Add pagination to ISAC registries

src/lib/server/pagination.ts

@@ -0,0 +1,18 @@
+import type { URL } from 'node:url';
+
+export const PAGE_SIZE_PRESETS = [10, 25, 50, 100] as const;
+
+export function getPagination(url: URL, total: number) {
+	const requestedSize = Number(url.searchParams.get('perPage'));
+	const perPage = PAGE_SIZE_PRESETS.includes(requestedSize as (typeof PAGE_SIZE_PRESETS)[number]) ? requestedSize : 25;
+	const pageCount = Math.max(1, Math.ceil(total / perPage));
+	const requestedPage = Number(url.searchParams.get('page'));
+	const page = Math.min(pageCount, Math.max(1, Number.isInteger(requestedPage) ? requestedPage : 1));
+	return {
+		page,
+		perPage,
+		total,
+		pageCount,
+		offset: (page - 1) * perPage
+	};
+}