import { useState, useEffect } from 'react';
import { useNavigate, Link, useLocation } from 'react-router-dom';
import { useAuth } from '@/hooks/useAuth';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { Label } from '@/components/ui/label';
import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card';
import { toast } from '@/hooks/use-toast';
import { z } from 'zod';
import { ArrowLeft, Mail } from 'lucide-react';

const emailSchema = z.string().email('Invalid email address');
const passwordSchema = z.string().min(6, 'Password must be at least 6 characters');

export default function Auth() {
  const [isLogin, setIsLogin] = useState(true);
  const [showOTP, setShowOTP] = useState(false);
  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [name, setName] = useState('');
  const [otpCode, setOtpCode] = useState('');
  const [loading, setLoading] = useState(false);
  const [pendingUserId, setPendingUserId] = useState<string | null>(null);
  const [resendCountdown, setResendCountdown] = useState(0);
  const [isResendOTP, setIsResendOTP] = useState(false); // Track if this is resend OTP for existing user
  const { signIn, signUp, user, sendAuthOTP, verifyAuthOTP, getUserByEmail } = useAuth();
  const navigate = useNavigate();
  const location = useLocation();

  useEffect(() => {
    if (user) {
      // Check if there's a saved redirect path
      const savedRedirect = sessionStorage.getItem('redirectAfterLogin');
      if (savedRedirect) {
        sessionStorage.removeItem('redirectAfterLogin');
        navigate(savedRedirect);
      } else {
        navigate('/dashboard');
      }
    }
  }, [user, navigate]);

  // Countdown timer for resend OTP
  useEffect(() => {
    if (resendCountdown > 0) {
      const timer = setTimeout(() => setResendCountdown(resendCountdown - 1), 1000);
      return () => clearTimeout(timer);
    }
  }, [resendCountdown]);

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault();

    try {
      emailSchema.parse(email);
      passwordSchema.parse(password);
    } catch (err) {
      if (err instanceof z.ZodError) {
        toast({ title: 'Validation Error', description: err.errors[0].message, variant: 'destructive' });
        return;
      }
    }

    setLoading(true);

    if (isLogin) {
      const { error } = await signIn(email, password);
      if (error) {
        console.log('Login error:', error.message);

        // Check if error is due to unconfirmed email
        // Supabase returns various error messages for unconfirmed email
        const isUnconfirmedEmail =
          error.message.includes('Email not confirmed') ||
          error.message.includes('Email not verified') ||
          error.message.includes('Email not confirmed') ||
          error.message.toLowerCase().includes('email') && error.message.toLowerCase().includes('not confirmed') ||
          error.message.toLowerCase().includes('unconfirmed');

        console.log('Is unconfirmed email?', isUnconfirmedEmail);

        if (isUnconfirmedEmail) {
          // Get user by email to fetch user_id
          console.log('Fetching user by email for OTP resend...');
          const userResult = await getUserByEmail(email);

          console.log('User lookup result:', userResult);

          if (userResult.success && userResult.user_id) {
            setPendingUserId(userResult.user_id);
            setIsResendOTP(true);
            setShowOTP(true);
            setResendCountdown(0); // Allow immediate resend on first attempt
            toast({
              title: 'Email Belum Dikonfirmasi',
              description: 'Silakan verifikasi email Anda. Kami akan mengirimkan kode OTP.',
            });
          } else {
            toast({
              title: 'Error',
              description: 'User tidak ditemukan. Silakan daftar terlebih dahulu.',
              variant: 'destructive'
            });
          }
          setLoading(false);
          return;
        }
        toast({ title: 'Error', description: error.message, variant: 'destructive' });
        setLoading(false);
      } else {
        // Get redirect from sessionStorage or use default
        const savedRedirect = sessionStorage.getItem('redirectAfterLogin');
        const redirectTo = savedRedirect || '/dashboard';
        if (savedRedirect) {
          sessionStorage.removeItem('redirectAfterLogin');
        }
        navigate(redirectTo);
        setLoading(false);
      }
    } else {
      if (!name.trim()) {
        toast({ title: 'Error', description: 'Name is required', variant: 'destructive' });
        setLoading(false);
        return;
      }

      const { error, data } = await signUp(email, password, name);

      console.log('SignUp result:', { error, data, hasUser: !!data?.user, hasSession: !!data?.session });

      if (error) {
        if (error.message.includes('already registered')) {
          toast({ title: 'Error', description: 'This email is already registered. Please login instead.', variant: 'destructive' });
        } else {
          toast({ title: 'Error', description: error.message, variant: 'destructive' });
        }
        setLoading(false);
        return;
      }

      if (!data?.user) {
        toast({ title: 'Error', description: 'Failed to create user account. Please try again.', variant: 'destructive' });
        setLoading(false);
        return;
      }

      // User created, now send OTP
      const userId = data.user.id;
      console.log('User created successfully:', { userId, email, session: data.session });

      const result = await sendAuthOTP(userId, email);

      console.log('OTP send result:', result);

      if (result.success) {
        setPendingUserId(userId);
        setShowOTP(true);
        setResendCountdown(60); // 60 seconds cooldown
        toast({
          title: 'OTP Terkirim',
          description: 'Kode verifikasi telah dikirim ke email Anda. Silakan cek inbox.',
        });
      } else {
        toast({ title: 'Error', description: result.message, variant: 'destructive' });
      }
      setLoading(false);
    }
  };

  const handleOTPSubmit = async (e: React.FormEvent) => {
    e.preventDefault();

    if (!pendingUserId) {
      toast({ title: 'Error', description: 'Session expired. Please try again.', variant: 'destructive' });
      setShowOTP(false);
      return;
    }

