[skip ci] Initial commit — CodexBar Mobile Expo app

lib/api/codexApi.ts

@@ -0,0 +1,25 @@
+import type { CodexAuth, CodexUsageResponse } from "@/types/codex";
+
+const USAGE_URL = "https://chatgpt.com/backend-api/wham/usage";
+
+export async function fetchCodexUsage(auth: CodexAuth): Promise<CodexUsageResponse> {
+  const headers: Record<string, string> = {
+    Authorization: `Bearer ${auth.accessToken}`,
+    "Content-Type": "application/json",
+  };
+
+  if (auth.accountId) {
+    headers["ChatGPT-Account-Id"] = auth.accountId;
+  }
+
+  const response = await fetch(USAGE_URL, { headers });
+
+  if (response.status === 401 || response.status === 403) {
+    throw new Error("TOKEN_EXPIRED");
+  }
+  if (!response.ok) {
+    throw new Error(`HTTP_ERROR_${response.status}`);
+  }
+
+  return response.json() as Promise<CodexUsageResponse>;
+}