import axios from 'axios';
import { message } from 'antd';
import { getRequestErrorMessage, isAuthSessionFailure } from './authSessionPolicy';
import { requestDesktopSessionRenewal } from '../utils/desktopEmbedSession';

const DEFAULT_REQUEST_TIMEOUT_MS = Math.max(
  Number(import.meta.env.VITE_API_REQUEST_TIMEOUT_MS) || 120000,
  15000
);

const request = axios.create({
  baseURL: '', // Proxy handles the base URL
  timeout: DEFAULT_REQUEST_TIMEOUT_MS,
});
const AUTH_USER_STORAGE_KEY = 'auth_user';

// 后端重启窗口内的自动重连
// ------------------------------------------------------------------
// 本地/线上后端在「隧道掉线 -> 监督器重启后端」期间会有 20~90 秒不可用，
// 此时 Vite 代理拿不到后端，会直接回 500（响应体是 HTML，没有 error 字段），
// 用户看到的就是一句没头没尾的 "Request failed with status code 500"。
// 这里对**幂等请求**（GET/HEAD/OPTIONS）在网络错误或 5xx 时做退避重试，
// 重启窗口过去后请求会自己成功，页面不再报错。
// 累计等待约 80 秒，覆盖最坏情况下的后端启动耗时。
const RETRY_BACKOFF_MS = [1500, 3000, 5000, 8000, 13000, 21000, 30000];
const RETRYABLE_METHODS = ['get', 'head', 'options'];
const RETRY_NOTICE_KEY = 'api-reconnect-notice';

function isRetryableRequest(config) {
  if (!config || config.retry === false) {
    return false;
  }
  const method = String(config.method || 'get').toLowerCase();
  return RETRYABLE_METHODS.includes(method);
}

function isRetryableError(error) {
  if (axios.isCancel?.(error) || error?.code === 'ERR_CANCELED') {
    return false;
  }
  const status = error?.response?.status;
  // 无响应：网络中断、连接被拒（后端还没起来）、代理转发失败
  if (!status) {
    return true;
  }
  // 5xx：后端内部错误 / 网关与代理错误
  return status >= 500 && status <= 599;
}

function sleep(ms) {
  return new Promise((resolve) => { setTimeout(resolve, ms); });
}

function notifyReconnecting() {
  message.open({
    key: RETRY_NOTICE_KEY,
    type: 'loading',
    content: '服务正在重启，正在自动重连…',
    duration: 0,
  });
}

function clearReconnectNotice() {
  message.destroy(RETRY_NOTICE_KEY);
}

function clearAuthSession() {
  localStorage.removeItem('token');
  localStorage.removeItem(AUTH_USER_STORAGE_KEY);
}

function parseJwtPayload(token) {
  if (!token) {
    return null;
  }

  try {
    const [, payload] = token.split('.');
    if (!payload) {
      return null;
    }

    const normalized = payload.replace(/-/g, '+').replace(/_/g, '/');
    const padded = normalized.padEnd(normalized.length + ((4 - normalized.length % 4) % 4), '=');
    return JSON.parse(window.atob(padded));
  } catch {
    return null;
  }
}

function isLocalPreviewSession() {
  const isLocalHost = ['localhost', '127.0.0.1'].includes(window.location.hostname);
  if (!isLocalHost) {
    return false;
  }

  const payload = parseJwtPayload(localStorage.getItem('token'));
  return payload?.authSource === 'local-preview';
}

function isPublicAuthPage() {
  return ['/login', '/callback', '/install'].includes(window.location.pathname);
}

function shouldBypass401Redirect(error) {
  const url = error?.config?.url || '';
  return url.includes('/api/auth/verify') || isLocalPreviewSession();
}

// Request interceptor
request.interceptors.request.use(
  (config) => {
    const token = localStorage.getItem('token');
    if (token) {
      config.headers['Authorization'] = `Bearer ${token}`;
    }
    return config;
  },
  (error) => {
    return Promise.reject(error);
  }
);

// Response interceptor
request.interceptors.response.use(
  (response) => {
    const res = response.data;
    // Compatible with backend interfaces that don't return code
    if (res && res.code && res.code !== 200) {
      const shouldBypassRedirect = res.code === 401 && shouldBypass401Redirect(response);

      if (!shouldBypassRedirect && !response.config?.silentError) {
        message.error(res.message || 'Error');
      }
      
      if (res.code === 401 && !shouldBypassRedirect) {
        // Handle unauthorized - 但如果已在登录页则不重定向
        clearAuthSession();
        if (!isPublicAuthPage()) {
          if (!requestDesktopSessionRenewal('api-unauthorized')) {
            window.location.href = '/login';
          }
        }
      }
      return Promise.reject(new Error(res.message || 'Error'));
    }
    clearReconnectNotice();
    return res;
  },
  async (error) => {
    const config = error?.config;

    // ---- 后端重启窗口内自动重试（只对幂等请求、只对网络错误/5xx）----
    // 说明：这里用 `return request(config)`（不带 await）而不是 await，
    // 这样重试失败时由「内层」这一分支继续退避；外层调用栈不会重新进入本函数，
    // 因此最终失败提示天然只会出现一次，也不会把重试次数叠加错。
    if (isRetryableRequest(config) && !config.__retryExhausted && isRetryableError(error)) {
      const attempt = Number(config.__retryAttempt || 0);
      if (attempt < RETRY_BACKOFF_MS.length) {
        config.__retryAttempt = attempt + 1;
        if (attempt === 0 && !config.silentError) {
          notifyReconnecting();
        }
        await sleep(RETRY_BACKOFF_MS[attempt]);
        return request(config);
      }
      // 次数用尽：标记后不再重试，并把连接提示收掉
      config.__retryExhausted = true;
      config.__retryAttempt = 0;
      clearReconnectNotice();
    }

    const authSessionFailure = isAuthSessionFailure(error.response);
    if (!authSessionFailure && !error?.config?.silentError) {
      message.error(getRequestErrorMessage(error));
    }
    if (authSessionFailure && !shouldBypass401Redirect(error)) {
      clearAuthSession();
      // 如果已在登录页则不重定向，避免无限循环
      if (!isPublicAuthPage()) {
        if (!requestDesktopSessionRenewal('api-unauthorized')) {
          window.location.href = '/login';
        }
      }
    }
    return Promise.reject(error);
  }
);

export default request;