
        final file = File(pfad);
        if (!await file.exists()) continue;
        final stat = await file.stat();
        final tags = Id3Reader.lesen(pfad);

        // ── Magic-Byte-Prüfung ──
        final istKorrupt = !hatValideMagicBytes(file);
        if (istKorrupt) {
          MeloLogger().fehler('magic_bytes_scan', 'Ungültiger Audio-Header: $pfad');
        }

        // Cover-Bytes als Bilddatei speichern
        String? coverPfad;
        if (tags['cover'] != null && tags['cover'] is List<int>) {
          final bytes = tags['cover'] as List<int>;
          if (bytes.isNotEmpty) {
            try {
              final docDir = await getApplicationDocumentsDirectory();
              final coversDir = Directory('${docDir.path}/covers');
              if (!await coversDir.exists()) await coversDir.create(recursive: true);
              final fileHash = pfad.hashCode.abs();
              final coverFile = File('${coversDir.path}/cover_$fileHash.jpg');
              await coverFile.writeAsBytes(bytes);
              coverPfad = coverFile.path;
            } catch (e) {
              MeloLogger().fehler('cover_speichern', e);
            }
          }
        }

        gefunden.add(Song(
          titel: (tags['titel'] as String).isNotEmpty ? tags['titel'] : _dateiNameOhneEndung(pfad),
          kuenstler: (tags['kuenstler'] as String).isNotEmpty ? tags['kuenstler'] : 'Unbekannt',
          album: tags['album'] ?? '',
          jahr: _nichtLeer(tags['jahr']),
          genre: _nichtLeer(tags['genre']),
          track: _nichtLeer(tags['track']),
          dauerSekunden: await _ermittleDauer(pfad),
          dateiPfad: pfad,
          coverPfad: coverPfad,
          groesseBytes: stat.size,
          istHeruntergeladen: true,
          istKorrupt: istKorrupt,
          downloadQuelle: 'local',
        ));
      } catch (e) {
        MeloLogger().fehler('scanner_datei', e);
        continue;
      }
    }

    // In DB speichern
    final vorhandene = await _db.alleSongs();
    final vorhandenePfade = vorhandene.map((s) => s.dateiPfad).toSet();

    final neue = gefunden.where((s) => !vorhandenePfade.contains(s.dateiPfad)).toList();
    if (neue.isNotEmpty) {
      await _db.songsEinfuegen(neue);
      _neueSongs = neue.length;
    }

    // ── YouTube-Quell-URLs für Songs ohne ytUrl nachschlagen ──
    await _sucheYtUrls();

    return gefunden;
  }

  Future<List<String>> _sammleMusikPfade() async {
    final pfade = <String>{};
    // 1. PRIMÄR: App-interner + Downloads-Ordner
    try {
      final appDir = await getApplicationDocumentsDirectory();
      final internDir = Directory('${appDir.path}/music');
      if (await internDir.exists()) await _durchsucheOrdner(internDir, pfade);

      // Downloads/Melo (für Dateimanager sichtbar)
      if (Platform.isAndroid) {
        final dlDir = await getDownloadsDirectory();
        if (dlDir != null) {
          final meloDir = Directory('${dlDir.path}/Melo');
          if (await meloDir.exists()) await _durchsucheOrdner(meloDir, pfade);
        }
      }
    } catch (e) {
      MeloLogger().fehler('scanner_intern_pfad', e);
    }

    // 2. Externe System-Ordner (nur Android, nur wenn Berechtigung vorhanden)
    if (Platform.isAndroid) {
      final hatZugriff = await frageSpeicherZugriff();
      if (!hatZugriff) return pfade.toList();

      final ordner = <String>[
        '/storage/emulated/0/Music',
        '/storage/emulated/0/Download',
        '/storage/emulated/0/Musik',
        '/storage/emulated/0/Downloads',
        '/sdcard/Music',
        '/sdcard/Download',
      ];

