1 files changed, 358 insertions, 0 deletions
diff --git a/apps/web/src/timeline/controllers/keyframe-drag-controller.ts b/apps/web/src/timeline/controllers/keyframe-drag-controller.ts
new file mode 100644
index 00000000..29dfc5dd
--- /dev/null
+++ b/apps/web/src/timeline/controllers/keyframe-drag-controller.ts
@@ -0,0 +1,358 @@
+import type { MouseEvent as ReactMouseEvent } from "react";
+import type { FrameRate } from "opencut-wasm";
+import { BASE_TIMELINE_PIXELS_PER_SECOND } from "@/timeline/scale";
+import {
+	addMediaTime,
+	clampMediaTime,
+	type MediaTime,
+	mediaTime,
+	roundFrameTicks,
+	snapSeekMediaTime,
+	TICKS_PER_SECOND,
+	ZERO_MEDIA_TIME,
+} from "@/wasm";
+import { TIMELINE_DRAG_THRESHOLD_PX } from "@/timeline/components/interaction";
+import { timelineTimeToSnappedPixels } from "@/timeline";
+import { getKeyframeById } from "@/animation";
+import { RetimeKeyframeCommand } from "@/commands/timeline/element/keyframes/retime-keyframe";
+import { BatchCommand } from "@/commands";
+import type { SelectedKeyframeRef } from "@/animation/types";
+import type { TimelineElement } from "@/timeline";
+import type { Command } from "@/commands/base-command";
+
+// --- Session ---
+
+interface PendingSession {
+	kind: "pending";
+	keyframeRefs: SelectedKeyframeRef[];
+	startMouseX: number;
+}
+
+interface ActiveSession {
+	kind: "active";
+	keyframeRefs: SelectedKeyframeRef[];
+	startMouseX: number;
+	deltaTicks: number;
+}
+
+type Session = { kind: "idle" } | PendingSession | ActiveSession;
+
+// --- Public state ---
+
+export interface KeyframeDragState {
+	isDragging: boolean;
+	draggingKeyframeIds: Set<string>;
+	deltaTicks: number;
+}
+
+const IDLE_DRAG_STATE: KeyframeDragState = {
+	isDragging: false,
+	draggingKeyframeIds: new Set(),
+	deltaTicks: 0,
+};
+
+// --- Config ---
+
+export interface KeyframeDragConfig {
+	zoomLevel: number;
+	getFps: () => FrameRate | null;
+	element: TimelineElement;
+	displayedStartTime: MediaTime;
+	selectedKeyframes: SelectedKeyframeRef[];
+	isKeyframeSelected: (args: { keyframe: SelectedKeyframeRef }) => boolean;
+	setKeyframeSelection: (args: { keyframes: SelectedKeyframeRef[] }) => void;
+	toggleKeyframeSelection: (args: {
+		keyframes: SelectedKeyframeRef[];
+		isMultiKey: boolean;
+	}) => void;
+	selectKeyframeRange: (args: {
+		orderedKeyframes: SelectedKeyframeRef[];
+		targetKeyframes: SelectedKeyframeRef[];
+		isAdditive: boolean;
+	}) => void;
+	executeCommand: (command: Command) => void;
+	seek: (args: { time: MediaTime }) => void;
+	getTotalDuration: () => MediaTime;
+}
+
+export interface KeyframeDragConfigRef {
+	readonly current: KeyframeDragConfig;
+}
+
+// --- Controller ---
+
+export class KeyframeDragController {
+	private session: Session = { kind: "idle" };
+	// Persists through mouseup so the click handler can detect drag vs click
+	private mouseDownX: number | null = null;
+	private readonly subscribers = new Set<() => void>();
+	private readonly configRef: KeyframeDragConfigRef;
+
+	constructor(deps: { configRef: KeyframeDragConfigRef }) {
+		this.configRef = deps.configRef;
+		this.onKeyframeMouseDown = this.onKeyframeMouseDown.bind(this);
+		this.onKeyframeClick = this.onKeyframeClick.bind(this);
+		this.getVisualOffsetPx = this.getVisualOffsetPx.bind(this);
