1 files changed, 102 insertions, 0 deletions
diff --git a/apps/web/src/preview/hit-test.ts b/apps/web/src/preview/hit-test.ts
new file mode 100644
index 00000000..0f5fd45e
--- /dev/null
+++ b/apps/web/src/preview/hit-test.ts
@@ -0,0 +1,102 @@
+import type { ElementWithBounds } from "./element-bounds";
+import type { ElementRef } from "@/timeline/types";
+
+function pointInRotatedRect({
+	px,
+	py,
+	cx,
+	cy,
+	width,
+	height,
+	rotation,
+}: {
+	px: number;
+	py: number;
+	cx: number;
+	cy: number;
+	width: number;
+	height: number;
+	rotation: number;
+}): boolean {
+	const angleRad = (rotation * Math.PI) / 180;
+	const cos = Math.cos(-angleRad);
+	const sin = Math.sin(-angleRad);
+	const dx = px - cx;
+	const dy = py - cy;
+	const localX = dx * cos - dy * sin;
+	const localY = dx * sin + dy * cos;
+	const halfW = Math.abs(width) / 2;
+	const halfH = Math.abs(height) / 2;
+	return (
+		localX >= -halfW && localX <= halfW && localY >= -halfH && localY <= halfH
+	);
+}
+
+export function getHitElements({
+	canvasX,
+	canvasY,
+	elementsWithBounds,
+}: {
+	canvasX: number;
+	canvasY: number;
+	elementsWithBounds: ElementWithBounds[];
+}): ElementWithBounds[] {
+	const hits: ElementWithBounds[] = [];
+
+	for (let i = elementsWithBounds.length - 1; i >= 0; i--) {
+		const { bounds } = elementsWithBounds[i];
+		if (
+			pointInRotatedRect({
+				px: canvasX,
+				py: canvasY,
+				cx: bounds.cx,
+				cy: bounds.cy,
+				width: bounds.width,
+				height: bounds.height,
+				rotation: bounds.rotation,
+			})
+		) {
+			hits.push(elementsWithBounds[i]);
+		}
+	}
+
+	return hits;
+}
+
+export function hitTest({
+	canvasX,
+	canvasY,
+	elementsWithBounds,
+}: {
+	canvasX: number;
+	canvasY: number;
+	elementsWithBounds: ElementWithBounds[];
+}): ElementWithBounds | null {
+	return (
+		getHitElements({
+			canvasX,
+			canvasY,
+			elementsWithBounds,
+		})[0] ?? null
+	);
+}
+
+export function resolvePreferredHit({
+	hits,
+	preferredElements,
+}: {
+	hits: ElementWithBounds[];
+	preferredElements: ElementRef[];
+}): ElementWithBounds | null {
+	if (preferredElements.length === 0) return null;
+
+	return (
+		hits.find((hit) =>
+			preferredElements.some(
+				(preferredElement) =>
+					preferredElement.trackId === hit.trackId &&
+					preferredElement.elementId === hit.elementId,
+			),
+		) ?? null
+	);
+}