      // Externen Speicherpfad NUR für App-eigene Daten, nicht ganz /storage
      try {
        final extern = await getExternalStorageDirectory();
        if (extern != null) {
          // Nur scannen wenn es ein spezifischer Unterordner ist (nicht Root)
          final externPath = extern.path;
          if (externPath.contains('Android/data') || externPath.contains('Melo')) {
            ordner.add(externPath);
          }
        }
      } catch (_) {}

      for (final ord in ordner) {
        try {
          final dir = Directory(ord);
          if (await dir.exists()) {
            await _durchsucheOrdner(dir, pfade);
          }
        } catch (e) {
          MeloLogger().fehler('scanner_ordner_zugriff_${ord.split('/').last}', e);
        }
      }
    }

    return pfade.toList();
  }

  Future<void> _durchsucheOrdner(Directory dir, Set<String> pfade, {int tiefe = 0}) async {
    if (tiefe > 4) return;
    try {
      final stream = dir.list(followLinks: false);
      await for (final entity in stream.handleError((_) {})) {
        if (entity is File) {
          final ext = entity.path.toLowerCase();
          if (ext.endsWith('.mp3') || ext.endsWith('.m4a') ||
              ext.endsWith('.flac') || ext.endsWith('.wav') ||
              ext.endsWith('.aac') || ext.endsWith('.ogg')) {
            pfade.add(entity.path);
          }
        } else if (entity is Directory) {
          await _durchsucheOrdner(entity, pfade, tiefe: tiefe + 1);
        }
      }
    } catch (e) {
      MeloLogger().fehler('scanner_durchsuchen_fehler', '$dir: $e');
    }
  }

  /// Leichtgewichtige Dauer-Ermittlung OHNE AudioPlayer (Issue #15).
  /// Parst Container-Header direkt aus der Datei – nur stdlib, kein neues Package:
  /// - MP3: MPEG-Frame-Header (Bitrate) → CBR-Schätzung
  /// - M4A: moov/mvhd-Box (Timescale + Duration)
  /// - FLAC: STREAMINFO (TotalSamples / SampleRate)
  /// - WAV: data-Chunk / ByteRate
  /// - OGG/AAC: 0 (überspringen, Dauer unbekannt)
  Future<int> _ermittleDauer(String pfad) async {
    try {
      final file = File(pfad);
      if (!await file.exists()) return 0;
      final size = await file.length();
      if (size < 16) return 0;

      final raf = await file.open();
      try {
        await raf.setPosition(0);
        final kopf = await raf.read(12);
        if (kopf.length < 4) return 0;

        // MP3: ID3v2-Tag oder direkter MPEG-Frame-Sync
        if (kopf[0] == 0x49 && kopf[1] == 0x44 && kopf[2] == 0x33) {
          return await _dauerMp3(raf, size, id3v2: true);
        }
        if (kopf[0] == 0xFF && (kopf[1] & 0xE0) == 0xE0) {
          return await _dauerMp3(raf, size, id3v2: false);
        }
        // FLAC: "fLaC"
        if (kopf[0] == 0x66 && kopf[1] == 0x4C &&
            kopf[2] == 0x61 && kopf[3] == 0x43) {
          return await _dauerFlac(raf);
        }
        // WAV: "RIFF"
        if (kopf[0] == 0x52 && kopf[1] == 0x49 &&
            kopf[2] == 0x46 && kopf[3] == 0x46) {
          return await _dauerWav(raf, size);
        }
        // M4A/AAC: ftyp-Box an Position 4
        if (kopf.length >= 8 &&
            kopf[4] == 0x66 && kopf[5] == 0x74 &&
            kopf[6] == 0x79 && kopf[7] == 0x70) {
          return await _dauerM4a(raf, size);
        }
        return 0; // OGG/AAC: überspringen
      } finally {
        await raf.close();
      }
    } catch (_) {
      return 0;
    }
  }

