1 files changed, 131 insertions, 0 deletions
diff --git a/lib/simfile.dart b/lib/simfile.dart
new file mode 100644
index 0000000..102c989
--- /dev/null
+++ b/lib/simfile.dart
@@ -0,0 +1,131 @@
+import 'dart:ffi';
+import 'dart:io';
+
+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 path;
+  String? lines;
+
+  // tags of simfile
+  Map<String, String> tags = {};
+
+  Chart? chartSimplest;
+
+  Map<double, double> bpms = {};
+  double offset = 0;
+
+  Simfile(this.path);
+
+  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];
+
+    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);
+      }
+
+      double bpm = bpms.entries.first.value;
+
+      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;
+    }
+  }
+
+  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);
+  }
+
+  void load() {
+    lines = File(path).readAsStringSync();
+
+    RegExp commentsRegExp = RegExp(r'//.*$');
+    lines = lines?.replaceAll(commentsRegExp, '');
+    RegExp fieldDataRegExp = RegExp(r'#([^;]+):([^;]*);');
+
+    for (final fieldData in fieldDataRegExp.allMatches(lines!)) {
+      _parseTag(fieldData);
+    }
+  }
+}