1 files changed, 175 insertions, 0 deletions
diff --git a/lib/utils/simfile.dart b/lib/utils/simfile.dart
new file mode 100644
index 0000000..71613a9
--- /dev/null
+++ b/lib/utils/simfile.dart
@@ -0,0 +1,175 @@
+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;
+  }
+}