  // ── MP3: MPEG-Frame-Header (Bitraten-Tabellen, kbps) ──

  static const List<int> _mpeg1Bitraten = [
    // Index 0 = free-format (nicht unterstützt)
    0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320,
  ];
  static const List<int> _mpeg2Bitraten = [
    0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160,
  ];

  /// Parst einen MPEG-Audio-Frame-Header ab Position [i].
  /// Liefert (bitrateKbps, frameLen) oder null bei ungültigem Header.
  (int, int)? _parseMpegHeader(Uint8List d, int i) {
    if (i + 3 >= d.length) return null;
    if (d[i] != 0xFF) return null;
    if ((d[i + 1] & 0xE0) != 0xE0) return null;

    final versionBits = (d[i + 1] >> 3) & 0x03;
    final layerBits = (d[i + 1] >> 1) & 0x03;
    if (versionBits == 1) return null; // reserviert
    if (layerBits == 0) return null;   // reserviert

    final bitrateIdx = d[i + 2] >> 4;
    final sampleIdx = (d[i + 2] >> 2) & 0x03;
    final padding = (d[i + 2] >> 1) & 0x01;
    if (bitrateIdx == 15 || bitrateIdx == 0 || sampleIdx == 3) return null;

    final isMpeg1 = versionBits == 3;
    final layer1 = layerBits == 3; // Layer I
    final bitrate = (isMpeg1 ? _mpeg1Bitraten : _mpeg2Bitraten)[bitrateIdx];

    final sampleRate = isMpeg1
        ? (sampleIdx == 0 ? 44100 : sampleIdx == 1 ? 48000 : 32000)
        : versionBits == 2
            ? (sampleIdx == 0 ? 22050 : sampleIdx == 1 ? 24000 : 16000)
            : (sampleIdx == 0 ? 11025 : sampleIdx == 1 ? 12000 : 8000);

    final frameLen = layer1
        ? (12 * bitrate * 1000 ~/ sampleRate + padding) * 4
        : 144 * bitrate * 1000 ~/ sampleRate + padding;
    if (frameLen < 24) return null;
    return (bitrate, frameLen);
  }

  Future<int> _dauerMp3(RandomAccessFile raf, int dateiGroesse,
      {required bool id3v2}) async {
    // ID3v2-Tag überspringen (Syncsafe-Größe in Bytes 6-9)
    var start = 0;
    if (id3v2) {
      await raf.setPosition(0);
      final id3 = await raf.read(10);
      if (id3.length >= 10) {
        var tagSize = 0;
        for (var i = 6; i < 10; i++) {
          tagSize = (tagSize << 7) | (id3[i] & 0x7F);
        }
        start = 10 + tagSize;
      }
    }

    // Ersten gültigen Frame-Header suchen (max. 2 MB Scan für große Cover-Tags)
    const maxScan = 2 * 1024 * 1024;
    final scanBis = (start + maxScan < dateiGroesse) ? start + maxScan : dateiGroesse;
    var scanPos = start;
    var rest = Uint8List(0); // bis zu 3 Bytes Überlappung zwischen Chunks

    while (scanPos < scanBis) {
      await raf.setPosition(scanPos);
      final chunk = await raf.read(4096);
      if (chunk.isEmpty) break;
      final data = Uint8List.fromList([...rest, ...chunk]);

      for (var i = 0; i < data.length - 4; i++) {
        final header = _parseMpegHeader(data, i);
        if (header == null) continue;
        final abs = scanPos - rest.length + i;
        final frameLen = header.$2;
        // 2 Folge-Frames müssen ebenfalls Sync haben (False-Positive-Schutz)
        if (abs + 2 * frameLen > dateiGroesse) continue;
        if (!await _hatFrameSync(raf, abs + frameLen)) continue;
        if (!await _hatFrameSync(raf, abs + 2 * frameLen)) continue;

        final audioBytes = dateiGroesse - abs;
        if (audioBytes <= 0) return 0;
        // CBR-Schätzung: audioBytes * 8 Bit / Bitrate
        return audioBytes * 8 ~/ (header.$1 * 1000);
      }

