import type { ApiError, ApiResponse } from "@umt/contracts";

export type { ApiResponse };

// ─── API Key 存储 ───────────────────────────────────────────────
const TOKEN_KEY = "umt-api-key";

export function getToken(): string {
  if (typeof localStorage === "undefined") return "";
  return localStorage.getItem(TOKEN_KEY) || "";
}

export function setToken(token: string) {
  localStorage.setItem(TOKEN_KEY, token);
}

export function clearAuth() {
  localStorage.removeItem(TOKEN_KEY);
}

// ─── 请求参数 ────────────────────────────────────────────────────
export type FetcherArg<B = unknown> = {
  /** 路径变量,如 { id: "..." } 替换 /api/v1/media/:id */
  pathParams?: Record<string, string | number>;
  params?: Record<string, string | number | boolean | undefined | null>;
  method?: "GET" | "POST" | "PUT" | "PATCH" | "DELETE";
  body?: B;
  headers?: Record<string, string>;
  signal?: AbortSignal;
};

export const API_BASE = import.meta.env.VITE_API_BASE_URL ?? "";

const fail = (code: ApiError["code"], message: string): ApiResponse<never> => ({
  ok: false,
  error: { code, message },
});

/**
 * 核心 fetcher:始终返回 ApiResponse 信封,不抛出网络/解析错误。
 *   queryFn:    () => apiFetch<HealthStatus>("/api/v1/health")
 *   mutationFn: (body) => apiFetch("/api/v1/xxx", { method: "POST", body })
 */
export async function apiFetch<T = unknown>(path: string, arg: FetcherArg = {}): Promise<ApiResponse<T>> {
  const { method = "GET", headers = {}, body, params, pathParams, signal } = arg;

  let url = `${API_BASE.replace(/\/+$/, "")}${path}`;
  if (pathParams) {
    for (const [key, value] of Object.entries(pathParams)) {
      url = url.replace(`:${key}`, encodeURIComponent(String(value)));
    }
  }
  if (params) {
    const qs = new URLSearchParams();
    for (const [key, value] of Object.entries(params)) {
      if (value !== undefined && value !== null) qs.append(key, String(value));
    }
    const s = qs.toString();
    if (s) url += (url.includes("?") ? "&" : "?") + s;
  }

  const reqHeaders: Record<string, string> = { ...headers };
  const token = getToken();
  if (token) reqHeaders.Authorization = `Bearer ${token}`;

  let reqBody: BodyInit | undefined;
  if (body instanceof FormData) {
    reqBody = body;
  } else if (body !== undefined && body !== null) {
    reqHeaders["Content-Type"] ??= "application/json";
    reqBody = JSON.stringify(body);
  }

  let res: Response;
  try {
    res = await fetch(url, { method, headers: reqHeaders, body: reqBody, signal });
  } catch (err) {
    if ((err as Error).name === "AbortError") throw err;
    return fail("upstream_unavailable", "无法连接服务");
  }

  if (res.status === 401 && typeof window !== "undefined") {
    window.dispatchEvent(new CustomEvent("unauthorized"));
  }

  try {
    return (await res.json()) as ApiResponse<T>;
  } catch {
    return fail("internal", `响应不是 JSON(HTTP ${res.status})`);
  }
}

/** 取出 data,失败时抛出(给 react-query 的 queryFn 用,错误进入 error 状态) */
export async function apiData<T>(path: string, arg?: FetcherArg): Promise<T> {
  const r = await apiFetch<T>(path, arg);
  if (!r.ok) throw Object.assign(new Error(r.error.message), { code: r.error.code });
  return r.data;
}

/** TanStack Query mutationFn 包装 */
export function mutateFetcher<B = unknown, T = unknown>(path: string, base?: Omit<FetcherArg<B>, "body">) {
  return (body: B) => apiFetch<T>(path, { method: "POST", ...base, body });
}

export const TTL_SECOND = 1_000;
export const TTL_MINUTE = TTL_SECOND * 60;
export const TTL_HOUR = TTL_MINUTE * 60;