import React, { useState } from 'react';
import { useNavigate } from 'react-router-dom';
import { apiClient, errorMessage } from '../services/api';
import './Login.css';

type TabType = 'login' | 'register';

function Login() {
  const navigate = useNavigate();
  const [activeTab, setActiveTab] = useState<TabType>('login');
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<string>('');

  // Login form
  const [loginEmail, setLoginEmail] = useState('');
  const [loginPassword, setLoginPassword] = useState('');

  // Register form
  const [regEmail, setRegEmail] = useState('');
  const [regGarminEmail, setRegGarminEmail] = useState('');
  const [regPassword, setRegPassword] = useState('');
  const [regConfirmPassword, setRegConfirmPassword] = useState('');

  const validateEmail = (email: string): boolean => {
    const re = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
    return re.test(email);
  };

  const validatePassword = (password: string): boolean => {
    return password.length >= 6;
  };

  const handleLogin = async (e: React.FormEvent) => {
    e.preventDefault();
    setError('');

    if (!validateEmail(loginEmail)) {
      setError('Please enter a valid email');
      return;
    }

    if (!validatePassword(loginPassword)) {
      setError('Password must be at least 6 characters');
      return;
    }

    setLoading(true);

    try {
      const { token } = await apiClient.login(loginEmail, loginPassword);
      apiClient.setSession(token);
      navigate('/');
    } catch (err: any) {
      setError(errorMessage(err, '登录失败'));
    } finally {
      setLoading(false);
    }
  };

  const handleRegister = async (e: React.FormEvent) => {
    e.preventDefault();
    setError('');

    if (!validateEmail(regEmail)) {
      setError('Please enter a valid email');
      return;
    }

    if (!validateEmail(regGarminEmail)) {
      setError('Please enter a valid Garmin email');
      return;
    }

    if (!validatePassword(regPassword)) {
      setError('Password must be at least 6 characters');
      return;
    }

    if (regPassword !== regConfirmPassword) {
      setError('Passwords do not match');
      return;
    }

    setLoading(true);

    try {
      const { token } = await apiClient.register(regEmail, regGarminEmail, regPassword);
      apiClient.setSession(token);
      navigate('/');
    } catch (err: any) {
      setError(errorMessage(err, '注册失败'));
    } finally {
      setLoading(false);
    }
  };

  return (
    <div className="login-container">
      <div className="login-card">
        <div className="login-header">
          <h1>🏃 Garmin Health Lab</h1>
          <p>健康数据分析平台</p>
        </div>

        <div className="login-tabs">
          <button
            className={`tab-button ${activeTab === 'login' ? 'active' : ''}`}
            onClick={() => {
              setActiveTab('login');
              setError('');
            }}
          >
            登录
          </button>
          <button
            className={`tab-button ${activeTab === 'register' ? 'active' : ''}`}
            onClick={() => {
              setActiveTab('register');
              setError('');
            }}
          >
            注册
          </button>
        </div>

        {error && <div className="error-message">{error}</div>}

        {activeTab === 'login' && (
          <form onSubmit={handleLogin} className="login-form">
            <div className="form-group">
              <label htmlFor="login-email">邮箱</label>
              <input
                id="login-email"
                type="email"
                value={loginEmail}
                onChange={(e) => setLoginEmail(e.target.value)}
                placeholder="example@example.com"
                required
                disabled={loading}
              />
            </div>

            <div className="form-group">
              <label htmlFor="login-password">密码</label>
              <input
                id="login-password"
                type="password"
                value={loginPassword}
                onChange={(e) => setLoginPassword(e.target.value)}
                placeholder="••••••••"
                required
                disabled={loading}
              />
            </div>

            <button type="submit" className="submit-button" disabled={loading}>
              {loading ? '登录中...' : '登录'}
            </button>
          </form>
        )}

        {activeTab === 'register' && (
          <form onSubmit={handleRegister} className="login-form">
            <div className="form-group">
              <label htmlFor="reg-email">邮箱</label>
              <input
                id="reg-email"
                type="email"
                value={regEmail}
                onChange={(e) => setRegEmail(e.target.value)}
                placeholder="example@example.com"
                required
                disabled={loading}
              />
            </div>

            <div className="form-group">
              <label htmlFor="reg-garmin-email">Garmin 邮箱</label>
              <input
                id="reg-garmin-email"
                type="email"
                value={regGarminEmail}
                onChange={(e) => setRegGarminEmail(e.target.value)}
                placeholder="garmin@example.com"
                required
                disabled={loading}
              />
            </div>

            <div className="form-group">
              <label htmlFor="reg-password">密码</label>
              <input
                id="reg-password"
                type="password"
                value={regPassword}
                onChange={(e) => setRegPassword(e.target.value)}
                placeholder="••••••••"
                required
                disabled={loading}
              />
            </div>

            <div className="form-group">
              <label htmlFor="reg-confirm-password">确认密码</label>
              <input
                id="reg-confirm-password"
                type="password"
                value={regConfirmPassword}
                onChange={(e) => setRegConfirmPassword(e.target.value)}
                placeholder="••••••••"
                required
                disabled={loading}
              />
            </div>

            <button type="submit" className="submit-button" disabled={loading}>
              {loading ? '注册中...' : '注册'}
            </button>
          </form>
        )}
      </div>
    </div>
  );
}

export default Login;