      // Nächster Chunk mit 3-Byte-Überlappung
      final uLen = data.length > 3 ? 3 : data.length;
      rest = Uint8List.fromList(data.sublist(data.length - uLen));
      scanPos += chunk.length;
    }
    return 0;
  }

  Future<bool> _hatFrameSync(RandomAccessFile raf, int pos) async {
    if (pos < 0) return false;
    await raf.setPosition(pos);
    final b = await raf.read(2);
    return b.length == 2 && b[0] == 0xFF && (b[1] & 0xE0) == 0xE0;
  }

  // ── M4A: moov → mvhd (Timescale + Duration) ──

  Future<int> _dauerM4a(RandomAccessFile raf, int dateiGroesse) async {
    var pos = 0;
    while (pos + 8 <= dateiGroesse) {
      await raf.setPosition(pos);
      final kopf = await raf.read(8);
      if (kopf.length < 8) break;
      var boxGroesse = _u32(kopf, 0);
      final typ = String.fromCharCodes(kopf.sublist(4, 8));
      if (boxGroesse == 1) {
        // 64-Bit-Größe (nur bei >4GB-Dateien relevant)
        final ext = await raf.read(8);
        if (ext.length < 8) break;
        final high = _u32(ext, 0);
        boxGroesse = high > 0 ? dateiGroesse - pos : _u32(ext, 4);
      } else if (boxGroesse == 0) {
        boxGroesse = dateiGroesse - pos; // Box reicht bis EOF
      }
      if (boxGroesse < 8) break;
      if (typ == 'moov') {
        return await _dauerMvhd(raf, pos + 8, boxGroesse - 8);
      }
      pos += boxGroesse;
    }
    return 0;
  }

  Future<int> _dauerMvhd(RandomAccessFile raf, int start, int laenge) async {
    final ende = start + laenge;
    var pos = start;
    while (pos + 8 <= ende) {
      await raf.setPosition(pos);
      final kopf = await raf.read(8);
      if (kopf.length < 8) break;
      var boxGroesse = _u32(kopf, 0);
      final typ = String.fromCharCodes(kopf.sublist(4, 8));
      if (boxGroesse == 0) boxGroesse = ende - pos;
      if (boxGroesse < 8) break;
      if (typ == 'mvhd') {
        await raf.setPosition(pos + 8);
        final payload = await raf.read(32);
        if (payload.length < 20) return 0;
        final version = payload[0];
        if (version == 1) {
          if (payload.length < 32) return 0;
          final timescale = _u32(payload, 20);
          final duration = _u64(payload, 24);
          if (timescale == 0) return 0;
          return duration ~/ timescale;
        }
        final timescale = _u32(payload, 12);
        final duration = _u32(payload, 16);
        if (timescale == 0) return 0;
        return duration ~/ timescale;
      }
      pos += boxGroesse;
    }
    return 0;
  }

  // ── FLAC: STREAMINFO (TotalSamples / SampleRate) ──

  Future<int> _dauerFlac(RandomAccessFile raf) async {
    await raf.setPosition(4);
    final blockKopf = await raf.read(4);
    if (blockKopf.length < 4) return 0;
    final blockTyp = blockKopf[0] & 0x7F;
    final blockLen = (blockKopf[1] << 16) | (blockKopf[2] << 8) | blockKopf[3];
    if (blockTyp != 0 || blockLen < 18) return 0; // STREAMINFO erwartet
    await raf.setPosition(8);
    final d = await raf.read(blockLen);
    if (d.length < 18) return 0;
    final sampleRate = (d[10] << 12) | (d[11] << 4) | (d[12] >> 4);
    final totalSamples = ((d[13] & 0x0F) << 32) |
        (d[14] << 24) | (d[15] << 16) | (d[16] << 8) | d[17];
    if (sampleRate == 0) return 0;
    return totalSamples ~/ sampleRate;
  }

