feat: create expense navigation helper function

src/lib/expense-list-navigation.ts

@@ -0,0 +1,39 @@
+type SearchParamsLike = {
+  get: (name: string) => string | null;
+};
+
+const EXPENSE_LIST_PATH = '/expense';
+
+export const getExpenseListReturnTo = (searchParams: SearchParamsLike) => {
+  const existingReturnTo = searchParams.get('returnTo');
+
+  if (existingReturnTo?.startsWith(EXPENSE_LIST_PATH)) {
+    return existingReturnTo;
+  }
+
+  const params = new URLSearchParams();
+  const page = searchParams.get('page');
+  const limit = searchParams.get('limit');
+
+  if (page) params.set('page', page);
+  if (limit) params.set('limit', limit);
+
+  const queryString = params.toString();
+
+  return queryString
+    ? `${EXPENSE_LIST_PATH}?${queryString}`
+    : EXPENSE_LIST_PATH;
+};
+
+export const buildExpenseActionHref = (
+  path: string,
+  expenseId: number | string,
+  searchParams: SearchParamsLike
+) => {
+  const params = new URLSearchParams({
+    expenseId: String(expenseId),
+    returnTo: getExpenseListReturnTo(searchParams),
+  });
+
+  return `${path}?${params.toString()}`;
+};