feat(scale): add class and fromNote method

.vscode/settings.json

@@ -1,6 +1,6 @@
 {
   "cSpell.ignoreWords": ["music"],
-  "cSpell.words": ["helmholtz"],
+  "cSpell.words": ["helmholtz", "octatonic"],
   "editor.unicodeHighlight.allowedCharacters": {
     "′": true
   }

lib/music_notes.dart

@@ -23,6 +23,7 @@ part 'src/note/enharmonic_note.dart';
 part 'src/note/note.dart';
 part 'src/note/notes.dart';
 part 'src/note/positioned_note.dart';
+part 'src/scale/scale.dart';
 part 'src/tonality/key_signature.dart';
 part 'src/tonality/modes.dart';
 part 'src/tonality/tonality.dart';

lib/src/scale/scale.dart

@@ -0,0 +1,99 @@
+part of '../../music_notes.dart';
+
+class Scale {
+  /// The interval steps that define the scale.
+  final List<Interval> intervalSteps;
+
+  /// Creates a new [Scale] from [intervalSteps].
+  const Scale(this.intervalSteps);
+
+  static const major = Scale([
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+  ]);
+  static const naturalMinor = Scale([
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.majorSecond,
+  ]);
+  static const harmonicMinor = Scale([
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.augmentedSecond,
+  ]);
+  static const melodicMinor = Scale([
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+  ]);
+
+  static const chromatic = Scale([
+    Interval.augmentedUnison,
+    Interval.minorSecond,
+    Interval.augmentedUnison,
+    Interval.minorSecond,
+    Interval.minorSecond,
+    Interval.augmentedUnison,
+    Interval.minorSecond,
+    Interval.augmentedUnison,
+    Interval.minorSecond,
+    Interval.augmentedUnison,
+    Interval.minorSecond,
+  ]);
+  static const tones = Scale([
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.majorSecond,
+  ]);
+
+  static const pentatonic = Scale([
+    Interval.majorSecond,
+    Interval.majorSecond,
+    Interval.minorThird,
+    Interval.majorSecond,
+  ]);
+  static const octatonic = Scale([
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.majorSecond,
+    Interval.minorSecond,
+    Interval.majorSecond,
+  ]);
+
+  /// Returns the scale of notes starting from [note].
+  ///
+  /// Example:
+  /// ```dart
+  /// Scale.major.fromNote(Note.c)
+  ///   == const [Note.c, Note.d, Note.e, Note.f, Note.g, Note.a, Note.b]
+  ///
+  /// Scale.naturalMinor.fromNote(Note.a)
+  ///   == const [Note.a, Note.b, Note.c, Note.d, Note.e, Note.f, Note.g]
+  ///
+  /// Scale.melodicMinor.fromNote(Note.c)
+  ///   == const [Note.c, Note.d, Note.eFlat, Note.f, Note.g, Note.a, Note.b]
+  /// ```
+  List<Note> fromNote(Note note) =>
+      intervalSteps.fold([note], (scaleNotes, interval) {
+        final lastNote = scaleNotes.lastOrNull ?? note;
+
+        return [...scaleNotes, lastNote.transposeBy(interval)];
+      });
+}

test/src/main.dart

@@ -10,6 +10,7 @@ import 'note/enharmonic_note_test.dart' as enharmonic_note_test;
 import 'note/note_test.dart' as note_test;
 import 'note/notes_test.dart' as notes_test;
 import 'note/positioned_note_test.dart' as positioned_note_test;
+import 'scale/scale_test.dart' as scale_test;
 import 'tonality/key_signature_test.dart' as key_signature_test;
 import 'tonality/modes_test.dart' as modes_test;
 import 'tonality/tonality_test.dart' as tonality_test;
@@ -26,6 +27,7 @@ void main() {
   note_test.main();
   notes_test.main();
   positioned_note_test.main();
+  scale_test.main();
   key_signature_test.main();
   modes_test.main();
   tonality_test.main();

