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feat(key_signature): ✨ add incrementBy method #428

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Mar 7, 2024
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feat(key_signature): ✨ add incrementBy method #428

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21 changes: 21 additions & 0 deletions lib/src/key/key_signature.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -139,6 +139,27 @@ final class KeySignature implements Comparable<KeySignature> {

static const _noteNotation = EnglishNoteNotation(showNatural: true);

/// Returns a new [KeySignature] incrementing its fifths [distance].
///
/// Example:
/// ```dart
/// KeySignature.empty.incrementBy(1) == KeySignature([Note.f.sharp])
///
/// KeySignature([Note.f.sharp, Note.c.sharp]).incrementBy(3)
/// == KeySignature.fromDistance(5)
///
/// KeySignature.fromDistance(-3).incrementBy(-1)
/// == KeySignature([Note.b.flat, Note.e.flat])
///
/// KeySignature([Note.e.flat]).incrementBy(1) == null
/// ```
KeySignature? incrementBy(int distance) {
final cachedDistance = this.distance;
if (cachedDistance == null) return null;

return KeySignature.fromDistance(cachedDistance.incrementBy(distance));
}

@override
String toString() => '$distance (${notes.map(
(note) => note.toString(system: _noteNotation),
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21 changes: 21 additions & 0 deletions test/src/key/key_signature_test.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -251,6 +251,27 @@ void main() {
});
});

group('.incrementBy()', () {
test('returns a new KeyGignature increasing the fifths distance', () {
expect(KeySignature.empty.incrementBy(-1), KeySignature([Note.b.flat]));
expect(KeySignature.empty.incrementBy(0), KeySignature.empty);
expect(KeySignature.empty.incrementBy(1), KeySignature([Note.f.sharp]));

expect(
KeySignature([Note.f.sharp, Note.c.sharp]).incrementBy(3),
KeySignature.fromDistance(5),
);
expect(
KeySignature.fromDistance(-3).incrementBy(-1),
KeySignature([Note.b.flat, Note.e.flat]),
);
});

test('returns null when this KeySignature is not canonical', () {
expect(KeySignature([Note.e.flat]).incrementBy(1), isNull);
});
});

group('.toString()', () {
test('returns the string representation of this KeySignature', () {
expect(
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