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d2ypp2/web-console/lib/fetchJson.ts

@@ -0,0 +1,73 @@
+type JsonErrorPayload = {
+  error?: string;
+  message?: string;
+  detail?: string;
+};
+
+const MAX_ERROR_TEXT = 240;
+
+function summarizeResponseText(raw: string): string {
+  const compact = raw.replace(/\s+/g, " ").trim();
+  if (!compact) return "";
+  if (compact.length <= MAX_ERROR_TEXT) return compact;
+  return `${compact.slice(0, MAX_ERROR_TEXT - 3)}...`;
+}
+
+function defaultHttpMessage(response: Response): string {
+  const suffix = response.statusText?.trim() ? ` ${response.statusText.trim()}` : "";
+  return `HTTP ${response.status}${suffix}`;
+}
+
+function extractErrorMessage(
+  response: Response,
+  raw: string,
+  payload: JsonErrorPayload | null,
+): string {
+  const candidate =
+    (typeof payload?.error === "string" && payload.error.trim()) ||
+    (typeof payload?.message === "string" && payload.message.trim()) ||
+    (typeof payload?.detail === "string" && payload.detail.trim()) ||
+    summarizeResponseText(raw);
+  return candidate || defaultHttpMessage(response);
+}
+
+export async function fetchJsonResponse<T>(url: string, init?: RequestInit): Promise<T> {
+  const response = await fetch(url, init);
+  const raw = await response.text();
+  const trimmed = raw.trim();
+  let payload: (T & JsonErrorPayload) | null = null;
+
+  if (trimmed) {
+    try {
+      payload = JSON.parse(trimmed) as T & JsonErrorPayload;
+    } catch {
+      if (!response.ok) {
+        throw new Error(extractErrorMessage(response, trimmed, null));
+      }
+      throw new Error(`Invalid JSON response from ${url}`);
+    }
+  }
+
+  if (!response.ok) {
+    throw new Error(extractErrorMessage(response, trimmed, payload));
+  }
+
+  if (payload !== null) {
+    return payload as T;
+  }
+
+  return {} as T;
+}
+
+export async function readErrorMessage(response: Response): Promise<string> {
+  const raw = (await response.text()).trim();
+  let payload: JsonErrorPayload | null = null;
+  if (raw) {
+    try {
+      payload = JSON.parse(raw) as JsonErrorPayload;
+    } catch {
+      payload = null;
+    }
+  }
+  return extractErrorMessage(response, raw, payload);
+}