OpenCut/apps/web/src/lib/commands/timeline/clipboard/paste.ts

import { Command, type CommandResult } from "@/lib/commands/base-command";
import { EditorCore } from "@/core";
import type {
	SceneTracks,
	TimelineElement,
	ClipboardItem,
} from "@/lib/timeline";
import { generateUUID } from "@/utils/id";
import { applyPlacement, resolveTrackPlacement, enforceMainTrackStart } from "@/lib/timeline/placement";
import { cloneAnimations } from "@/lib/animation";

export class PasteCommand extends Command {
	private savedState: SceneTracks | null = null;
	private pastedElements: { trackId: string; elementId: string }[] = [];
	private readonly time: number;
	private readonly clipboardItems: ClipboardItem[];

	constructor({
		time,
		clipboardItems,
	}: {
		time: number;
		clipboardItems: ClipboardItem[];
	}) {
		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 { select: 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: ClipboardItem[];
}): Map<string, ClipboardItem[]> {
	const groupedItems = new Map<string, ClipboardItem[]>();

	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: ClipboardItem[];
	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;
}