'use client';

import { useState, useEffect } from "react";
import { cn } from "@/lib/utils"
import { Button } from "@/components/ui/button"
import { Input } from "@/components/ui/input"
import { Ship, InfoIcon, GlobeIcon, ChevronDownIcon, ArrowLeft } from "lucide-react";
import { useToast } from "@/hooks/use-toast";
import { DropdownMenu, DropdownMenuTrigger, DropdownMenuContent, DropdownMenuRadioGroup, DropdownMenuRadioItem } from "@/components/ui/dropdown-menu"
import { useTranslation } from '@/i18n/client'
import { useRouter, useParams, usePathname, useSearchParams } from 'next/navigation';
import { signIn, getSession } from 'next-auth/react';
import { buttonVariants } from "@/components/ui/button"
import Link from "next/link"
import Image from 'next/image';
import { useFormState } from 'react-dom';
import {
    InputOTP,
    InputOTPGroup,
    InputOTPSlot,
} from "@/components/ui/input-otp"
import { requestPasswordResetAction } from "@/lib/users/auth/partners-auth";

type LoginMethod = 'username' | 'sgips';

export function LoginForm({
    className,
    ...props
}: React.ComponentProps<"div">) {
    const params = useParams() || {};
    const pathname = usePathname() || '';
    const router = useRouter();
    const searchParams = useSearchParams();

    const lng = params.lng as string;
    const { t, i18n } = useTranslation(lng, 'login');
    const { toast } = useToast();

    // 상태 관리
    const [loginMethod, setLoginMethod] = useState<LoginMethod>('username');
    const [isLoading, setIsLoading] = useState(false);
    const [showForgotPassword, setShowForgotPassword] = useState(false);

    // MFA 관련 상태
    const [showMfaForm, setShowMfaForm] = useState(false);
    const [mfaToken, setMfaToken] = useState('');
    const [mfaUserId, setMfaUserId] = useState('');
    const [mfaUserEmail, setMfaUserEmail] = useState('');
    const [mfaCountdown, setMfaCountdown] = useState(0);

    // 일반 로그인 폼 데이터
    const [username, setUsername] = useState('');
    const [password, setPassword] = useState('');

    // S-Gips 로그인 폼 데이터  
    const [sgipsUsername, setSgipsUsername] = useState('');
    const [sgipsPassword, setSgipsPassword] = useState('');

    // 서버 액션 상태
    const [passwordResetState, passwordResetAction] = useFormState(requestPasswordResetAction, {
        success: false,
        error: undefined,
        message: undefined,
    });

    const handleChangeLanguage = (lang: string) => {
        const segments = pathname.split('/');
        segments[1] = lang;
        router.push(segments.join('/'));
    };

    const currentLanguageText = i18n.language === 'ko' ? t('languages.korean') : t('languages.english');

    const goToVendorRegistration = () => {
        router.push(`/${lng}/partners/repository`);
    };

    // MFA 카운트다운 효과
    useEffect(() => {
        if (mfaCountdown > 0) {
            const timer = setTimeout(() => setMfaCountdown(mfaCountdown - 1), 1000);
            return () => clearTimeout(timer);
        }
    }, [mfaCountdown]);

    // 서버 액션 결과 처리
    useEffect(() => {
        if (passwordResetState.success && passwordResetState.message) {
            toast({
                title: '재설정 링크 전송',
                description: passwordResetState.message,
            });
            setShowForgotPassword(false);
        } else if (passwordResetState.error) {
            toast({
                title: t('errorTitle'),
                description: passwordResetState.error,
                variant: 'destructive',
            });
        }
    }, [passwordResetState, toast, t]);

