1 files changed, 82 insertions, 0 deletions
diff --git a/apps/web/src/lib/animation/curve-bridge.ts b/apps/web/src/lib/animation/curve-bridge.ts
new file mode 100644
index 00000000..55f96933
--- /dev/null
+++ b/apps/web/src/lib/animation/curve-bridge.ts
@@ -0,0 +1,82 @@
+import { TIME_EPSILON_SECONDS } from "@/constants/animation-constants";
+import {
+	getDefaultLeftHandle,
+	getDefaultRightHandle,
+} from "@/lib/animation/bezier";
+import type {
+	CurveHandle,
+	NormalizedCubicBezier,
+	ScalarAnimationKey,
+} from "@/lib/animation/types";
+
+const VALUE_EPSILON = 1e-6;
+
+function clamp01({ value }: { value: number }): number {
+	return Math.max(0, Math.min(1, value));
+}
+
+export function getNormalizedCubicBezierForScalarSegment({
+	leftKey,
+	rightKey,
+}: {
+	leftKey: ScalarAnimationKey;
+	rightKey: ScalarAnimationKey;
+}): NormalizedCubicBezier | null {
+	const spanTime = rightKey.time - leftKey.time;
+	const spanValue = rightKey.value - leftKey.value;
+	if (
+		Math.abs(spanTime) <= TIME_EPSILON_SECONDS ||
+		Math.abs(spanValue) <= VALUE_EPSILON
+	) {
+		return null;
+	}
+
+	const rightHandle =
+		leftKey.rightHandle ?? getDefaultRightHandle({ leftKey, rightKey });
+	const leftHandle =
+		rightKey.leftHandle ?? getDefaultLeftHandle({ leftKey, rightKey });
+
+	return [
+		clamp01({ value: rightHandle.dt / spanTime }),
+		rightHandle.dv / spanValue,
+		clamp01({ value: 1 + leftHandle.dt / spanTime }),
+		1 + leftHandle.dv / spanValue,
+	];
+}
+
+export function getCurveHandlesForNormalizedCubicBezier({
+	leftKey,
+	rightKey,
+	cubicBezier,
+}: {
+	leftKey: ScalarAnimationKey;
+	rightKey: ScalarAnimationKey;
+	cubicBezier: NormalizedCubicBezier;
+}): {
+	rightHandle: CurveHandle;
+	leftHandle: CurveHandle;
+} | null {
+	const spanTime = rightKey.time - leftKey.time;
+	const spanValue = rightKey.value - leftKey.value;
+	if (
+		Math.abs(spanTime) <= TIME_EPSILON_SECONDS ||
+		Math.abs(spanValue) <= VALUE_EPSILON
+	) {
+		return null;
+	}
+
+	const [rawX1, y1, rawX2, y2] = cubicBezier;
+	const x1 = clamp01({ value: rawX1 });
+	const x2 = clamp01({ value: rawX2 });
+
+	return {
+		rightHandle: {
+			dt: spanTime * x1,
+			dv: spanValue * y1,
+		},
+		leftHandle: {
+			dt: spanTime * (x2 - 1),
+			dv: spanValue * (y2 - 1),
+		},
+	};
+}