feat(mode)!: use brightness as the Dorian Brightness Quotient (#83)

* feat(mode)!: use `brightness` as the Dorian Brightness Quotient

* feat(mode): add `ModalMode.mirrored` getter

.vscode/settings.json

@@ -3,6 +3,7 @@
   "cSpell.words": [
     "dorian",
     "helmholtz",
+    "heptatonic",
     "ionian",
     "locrian",
     "lydian",

lib/src/tonality/mode.dart

@@ -6,6 +6,13 @@ part of '../../music_notes.dart';
 /// See [Mode (music)](https://en.wikipedia.org/wiki/Mode_(music)).
 abstract class Mode implements Enum, Comparable<Mode> {
   Scale get scale;
+
+  /// The [Dorian Brightness Quotient](https://mynewmicrophone.com/dorian-brightness-quotient)
+  /// is a number we assign to a heptatonic scale that tells us how bright or
+  /// dark the scale is relative to [ModalMode.dorian].
+  ///
+  /// The lower the number, the darker the scale. The higher the number,
+  /// the brighter the scale.
   int get brightness;
 
   /// [Comparator] for [Mode]s.
@@ -17,10 +24,10 @@ abstract class Mode implements Enum, Comparable<Mode> {
 
 enum TonalMode implements Mode {
   /// See [Major mode](https://en.wikipedia.org/wiki/Major_mode).
-  major(Scale.major, brightness: 0),
+  major(Scale.major, brightness: 2),
 
   /// See [Minor mode](https://en.wikipedia.org/wiki/Minor_mode).
-  minor(Scale.naturalMinor, brightness: -3);
+  minor(Scale.naturalMinor, brightness: -1);
 
   @override
   final Scale scale;
@@ -46,25 +53,25 @@ enum TonalMode implements Mode {
 
 enum ModalMode implements Mode {
   /// See [Lydian mode](https://en.wikipedia.org/wiki/Lydian_mode).
-  lydian(Scale.lydian, brightness: 1),
+  lydian(Scale.lydian, brightness: 3),
 
   /// See [Ionian mode](https://en.wikipedia.org/wiki/Ionian_mode).
-  ionian(Scale.ionian, brightness: 0),
+  ionian(Scale.ionian, brightness: 2),
 
   /// See [Mixolydian mode](https://en.wikipedia.org/wiki/Mixolydian_mode).
-  mixolydian(Scale.mixolydian, brightness: -1),
+  mixolydian(Scale.mixolydian, brightness: 1),
 
   /// See [Dorian mode](https://en.wikipedia.org/wiki/Dorian_mode).
-  dorian(Scale.dorian, brightness: -2),
+  dorian(Scale.dorian, brightness: 0),
 
   /// See [Aeolian mode](https://en.wikipedia.org/wiki/Aeolian_mode).
-  aeolian(Scale.aeolian, brightness: -3),
+  aeolian(Scale.aeolian, brightness: -1),
 
   /// See [Phrygian mode](https://en.wikipedia.org/wiki/Phrygian_mode).
-  phrygian(Scale.phrygian, brightness: -4),
+  phrygian(Scale.phrygian, brightness: -2),
 
   /// See [Locrian mode](https://en.wikipedia.org/wiki/Locrian_mode).
-  locrian(Scale.locrian, brightness: -5);
+  locrian(Scale.locrian, brightness: -3);
 
   @override
   final Scale scale;
@@ -74,6 +81,20 @@ enum ModalMode implements Mode {
 
   const ModalMode(this.scale, {required this.brightness});
 
+  /// Returns the mirrored version of this [ModalMode].
+  ///
+  /// Follows the DBQ property where the mirrored mode has the opposite
+  /// [brightness] value.
+  ///
+  /// Example:
+  /// ```dart
+  /// ModalMode.dorian.mirrored == ModalMode.dorian
+  /// ModalMode.ionian.mirrored == ModalMode.phrygian
+  /// ModalMode.aeolian.mirrored == ModalMode.mixolydian
+  /// ```
+  ModalMode get mirrored =>
+      values.firstWhere((mode) => mode.brightness == -brightness);
+
   @override
   int compareTo(Mode other) => Mode.compareModes(this, other);
 }

test/src/tonality/mode_test.dart

@@ -4,14 +4,7 @@ import 'package:music_notes/music_notes.dart';
 import 'package:test/test.dart';
 
 void main() {
-  group('TonalMode', () {
-    group('.opposite', () {
-      test('should return the correct opposite mode', () {
-        expect(TonalMode.major.opposite, TonalMode.minor);
-        expect(TonalMode.minor.opposite, TonalMode.major);
-      });
-    });
-
+  group('Mode', () {
     group('.compareTo', () {
       test('should correctly sort Mode items in a collection', () {
         final orderedSet = SplayTreeSet<Mode>.of(const [
@@ -33,4 +26,25 @@ void main() {
       });
     });
   });
+
+  group('TonalMode', () {
+    group('.opposite', () {
+      test('should return the correct opposite TonalMode', () {
+        expect(TonalMode.major.opposite, TonalMode.minor);
+        expect(TonalMode.minor.opposite, TonalMode.major);
+      });
+    });
+  });
+
+  group('ModalMode', () {
+    group('.mirrored', () {
+      test('should return the mirrored version of this ModalMode', () {
+        expect(ModalMode.dorian.mirrored, ModalMode.dorian);
+        expect(ModalMode.mixolydian.mirrored, ModalMode.aeolian);
+        expect(ModalMode.ionian.mirrored, ModalMode.phrygian);
+        expect(ModalMode.locrian.mirrored, ModalMode.lydian);
+        expect(ModalMode.lydian.mirrored, ModalMode.locrian);
+      });
+    });
+  });
 }