1 files changed, 235 insertions, 0 deletions
diff --git a/apps/web/src/timeline/components/graph-editor/bezier-graph.tsx b/apps/web/src/timeline/components/graph-editor/bezier-graph.tsx
new file mode 100644
index 00000000..7d77b985
--- /dev/null
+++ b/apps/web/src/timeline/components/graph-editor/bezier-graph.tsx
@@ -0,0 +1,235 @@
+"use client";
+
+import { useRef, useState, type PointerEvent } from "react";
+import { useShiftKey } from "@/hooks/use-shift-key";
+import { getBezierPoint } from "@/animation/bezier";
+import type { NormalizedCubicBezier } from "@/animation/types";
+import { cn } from "@/utils/ui";
+
+const GRAPH_WIDTH = 140;
+const GRAPH_HEIGHT = 94;
+const GRAPH_PADDING = 12;
+const SVG_WIDTH = GRAPH_WIDTH + GRAPH_PADDING * 2;
+const SVG_HEIGHT = GRAPH_HEIGHT + GRAPH_PADDING * 2;
+const HANDLE_RADIUS = 3.5;
+const ENDPOINT_RADIUS = 2;
+const SNAP_THRESHOLD = 0.06;
+const SNAP_TARGETS = [0, 1];
+const CURVE_SEGMENTS = 64;
+const Y_CLAMP_MIN = -0.5;
+const Y_CLAMP_MAX = 1.5;
+
+type BezierHandle = "c1" | "c2";
+
+export const BEZIER_GRAPH_MIN_HEIGHT = SVG_HEIGHT;
+
+function snap({
+	value,
+	targets,
+	isEnabled,
+}: {
+	value: number;
+	targets: number[];
+	isEnabled: boolean;
+}) {
+	if (!isEnabled) return value;
+	for (const target of targets) {
+		if (Math.abs(value - target) < SNAP_THRESHOLD) return target;
+	}
+	return value;
+}
+
+function toSvgX({ value }: { value: number }) {
+	return GRAPH_PADDING + value * GRAPH_WIDTH;
+}
+
+function toSvgY({ value }: { value: number }) {
+	return GRAPH_PADDING + (1 - value) * GRAPH_HEIGHT;
+}
+
+function fromSvgX({ svgX }: { svgX: number }) {
+	return Math.max(0, Math.min(1, (svgX - GRAPH_PADDING) / GRAPH_WIDTH));
+}
+
+function fromSvgY({ svgY }: { svgY: number }) {
+	return Math.max(
+		Y_CLAMP_MIN,
+		Math.min(Y_CLAMP_MAX, 1 - (svgY - GRAPH_PADDING) / GRAPH_HEIGHT),
+	);
+}
+
+function curvePath({ curve }: { curve: NormalizedCubicBezier }) {
+	const points: string[] = [];
+	for (let i = 0; i <= CURVE_SEGMENTS; i++) {
+		const progress = i / CURVE_SEGMENTS;
+		const x = toSvgX({ value: getBezierPoint({ progress, p0: 0, p1: curve[0], p2: curve[2], p3: 1 }) });
+		const y = toSvgY({ value: getBezierPoint({ progress, p0: 0, p1: curve[1], p2: curve[3], p3: 1 }) });
+		points.push(`${x},${y}`);
+	}
+	return `M${points.join("L")}`;
+}
+
+function clampHandleY({ svgY }: { svgY: number }) {
+	return Math.max(HANDLE_RADIUS, Math.min(SVG_HEIGHT - HANDLE_RADIUS, svgY));
+}
+
+export function BezierGraph({
+	value,
+	onChange,
+	onChangeEnd,
+	onCancel,
+}: {
+	value: NormalizedCubicBezier;
+	onChange?: (value: NormalizedCubicBezier) => void;
+	onChangeEnd?: (value: NormalizedCubicBezier) => void;
+	onCancel?: () => void;
+}) {
+	const svgRef = useRef<SVGSVGElement>(null);
+	const [activeHandle, setActiveHandle] = useState<BezierHandle | null>(null);
+	const isShiftPressedRef = useShiftKey();
+	const latestValueRef = useRef(value);
+
+	latestValueRef.current = value;
+
+	function getPointerPosition({
+		event,
+	}: {
+		event: PointerEvent;
+	}): { x: number; y: number } {
+		const svg = svgRef.current;
+		if (!svg) return { x: 0, y: 0 };
+		const rect = svg.getBoundingClientRect();
+		const scale = SVG_WIDTH / rect.width;
+		return {
+			x: (event.clientX - rect.left) * scale,
