SpotiFLAC-Mobile/lib/utils/audio_conversion_utils.dart

const List<String> audioConversionTargetFormats = [
  'ALAC',
  'FLAC',
  'WAV',
  'AIFF',
  'AAC',
  'MP3',
  'Opus',
];

const List<int> losslessConversionSampleRateOptions = [
  192000,
  96000,
  48000,
  44100,
];

const List<int> losslessConversionBitDepthOptions = [16, 24];

List<int> availableLosslessBitDepthOptions(int? sourceBitDepth) {
  if (sourceBitDepth == null || sourceBitDepth <= 0) {
    return losslessConversionBitDepthOptions;
  }
  return losslessConversionBitDepthOptions
      .where((depth) => depth < sourceBitDepth)
      .toList();
}

List<int> availableLosslessSampleRateOptions(int? sourceSampleRate) {
  if (sourceSampleRate == null || sourceSampleRate <= 0) {
    return losslessConversionSampleRateOptions;
  }
  return losslessConversionSampleRateOptions
      .where((rate) => rate < sourceSampleRate)
      .toList();
}

int? lowestKnownPositiveInt(Iterable<int?> values) {
  int? lowest;
  for (final value in values) {
    if (value == null || value <= 0) continue;
    if (lowest == null || value < lowest) {
      lowest = value;
    }
  }
  return lowest;
}

class LosslessConversionQuality {
  final int? maxBitDepth;
  final int? maxSampleRate;

  const LosslessConversionQuality({this.maxBitDepth, this.maxSampleRate});

  bool get hasCaps => maxBitDepth != null || maxSampleRate != null;

  int? effectiveBitDepth(int? sourceBitDepth) {
    if (maxBitDepth == null) return sourceBitDepth;
    if (sourceBitDepth == null || sourceBitDepth <= 0) return maxBitDepth;
    return sourceBitDepth > maxBitDepth! ? maxBitDepth : sourceBitDepth;
  }

  int? effectiveSampleRate(int? sourceSampleRate) {
    if (maxSampleRate == null) return sourceSampleRate;
    if (sourceSampleRate == null || sourceSampleRate <= 0) {
      return maxSampleRate;
    }
    return sourceSampleRate > maxSampleRate! ? maxSampleRate : sourceSampleRate;
  }
}

bool isLosslessConversionTarget(String targetFormat) {
  final normalized = targetFormat.trim().toLowerCase();
  return normalized == 'alac' ||
      normalized == 'flac' ||
      normalized == 'wav' ||
      normalized == 'aiff' ||
      normalized == 'aif';
}

bool isLosslessConversionSource(String sourceFormat) {
  switch (sourceFormat.trim().toUpperCase()) {
    case 'FLAC':
    case 'ALAC':
    case 'M4A':
    case 'WAV':
    case 'AIFF':
    case 'AIF':
      return true;
    default:
      return false;
  }
}

bool canConvertAudioFormat({
  required String sourceFormat,
  required String targetFormat,
}) {
  if (sourceFormat.trim().toUpperCase() == targetFormat.trim().toUpperCase()) {
    return false;
  }
  if (isLosslessConversionTarget(targetFormat) &&
      !isLosslessConversionSource(sourceFormat)) {
    return false;
  }
  return true;
}

String? convertibleAudioSourceFormat({
  String? storedFormat,
  String? filePath,
  String? fileName,
}) {
  final fromStored = _convertibleAudioFormatLabel(storedFormat);
  if (fromStored != null) return fromStored;

  final name = (fileName != null && fileName.trim().isNotEmpty)
      ? fileName
      : filePath;
  if (name == null || name.trim().isEmpty) return null;

  final normalizedName = name.trim().toLowerCase();
  final dotIndex = normalizedName.lastIndexOf('.');
  if (dotIndex < 0 || dotIndex == normalizedName.length - 1) {
    return null;
  }
  return _convertibleAudioFormatLabel(normalizedName.substring(dotIndex + 1));
}

