const API_BASE = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:3001/api/v1';

let apiAvailable: boolean | null = null;
let probePromise: Promise<boolean> | null = null;

async function checkApi(): Promise<boolean> {
  if (apiAvailable !== null) return apiAvailable;
  if (probePromise) return probePromise;
  probePromise = (async () => {
    try {
      const res = await fetch(`${API_BASE}/products`, { method: 'HEAD', signal: AbortSignal.timeout(300) });
      apiAvailable = res.ok;
    } catch {
      apiAvailable = false;
    }
    return apiAvailable;
  })();
  return probePromise;
}

async function request<T>(path: string, options?: RequestInit): Promise<T> {
  const available = await checkApi();
  if (!available) throw new Error('API 不可用');
  const res = await fetch(`${API_BASE}${path}`, {
    headers: { 'Content-Type': 'application/json', ...options?.headers },
    ...options,
  }).catch(() => null);
  if (!res) throw new Error('API 不可用');
  if (!res.ok) {
    const error = await res.json().catch(() => ({}));
    throw new Error(error.message || `请求失败: ${res.status}`);
  }
  return res.json();
}

export const api = {
  get: <T>(path: string) => request<T>(path),
  post: <T>(path: string, data: unknown) =>
    request<T>(path, { method: 'POST', body: JSON.stringify(data) }),
  patch: <T>(path: string, data: unknown) =>
    request<T>(path, { method: 'PATCH', body: JSON.stringify(data) }),
  delete: <T>(path: string) => request<T>(path, { method: 'DELETE' }),
};