1 files changed, 193 insertions, 0 deletions
diff --git a/apps/web/src/commands/timeline/clipboard/paste.ts b/apps/web/src/commands/timeline/clipboard/paste.ts
new file mode 100644
index 00000000..4523566e
--- /dev/null
+++ b/apps/web/src/commands/timeline/clipboard/paste.ts
@@ -0,0 +1,193 @@
+import {
+	Command,
+	createElementSelectionResult,
+	type CommandResult,
+} from "@/commands/base-command";
+import { EditorCore } from "@/core";
+import type { SceneTracks, TimelineElement } from "@/timeline";
+import type { ElementClipboardItem } from "@/clipboard";
+import { generateUUID } from "@/utils/id";
+import {
+	applyPlacement,
+	resolveTrackPlacement,
+	enforceMainTrackStart,
+} from "@/timeline/placement";
+import { cloneAnimations } from "@/animation";
+
+export class PasteCommand extends Command {
+	private savedState: SceneTracks | null = null;
+	private pastedElements: { trackId: string; elementId: string }[] = [];
+	private readonly time: number;
+	private readonly clipboardItems: ElementClipboardItem[];
+
+	constructor({
+		time,
+		clipboardItems,
+	}: {
+		time: number;
+		clipboardItems: ElementClipboardItem[];
+	}) {
+		super();
+		this.time = time;
+		this.clipboardItems = clipboardItems;
+	}
+
+	execute(): CommandResult | undefined {
+		if (this.clipboardItems.length === 0) return undefined;
+
+		const editor = EditorCore.getInstance();
+		this.savedState = editor.scenes.getActiveScene().tracks;
+		this.pastedElements = [];
+
+		const minStart = Math.min(
+			...this.clipboardItems.map((item) => item.element.startTime),
+		);
+
+		let updatedTracks = this.savedState;
+		const itemsByTrackId = groupClipboardItemsByTrackId({
+			clipboardItems: this.clipboardItems,
+		});
+
+		for (const [trackId, items] of itemsByTrackId) {
+			const elementsToAdd = buildPastedElements({
+				items,
+				minStart,
+				time: this.time,
+			});
+
+			if (elementsToAdd.length === 0) {
+				continue;
+			}
+
+			const trackType = items[0].trackType;
+			const sourceTrackIndex = [
+				...updatedTracks.overlay,
+				updatedTracks.main,
+				...updatedTracks.audio,
+			].findIndex((track) => track.id === trackId);
+			const placementResult = resolveTrackPlacement({
+				tracks: updatedTracks,
+				trackType,
+				timeSpans: elementsToAdd.map((element) => ({
+					startTime: element.startTime,
+					duration: element.duration,
+				})),
+				strategy: { type: "aboveSource", sourceTrackIndex },
+			});
+			if (!placementResult) {
+				continue;
+			}
+
+			let elementsForPlacement = elementsToAdd;
+			if (placementResult.kind === "existingTrack") {
+				const targetTrack =
+					placementResult.trackIndex < updatedTracks.overlay.length
+						? updatedTracks.overlay[placementResult.trackIndex]
+						: placementResult.trackIndex === updatedTracks.overlay.length
+							? updatedTracks.main
+							: updatedTracks.audio[
+									placementResult.trackIndex - updatedTracks.overlay.length - 1
+								];
+				if (targetTrack?.id === updatedTracks.main.id) {
+					const earliestElement = elementsToAdd.reduce((earliest, element) =>
+						element.startTime < earliest.startTime ? element : earliest,
+					);
+					const adjustedEarliestStartTime = enforceMainTrackStart({
+						tracks: updatedTracks,
+						targetTrackId: targetTrack.id,
+						requestedStartTime: earliestElement.startTime,
+					});
+					const delta = adjustedEarliestStartTime - earliestElement.startTime;
+
+					if (delta !== 0) {
+						elementsForPlacement = elementsToAdd.map((element) => ({
+							...element,
+							startTime: Math.max(0, element.startTime + delta),
+						}));
+					}
+				}
+			}
+
+			const applied = applyPlacement({
+				tracks: updatedTracks,
+				placementResult,
+				elements: elementsForPlacement,
+			});
+			if (!applied) {
+				continue;
+			}
+
+			updatedTracks = applied.updatedTracks;
+
+			for (const element of elementsForPlacement) {
+				this.pastedElements.push({
+					trackId: applied.targetTrackId,
+					elementId: element.id,
+				});
+			}
+		}
+
+		editor.timeline.updateTracks(updatedTracks);
+
+		if (this.pastedElements.length > 0) {
+			return createElementSelectionResult(this.pastedElements);
+		}
+		return undefined;
+	}
+
+	undo(): void {
+		if (this.savedState) {
+			const editor = EditorCore.getInstance();
+			editor.timeline.updateTracks(this.savedState);
+		}
+	}
+
+	getPastedElements(): { trackId: string; elementId: string }[] {
+		return this.pastedElements;
+	}
+}
+
+function groupClipboardItemsByTrackId({
+	clipboardItems,
+}: {
+	clipboardItems: ElementClipboardItem[];
+}): Map<string, ElementClipboardItem[]> {
+	const groupedItems = new Map<string, ElementClipboardItem[]>();
+
+	for (const item of clipboardItems) {
+		const existingItems = groupedItems.get(item.trackId) ?? [];
+		groupedItems.set(item.trackId, [...existingItems, item]);
+	}
+
+	return groupedItems;
+}
+
+function buildPastedElements({
+	items,
+	minStart,
+	time,
+}: {
+	items: ElementClipboardItem[];
+	minStart: number;
+	time: number;
+}): TimelineElement[] {
+	const elementsToAdd: TimelineElement[] = [];
+
+	for (const item of items) {
+		const relativeOffset = item.element.startTime - minStart;
+		const startTime = Math.max(0, time + relativeOffset);
+		const newElementId = generateUUID();
+
+		elementsToAdd.push({
+			...item.element,
+			id: newElementId,
+			startTime,
+			animations: cloneAnimations({
+				animations: item.element.animations,
+				shouldRegenerateKeyframeIds: true,
+			}),
+		} as TimelineElement);
+	}
+
+	return elementsToAdd;
+}