String? _convertibleAudioFormatLabel(String? rawFormat) {
  final format = rawFormat?.trim().toLowerCase();
  if (format == null || format.isEmpty) return null;

  switch (format) {
    case 'flac':
      return 'FLAC';
    case 'alac':
      return 'ALAC';
    case 'wav':
    case 'wave':
      return 'WAV';
    case 'aiff':
    case 'aif':
    case 'aifc':
      return 'AIFF';
    case 'm4a':
    case 'mp4':
      return 'M4A';
    case 'aac':
    case 'mp4a':
      return 'AAC';
    case 'mp3':
      return 'MP3';
    case 'opus':
    case 'ogg':
      return 'Opus';
    case 'eac3':
    case 'ec-3':
      return 'EAC3';
    case 'ac3':
    case 'ac-3':
      return 'AC3';
    case 'ac4':
    case 'ac-4':
      return 'AC4';
    default:
      return null;
  }
}

String losslessBitDepthLabel(int? bitDepth) {
  return bitDepth == null ? 'Original' : '$bitDepth-bit';
}

String losslessSampleRateLabel(int? sampleRate) {
  if (sampleRate == null) return 'Original';
  final khz = sampleRate / 1000;
  final precision = sampleRate % 1000 == 0 ? 0 : 1;
  return '${khz.toStringAsFixed(precision)} kHz';
}

String losslessQualityLabel(LosslessConversionQuality quality) {
  final parts = <String>[];
  if (quality.maxBitDepth != null) {
    parts.add(losslessBitDepthLabel(quality.maxBitDepth));
  }
  if (quality.maxSampleRate != null) {
    parts.add(losslessSampleRateLabel(quality.maxSampleRate));
  }
  return parts.isEmpty ? 'Original quality' : parts.join(' / ');
}

String convertedAudioQualityLabel({
  required String targetFormat,
  required String bitrate,
  LosslessConversionQuality losslessQuality = const LosslessConversionQuality(),
  int? actualBitDepth,
  int? actualSampleRate,
}) {
  final upper = targetFormat.toUpperCase();
  if (isLosslessConversionTarget(targetFormat)) {
    if (actualBitDepth != null &&
        actualBitDepth > 0 &&
        actualSampleRate != null &&
        actualSampleRate > 0) {
      return '$upper ${losslessBitDepthLabel(actualBitDepth)}/${losslessSampleRateLabel(actualSampleRate)}';
    }
    if (losslessQuality.hasCaps) {
      return '$upper ${losslessQualityLabel(losslessQuality)}';
    }
    return '$upper Lossless';
  }
  return '$upper ${bitrate.trim().toLowerCase()}';
}

int? readPositiveAudioInt(Object? value) {
  if (value is num) {
    final intValue = value.toInt();
    return intValue > 0 ? intValue : null;
  }
  final parsed = int.tryParse(value?.toString() ?? '');
  return parsed != null && parsed > 0 ? parsed : null;
}

String normalizedConvertedAudioFormat(String targetFormat) {
  return targetFormat.trim().toLowerCase();
}

/// Returns the output file extension (with dot) and MIME type for a conversion
/// target format. Used when creating the converted file via SAF so WAV/AIFF and
/// the other formats get the correct extension + MIME.
({String ext, String mime}) convertTargetExtAndMime(String targetFormat) {
  switch (targetFormat.trim().toLowerCase()) {
    case 'opus':
      return (ext: '.opus', mime: 'audio/opus');
    case 'alac':
    case 'aac':
      return (ext: '.m4a', mime: 'audio/mp4');
    case 'flac':
      return (ext: '.flac', mime: 'audio/flac');
    case 'wav':
      return (ext: '.wav', mime: 'audio/wav');
    case 'aiff':
    case 'aif':
      return (ext: '.aiff', mime: 'audio/aiff');
    default:
      return (ext: '.mp3', mime: 'audio/mpeg');
  }
}

int? convertedAudioBitrateKbps({
  required String targetFormat,
  required String bitrate,
}) {
  if (isLosslessConversionTarget(targetFormat)) return null;
  final match = RegExp(r'(\d+)').firstMatch(bitrate);
  return match != null ? int.tryParse(match.group(1)!) : null;
}