feat: implemented global tempo (bpm) track

src/core/commands/global-region/UpdateTempoRegionCommand.ts

@@ -0,0 +1,47 @@
+import { KGCommand } from '../KGCommand';
+import { KGCore } from '../../KGCore';
+import { GlobalTrackType } from '../../global-track';
+import { KGTempoRegion } from '../../region/KGTempoRegion';
+import { findGlobalTrackByType } from '../../../util/globalTrackUtil';
+
+export class UpdateTempoRegionCommand extends KGCommand {
+  private readonly regionId: string;
+  private readonly nextBpm: number;
+  private previousBpm: number | null = null;
+  private targetRegion: KGTempoRegion | null = null;
+
+  constructor(regionId: string, nextBpm: number) {
+    super();
+    this.regionId = regionId;
+    this.nextBpm = nextBpm;
+  }
+
+  execute(): void {
+    const project = KGCore.instance().getCurrentProject();
+    const track = findGlobalTrackByType(project, GlobalTrackType.Tempo);
+    if (!track) {
+      throw new Error('Tempo global track not found');
+    }
+
+    const region = track.getRegions().find(candidate => candidate.getId() === this.regionId);
+    if (!(region instanceof KGTempoRegion)) {
+      throw new Error(`Tempo region with ID ${this.regionId} not found`);
+    }
+
+    this.targetRegion = region;
+    this.previousBpm = region.getBpm();
+    region.setBpm(this.nextBpm);
+  }
+
+  undo(): void {
+    if (!this.targetRegion || this.previousBpm === null) {
+      throw new Error('Cannot undo tempo update without previous state');
+    }
+
+    this.targetRegion.setBpm(this.previousBpm);
+  }
+
+  getDescription(): string {
+    return `Change tempo to "${this.nextBpm} BPM"`;
+  }
+}