import React, { useEffect, useState } from 'react';
import { useNavigate, useSearchParams } from 'react-router-dom';
import { authService } from '../services/authService';
import { Loader2, CheckCircle2, AlertCircle } from 'lucide-react';

const API_BASE = import.meta.env.VITE_API_BASE_URL ?? 'http://localhost:8010';

/**
 * SSO 回调页面
 * 
 * 支持两种模式：
 * 1. OAuth2 授权码模式：统一认证平台跳转携带 code 参数
 *    URL: /sso-callback?code=xxx
 * 2. 旧模式兼容：携带 sso_token 参数（直接验证 token）
 *    URL: /sso-callback?sso_token=xxx&redirect=/models
 */
const SSOCallback: React.FC = () => {
  const navigate = useNavigate();
  const [searchParams] = useSearchParams();
  const [status, setStatus] = useState<'loading' | 'success' | 'error'>('loading');
  const [message, setMessage] = useState('正在验证身份...');

  useEffect(() => {
    const code = searchParams.get('code');
    const ssoToken = searchParams.get('sso_token');
    let redirect = searchParams.get('redirect') || '/';

    // 安全归一化
    const forbidden = ['/login', '/register', '/sso-callback'];
    if (!redirect || forbidden.includes(redirect)) {
      redirect = '/';
    }

    if (code) {
      // OAuth2 授权码模式：用 code 换取本地 token
      handleOAuth2Code(code, redirect);
    } else if (ssoToken) {
      // 旧模式兼容：直接用 sso_token 登录
      handleSsoToken(ssoToken, redirect);
    } else {
      setStatus('error');
      setMessage('缺少认证参数，请从统一认证平台重新登录');
      setTimeout(() => navigate('/login'), 3000);
    }
  }, []);

  const handleOAuth2Code = async (code: string, redirect: string) => {
    try {
      const response = await fetch(`${API_BASE}/api/oauth/exchange-code`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ code })
      });

      const result = await response.json();

      if (result.code === 200 && result.data?.token) {
        // 保存 token 和用户信息
        const { token, user } = result.data;
        authService.setToken(token, user);

        setStatus('success');
        setMessage('登录成功，正在跳转...');
        setTimeout(() => navigate(redirect, { replace: true }), 1000);
      } else {
        setStatus('error');
        setMessage(result.detail || result.message || 'SSO 登录失败');
        setTimeout(() => navigate('/login'), 3000);
      }
    } catch (err) {
      setStatus('error');
      setMessage(err instanceof Error ? err.message : 'SSO 登录失败，请稍后重试');
      setTimeout(() => navigate('/login'), 3000);
    }
  };

  const handleSsoToken = async (ssoToken: string, redirect: string) => {
    try {
      const response = await authService.ssoLogin(ssoToken);
      if (response.code === 200) {
        setStatus('success');
        setMessage('登录成功，正在跳转...');
        setTimeout(() => navigate(redirect, { replace: true }), 1000);
      } else {
        setStatus('error');
        setMessage(response.message || 'SSO 登录失败');
        setTimeout(() => navigate('/login'), 3000);
      }
    } catch (err) {
      setStatus('error');
      setMessage(err instanceof Error ? err.message : 'SSO 登录失败，请稍后重试');
      setTimeout(() => navigate('/login'), 3000);
    }
  };

  return (
    <div className="min-h-screen flex items-center justify-center bg-gradient-to-br from-blue-50 via-white to-indigo-50 px-4">
      <div className="w-full max-w-md">
        <div className="bg-white rounded-2xl shadow-2xl border border-gray-100 p-12 text-center">
          {status === 'loading' && (
            <>
              <Loader2 className="w-16 h-16 text-blue-600 animate-spin mx-auto mb-6" />
              <h2 className="text-xl font-bold text-gray-900 mb-2">正在验证身份</h2>
              <p className="text-sm text-gray-500">{message}</p>
            </>
          )}

          {status === 'success' && (
            <>
              <CheckCircle2 className="w-16 h-16 text-green-500 mx-auto mb-6" />
              <h2 className="text-xl font-bold text-gray-900 mb-2">登录成功</h2>
              <p className="text-sm text-gray-500">{message}</p>
            </>
          )}

          {status === 'error' && (
            <>
              <AlertCircle className="w-16 h-16 text-red-500 mx-auto mb-6" />
              <h2 className="text-xl font-bold text-gray-900 mb-2">登录失败</h2>
              <p className="text-sm text-gray-500 mb-4">{message}</p>
              <p className="text-xs text-gray-400">3秒后自动跳转到登录页面</p>
            </>
          )}
        </div>
      </div>
    </div>
  );
};

export default SSOCallback;