1 files changed, 112 insertions, 0 deletions
diff --git a/apps/web/src/lib/masks/geometry.ts b/apps/web/src/lib/masks/geometry.ts
new file mode 100644
index 00000000..c6d386f8
--- /dev/null
+++ b/apps/web/src/lib/masks/geometry.ts
@@ -0,0 +1,112 @@
+import type { ElementBounds } from "@/lib/preview/element-bounds";
+import type { SnapLine } from "@/lib/preview/preview-snap";
+import { MIN_MASK_DIMENSION } from "@/constants/mask-constants";
+import type { ParamValues } from "@/lib/params";
+import type { RectangleMaskParams } from "@/lib/masks/types";
+
+export function hasCenterParams(params: ParamValues): params is ParamValues & {
+	centerX: number;
+	centerY: number;
+} {
+	return (
+		typeof params.centerX === "number" && typeof params.centerY === "number"
+	);
+}
+
+export function isRectangleMaskParams(
+	params: ParamValues,
+): params is RectangleMaskParams {
+	return (
+		hasCenterParams(params) &&
+		typeof params.width === "number" &&
+		typeof params.height === "number" &&
+		typeof params.rotation === "number" &&
+		typeof params.scale === "number"
+	);
+}
+
+export function getMaskLocalCenter({
+	params,
+	bounds,
+}: {
+	params: ParamValues;
+	bounds: ElementBounds;
+}): { x: number; y: number } | null {
+	if (!hasCenterParams(params)) return null;
+
+	return {
+		x: params.centerX * bounds.width,
+		y: params.centerY * bounds.height,
+	};
+}
+
+export function setMaskLocalCenter({
+	center,
+	bounds,
+}: {
+	center: { x: number; y: number };
+	bounds: ElementBounds;
+}): Pick<ParamValues, "centerX" | "centerY"> {
+	return {
+		centerX: bounds.width === 0 ? 0 : center.x / bounds.width,
+		centerY: bounds.height === 0 ? 0 : center.y / bounds.height,
+	};
+}
+
+export function getMaskSnapGeometry({
+	params,
+	bounds,
+}: {
+	params: ParamValues;
+	bounds: ElementBounds;
+}): {
+	position: { x: number; y: number };
+	size: { width: number; height: number };
+	rotation: number;
+} | null {
+	const position = getMaskLocalCenter({ params, bounds });
+	if (!position) return null;
+
+	if (isRectangleMaskParams(params)) {
+		return {
+			position,
+			size: {
+				width: Math.max(params.width, MIN_MASK_DIMENSION) * bounds.width,
+				height: Math.max(params.height, MIN_MASK_DIMENSION) * bounds.height,
+			},
+			rotation: params.rotation,
+		};
+	}
+
+	return {
+		position,
+		size: { width: 0, height: 0 },
+		rotation: typeof params.rotation === "number" ? params.rotation : 0,
+	};
+}
+
+export function toGlobalMaskSnapLines({
+	lines,
+	bounds,
+	canvasSize,
+}: {
+	lines: SnapLine[];
+	bounds: ElementBounds;
+	canvasSize: { width: number; height: number };
+}): SnapLine[] {
+	const centerX = bounds.cx - canvasSize.width / 2;
+	const centerY = bounds.cy - canvasSize.height / 2;
+
+	return lines.map((line) =>
+		line.type === "vertical"
+			? {
+					type: "vertical" as const,
+					position: centerX + line.position,
+				}
+			: {
+					type: "horizontal" as const,
+					position: centerY + line.position,
+				},
+	);
+}
+