5 files changed, 348 insertions, 0 deletions
diff --git a/apps/web/src/lib/clipboard/handlers/elements.ts b/apps/web/src/lib/clipboard/handlers/elements.ts
new file mode 100644
index 00000000..1b58ac78
--- /dev/null
+++ b/apps/web/src/lib/clipboard/handlers/elements.ts
@@ -0,0 +1,48 @@
+import { PasteCommand } from "@/lib/commands/timeline";
+import type { ClipboardHandler } from "../types";
+
+export const ElementsClipboardHandler = {
+	type: "elements",
+
+	canCopy({ selectedElements }) {
+		return selectedElements.length > 0;
+	},
+
+	copy({ editor, selectedElements }) {
+		if (selectedElements.length === 0) {
+			return null;
+		}
+
+		const results = editor.timeline.getElementsWithTracks({
+			elements: selectedElements,
+		});
+		const items = results.map(({ track, element }) => {
+			const { id: _elementId, ...elementWithoutId } = element;
+			return {
+				trackId: track.id,
+				trackType: track.type,
+				element: elementWithoutId,
+			};
+		});
+
+		if (items.length === 0) {
+			return null;
+		}
+
+		return {
+			type: "elements",
+			items,
+		};
+	},
+
+	paste(entry, context) {
+		if (entry.items.length === 0) {
+			return null;
+		}
+
+		return new PasteCommand({
+			time: context.time,
+			clipboardItems: entry.items,
+		});
+	},
+} satisfies ClipboardHandler<"elements">;
diff --git a/apps/web/src/lib/clipboard/handlers/index.ts b/apps/web/src/lib/clipboard/handlers/index.ts
new file mode 100644
index 00000000..29d4d1d0
--- /dev/null
+++ b/apps/web/src/lib/clipboard/handlers/index.ts
@@ -0,0 +1,49 @@
+import type {
+	ClipboardEntry,
+	ClipboardEntryType,
+	ClipboardHandler,
+	ClipboardHandlerMap,
+	CopyContext,
+	PasteContext,
+} from "../types";
+import { ElementsClipboardHandler } from "./elements";
+import { KeyframesClipboardHandler } from "./keyframes";
+
+export const clipboardHandlers = {
+	elements: ElementsClipboardHandler,
+	keyframes: KeyframesClipboardHandler,
+} satisfies ClipboardHandlerMap;
+
+export const clipboardCopyHandlers = [
+	KeyframesClipboardHandler,
+	ElementsClipboardHandler,
+] as const satisfies readonly ClipboardHandler<ClipboardEntryType>[];
+
+export function copyClipboardEntry({
+	context,
+}: {
+	context: CopyContext;
+}): ClipboardEntry | null {
+	for (const handler of clipboardCopyHandlers) {
+		if (!handler.canCopy(context)) {
+			continue;
+		}
+
+		return handler.copy(context);
+	}
+
+	return null;
+}
+
+export function buildPasteClipboardCommand({
+	entry,
+	context,
+}: {
+	entry: ClipboardEntry;
+	context: PasteContext;
+}) {
+	const handler = clipboardHandlers[entry.type] as ClipboardHandler<
+		typeof entry.type
+	>;
+	return handler.paste(entry as never, context);
+}
diff --git a/apps/web/src/lib/clipboard/handlers/keyframes.ts b/apps/web/src/lib/clipboard/handlers/keyframes.ts
new file mode 100644
index 00000000..b746c179
--- /dev/null
+++ b/apps/web/src/lib/clipboard/handlers/keyframes.ts
@@ -0,0 +1,170 @@
+import { getKeyframeById } from "@/lib/animation";
+import type { SelectedKeyframeRef } from "@/lib/animation/types";
+import type { TimelineElement } from "@/lib/timeline";
+import { PasteKeyframesCommand } from "@/lib/commands/timeline";
+import type {
+	ClipboardHandler,
+	KeyframeClipboardCurvePatch,
+	KeyframeClipboardItem,
+} from "../types";
+
+function resolveSingleSourceElement({
+	selectedKeyframes,
+}: {
+	selectedKeyframes: SelectedKeyframeRef[];
+}) {
+	const firstKeyframe = selectedKeyframes[0];
+	if (!firstKeyframe) {
+		return null;
+	}
+
+	const sourceElement = {
+		trackId: firstKeyframe.trackId,
+		elementId: firstKeyframe.elementId,
+	};
+	const isSingleSource = selectedKeyframes.every(
+		(keyframe) =>
+			keyframe.trackId === sourceElement.trackId &&
+			keyframe.elementId === sourceElement.elementId,
+	);
+
+	return isSingleSource ? sourceElement : null;
+}
+
+function getCurvePatches({
+	element,
+	propertyPath,
+	keyframeId,
+}: {
+	element: TimelineElement;
+	propertyPath: KeyframeClipboardItem["propertyPath"];
+	keyframeId: string;
+}): KeyframeClipboardCurvePatch[] {
+	const binding = element.animations?.bindings[propertyPath];
+	if (!binding) {
+		return [];
+	}
+
+	return binding.components.flatMap((component) => {
+		const channel = element.animations?.channels[component.channelId];
+		if (channel?.kind !== "scalar") {
+			return [];
+		}
+
+		const keyframe = channel.keys.find(
+			(candidate) => candidate.id === keyframeId,
+		);
+		if (!keyframe) {
+			return [];
+		}
+
+		return [
+			{
+				componentKey: component.key,
+				patch: {
+					leftHandle: keyframe.leftHandle ?? null,
+					rightHandle: keyframe.rightHandle ?? null,
+					segmentToNext: keyframe.segmentToNext,
+					tangentMode: keyframe.tangentMode,
