fix: treat empty IMGW warning products as no warnings

lib/imgw-empty-response.ts

@@ -0,0 +1,17 @@
+export function isImgwNoProductsResponse(value: unknown) {
+  if (!value || typeof value !== "object") return false;
+  const response = value as { status?: unknown; message?: unknown };
+  return response.status === false
+    && typeof response.message === "string"
+    && response.message.toLocaleLowerCase("en-US").includes("no products were found");
+}
+
+export async function readImgwResponseBody(response: Response) {
+  const text = await response.text().catch(() => "");
+  if (!text) return { text, json: null as unknown };
+  try {
+    return { text, json: JSON.parse(text) as unknown };
+  } catch {
+    return { text, json: null as unknown };
+  }
+}

lib/server-warnings.ts

@@ -1,4 +1,5 @@
 import { normalizeWarning } from "@/lib/weather-utils";
+import { isImgwNoProductsResponse, readImgwResponseBody } from "@/lib/imgw-empty-response";
 import type { RawWarning, WeatherWarning } from "@/types/imgw";
 
 const IMGW_WARNINGS_METEO_URL = "https://danepubliczne.imgw.pl/api/data/warningsmeteo";
@@ -11,8 +12,9 @@ export async function fetchMeteoWarnings(signal?: AbortSignal): Promise<WeatherW
     signal,
   });
   if (!response.ok) {
-    const details = await response.text().catch(() => "");
-    throw new Error(`Unable to load IMGW meteorological warnings: ${response.status}${details ? ` ${details.slice(0, 240)}` : ""}`);
+    const details = await readImgwResponseBody(response);
+    if (response.status === 404 && isImgwNoProductsResponse(details.json)) return [];
+    throw new Error(`Unable to load IMGW meteorological warnings: ${response.status}${details.text ? ` ${details.text.slice(0, 240)}` : ""}`);
   }
   const rows = await response.json() as RawWarning[];
   return Array.isArray(rows) ? rows.map((warning, index) => normalizeWarning(warning, "meteo", index)) : [];