    // SMS 토큰 전송
    const handleSendSms = async () => {
        if (!mfaUserId || mfaCountdown > 0) return;

        setIsLoading(true);
        try {
            // SMS 전송 API 호출 (실제 구현 필요)
            const response = await fetch('/api/auth/send-sms', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ userId: mfaUserId }),
            });

            if (response.ok) {
                setMfaCountdown(60); // 60초 카운트다운
                toast({
                    title: 'SMS 전송 완료',
                    description: '인증번호를 전송했습니다.',
                });
            } else {
                toast({
                    title: t('errorTitle'),
                    description: 'SMS 전송에 실패했습니다.',
                    variant: 'destructive',
                });
            }
        } catch (error) {
            console.error('SMS send error:', error);
            toast({
                title: t('errorTitle'),
                description: 'SMS 전송 중 오류가 발생했습니다.',
                variant: 'destructive',
            });
        } finally {
            setIsLoading(false);
        }
    };

    // MFA 토큰 검증
    const handleMfaSubmit = async (e: React.FormEvent) => {
        e.preventDefault();

        if (!mfaToken || mfaToken.length !== 6) {
            toast({
                title: t('errorTitle'),
                description: '6자리 인증번호를 입력해주세요.',
                variant: 'destructive',
            });
            return;
        }

        setIsLoading(true);

        try {
            // MFA 토큰 검증 API 호출
            const response = await fetch('/api/auth/verify-mfa', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({
                    userId: mfaUserId,
                    token: mfaToken
                }),
            });

            if (response.ok) {
                toast({
                    title: '인증 완료',
                    description: '로그인이 완료되었습니다.',
                });

                // callbackUrl 처리
                const callbackUrlParam = searchParams?.get('callbackUrl');
                if (callbackUrlParam) {
                    try {
                        const callbackUrl = new URL(callbackUrlParam);
                        const relativeUrl = callbackUrl.pathname + callbackUrl.search;
                        router.push(relativeUrl);
                    } catch (e) {
                        router.push(callbackUrlParam);
                    }
                } else {
                    router.push(`/${lng}/partners/dashboard`);
                }
            } else {
                const errorData = await response.json();
                toast({
                    title: t('errorTitle'),
                    description: errorData.message || '인증번호가 올바르지 않습니다.',
                    variant: 'destructive',
                });
            }
        } catch (error) {
            console.error('MFA verification error:', error);
            toast({
                title: t('errorTitle'),
                description: 'MFA 인증 중 오류가 발생했습니다.',
                variant: 'destructive',
            });
        } finally {
            setIsLoading(false);
        }
    };

    // 일반 사용자명/패스워드 로그인 처리 (간소화된 버전)
    const handleUsernameLogin = async (e: React.FormEvent) => {
        e.preventDefault();

        if (!username || !password) {
            toast({
                title: t('errorTitle'),
                description: t('credentialsRequired'),
                variant: 'destructive',
            });
            return;
        }

        setIsLoading(true);

        try {
            // NextAuth credentials-password provider로 로그인
            const result = await signIn('credentials-password', {
                username: username,
                password: password,
                redirect: false,
            });

            if (result?.ok) {
                // 로그인 1차 성공 - 바로 MFA 화면으로 전환
                toast({
                    title: t('loginSuccess'),
                    description: '1차 인증이 완료되었습니다.',
                });

                // 모든 사용자는 MFA 필수이므로 바로 MFA 폼으로 전환
                setMfaUserId(username); // 입력받은 username 사용
                setMfaUserEmail(username); // 입력받은 username 사용 (보통 이메일)
                setShowMfaForm(true);

                // 자동으로 SMS 전송
                setTimeout(() => {
                    handleSendSms();
                }, 500);

                toast({
                    title: 'SMS 인증 필요',
                    description: '등록된 전화번호로 인증번호를 전송합니다.',
                });

            } else {
                // 로그인 실패 처리
                let errorMessage = t('invalidCredentials');

                if (result?.error) {
                    switch (result.error) {
                        case 'CredentialsSignin':
                            errorMessage = t('invalidCredentials');
                            break;
                        case 'AccessDenied':
                            errorMessage = t('accessDenied');
                            break;
                        default:
                            errorMessage = t('defaultErrorMessage');
                    }
                }

                toast({
                    title: t('errorTitle'),
                    description: errorMessage,
                    variant: 'destructive',
                });
            }
        } catch (error) {
            console.error('S-GIPS Login error:', error);
            toast({
                title: t('errorTitle'),
                description: t('defaultErrorMessage'),
                variant: 'destructive',
            });
        } finally {
            setIsLoading(false);
        }
    };


