refactor: dedupe provider usage fetch logic and tests

src/infra/provider-usage.fetch.shared.ts

@@ -1,3 +1,6 @@
+import { PROVIDER_LABELS } from "./provider-usage.shared.js";
+import type { ProviderUsageSnapshot, UsageProviderId } from "./provider-usage.types.js";
+
 export async function fetchJson(
   url: string,
   init: RequestInit,
@@ -12,3 +15,33 @@ export async function fetchJson(
     clearTimeout(timer);
   }
 }
+
+type BuildUsageHttpErrorSnapshotOptions = {
+  provider: UsageProviderId;
+  status: number;
+  message?: string;
+  tokenExpiredStatuses?: readonly number[];
+};
+
+export function buildUsageErrorSnapshot(
+  provider: UsageProviderId,
+  error: string,
+): ProviderUsageSnapshot {
+  return {
+    provider,
+    displayName: PROVIDER_LABELS[provider],
+    windows: [],
+    error,
+  };
+}
+
+export function buildUsageHttpErrorSnapshot(
+  options: BuildUsageHttpErrorSnapshotOptions,
+): ProviderUsageSnapshot {
+  const tokenExpiredStatuses = options.tokenExpiredStatuses ?? [];
+  if (tokenExpiredStatuses.includes(options.status)) {
+    return buildUsageErrorSnapshot(options.provider, "Token expired");
+  }
+  const suffix = options.message?.trim() ? `: ${options.message.trim()}` : "";
+  return buildUsageErrorSnapshot(options.provider, `HTTP ${options.status}${suffix}`);
+}