feat: implement scale-of-fifth based key signature picker

2026-05-23 13:36:59 -07:00
parent fb3c6cde70
commit 247c76237d
12 changed files with 854 additions and 30 deletions
@@ -0,0 +1,92 @@
+import { KEY_SIGNATURE_MAP } from '../constants/coreConstants';
+import type { KeySignature } from '../core/KGProject';
+
+type KeyQuality = 'major' | 'minor';
+
+interface KeySignatureSlotDefinition {
+  id: string;
+  majorKeys: KeySignature[];
+  minorKeys: KeySignature[];
+}
+
+export interface KeySignatureCircleItem {
+  keySignature: KeySignature;
+  label: string;
+  quality: KeyQuality;
+}
+
+export interface KeySignatureCircleSlot {
+  id: string;
+  angleDeg: number;
+  outerItems: KeySignatureCircleItem[];
+  innerItems: KeySignatureCircleItem[];
+  accidentalLabel: string;
+}
+
+const CIRCLE_SLOT_DEFINITIONS: KeySignatureSlotDefinition[] = [
+  { id: 'c', majorKeys: ['C major'], minorKeys: ['A minor'] },
+  { id: 'g', majorKeys: ['G major'], minorKeys: ['E minor'] },
+  { id: 'd', majorKeys: ['D major'], minorKeys: ['B minor'] },
+  { id: 'a', majorKeys: ['A major'], minorKeys: ['F# minor'] },
+  { id: 'e', majorKeys: ['E major'], minorKeys: ['C# minor'] },
+  { id: 'b-cb', majorKeys: ['B major', 'Cb major'], minorKeys: ['G# minor', 'Ab minor'] },
+  { id: 'gb-fsharp', majorKeys: ['Gb major', 'F# major'], minorKeys: ['Eb minor', 'D# minor'] },
+  { id: 'db-csharp', majorKeys: ['Db major', 'C# major'], minorKeys: ['Bb minor', 'A# minor'] },
+  { id: 'ab', majorKeys: ['Ab major'], minorKeys: ['F minor'] },
+  { id: 'eb', majorKeys: ['Eb major'], minorKeys: ['C minor'] },
+  { id: 'bb', majorKeys: ['Bb major'], minorKeys: ['G minor'] },
+  { id: 'f', majorKeys: ['F major'], minorKeys: ['D minor'] },
+];
+
+function assertKnownKeySignature(keySignature: KeySignature): KeySignature {
+  if (!(keySignature in KEY_SIGNATURE_MAP)) {
+    throw new Error(`Unknown key signature in circle layout: ${keySignature}`);
+  }
+
+  return keySignature;
+}
+
+function getLabelForKeySignature(keySignature: KeySignature): string {
+  const [tonic, quality] = keySignature.split(' ');
+  return quality === 'major' ? tonic : tonic.toLowerCase();
+}
+
+function formatAccidentalCount(keySignatures: KeySignature[]): string {
+  const segments = keySignatures.map((keySignature) => {
+    const entry = KEY_SIGNATURE_MAP[keySignature];
+    if (entry.sharps > 0) {
+      return `${entry.sharps}♯`;
+    }
+    if (entry.flats > 0) {
+      return `${entry.flats}♭`;
+    }
+    return 'natural';
+  });
+
+  return [...new Set(segments)].join(' / ');
+}
+
+export function buildKeySignatureCircleSlots(): KeySignatureCircleSlot[] {
+  const totalSlots = CIRCLE_SLOT_DEFINITIONS.length;
+
+  return CIRCLE_SLOT_DEFINITIONS.map((slot, index) => {
+    const outerItems = slot.majorKeys.map((keySignature) => ({
+      keySignature: assertKnownKeySignature(keySignature),
+      label: getLabelForKeySignature(keySignature),
+      quality: 'major' as const,
+    }));
+    const innerItems = slot.minorKeys.map((keySignature) => ({
+      keySignature: assertKnownKeySignature(keySignature),
+      label: getLabelForKeySignature(keySignature),
+      quality: 'minor' as const,
+    }));
+
+    return {
+      id: slot.id,
+      angleDeg: -90 + (360 / totalSlots) * index,
+      outerItems,
+      innerItems,
+      accidentalLabel: formatAccidentalCount(slot.majorKeys),
+    };
+  });
+}