1 files changed, 50 insertions, 0 deletions
diff --git a/apps/web/src/lib/selection/hit-testing.ts b/apps/web/src/lib/selection/hit-testing.ts
new file mode 100644
index 00000000..ba086425
--- /dev/null
+++ b/apps/web/src/lib/selection/hit-testing.ts
@@ -0,0 +1,50 @@
+function isIntersecting({
+	selectionRect,
+	itemRect,
+}: {
+	selectionRect: DOMRect;
+	itemRect: DOMRect;
+}) {
+	return !(
+		itemRect.right < selectionRect.left ||
+		itemRect.left > selectionRect.right ||
+		itemRect.bottom < selectionRect.top ||
+		itemRect.top > selectionRect.bottom
+	);
+}
+
+function createSelectionRect({
+	startPos,
+	currentPos,
+}: {
+	startPos: { x: number; y: number };
+	currentPos: { x: number; y: number };
+}) {
+	return new DOMRect(
+		Math.min(startPos.x, currentPos.x),
+		Math.min(startPos.y, currentPos.y),
+		Math.abs(currentPos.x - startPos.x),
+		Math.abs(currentPos.y - startPos.y),
+	);
+}
+
+export function resolveElementIntersections({
+	startPos,
+	currentPos,
+	elements,
+}: {
+	startPos: { x: number; y: number };
+	currentPos: { x: number; y: number };
+	elements: Map<string, HTMLElement>;
+}) {
+	const selectionRect = createSelectionRect({ startPos, currentPos });
+
+	return [...elements.entries()]
+		.filter(([, element]) =>
+			isIntersecting({
+				selectionRect,
+				itemRect: element.getBoundingClientRect(),
+			}),
+		)
+		.map(([id]) => id);
+}