test/src/scale/scale_test.dart

@@ -0,0 +1,167 @@
+import 'package:music_notes/music_notes.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Scale', () {
+    group('.fromNote()', () {
+      test('should return the major scale notes starting from Note', () {
+        expect(
+          Scale.major.fromNote(Note.aFlat),
+          const [
+            Note.aFlat,
+            Note.bFlat,
+            Note.c,
+            Note.dFlat,
+            Note.eFlat,
+            Note.f,
+            Note.g,
+          ],
+        );
+        expect(
+          Scale.major.fromNote(Note.f),
+          const [Note.f, Note.g, Note.a, Note.bFlat, Note.c, Note.d, Note.e],
+        );
+        expect(
+          Scale.major.fromNote(Note.c),
+          const [Note.c, Note.d, Note.e, Note.f, Note.g, Note.a, Note.b],
+        );
+        expect(
+          Scale.major.fromNote(Note.d),
+          const [
+            Note.d,
+            Note.e,
+            Note.fSharp,
+            Note.g,
+            Note.a,
+            Note.b,
+            Note.cSharp,
+          ],
+        );
+      });
+
+      test(
+        'should return the natural minor scale notes starting from Note',
+        () {
+          expect(
+            Scale.naturalMinor.fromNote(Note.dSharp),
+            const [
+              Note.dSharp,
+              Note(Notes.e, Accidental.sharp),
+              Note.fSharp,
+              Note.gSharp,
+              Note.aSharp,
+              Note.b,
+              Note.cSharp,
+            ],
+          );
+          expect(
+            Scale.naturalMinor.fromNote(Note.d),
+            const [Note.d, Note.e, Note.f, Note.g, Note.a, Note.bFlat, Note.c],
+          );
+        },
+      );
+
+      test(
+        'should return the harmonic minor scale notes starting from Note',
+        () {
+          expect(
+            Scale.harmonicMinor.fromNote(Note.bFlat),
+            const [
+              Note.bFlat,
+              Note.c,
+              Note.dFlat,
+              Note.eFlat,
+              Note.f,
+              Note.gFlat,
+              Note.a,
+            ],
+          );
+          expect(
+            Scale.harmonicMinor.fromNote(Note.d),
+            const [
+              Note.d,
+              Note.e,
+              Note.f,
+              Note.g,
+              Note.a,
+              Note.bFlat,
+              Note.cSharp,
+            ],
+          );
+        },
+      );
+
+      test(
+        'should return the melodic minor scale notes starting from Note',
+        () {
+          expect(
+            Scale.melodicMinor.fromNote(Note.d),
+            const [
+              Note.d,
+              Note.e,
+              Note.f,
+              Note.g,
+              Note.a,
+              Note.b,
+              Note.cSharp,
+            ],
+          );
+          expect(
+            Scale.melodicMinor.fromNote(Note.gSharp),
+            const [
+              Note.gSharp,
+              Note.aSharp,
+              Note.b,
+              Note.cSharp,
+              Note.dSharp,
+              Note(Notes.e, Accidental.sharp),
+              Note(Notes.f, Accidental.doubleSharp),
+            ],
+          );
+        },
+      );
+
+      test('should return the tones scale notes starting from Note', () {
+        expect(
+          Scale.tones.fromNote(Note.c),
+          const [Note.c, Note.d, Note.e, Note.fSharp, Note.gSharp, Note.aSharp],
+        );
+        expect(
+          Scale.tones.fromNote(Note.dFlat),
+          const [Note.dFlat, Note.eFlat, Note.f, Note.g, Note.a, Note.b],
+        );
+        expect(
+          Scale.tones.fromNote(Note.cSharp),
+          const [
+            Note.cSharp,
+            Note.dSharp,
+            Note(Notes.e, Accidental.sharp),
+            Note(Notes.f, Accidental.doubleSharp),
+            Note(Notes.g, Accidental.doubleSharp),
+            Note(Notes.a, Accidental.doubleSharp),
+          ],
+        );
+      });
+
+      test('should return the chromatic scale notes starting from Note', () {
+        expect(
+          Scale.chromatic.fromNote(Note.c),
+          const [
+            Note.c,
+            Note.cSharp,
+            Note.d,
+            Note.dSharp,
+            Note.e,
+            Note.f,
+            Note.fSharp,
+            Note.g,
+            Note.gSharp,
+            Note.a,
+            Note.aSharp,
+            Note.b,
+          ],
+        );
+      });
+    });
+  });
+}