    // S-Gips 로그인 처리
    // S-Gips 로그인 처리 (간소화된 버전)
    const handleSgipsLogin = async (e: React.FormEvent) => {
        e.preventDefault();

        if (!sgipsUsername || !sgipsPassword) {
            toast({
                title: t('errorTitle'),
                description: t('credentialsRequired'),
                variant: 'destructive',
            });
            return;
        }

        setIsLoading(true);

        try {
            // NextAuth credentials-password provider로 로그인 (S-Gips 구분)
            const result = await signIn('credentials-password', {
                username: sgipsUsername,
                password: sgipsPassword,
                provider: 'sgips', // S-Gips 구분을 위한 추가 파라미터
                redirect: false,
            });

            if (result?.ok) {
                // S-Gips 1차 인증 성공 - 바로 MFA 화면으로 전환
                toast({
                    title: t('loginSuccess'),
                    description: 'S-Gips 인증이 완료되었습니다.',
                });

                // S-Gips도 MFA 필수이므로 바로 MFA 폼으로 전환
                setMfaUserId(sgipsUsername);
                setMfaUserEmail(sgipsUsername);
                setShowMfaForm(true);

                // 자동으로 SMS 전송
                setTimeout(() => {
                    handleSendSms();
                }, 500);

                toast({
                    title: 'SMS 인증 시작',
                    description: 'S-Gips 등록 전화번호로 인증번호를 전송합니다.',
                });

            } else {
                let errorMessage = t('sgipsLoginFailed');

                if (result?.error) {
                    switch (result.error) {
                        case 'CredentialsSignin':
                            errorMessage = t('invalidSgipsCredentials');
                            break;
                        case 'AccessDenied':
                            errorMessage = t('sgipsAccessDenied');
                            break;
                        default:
                            errorMessage = t('sgipsSystemError');
                    }
                }

                toast({
                    title: t('errorTitle'),
                    description: errorMessage,
                    variant: 'destructive',
                });
            }
        } catch (error) {
            console.error('S-Gips login error:', error);
            toast({
                title: t('errorTitle'),
                description: t('sgipsSystemError'),
                variant: 'destructive',
            });
        } finally {
            setIsLoading(false);
        }
    };

    return (
        <div className="container relative flex h-screen flex-col items-center justify-center md:grid lg:max-w-none lg:grid-cols-2 lg:px-0">
            {/* Left Content */}
            <div className="flex flex-col w-full h-screen lg:p-2">
                {/* Top bar with Logo + eVCP (left) and "Request Vendor Repository" (right) */}
                <div className="flex items-center justify-between">
                    <div className="flex items-center space-x-2">
                        <Ship className="w-4 h-4" />
                        <span className="text-md font-bold">eVCP</span>
                    </div>
                    <Link
                        href="/partners/repository"
                        className={cn(buttonVariants({ variant: "ghost" }))}
                    >
                        <InfoIcon className="w-4 h-4 mr-1" />
                        {'업체 등록 신청'}
                    </Link>
                </div>

