import { memo, useCallback, useEffect, useState } from 'react'
import { useNavigate } from 'react-router'
import { Activity, Eye, EyeOff, Shield, ServerOff } from 'lucide-react'
import { Button } from '@/components/ui/button'
import { Input } from '@/components/ui/input'
import { Label } from '@/components/ui/label'
import { authApi } from '@/api'
import { toast } from 'sonner'

/**
 * Login 页面 - 优化版本
 * 
 * 优化点：
 * 1. React.memo 包裹组件
 * 2. 表单处理使用 useCallback 缓存
 * 3. 错误处理使用 sonner toast 替代 alert
 * 4. 清理 useEffect 中的未使用变量
 */
const Login = memo(function Login() {
  const [username, setUsername] = useState('admin')
  const [password, setPassword] = useState('admin123')
  const [showPassword, setShowPassword] = useState(false)
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState('')
  const [backendStatus, setBackendStatus] = useState<'checking' | 'online' | 'offline'>('checking')
  const navigate = useNavigate()

  useEffect(() => {
    // Check if already logged in
    const token = localStorage.getItem('token')
    if (token) {
      navigate('/')
      return
    }
    // Quick backend check
    checkBackend()
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [navigate])

  // 后端状态检查 - useCallback缓存
  const checkBackend = useCallback(async () => {
    try {
      const controller = new AbortController()
      const timeoutId = setTimeout(() => controller.abort(), 3000)
      // 用公开的健康检查端点探活；避免打 /auth/login（生产环境被 nginx 限流 5r/m，
      // 反复刷新登录页会触发限流并锁死真正的登录请求）
      const res = await fetch('/api/v1/health', {
        method: 'GET',
        signal: controller.signal,
      })
      clearTimeout(timeoutId)
      setBackendStatus(res.ok ? 'online' : 'offline')
    } catch {
      setBackendStatus('offline')
    }
  }, [])

  // 表单提交处理 - useCallback缓存
  const handleSubmit = useCallback(
    async (e: React.FormEvent) => {
      e.preventDefault()
      setLoading(true)
      setError('')

      try {
        const result = await authApi.login(username, password)
        localStorage.setItem('token', result.accessToken)
        localStorage.setItem('refreshToken', result.refreshToken)
        localStorage.setItem('user', JSON.stringify(result.user))
        toast.success('登录成功')
        navigate('/')
      } catch (err: unknown) {
        const message = err instanceof Error ? err.message : '登录失败'
        if (message.includes('Cannot connect')) {
          setError('无法连接后端服务，请确认后端已启动（端口 8080）。')
          setBackendStatus('offline')
        } else if (
          message.includes('invalid') ||
          message.includes('password') ||
          message.includes('密码') ||
          message.includes('Unauthorized')
        ) {
          setError('用户名或密码错误')
        } else {
          setError(message)
        }
      } finally {
        setLoading(false)
      }
    },
    [username, password, navigate]
  )

  // 密码显示切换 - useCallback缓存
  const togglePassword = useCallback(() => {
    setShowPassword((prev) => !prev)
  }, [])

  return (
    <div className="min-h-screen bg-slate-50 dark:bg-slate-950 flex items-center justify-center p-4">
      <div className="w-full max-w-md">
        {/* Logo */}
        <div className="text-center mb-8">
          <div className="inline-flex items-center justify-center w-16 h-16 rounded-2xl bg-emerald-500 mb-4">
            <Activity className="w-9 h-9 text-white" />
          </div>
          <h1 className="text-2xl font-bold text-slate-900 dark:text-white">LokiDeploy</h1>
          <p className="text-sm text-slate-500 mt-1">Kubernetes Loki 日志部署平台</p>
        </div>

        {/* Backend Status */}
        {backendStatus === 'offline' && (
          <div className="mb-4 p-4 rounded-xl bg-amber-50 border border-amber-200 flex items-start gap-3">
            <ServerOff className="w-5 h-5 text-amber-600 flex-shrink-0 mt-0.5" />
            <div>
              <p className="text-sm font-medium text-amber-800">后端服务未启动</p>
              <p className="text-xs text-amber-700 mt-1">
                无法连接 API 服务，请先启动后端：
              </p>
              <code className="block mt-2 px-3 py-2 bg-amber-100 rounded text-xs font-mono text-amber-900">
                ./run.sh
              </code>
            </div>
          </div>
        )}

        {/* Login Card */}
        <div className="bg-white dark:bg-slate-900 rounded-2xl shadow-lg border border-slate-200 dark:border-slate-800 p-8">
          <div className="flex items-center gap-2 mb-6">
            <Shield className="w-5 h-5 text-emerald-500" />
            <h2 className="text-lg font-semibold text-slate-800 dark:text-white">登录</h2>
          </div>

          {error && (
            <div className="mb-4 p-3 rounded-lg bg-red-50 border border-red-200 text-red-600 text-sm">
              {error}
            </div>
          )}

          <form onSubmit={handleSubmit} className="space-y-4">
            <div className="space-y-2">
              <Label htmlFor="username">用户名</Label>
              <Input
                id="username"
                value={username}
                onChange={(e) => setUsername(e.target.value)}
                placeholder="请输入用户名"
                required
                className="h-10"
                autoComplete="username"
              />
            </div>

            <div className="space-y-2">
              <Label htmlFor="password">密码</Label>
              <div className="relative">
                <Input
                  id="password"
                  type={showPassword ? 'text' : 'password'}
                  value={password}
                  onChange={(e) => setPassword(e.target.value)}
                  placeholder="请输入密码"
                  required
                  className="h-10 pr-10"
                  autoComplete="current-password"
                />
                <button
                  type="button"
                  onClick={togglePassword}
                  className="absolute right-3 top-1/2 -translate-y-1/2 text-slate-400 hover:text-slate-600"
                  tabIndex={-1}
                >
                  {showPassword ? (
                    <EyeOff className="w-4 h-4" />
                  ) : (
                    <Eye className="w-4 h-4" />
                  )}
                </button>
              </div>
            </div>

            <Button
              type="submit"
              className="w-full h-10 bg-emerald-600 hover:bg-emerald-700 text-white"
              disabled={loading}
            >
              {loading ? '登录中...' : '登录'}
            </Button>
          </form>

          <div className="mt-6 pt-4 border-t border-slate-100 dark:border-slate-800">
            <p className="text-xs text-center text-slate-500">
              默认账号：admin / admin123
            </p>
          </div>
        </div>
      </div>
    </div>
  )
})

export default Login