    if (otpCode.length !== 6) {
      toast({ title: 'Error', description: 'OTP harus 6 digit', variant: 'destructive' });
      return;
    }

    setLoading(true);

    const result = await verifyAuthOTP(pendingUserId, otpCode);

    if (result.success) {
      toast({
        title: 'Verifikasi Berhasil',
        description: 'Email Anda telah terverifikasi. Silakan login.',
      });
      setShowOTP(false);
      setIsLogin(true);
      // Reset form
      setName('');
      setOtpCode('');
      setPendingUserId(null);
    } else {
      toast({ title: 'Error', description: result.message, variant: 'destructive' });
    }

    setLoading(false);
  };

  const handleResendOTP = async () => {
    if (resendCountdown > 0 || !pendingUserId) return;

    setLoading(true);

    const result = await sendAuthOTP(pendingUserId, email);

    if (result.success) {
      setResendCountdown(60);
      toast({ title: 'OTP Terkirim Ulang', description: 'Kode verifikasi baru telah dikirim ke email Anda.' });
    } else {
      toast({ title: 'Error', description: result.message, variant: 'destructive' });
    }

    setLoading(false);
  };

  return (
    <div className="min-h-screen flex items-center justify-center bg-background p-4">
      <div className="w-full max-w-md space-y-4">
        {/* Back to Home Button */}
        <Link to="/">
          <Button variant="ghost" className="gap-2">
            <ArrowLeft className="w-4 h-4" />
            Kembali ke Beranda
          </Button>
        </Link>

        {!showOTP ? (
          <Card className="border-2 border-border shadow-md">
            <CardHeader>
              <CardTitle className="text-2xl">{isLogin ? 'Login' : 'Daftar'}</CardTitle>
              <CardDescription>
                {isLogin ? 'Masuk untuk mengakses akun Anda' : 'Buat akun baru untuk memulai'}
              </CardDescription>
            </CardHeader>
            <CardContent>
              <form onSubmit={handleSubmit} className="space-y-4">
                {!isLogin && (
                  <div className="space-y-2">
                    <Label htmlFor="name">Nama</Label>
                    <Input
                      id="name"
                      type="text"
                      value={name}
                      onChange={(e) => setName(e.target.value)}
                      placeholder="Nama lengkap"
                      className="border-2"
                    />
                  </div>
                )}
                <div className="space-y-2">
                  <Label htmlFor="email">Email</Label>
                  <Input
                    id="email"
                    type="email"
                    value={email}
                    onChange={(e) => setEmail(e.target.value)}
                    placeholder="email@anda.com"
                    className="border-2"
                  />
                </div>
                <div className="space-y-2">
                  <Label htmlFor="password">Password</Label>
                  <Input
                    id="password"
                    type="password"
                    value={password}
                    onChange={(e) => setPassword(e.target.value)}
                    placeholder="••••••••"
                    className="border-2"
                  />
                </div>
                <Button type="submit" className="w-full shadow-sm" disabled={loading}>
                  {loading ? 'Memuat...' : isLogin ? 'Masuk' : 'Daftar'}
                </Button>
              </form>

              <div className="mt-4 text-center">
                <button
                  type="button"
                  onClick={() => setIsLogin(!isLogin)}
                  className="text-sm text-muted-foreground hover:underline"
                >
                  {isLogin ? 'Belum punya akun? Daftar' : 'Sudah punya akun? Masuk'}
                </button>
              </div>
            </CardContent>
          </Card>
        ) : (
          <Card className="border-2 border-border shadow-md">
            <CardHeader>
              <CardTitle className="text-2xl flex items-center gap-2">
                <Mail className="w-6 h-6" />
                Verifikasi Email
              </CardTitle>
              <CardDescription>
                Masukkan kode 6 digit yang telah dikirim ke <strong>{email}</strong>
              </CardDescription>
            </CardHeader>
            <CardContent>
              <form onSubmit={handleOTPSubmit} className="space-y-4">
                <div className="space-y-2">
                  <Label htmlFor="otp">Kode OTP</Label>
                  <Input
                    id="otp"
                    type="text"
                    value={otpCode}
                    onChange={(e) => {
                      // Only allow numbers, max 6 digits
                      const value = e.target.value.replace(/\D/g, '').slice(0, 6);
                      setOtpCode(value);
                    }}
                    placeholder="123456"
                    className="border-2 text-center text-2xl tracking-widest font-mono"
                    maxLength={6}
                    autoFocus
                  />
                  <p className="text-xs text-muted-foreground">
                    Masukkan 6 digit kode dari email Anda
                  </p>
                </div>

                <Button type="submit" className="w-full shadow-sm" disabled={loading || otpCode.length !== 6}>
                  {loading ? 'Memverifikasi...' : 'Verifikasi'}
                </Button>

                <div className="text-center space-y-2">
                  <p className="text-sm text-muted-foreground">
                    Tidak menerima kode?
                  </p>
                  <Button
                    type="button"
                    variant="link"
                    onClick={handleResendOTP}
                    disabled={resendCountdown > 0 || loading}
                    className="text-sm"
                  >
                    {resendCountdown > 0
                      ? `Kirim ulang dalam ${resendCountdown} detik`
                      : 'Kirim ulang kode'}
                  </Button>
                </div>

                <div className="pt-4 border-t">
                  <Button
                    type="button"
                    variant="ghost"
                    onClick={() => {
                      setShowOTP(false);
                      setOtpCode('');
                      setPendingUserId(null);
                      setResendCountdown(0);
                    }}
                    className="w-full text-sm"
                  >
                    Kembali ke form pendaftaran
                  </Button>
                </div>
              </form>
            </CardContent>
          </Card>
        )}
      </div>
    </div>
  );
}