From dc82826951c03cca91ea1431b0b8abdfd9dba583 Mon Sep 17 00:00:00 2001
From: Maze Winther <mazewinther@gmail.com>
Date: Tue, 31 Mar 2026 23:39:43 +0200
Subject: refactor: move track pruning into a post-command reactor

---
 apps/web/src/core/index.ts             | 116 ++++++++++++++++++---------------
 apps/web/src/core/managers/commands.ts |  13 ++++
 2 files changed, 76 insertions(+), 53 deletions(-)

(limited to 'apps/web/src/core')

diff --git a/apps/web/src/core/index.ts b/apps/web/src/core/index.ts
index f1c2d032..1086a6d2 100644
--- a/apps/web/src/core/index.ts
+++ b/apps/web/src/core/index.ts
@@ -1,53 +1,63 @@
-import { PlaybackManager } from "./managers/playback-manager";
-import { TimelineManager } from "./managers/timeline-manager";
-import { ScenesManager } from "./managers/scenes-manager";
-import { ProjectManager } from "./managers/project-manager";
-import { MediaManager } from "./managers/media-manager";
-import { RendererManager } from "./managers/renderer-manager";
-import { CommandManager } from "./managers/commands";
-import { SaveManager } from "./managers/save-manager";
-import { AudioManager } from "./managers/audio-manager";
-import { SelectionManager } from "./managers/selection-manager";
-import { registerDefaultEffects } from "@/lib/effects";
-import { registerDefaultMasks } from "@/lib/masks";
-
-export class EditorCore {
-	private static instance: EditorCore | null = null;
-	public readonly timeline: TimelineManager;
-	public readonly command: CommandManager;
-	public readonly playback: PlaybackManager;
-	public readonly scenes: ScenesManager;
-	public readonly project: ProjectManager;
-	public readonly media: MediaManager;
-	public readonly renderer: RendererManager;
-	public readonly save: SaveManager;
-	public readonly audio: AudioManager;
-	public readonly selection: SelectionManager;
-
-	private constructor() {
-		registerDefaultEffects();
-		registerDefaultMasks();
-		this.command = new CommandManager(this);
-		this.timeline = new TimelineManager(this);
-		this.playback = new PlaybackManager(this);
-		this.scenes = new ScenesManager(this);
-		this.project = new ProjectManager(this);
-		this.media = new MediaManager(this);
-		this.renderer = new RendererManager(this);
-		this.save = new SaveManager(this);
-		this.audio = new AudioManager(this);
-		this.selection = new SelectionManager(this);
-		this.save.start();
-	}
-
-	static getInstance(): EditorCore {
-		if (!EditorCore.instance) {
-			EditorCore.instance = new EditorCore();
-		}
-		return EditorCore.instance;
-	}
-
-	static reset(): void {
-		EditorCore.instance = null;
-	}
-}
+import { PlaybackManager } from "./managers/playback-manager";
+import { TimelineManager } from "./managers/timeline-manager";
+import { ScenesManager } from "./managers/scenes-manager";
+import { ProjectManager } from "./managers/project-manager";
+import { MediaManager } from "./managers/media-manager";
+import { RendererManager } from "./managers/renderer-manager";
+import { CommandManager } from "./managers/commands";
+import { SaveManager } from "./managers/save-manager";
+import { AudioManager } from "./managers/audio-manager";
+import { SelectionManager } from "./managers/selection-manager";
+import { registerDefaultEffects } from "@/lib/effects";
+import { registerDefaultMasks } from "@/lib/masks";
+import { isMainTrack } from "@/lib/timeline/placement";
+
+export class EditorCore {
+	private static instance: EditorCore | null = null;
+	public readonly timeline: TimelineManager;
+	public readonly command: CommandManager;
+	public readonly playback: PlaybackManager;
+	public readonly scenes: ScenesManager;
+	public readonly project: ProjectManager;
+	public readonly media: MediaManager;
+	public readonly renderer: RendererManager;
+	public readonly save: SaveManager;
+	public readonly audio: AudioManager;
+	public readonly selection: SelectionManager;
+
+	private constructor() {
+		registerDefaultEffects();
+		registerDefaultMasks();
+		this.command = new CommandManager(this);
+		this.timeline = new TimelineManager(this);
+		this.playback = new PlaybackManager(this);
+		this.scenes = new ScenesManager(this);
+		this.project = new ProjectManager(this);
+		this.media = new MediaManager(this);
+		this.renderer = new RendererManager(this);
+		this.save = new SaveManager(this);
+		this.audio = new AudioManager(this);
+		this.selection = new SelectionManager(this);
+		this.command.registerReactor(() => {
+			const tracks = this.timeline.getTracks();
+			const prunedTracks = tracks.filter(
+				(track) => track.elements.length > 0 || isMainTrack(track),
+			);
+			if (prunedTracks.length !== tracks.length) {
+				this.timeline.updateTracks(prunedTracks);
+			}
+		});
+		this.save.start();
+	}
+
+	static getInstance(): EditorCore {
+		if (!EditorCore.instance) {
+			EditorCore.instance = new EditorCore();
+		}
+		return EditorCore.instance;
+	}
+
+	static reset(): void {
+		EditorCore.instance = null;
+	}
+}
diff --git a/apps/web/src/core/managers/commands.ts b/apps/web/src/core/managers/commands.ts
index 4c53857b..918fc33e 100644
--- a/apps/web/src/core/managers/commands.ts
+++ b/apps/web/src/core/managers/commands.ts
@@ -11,6 +11,7 @@ interface CommandHistoryEntry {
 export class CommandManager {
 	private history: CommandHistoryEntry[] = [];
 	private redoStack: CommandHistoryEntry[] = [];
+	private reactors: Array<() => void> = [];
 
 	constructor(private editor: EditorCore) {}
 
@@ -18,6 +19,7 @@ export class CommandManager {
 		const previousSelection = this.getSelectionSnapshot();
 		const result = command.execute();
 		const selectionOverride = this.applySelectionOverride(result);
+		this.runReactors();
 		this.history.push({
 			command,
 			previousSelection,
@@ -35,6 +37,10 @@ export class CommandManager {
 		this.redoStack = [];
 	}
 
+	registerReactor(reactor: () => void): void {
+		this.reactors.push(reactor);
+	}
+
 	undo(): void {
 		if (this.history.length === 0) return;
 		const entry = this.history.pop();
@@ -64,6 +70,7 @@ export class CommandManager {
 		const previousSelection = this.getSelectionSnapshot();
 		const result = entry.command.redo();
 		const selectionOverride = this.applySelectionOverride(result);
+		this.runReactors();
 
 		this.history.push({
 			command: entry.command,
@@ -100,4 +107,10 @@ export class CommandManager {
 		this.editor.selection.setSelectedElements({ elements: selectionOverride });
 		return selectionOverride;
 	}
+
+	private runReactors(): void {
+		for (const reactor of this.reactors) {
+			reactor();
+		}
+	}
 }
-- 
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