                {/* Content section that occupies remaining space, centered vertically */}
                <div className="flex-1 flex items-center justify-center">
                    <div className="mx-auto w-full flex flex-col space-y-6 sm:w-[350px]">
                        <div className="p-6 md:p-8">
                            <div className="flex flex-col gap-6">
                                {/* Header */}
                                <div className="flex flex-col items-center text-center">
                                    {!showMfaForm ? (
                                        <>
                                            <h1 className="text-2xl font-bold">{t('loginMessage')}</h1>
                                            <p className="text-xs text-muted-foreground mt-2">
                                                {'등록된 업체만 로그인하실 수 있습니다. 아직 등록되지 않은 업체라면 상단의 업체 등록 신청 버튼을 이용해주세요.'}
                                            </p>
                                        </>
                                    ) : (
                                        <>
                                            <div className="flex items-center justify-center w-12 h-12 rounded-full bg-blue-100 mb-4">
                                                🔐
                                            </div>
                                            <h1 className="text-2xl font-bold">SMS 인증</h1>
                                            <p className="text-sm text-muted-foreground mt-2">
                                                {mfaUserEmail}로 로그인하셨습니다
                                            </p>
                                            <p className="text-xs text-muted-foreground mt-1">
                                                등록된 전화번호로 전송된 6자리 인증번호를 입력해주세요
                                            </p>
                                        </>
                                    )}
                                </div>

                                {/* 로그인 폼 또는 MFA 폼 */}
                                {!showMfaForm ? (
                                    <>
                                        {/* Login Method Tabs */}
                                        <div className="flex rounded-lg bg-muted p-1">
                                            <button
                                                type="button"
                                                onClick={() => setLoginMethod('username')}
                                                className={cn(
                                                    "flex-1 rounded-md px-3 py-2 text-sm font-medium transition-all",
                                                    loginMethod === 'username'
                                                        ? "bg-background text-foreground shadow-sm"
                                                        : "text-muted-foreground hover:text-foreground"
                                                )}
                                            >
                                                일반 로그인
                                            </button>
                                            <button
                                                type="button"
                                                onClick={() => setLoginMethod('sgips')}
                                                className={cn(
                                                    "flex-1 rounded-md px-3 py-2 text-sm font-medium transition-all",
                                                    loginMethod === 'sgips'
                                                        ? "bg-background text-foreground shadow-sm"
                                                        : "text-muted-foreground hover:text-foreground"
                                                )}
                                            >
                                                S-Gips 로그인
                                            </button>
                                        </div>

                                        {/* Username Login Form */}
                                        {loginMethod === 'username' && (
                                            <form onSubmit={handleUsernameLogin} className="grid gap-4">
                                                <div className="grid gap-2">
                                                    <Input
                                                        id="username"
                                                        type="text"
                                                        placeholder="이메일을 넣으세요"
                                                        required
                                                        className="h-10"
                                                        value={username}
                                                        onChange={(e) => setUsername(e.target.value)}
                                                        disabled={isLoading}
                                                    />
                                                </div>
                                                <div className="grid gap-2">
                                                    <Input
                                                        id="password"
                                                        type="password"
                                                        placeholder={t('password')}
                                                        required
                                                        className="h-10"
                                                        value={password}
                                                        onChange={(e) => setPassword(e.target.value)}
                                                        disabled={isLoading}
                                                    />
                                                </div>
                                                <Button
                                                    type="submit"
                                                    className="w-full"
                                                    variant="samsung"
                                                    disabled={isLoading || !username || !password}
                                                >
                                                    {isLoading ? '로그인 중...' : t('login')}
                                                </Button>
                                            </form>
                                        )}

                                        {/* S-Gips Login Form */}
                                        {loginMethod === 'sgips' && (
                                            <form onSubmit={handleSgipsLogin} className="grid gap-4">
                                                <div className="grid gap-2">
                                                    <Input
                                                        id="sgipsUsername"
                                                        type="text"
                                                        placeholder="S-Gips ID"
                                                        required
                                                        className="h-10"
                                                        value={sgipsUsername}
                                                        onChange={(e) => setSgipsUsername(e.target.value)}
                                                        disabled={isLoading}
                                                    />
                                                </div>
                                                <div className="grid gap-2">
                                                    <Input
                                                        id="sgipsPassword"
                                                        type="password"
                                                        placeholder="S-Gips 비밀번호"
                                                        required
                                                        className="h-10"
                                                        value={sgipsPassword}
                                                        onChange={(e) => setSgipsPassword(e.target.value)}
                                                        disabled={isLoading}
                                                    />
                                                </div>
                                                <Button
                                                    type="submit"
                                                    className="w-full"
                                                    variant="default"
                                                    disabled={isLoading || !sgipsUsername || !sgipsPassword}
                                                >
                                                    {isLoading ? 'S-Gips 인증 중...' : 'S-Gips 로그인'}
                                                </Button>
                                                <p className="text-xs text-muted-foreground text-center">
                                                    S-Gips 계정으로 로그인하면 자동으로 SMS 인증이 진행됩니다.
                                                </p>
                                            </form>
                                        )}