+				},
+			},
+		];
+	});
+}
+
+function buildClipboardItem({
+	element,
+	propertyPath,
+	keyframeId,
+}: {
+	element: TimelineElement;
+	propertyPath: KeyframeClipboardItem["propertyPath"];
+	keyframeId: string;
+}): (Omit<KeyframeClipboardItem, "timeOffset"> & { time: number }) | null {
+	const keyframe = getKeyframeById({
+		animations: element.animations,
+		propertyPath,
+		keyframeId,
+	});
+	if (!keyframe) {
+		return null;
+	}
+
+	return {
+		propertyPath,
+		time: keyframe.time,
+		value: keyframe.value,
+		interpolation: keyframe.interpolation,
+		curvePatches: getCurvePatches({
+			element,
+			propertyPath,
+			keyframeId,
+		}),
+	};
+}
+
+export const KeyframesClipboardHandler = {
+	type: "keyframes",
+
+	canCopy({ selectedKeyframes }) {
+		return selectedKeyframes.length > 0;
+	},
+
+	copy({ editor, selectedKeyframes }) {
+		const sourceElement = resolveSingleSourceElement({ selectedKeyframes });
+		if (!sourceElement) {
+			return null;
+		}
+
+		const [result] = editor.timeline.getElementsWithTracks({
+			elements: [sourceElement],
+		});
+		if (!result) {
+			return null;
+		}
+
+		const rawItems = selectedKeyframes.flatMap((keyframeRef) => {
+			const item = buildClipboardItem({
+				element: result.element,
+				propertyPath: keyframeRef.propertyPath,
+				keyframeId: keyframeRef.keyframeId,
+			});
+			return item ? [item] : [];
+		});
+		if (rawItems.length === 0) {
+			return null;
+		}
+
+		const minTime = Math.min(...rawItems.map((item) => item.time));
+		const items = rawItems
+			.map(({ time, ...item }) => ({
+				...item,
+				timeOffset: time - minTime,
+			}))
+			.sort(
+				(left, right) =>
+					left.timeOffset - right.timeOffset ||
+					left.propertyPath.localeCompare(right.propertyPath),
+			);
+
+		return {
+			type: "keyframes",
+			sourceElement,
+			items,
+		};
+	},
+
+	paste(entry, { selectedElements, time }) {
+		const targetElement = selectedElements[0];
+		if (!targetElement || entry.items.length === 0) {
+			return null;
+		}
+
+		return new PasteKeyframesCommand({
+			trackId: targetElement.trackId,
+			elementId: targetElement.elementId,
+			time,
+			clipboardItems: entry.items,
+		});
+	},
+} satisfies ClipboardHandler<"keyframes">;
diff --git a/apps/web/src/lib/clipboard/index.ts b/apps/web/src/lib/clipboard/index.ts
new file mode 100644
index 00000000..76d5bddf
--- /dev/null
+++ b/apps/web/src/lib/clipboard/index.ts
@@ -0,0 +1,2 @@
+export * from "./types";
+export * from "./handlers";
diff --git a/apps/web/src/lib/clipboard/types.ts b/apps/web/src/lib/clipboard/types.ts
new file mode 100644
index 00000000..41e107ef
--- /dev/null
+++ b/apps/web/src/lib/clipboard/types.ts
@@ -0,0 +1,79 @@
+import type { EditorCore } from "@/core";
+import type {
+	AnimationInterpolation,
+	AnimationPath,
+	AnimationValue,
+	ScalarCurveKeyframePatch,
+	SelectedKeyframeRef,
+} from "@/lib/animation/types";
+import type { Command } from "@/lib/commands/base-command";
+import type {
+	CreateTimelineElement,
+	ElementRef,
+	TrackType,
+} from "@/lib/timeline";
+
+export interface ElementClipboardItem {
+	trackId: string;
+	trackType: TrackType;
+	element: CreateTimelineElement;
+}
+
+export interface KeyframeClipboardCurvePatch {
+	componentKey: string;
+	patch: ScalarCurveKeyframePatch;
+}
+
+export interface KeyframeClipboardItem {
+	propertyPath: AnimationPath;
+	timeOffset: number;
+	value: AnimationValue;
+	interpolation: AnimationInterpolation;
+	curvePatches: KeyframeClipboardCurvePatch[];
+}
+
+export interface ElementsClipboardEntry {
+	type: "elements";
+	items: ElementClipboardItem[];
+}
+
+export interface KeyframesClipboardEntry {
+	type: "keyframes";
+	sourceElement: ElementRef;
+	items: KeyframeClipboardItem[];
+}
+
+export interface ClipboardEntryByType {
+	elements: ElementsClipboardEntry;
+	keyframes: KeyframesClipboardEntry;
+}
+
+export type ClipboardEntry = ClipboardEntryByType[keyof ClipboardEntryByType];
+export type ClipboardEntryType = keyof ClipboardEntryByType;
+
+export interface CopyContext {
+	editor: EditorCore;
+	selectedElements: ElementRef[];
+	selectedKeyframes: SelectedKeyframeRef[];
+}
+
+export interface PasteContext {
+	editor: EditorCore;
+	selectedElements: ElementRef[];
+	selectedKeyframes: SelectedKeyframeRef[];
+	time: number;
+}
+
+export interface ClipboardHandler<TType extends ClipboardEntryType> {
+	type: TType;
+	canCopy(context: CopyContext): boolean;
+	copy(context: CopyContext): ClipboardEntryByType[TType] | null;
+	paste(
+		entry: ClipboardEntryByType[TType],
+		context: PasteContext,
+	): Command | null;
+}
+
+export type ClipboardHandlerMap = {
+	[TType in ClipboardEntryType]: ClipboardHandler<TType>;
+};