  // ── WAV: data-Chunk / ByteRate ──

  Future<int> _dauerWav(RandomAccessFile raf, int dateiGroesse) async {
    // fmt-Chunk: ByteRate liegt bei Offset 28 (nach RIFF+WAVE+fmt -Header)
    await raf.setPosition(24);
    final b = await raf.read(8);
    if (b.length < 8) return 0;
    final byteRate = _u32le(b, 4);

    // data-Chunk finden (Chunks word-aligned)
    var pos = 12;
    while (pos + 8 <= dateiGroesse) {
      await raf.setPosition(pos);
      final kopf = await raf.read(8);
      if (kopf.length < 8) break;
      final size = _u32le(kopf, 4);
      final typ = String.fromCharCodes(kopf.sublist(0, 4));
      if (typ == 'data') {
        if (byteRate == 0) return 0;
        return size ~/ byteRate;
      }
      if (size < 8) break;
      pos += 8 + size + (size % 2);
    }
    return 0;
  }

  // ── Byte-Helfer ──

  static int _u32(List<int> b, int o) =>
      (b[o] << 24) | (b[o + 1] << 16) | (b[o + 2] << 8) | b[o + 3];

  static int _u32le(List<int> b, int o) =>
      (b[o + 3] << 24) | (b[o + 2] << 16) | (b[o + 1] << 8) | b[o];

  static int _u64(List<int> b, int o) =>
      (b[o] << 56) | (b[o + 1] << 48) | (b[o + 2] << 40) | (b[o + 3] << 32) |
      (b[o + 4] << 24) | (b[o + 5] << 16) | (b[o + 6] << 8) | b[o + 7];

  String _dateiNameOhneEndung(String pfad) {
    final name = pfad.split('/').last;
    final dot = name.lastIndexOf('.');
    return dot > 0 ? name.substring(0, dot) : name;
  }

  String? _nichtLeer(dynamic wert) {
    if (wert == null) return null;
    final s = wert.toString().trim();
    return s.isEmpty ? null : s;
  }

  /// Sucht YouTube-Quell-URLs für Songs ohne ytUrl (max 50 pro Scan, 1/s Rate-Limit)
  Future<void> _sucheYtUrls() async {
    const maxSuchanfragen = 50;
    const suchUrlBasis = 'https://yt.baka-net.de/api/search';

    final songsOhneUrl = await _db.songsOhneYtUrl(limit: maxSuchanfragen);
    if (songsOhneUrl.isEmpty) return;

    int gefunden = 0;
    for (final song in songsOhneUrl) {
      if (gefunden >= maxSuchanfragen) break;

      try {
        final query = '${song.kuenstler} ${song.titel}';
        final url = '$suchUrlBasis?q=${Uri.encodeQueryComponent(query)}';

        final antwort = await http.get(
          Uri.parse(url),
          headers: {'X-API-Key': AppConfig.ytProxyApiKey},
        ).timeout(
          const Duration(seconds: 10),
        );

        if (antwort.statusCode == 200) {
          final daten = jsonDecode(antwort.body);
          if (daten is List && daten.isNotEmpty) {
            final erstes = daten[0];
            final ytUrl = erstes['url'] as String?;
            if (ytUrl != null && ytUrl.isNotEmpty) {
              await _db.ytUrlAktualisieren(song.id!, ytUrl);
              gefunden++;
              MeloLogger().zustand('yt_suche_treffer', {
                'song_id': song.id,
                'titel': song.titel,
                'yt_url': ytUrl,
              });
            }
          }
        }
      } catch (e) {
        MeloLogger().fehler('yt_suche_fehler', '${song.titel}: $e');
      }

      // Rate-Limit: 1 Anfrage pro Sekunde
      await Future.delayed(const Duration(seconds: 1));
    }

    if (gefunden > 0) {
      MeloLogger().zustand('yt_suche_abschluss', {'gefunden': gefunden});
    }
  }
}