+			y: (event.clientY - rect.top) * (SVG_HEIGHT / rect.height),
+		};
+	}
+
+	function onHandlePointerDown({ handle }: { handle: BezierHandle }) {
+		return (event: PointerEvent<SVGCircleElement>) => {
+			event.preventDefault();
+			event.stopPropagation();
+			setActiveHandle(handle);
+			event.currentTarget.setPointerCapture(event.pointerId);
+		};
+	}
+
+	function onPointerMove({ event }: { event: PointerEvent<SVGSVGElement> }) {
+		if (!activeHandle) return;
+		const pointerPos = getPointerPosition({ event });
+		const x = fromSvgX({ svgX: pointerPos.x });
+		const y = snap({
+			value: fromSvgY({ svgY: pointerPos.y }),
+			targets: SNAP_TARGETS,
+			isEnabled: !isShiftPressedRef.current,
+		});
+		const next: NormalizedCubicBezier = [...value];
+		if (activeHandle === "c1") {
+			next[0] = x;
+			next[1] = y;
+		} else {
+			next[2] = x;
+			next[3] = y;
+		}
+		latestValueRef.current = next;
+		onChange?.(next);
+	}
+
+	function onPointerUp() {
+		if (!activeHandle) return;
+		setActiveHandle(null);
+		onChangeEnd?.(latestValueRef.current);
+	}
+
+	function onPointerCancel() {
+		if (!activeHandle) return;
+		setActiveHandle(null);
+		onCancel?.();
+	}
+
+	const path = curvePath({ curve: value });
+	const c1 = { x: toSvgX({ value: value[0] }), y: toSvgY({ value: value[1] }) };
+	const c2 = { x: toSvgX({ value: value[2] }), y: toSvgY({ value: value[3] }) };
+	const c1Clamped = { x: c1.x, y: clampHandleY({ svgY: c1.y }) };
+	const c2Clamped = { x: c2.x, y: clampHandleY({ svgY: c2.y }) };
+	const p0 = { x: toSvgX({ value: 0 }), y: toSvgY({ value: 0 }) };
+	const p1 = { x: toSvgX({ value: 1 }), y: toSvgY({ value: 1 }) };
+
+	return (
+		<svg
+			ref={svgRef}
+			viewBox={`0 0 ${SVG_WIDTH} ${SVG_HEIGHT}`}
+			className="bg-foreground/3 w-full cursor-crosshair select-none"
+			onPointerMove={(event) => onPointerMove({ event })}
+			onPointerUp={onPointerUp}
+			onPointerCancel={onPointerCancel}
+		>
+			<title>Bezier curve editor</title>
+			<line
+				x1={p0.x}
+				y1={p0.y}
+				x2={p1.x}
+				y2={p1.y}
+				className="stroke-foreground/8"
+				strokeWidth={1}
+				strokeDasharray="3 3"
+			/>
+			<line
+				x1={p0.x}
+				y1={p0.y}
+				x2={c1Clamped.x}
+				y2={c1Clamped.y}
+				className="stroke-primary/30"
+				strokeWidth={1}
+			/>
+			<line
+				x1={p1.x}
+				y1={p1.y}
+				x2={c2Clamped.x}
+				y2={c2Clamped.y}
+				className="stroke-primary/30"
+				strokeWidth={1}
+			/>
+			<path
+				d={path}
+				fill="none"
+				className="stroke-primary"
+				strokeWidth={2}
+				strokeLinecap="round"
+			/>
+			<circle
+				cx={p0.x}
+				cy={p0.y}
+				r={ENDPOINT_RADIUS}
+				className="fill-foreground/20"
+			/>
+			<circle
+				cx={p1.x}
+				cy={p1.y}
+				r={ENDPOINT_RADIUS}
+				className="fill-foreground/20"
+			/>
+			<circle
+				cx={c1Clamped.x}
+				cy={c1Clamped.y}
+				r={HANDLE_RADIUS}
+				className={cn(
+					"fill-primary cursor-grab",
+					activeHandle === "c1" && "cursor-grabbing",
+				)}
+				onPointerDown={onHandlePointerDown({ handle: "c1" })}
+			/>
+			<circle
+				cx={c2Clamped.x}
+				cy={c2Clamped.y}
+				r={HANDLE_RADIUS}
+				className={cn(
+					"fill-primary cursor-grab",
+					activeHandle === "c2" && "cursor-grabbing",
+				)}
+				onPointerDown={onHandlePointerDown({ handle: "c2" })}
+			/>
+		</svg>
+	);
+}