1 files changed, 59 insertions, 0 deletions
diff --git a/apps/web/src/lib/masks/param-update.ts b/apps/web/src/lib/masks/param-update.ts
new file mode 100644
index 00000000..967a4be0
--- /dev/null
+++ b/apps/web/src/lib/masks/param-update.ts
@@ -0,0 +1,59 @@
+import { FEATHER_HANDLE_SCALE, MAX_FEATHER } from "@/constants/mask-constants";
+import { masksRegistry } from "@/lib/masks";
+import type { ParamValues } from "@/lib/params";
+import type {
+	BaseMaskParams,
+	MaskParamUpdateArgs,
+	MaskType,
+} from "@/lib/masks/types";
+
+function compactMaskParamValues({
+	params,
+}: {
+	params: Partial<ParamValues>;
+}): ParamValues {
+	const nextParams: ParamValues = {};
+	for (const [key, value] of Object.entries(params)) {
+		if (value !== undefined) {
+			nextParams[key] = value;
+		}
+	}
+	return nextParams;
+}
+
+export function computeFeatherUpdate({
+	startFeather,
+	deltaX,
+	deltaY,
+	directionX,
+	directionY,
+}: {
+	startFeather: number;
+	deltaX: number;
+	deltaY: number;
+	directionX: number;
+	directionY: number;
+}): ParamValues {
+	const projection = deltaX * directionX + deltaY * directionY;
+	return {
+		feather: Math.max(
+			0,
+			Math.min(
+				MAX_FEATHER,
+				Math.round(startFeather + projection / FEATHER_HANDLE_SCALE),
+			),
+		),
+	};
+}
+
+export function computeMaskParamUpdate({
+	maskType,
+	...args
+}: {
+	maskType: MaskType;
+} & MaskParamUpdateArgs<BaseMaskParams & ParamValues>): ParamValues {
+	const definition = masksRegistry.get(maskType);
+	return compactMaskParamValues({
+		params: definition.computeParamUpdate(args),
+	});
+}