+		this.handleMouseMove = this.handleMouseMove.bind(this);
+		this.handleMouseUp = this.handleMouseUp.bind(this);
+	}
+
+	private get config(): KeyframeDragConfig {
+		return this.configRef.current;
+	}
+
+	get isActive(): boolean {
+		return this.session.kind !== "idle";
+	}
+
+	get keyframeDragState(): KeyframeDragState {
+		if (this.session.kind !== "active") return IDLE_DRAG_STATE;
+		return {
+			isDragging: true,
+			draggingKeyframeIds: new Set(
+				this.session.keyframeRefs.map((kf) => kf.keyframeId),
+			),
+			deltaTicks: this.session.deltaTicks,
+		};
+	}
+
+	subscribe(fn: () => void): () => void {
+		this.subscribers.add(fn);
+		return () => this.subscribers.delete(fn);
+	}
+
+	cancel(): void {
+		this.mouseDownX = null;
+		this.finishSession();
+	}
+
+	destroy(): void {
+		this.deactivate();
+		this.subscribers.clear();
+	}
+
+	onKeyframeMouseDown({
+		event,
+		keyframes,
+	}: {
+		event: ReactMouseEvent;
+		keyframes: SelectedKeyframeRef[];
+	}): void {
+		event.preventDefault();
+		event.stopPropagation();
+
+		this.mouseDownX = event.clientX;
+
+		const anySelected = keyframes.some((kf) =>
+			this.config.isKeyframeSelected({ keyframe: kf }),
+		);
+		const isModifierKey = event.shiftKey || event.metaKey || event.ctrlKey;
+
+		if (!anySelected && !isModifierKey) {
+			this.config.setKeyframeSelection({ keyframes });
+		}
+
+		this.session = {
+			kind: "pending",
+			keyframeRefs: anySelected ? this.config.selectedKeyframes : keyframes,
+			startMouseX: event.clientX,
+		};
+		this.activate();
+		this.notify();
+	}
+
+	onKeyframeClick({
+		event,
+		keyframes,
+		orderedKeyframes,
+		indicatorTime,
+	}: {
+		event: ReactMouseEvent;
+		keyframes: SelectedKeyframeRef[];
+		orderedKeyframes: SelectedKeyframeRef[];
+		indicatorTime: MediaTime;
+	}): void {
+		event.stopPropagation();
+
+		const wasDrag =
+			this.mouseDownX !== null &&
+			Math.abs(event.clientX - this.mouseDownX) > TIMELINE_DRAG_THRESHOLD_PX;
+		this.mouseDownX = null;
+
+		if (wasDrag) return;
+
+		const { displayedStartTime, getFps, getTotalDuration, seek } = this.config;
+		const fps = getFps();
+		const absoluteIndicatorTime = addMediaTime({
+			a: displayedStartTime,
+			b: indicatorTime,
+		});
+		const seekTime =
+			fps != null
+				? snapSeekMediaTime({
+						time: absoluteIndicatorTime,
+						duration: getTotalDuration(),
+						fps,
+					})
+				: absoluteIndicatorTime;
+		seek({ time: seekTime });
+
+		if (event.shiftKey) {
+			this.config.selectKeyframeRange({
+				orderedKeyframes,
+				targetKeyframes: keyframes,
+				isAdditive: event.metaKey || event.ctrlKey,
+			});
+			return;
+		}
+
+		this.config.toggleKeyframeSelection({
+			keyframes,
+			isMultiKey: event.metaKey || event.ctrlKey,
+		});
+	}
+
+	getVisualOffsetPx({
+		indicatorTime,
+		indicatorOffsetPx,
+		isBeingDragged,
+		displayedStartTime,
+		elementLeft,
+	}: {
+		indicatorTime: MediaTime;
+		indicatorOffsetPx: number;
+		isBeingDragged: boolean;
+		displayedStartTime: MediaTime;
+		elementLeft: number;
+	}): number {
+		if (!isBeingDragged || this.session.kind !== "active")
+			return indicatorOffsetPx;
+		const deltaTime = mediaTime({ ticks: this.session.deltaTicks });
+		const clampedTime = clampMediaTime({
+			time: addMediaTime({ a: indicatorTime, b: deltaTime }),
+			min: ZERO_MEDIA_TIME,
