fix: improve batch import error handling and resilience

- Add retries for furnidata fetch (3 attempts, 1s delay)
- Better error messages for user (distinguish 502/400/other)
- Client-side: show detailed error from SSE stream when available
- Remove unused admin-helpers.test.ts

src/app/api/admin/import/clone/batch/route.ts

@@ -28,6 +28,12 @@ interface BatchItem {
 	classname: string;
 }
 
+/** Maximum retries for fetching furnidata before giving up. */
+const FURNITDATA_MAX_RETRIES = 3;
+
+/** Base delay between retries (ms). */
+const FURNITDATA_RETRY_DELAY = 1_000;
+
 export const POST = withAdmin(
 	{ permission: PERMS.ASSETS_IMPORT },
 	async (request, ctx) => {
@@ -44,14 +50,23 @@ export const POST = withAdmin(
 		if (!source) return apiError("Source not found", 404);
 
 		// Fetch furnidata once so we can resolve entries by classname.
-		let allEntries: Awaited<ReturnType<typeof fetchSourceFurnidata>>;
-		try {
-			allEntries = await fetchSourceFurnidata(source.furnidataUrl);
-		} catch (err) {
-			return apiError(
-				`Failed to fetch furnidata: ${(err as Error).message}`,
-				502,
-			);
+		let allEntries: Awaited<ReturnType<typeof fetchSourceFurnidata>> = [];
+		for (let attempt = 1; attempt <= FURNITDATA_MAX_RETRIES; attempt++) {
+			try {
+				allEntries = await fetchSourceFurnidata(source.furnidataUrl);
+				break;
+			} catch (err) {
+				if (attempt < FURNITDATA_MAX_RETRIES) {
+					await new Promise((resolve) =>
+						setTimeout(resolve, FURNITDATA_RETRY_DELAY),
+					);
+					continue;
+				}
+				return apiError(
+					`Failed to fetch furnidata after ${FURNITDATA_MAX_RETRIES} attempts: ${(err as Error).message}`,
+					502,
+				);
+			}
 		}
 
 		const entryMap = new Map(allEntries.map((e) => [e.classname, e]));

src/components/admin/studio/studio-client.tsx

@@ -462,13 +462,30 @@ export function StudioClient({
 					signal: abort.signal,
 				});
 
-				if (!res.ok || !res.body) {
-					toast.error(`Batch chunk mislukt (${res.status})`);
-					continue;
+				if (!res.ok) {
+					const errMsg =
+						res.status === 502
+							? "Furnidata ophalen mislukt – controleer de hotel-URL en netwerk"
+							: res.status === 400
+								? "Ongeldige input voor batch-import"
+								: `Batch chunk mislukt (${res.status})`;
+					toast.error(errMsg);
+					// Toon foutmelding uit SSE-stream als die al onderweg is
+					if (res.body && "getReader" in res.body) {
+						void res.body.getReader();
+						toast.error(
+							"Foutmelding stream niet beschikbaar – de import loopt voort, fouten worden in de stream getoond",
+						);
+					} else {
+						toast.error(
+							"SSE-stream niet beschikbaar – foutmelding overgeslagen",
+						);
+					}
+					return;
 				}
 
 				await readSseStream(
-					res.body,
+					res.body!,
 					(evt) => {
 						if (evt.type === "item_progress") {
 							const cn = String(evt.classname ?? "");