import axios, { type AxiosRequestConfig } from "axios";

// ============================================================
// Token 存储 Key
// ============================================================

const ACCESS_TOKEN_KEY = "track_admin_token";
const REFRESH_TOKEN_KEY = "track_admin_refresh_token";
const USER_KEY = "track_admin_user";

// ============================================================
// Token 读写工具
// ============================================================

export function getAccessToken(): string | null {
  return localStorage.getItem(ACCESS_TOKEN_KEY);
}

export function getRefreshToken(): string | null {
  return localStorage.getItem(REFRESH_TOKEN_KEY);
}

export function setTokens(accessToken: string, refreshToken: string) {
  localStorage.setItem(ACCESS_TOKEN_KEY, accessToken);
  localStorage.setItem(REFRESH_TOKEN_KEY, refreshToken);
}

export function clearAuth() {
  localStorage.removeItem(ACCESS_TOKEN_KEY);
  localStorage.removeItem(REFRESH_TOKEN_KEY);
  localStorage.removeItem(USER_KEY);
}

// ============================================================
// Axios 实例
// ============================================================

const api = axios.create({
  baseURL: import.meta.env.VITE_API_BASE_URL,
  timeout: 10000,
  headers: {
    "Content-Type": "application/json",
  },
});

// ============================================================
// 请求拦截器 — 注入 Access Token
// ============================================================

api.interceptors.request.use(
  (config) => {
    const token = getAccessToken();
    if (token) {
      config.headers.Authorization = `Bearer ${token}`;
    }
    return config;
  },
  (error) => Promise.reject(error),
);

// ============================================================
// 响应拦截器 — 双 Token 无感刷新 + 并发请求队列
// ============================================================

let isRefreshing = false;
let retryQueue: Array<{
  resolve: (token: string) => void;
  reject: (error: unknown) => void;
}> = [];

/** 处理队列中的所有挂起请求 */
function processQueue(error: unknown, token: string | null) {
  retryQueue.forEach((p) => {
    if (token) {
      p.resolve(token);
    } else {
      p.reject(error);
    }
  });
  retryQueue = [];
}

api.interceptors.response.use(
  (response) => response,
  async (error) => {
    const originalRequest: AxiosRequestConfig & { _retry?: boolean } =
      error.config;
    const status = error.response?.status;

    // 仅处理 401
    if (status !== 401) {
      return Promise.reject(error);
    }

    // 跳过登录和刷新接口自身（避免死循环）
    const url = originalRequest.url ?? "";
    if (url.includes("/auth/login") || url.includes("/auth/refresh")) {
      return Promise.reject(error);
    }

    // 避免对同一请求重复刷新
    if (originalRequest._retry) {
      clearAuth();
      if (window.location.pathname.startsWith("/admin")) {
        window.location.href = "/admin/login";
      }
      return Promise.reject(error);
    }
    originalRequest._retry = true;

    // ---- 并发请求队列机制 ----
    if (isRefreshing) {
      // 已有刷新进行中，加入队列等待
      return new Promise<string>((resolve, reject) => {
        retryQueue.push({ resolve, reject });
      }).then((newToken) => {
        originalRequest.headers = originalRequest.headers || {};
        originalRequest.headers.Authorization = `Bearer ${newToken}`;
        return api(originalRequest);
      });
    }

    isRefreshing = true;

    try {
      const refreshToken = getRefreshToken();
      if (!refreshToken) {
        throw new Error("无 Refresh Token");
      }

      // 调用刷新接口
      const { data } = await axios.post(
        `${import.meta.env.VITE_API_BASE_URL}/auth/refresh`,
        { refresh_token: refreshToken },
        { headers: { "Content-Type": "application/json" } },
      );

      const newAccessToken: string = data.access_token;
      setTokens(newAccessToken, refreshToken); // 更新 Access Token

      // 重放队列中的所有请求
      processQueue(null, newAccessToken);

      // 重试当前请求
      originalRequest.headers = originalRequest.headers || {};
      originalRequest.headers.Authorization = `Bearer ${newAccessToken}`;
      return api(originalRequest);
    } catch (refreshError) {
      // Refresh Token 也过期 — 彻底登出
      processQueue(refreshError, null);
      clearAuth();
      if (window.location.pathname.startsWith("/admin")) {
        window.location.href = "/admin/login";
      }
      return Promise.reject(refreshError);
    } finally {
      isRefreshing = false;
    }
  },
);

export default api;