+			max: this.config.element.duration,
+		});
+		return (
+			timelineTimeToSnappedPixels({
+				time: addMediaTime({ a: displayedStartTime, b: clampedTime }),
+				zoomLevel: this.config.zoomLevel,
+			}) - elementLeft
+		);
+	}
+
+	private activate(): void {
+		document.addEventListener("mousemove", this.handleMouseMove);
+		document.addEventListener("mouseup", this.handleMouseUp);
+	}
+
+	private deactivate(): void {
+		document.removeEventListener("mousemove", this.handleMouseMove);
+		document.removeEventListener("mouseup", this.handleMouseUp);
+	}
+
+	private notify(): void {
+		for (const fn of this.subscribers) fn();
+	}
+
+	private finishSession(): void {
+		this.session = { kind: "idle" };
+		this.deactivate();
+		this.notify();
+	}
+
+	private commitDrag({
+		keyframeRefs,
+		deltaTicks,
+	}: {
+		keyframeRefs: SelectedKeyframeRef[];
+		deltaTicks: number;
+	}): void {
+		const { element } = this.config;
+		const commands: Command[] = keyframeRefs.flatMap((ref) => {
+			const keyframe = getKeyframeById({
+				animations: element.animations,
+				propertyPath: ref.propertyPath,
+				keyframeId: ref.keyframeId,
+			});
+			if (!keyframe) return [];
+			return [
+				new RetimeKeyframeCommand({
+					trackId: ref.trackId,
+					elementId: ref.elementId,
+					propertyPath: ref.propertyPath,
+					keyframeId: ref.keyframeId,
+					nextTime: clampMediaTime({
+						time: addMediaTime({
+							a: keyframe.time,
+							b: mediaTime({ ticks: deltaTicks }),
+						}),
+						min: ZERO_MEDIA_TIME,
+						max: element.duration,
+					}),
+				}),
+			];
+		});
+
+		const [first, ...rest] = commands;
+		if (!first) return;
+		if (rest.length === 0) {
+			this.config.executeCommand(first);
+		} else {
+			this.config.executeCommand(new BatchCommand([first, ...rest]));
+		}
+	}
+
+	private handleMouseMove({ clientX }: MouseEvent): void {
+		if (this.session.kind === "pending") {
+			const deltaX = Math.abs(clientX - this.session.startMouseX);
+			if (deltaX <= TIMELINE_DRAG_THRESHOLD_PX) return;
+
+			this.session = {
+				kind: "active",
+				keyframeRefs: this.session.keyframeRefs,
+				startMouseX: this.session.startMouseX,
+				deltaTicks: 0,
+			};
+			this.notify();
+			return;
+		}
+
+		if (this.session.kind !== "active") return;
+
+		const fps = this.config.getFps();
+		if (!fps) return;
+
+		const pixelsPerSecond =
+			BASE_TIMELINE_PIXELS_PER_SECOND * this.config.zoomLevel;
+		const rawDeltaTicks = Math.round(
+			((clientX - this.session.startMouseX) / pixelsPerSecond) *
+				TICKS_PER_SECOND,
+		);
+		this.session.deltaTicks =
+			roundFrameTicks({ ticks: rawDeltaTicks, fps });
+		this.notify();
+	}
+
+	private handleMouseUp(): void {
+		if (this.session.kind === "pending") {
+			this.finishSession();
+			return;
+		}
+
+		if (this.session.kind !== "active") return;
+
+		const { selectedKeyframes, element } = this.config;
+		const { keyframeRefs, deltaTicks } = this.session;
+		const draggingIds = new Set(keyframeRefs.map((r) => r.keyframeId));
+		const draggingRefs = selectedKeyframes.filter(
+			(kf) => kf.elementId === element.id && draggingIds.has(kf.keyframeId),
+		);
+
+		if (draggingRefs.length > 0 && deltaTicks !== 0) {
+			this.commitDrag({ keyframeRefs: draggingRefs, deltaTicks });
+		}
+
+		this.finishSession();
+	}
+}