1 files changed, 134 insertions, 0 deletions
diff --git a/apps/web/src/commands/timeline/element/duplicate-elements.ts b/apps/web/src/commands/timeline/element/duplicate-elements.ts
new file mode 100644
index 00000000..8f65f7c7
--- /dev/null
+++ b/apps/web/src/commands/timeline/element/duplicate-elements.ts
@@ -0,0 +1,134 @@
+import {
+	Command,
+	createElementSelectionResult,
+	type CommandResult,
+} from "@/commands/base-command";
+import type { SceneTracks, TimelineElement } from "@/timeline";
+import { generateUUID } from "@/utils/id";
+import { EditorCore } from "@/core";
+import { applyPlacement, resolveTrackPlacement } from "@/timeline/placement";
+import { cloneAnimations } from "@/animation";
+
+interface DuplicateElementsParams {
+	elements: { trackId: string; elementId: string }[];
+}
+
+export class DuplicateElementsCommand extends Command {
+	private duplicatedElements: { trackId: string; elementId: string }[] = [];
+	private savedState: SceneTracks | null = null;
+	private elements: DuplicateElementsParams["elements"];
+
+	constructor({ elements }: DuplicateElementsParams) {
+		super();
+		this.elements = elements;
+	}
+
+	execute(): CommandResult | undefined {
+		const editor = EditorCore.getInstance();
+		this.savedState = editor.scenes.getActiveScene().tracks;
+		this.duplicatedElements = [];
+
+		let updatedTracks = this.savedState;
+
+		for (const track of [
+			...this.savedState.overlay,
+			this.savedState.main,
+			...this.savedState.audio,
+		]) {
+			const elementsToDuplicate = this.elements.filter(
+				(elementEntry) => elementEntry.trackId === track.id,
+			);
+
+			if (elementsToDuplicate.length === 0) {
+				continue;
+			}
+
+			const elementIdsToDuplicate = new Set(
+				elementsToDuplicate.map((element) => element.elementId),
+			);
+			const newTrackElements: TimelineElement[] = [];
+
+			for (const element of track.elements) {
+				if (!elementIdsToDuplicate.has(element.id)) {
+					continue;
+				}
+
+				const newId = generateUUID();
+				newTrackElements.push(
+					buildDuplicateElement({
+						element,
+						id: newId,
+						startTime: element.startTime,
+					}),
+				);
+			}
+
+			const placementResult = resolveTrackPlacement({
+				tracks: updatedTracks,
+				trackType: track.type,
+				timeSpans: [],
+				strategy: { type: "alwaysNew", position: "highest" },
+			});
+			if (!placementResult || placementResult.kind !== "newTrack") {
+				continue;
+			}
+
+			const applied = applyPlacement({
+				tracks: updatedTracks,
+				placementResult,
+				elements: newTrackElements,
+			});
+			if (!applied) {
+				continue;
+			}
+
+			updatedTracks = applied.updatedTracks;
+
+			for (const element of newTrackElements) {
+				this.duplicatedElements.push({
+					trackId: applied.targetTrackId,
+					elementId: element.id,
+				});
+			}
+		}
+
+		editor.timeline.updateTracks(updatedTracks);
+
+		if (this.duplicatedElements.length > 0) {
+			return createElementSelectionResult(this.duplicatedElements);
+		}
+		return undefined;
+	}
+
+	undo(): void {
+		if (this.savedState) {
+			const editor = EditorCore.getInstance();
+			editor.timeline.updateTracks(this.savedState);
+		}
+	}
+
+	getDuplicatedElements(): { trackId: string; elementId: string }[] {
+		return this.duplicatedElements;
+	}
+}
+
+function buildDuplicateElement({
+	element,
+	id,
+	startTime,
+}: {
+	element: TimelineElement;
+	id: string;
+	startTime: number;
+}): TimelineElement {
+	return {
+		...element,
+		id,
+		name: `${element.name} (copy)`,
+		startTime,
+		animations: cloneAnimations({
+			animations: element.animations,
+			shouldRegenerateKeyframeIds: true,
+		}),
+	};
+}