Sense_the_Rhythm/lib/utils/simfile.dart

import 'dart:io';

import 'package:audioplayers/audioplayers.dart';

enum Difficulty { Beginner, Easy, Medium, Hard, Challenge, Edit }

// These are the standard note values:
//
//     0 – No note
//     1 – Normal note
//     2 – Hold head
//     3 – Hold/Roll tail
//     4 – Roll head
//     M – Mine (or other negative note)
//
// Later versions of StepMania accept other note values which may not work in older versions:
//
//     K – Automatic keysound
//     L – Lift note
//     F – Fake note

RegExp noteTypes = RegExp(r'^([012345MKLF]+)\s*([,;])?');

class Chart {
  String? chartType;
  // Description/author
  String? author;
  // Difficulty (one of Beginner, Easy, Medium, Hard, Challenge, Edit)
  Difficulty? difficulty;
  // Numerical meter
  int? numericalMeter;
  // Groove radar values, generated by the program
  String? radarValues;

  List<List<String>>? measures;

  Map<double, String> beats = {};
}

class Simfile {
  String? directoryPath;
  String simfilePath;
  String? audioPath;
  String? bannerPath;
  String? lines;

  Duration? duration;
  // tags of simfile
  Map<String, String> tags = {};

  Chart? chartSimplest;

  Map<double, double> bpms = {};
  double offset = 0;

  Simfile(this.simfilePath);

  /// parses a chart tag with metadata [keys] and note data [value]
  void _parseChart({required List<String> keys, required String value}) {
    Chart chart = Chart();
    chart.chartType = keys[1];
    chart.author = keys[2];
    chart.difficulty = Difficulty.values.byName(keys[3]);
    chart.numericalMeter = int.parse(keys[4]);
    chart.radarValues = keys[5];

    // find simplest chart
    if (chartSimplest == null ||
        (chart.difficulty!.index <= chartSimplest!.difficulty!.index &&
            chart.numericalMeter! <= chartSimplest!.numericalMeter!)) {
      List<List<String>> measures = [];
      for (final measureRaw in value.split(',')) {
        List<String> measure = [];
        for (final noteRaw in measureRaw.split('\n')) {
          String note = noteRaw.trim();
          if (noteTypes.hasMatch(note)) {
            measure.add(note);
          }
        }
        measures.add(measure);
      }

      // for now only use the first bpm value
      double bpm = bpms.entries.first.value;

      // calculate timing for all notes based on offset, bpm and measure
      for (final (measureIndex, measure) in measures.indexed) {
        for (final (noteIndex, noteData) in measure.indexed) {
          double beat = measureIndex * 4.0 +
              (noteIndex.toDouble() / measure.length) * 4.0;
          double minutesPerBeat = 1.0 / bpm;
          double offsetMinutes = offset / 60.0;
          chart.beats[beat * minutesPerBeat + offsetMinutes] = noteData;
        }
      }

      chart.measures = measures;
      chartSimplest = chart;
    }
  }

  /// parse a tag based on a regex match [fieldData] and parsing the value based
  /// on the key
  void _parseTag(RegExpMatch fieldData) {
    List<String> keys =
        fieldData[1]!.split(':').map((key) => key.trim()).toList();
    String value = fieldData[2]!;

    if (keys[0] == "BPMS") {
      for (final pairRaw in value.split(',')) {
        List<String> pair = pairRaw.split('=');
        if (pair.length != 2) {
          continue;
        }
        double time = double.parse(pair[0]);
        double bpm = double.parse(pair[1]);
        bpms[time] = bpm;
      }
    }

    if (keys[0] == "OFFSET") {
      offset = double.parse(value);
    }

    if (keys[0] != "NOTES") {
      tags[keys[0]] = value;
      return;
    }
    _parseChart(keys: keys, value: value);
  }

  /// load the simfile
  Future<bool> load() async {
    directoryPath = File(simfilePath).parent.path;
    lines = File(simfilePath).readAsStringSync();
    
    // remove comments
    RegExp commentsRegExp = RegExp(r'//.*$');
    lines = lines?.replaceAll(commentsRegExp, '');
    // find all tags
    RegExp fieldDataRegExp = RegExp(r'#([^;]+):([^;]*);');

    // parse all tags
    for (final fieldData in fieldDataRegExp.allMatches(lines!)) {
      try {
        _parseTag(fieldData);
      } catch (err) {
        return false;
      }
    }

    // searching for audio and banned in the directory is more robust than using
    // values from metadata as they are wrong more often
    for (FileSystemEntity entity in Directory(directoryPath!).listSync()) {
      if (entity.path.endsWith('.ogg')) {
        audioPath = entity.path;
      }
      if (entity.path.endsWith('anner.png')) {
        bannerPath = entity.path;
      }
    }

    // dont use this simfile of files are missing
    if (audioPath == null) return false;
    if (bannerPath == null) return false;

    // get duration from audio
    AudioPlayer audioplayer = AudioPlayer();
    await audioplayer.setSource(DeviceFileSource(audioPath!));
    duration = await audioplayer.getDuration();
    audioplayer.dispose();

    return true;
  }
}