const API_BASE_URL =
  process.env.NEXT_PUBLIC_API_BASE_URL ?? "/backend";

export class ApiError extends Error {
  status: number;
  code: number | string | undefined;

  constructor(message: string, status: number, code?: number | string) {
    super(message);
    this.name = "ApiError";
    this.status = status;
    this.code = code;
  }
}

export async function apiFetch<T>(path: string, init: RequestInit = {}): Promise<T> {
  const token = typeof window === "undefined" ? null : localStorage.getItem("huaxia_token");
  const headers = new Headers(init.headers);
  headers.set("Content-Type", "application/json");
  if (token) headers.set("Authorization", `Bearer ${token}`);

  const response = await fetch(`${API_BASE_URL}${path}`, {
    ...init,
    headers,
    cache: "no-store",
  });

  const payload = await response.json().catch(() => null);
  if (response.status === 401 && typeof window !== "undefined") {
    localStorage.removeItem("huaxia_token");
    if (!window.location.pathname.startsWith("/login")) window.location.href = "/login";
  }
  if (!response.ok || (payload && payload.code !== 200)) {
    throw new ApiError(
      payload?.message ?? "请求失败，请稍后重试",
      response.status,
      payload?.code
    );
  }

  return (payload?.data ?? payload) as T;
}

export async function apiStream(path: string, body: unknown): Promise<string> {
  const token = typeof window === "undefined" ? null : localStorage.getItem("huaxia_token");
  const headers = new Headers({ "Content-Type": "application/json", Accept: "text/event-stream" });
  if (token) headers.set("Authorization", `Bearer ${token}`);
  const response = await fetch(`${API_BASE_URL}${path}`, {
    method: "POST",
    headers,
    body: JSON.stringify(body),
    cache: "no-store",
  });
  if (!response.ok) throw new ApiError("请求失败，请稍后重试", response.status);
  const text = await response.text();
  const event = text.split("\n").find((line) => line.startsWith("data:"));
  if (!event) return text;
  const payload = JSON.parse(event.slice(5).trim()) as { content?: string; answer?: string; message?: string };
  return payload.content ?? payload.answer ?? payload.message ?? text;
}