import axios, {
  AxiosRequestConfig,
  AxiosResponse,
  AxiosError,
  InternalAxiosRequestConfig,
} from 'axios';
import { toast } from 'react-toastify';
import { getRouteLang } from './getLanguage';

// ─── Error message extractor ───────────────────────────────────────────────────

function extractErrorMessage(error: AxiosError): string {
  const data = error.response?.data as Record<string, unknown> | undefined;

  if (!data) {
    if (error.code === 'ECONNABORTED')
      return 'Request timed out. Please try again.';
    if (!navigator.onLine) return 'No internet connection.';
    return error.message || 'An unexpected error occurred.';
  }

  // Simple string fields: { message, detail, error }
  if (typeof data.message === 'string' && data.message) return data.message;
  if (typeof data.detail === 'string' && data.detail) return data.detail;
  if (typeof data.error === 'string' && data.error) return data.error;

  // Wrapped: { errors: { field: ["msg"] } }
  if (data.errors && typeof data.errors === 'object') {
    const first = Object.values(data.errors as Record<string, unknown>)[0];
    if (Array.isArray(first) && first.length > 0) return String(first[0]);
    if (typeof first === 'string') return first;
  }

  // DRF field-level errors at top level: { phone: ["msg"], name: ["msg"] }
  for (const val of Object.values(data)) {
    if (Array.isArray(val) && val.length > 0 && typeof val[0] === 'string') {
      return val[0];
    }
    if (typeof val === 'string' && val) return val;
  }

  return 'An unexpected error occurred.';
}

// ─── Constants ─────────────────────────────────────────────────────────────────

// const baseUrl = process.env.NEXT_PUBLIC_API_BASE_URL;
const baseUrl = 'https://api.anti-plagiat.uz/api/v1';
const DEFAULT_LOCALE = 'uz'; // fallback locale for redirect

// ─── Token helpers ─────────────────────────────────────────────────────────────
// Adjust key names to match whatever your auth stores them under.

export const TokenStorage = {
  getAccess: (): string | null => localStorage.getItem('access_token'),
  getRefresh: (): string | null => localStorage.getItem('refresh_token'),

  setAccess: (token: string): void =>
    localStorage.setItem('access_token', token),
  setRefresh: (token: string): void =>
    localStorage.setItem('refresh_token', token),

  setTokens: (access: string, refresh: string): void => {
    localStorage.setItem('access_token', access);
    localStorage.setItem('refresh_token', refresh);
  },

  clear: (): void => {
    localStorage.removeItem('access_token');
    localStorage.removeItem('refresh_token');
  },
};

// ─── Redirect helper ───────────────────────────────────────────────────────────

function redirectToMain(): void {
  // Detect current locale from the URL path, fall back to DEFAULT_LOCALE
  const pathLocale = window.location.pathname.split('/')[1];
  const validLocales = ['uz', 'ru', 'en'];
  const locale = validLocales.includes(pathLocale)
    ? pathLocale
    : DEFAULT_LOCALE;

  window.location.href = `/${locale}`;
}

// ─── Axios instance ────────────────────────────────────────────────────────────

const api = axios.create({
  baseURL: baseUrl,
  timeout: 15_000,
});

// ─── Flag to prevent multiple simultaneous refresh calls ──────────────────────

let isRefreshing = false;

// Queue of failed requests waiting for the new token
type FailedRequestResolver = (token: string) => void;
let failedQueue: {
  resolve: FailedRequestResolver;
  reject: (err: unknown) => void;
}[] = [];

function processQueue(error: unknown, token: string | null = null): void {
  failedQueue.forEach(({ resolve, reject }) => {
    if (error) {
      reject(error);
    } else if (token) {
      resolve(token);
    }
  });
  failedQueue = [];
}

// ─── Request interceptor — attach access token ────────────────────────────────

api.interceptors.request.use(
  (config: InternalAxiosRequestConfig) => {
    const token = TokenStorage.getAccess();

    if (token) {
      config.headers.Authorization = `Bearer ${token}`;
    }

    config.headers['Accept-Language'] = getRouteLang();

    return config;
  },
  (error: AxiosError) => Promise.reject(error),
);

// ─── Response interceptor — handle 401, refresh, retry ───────────────────────

api.interceptors.response.use(
  // ── 2xx: pass through unchanged ────────────────────────────────────────────
  (response: AxiosResponse) => response,

  // ── Error: attempt token refresh on 401 ────────────────────────────────────
  async (error: AxiosError) => {
    const originalRequest = error.config as InternalAxiosRequestConfig & {
      _retry?: boolean;
    };

    const status = error.response?.status;
    // const responseData = error.response?.data as Record<string, unknown> | undefined;
    const requestUrl = originalRequest.url ?? '';
    const isAuthEndpoint =
      requestUrl.includes('/users/login/') ||
      requestUrl.includes('/users/register/');

    // 403 with token_not_valid means the token is expired — clear and redirect
    if (status === 403) {
      TokenStorage.clear();
      redirectToMain();
      return Promise.reject(error);
    }

    // For auth endpoints, 401 means wrong credentials — show error, don't refresh
    if (isAuthEndpoint || status !== 401 || originalRequest._retry) {
      toast.error(extractErrorMessage(error));
      return Promise.reject(error);
    }

    const refreshToken = TokenStorage.getRefresh();

    // No refresh token available — clear everything and redirect
    if (!refreshToken) {
      TokenStorage.clear();
      redirectToMain();
      return Promise.reject(error);
    }

    // If a refresh is already in progress, queue this request
    if (isRefreshing) {
      return new Promise((resolve, reject) => {
        failedQueue.push({
          resolve: (token: string) => {
            originalRequest.headers.Authorization = `Bearer ${token}`;
            resolve(api(originalRequest));
          },
          reject,
        });
      });
    }

    // Mark that we're refreshing and this request has been retried
    originalRequest._retry = true;
    isRefreshing = true;

    try {
      // ── Call your refresh endpoint ──────────────────────────────────────────
      // Adjust the URL and payload shape to match your backend.
      const { data } = await axios.post<{
        access_token: string;
        refresh_token: string;
      }>(
        `${baseUrl}/auth/refresh`, // ← your refresh endpoint
        { refresh_token: refreshToken },
        { headers: { 'Accept-Language': getRouteLang() } },
      );

      const { access_token, refresh_token } = data;

      TokenStorage.setTokens(access_token, refresh_token);

      // Update the Authorization header for the retried request
      originalRequest.headers.Authorization = `Bearer ${access_token}`;

      // Unblock all queued requests with the new token
      processQueue(null, access_token);

      // Retry the original failed request
      return api(originalRequest);
    } catch (refreshError) {
      // Refresh itself failed — clear tokens and redirect to home
      processQueue(refreshError, null);
      TokenStorage.clear();
      redirectToMain();
      return Promise.reject(refreshError);
    } finally {
      isRefreshing = false;
    }
  },
);

// ─── Public request function ───────────────────────────────────────────────────

export const apiRequest = async <T>(
  method: 'GET' | 'POST' | 'PUT' | 'PATCH' | 'DELETE',
  url: string,
  data?: unknown,
  config?: Omit<AxiosRequestConfig, 'method' | 'url' | 'data'>,
): Promise<AxiosResponse<T>> => {
  const response = await api.request<T>({
    method,
    url,
    data,
    ...config,
    headers: {
      ...config?.headers,
      // Accept-Language is already set in the request interceptor,
      // but config?.headers can still override it if needed.
    },
  });

  console.log('resposne: ', response);

  return response;
};