                                        {/* Additional Links */}
                                        <div className="flex flex-col gap-2 text-center">
                                            <Button
                                                type="button"
                                                variant="link"
                                                className="text-blue-600 hover:text-blue-800 text-sm"
                                                onClick={goToVendorRegistration}
                                            >
                                                {'신규 업체이신가요? 여기서 등록하세요'}
                                            </Button>

                                            {loginMethod === 'username' && (
                                                <Button
                                                    type="button"
                                                    variant="link"
                                                    className="text-blue-600 hover:text-blue-800 text-sm"
                                                    onClick={() => setShowForgotPassword(true)}
                                                >
                                                    비밀번호를 잊으셨나요?
                                                </Button>
                                            )}

                                            {/* 테스트용 MFA 화면 버튼 */}
                                            {process.env.NODE_ENV === 'development' && (
                                                <Button
                                                    type="button"
                                                    variant="link"
                                                    className="text-green-600 hover:text-green-800 text-sm"
                                                    onClick={() => {
                                                        setMfaUserId('test-user');
                                                        setMfaUserEmail('test@example.com');
                                                        setShowMfaForm(true);
                                                    }}
                                                >
                                                    [개발용] MFA 화면 테스트
                                                </Button>
                                            )}
                                        </div>
                                    </>
                                ) : (
                                    /* MFA 입력 폼 */
                                    <div className="space-y-6">
                                        {/* 뒤로 가기 버튼 */}
                                        <div className="flex items-center justify-start">
                                            <Button
                                                type="button"
                                                variant="ghost"
                                                size="sm"
                                                onClick={() => {
                                                    setShowMfaForm(false);
                                                    setMfaToken('');
                                                    setMfaUserId('');
                                                    setMfaUserEmail('');
                                                    setMfaCountdown(0);
                                                }}
                                                className="text-blue-600 hover:text-blue-800"
                                            >
                                                <ArrowLeft className="w-4 h-4 mr-1" />
                                                다시 로그인하기
                                            </Button>
                                        </div>

                                        {/* SMS 재전송 섹션 */}
                                        <div className="bg-gray-50 p-4 rounded-lg">
                                            <h3 className="text-sm font-medium text-gray-900 mb-2">
                                                인증번호 재전송
                                            </h3>
                                            <p className="text-xs text-gray-600 mb-3">
                                                인증번호를 받지 못하셨나요?
                                            </p>
                                            <Button
                                                onClick={handleSendSms}
                                                disabled={isLoading || mfaCountdown > 0}
                                                variant="outline"
                                                size="sm"
                                                className="w-full"
                                            >
                                                {isLoading ? (
                                                    '전송 중...'
                                                ) : mfaCountdown > 0 ? (
                                                    `재전송 가능 (${mfaCountdown}초)`
                                                ) : (
                                                    '인증번호 재전송'
                                                )}
                                            </Button>
                                        </div>

                                        {/* SMS 토큰 입력 폼 */}
                                        <form onSubmit={handleMfaSubmit} className="space-y-6">
                                            <div className="space-y-4">
                                                <div className="text-center">
                                                    <label className="block text-sm font-medium text-gray-700 mb-3">
                                                        6자리 인증번호를 입력해주세요
                                                    </label>
                                                    <div className="flex justify-center">
                                                        <InputOTP
                                                            maxLength={6}
                                                            value={mfaToken}
                                                            onChange={(value) => setMfaToken(value)}
                                                        >
                                                            <InputOTPGroup>
                                                                <InputOTPSlot index={0} />
                                                                <InputOTPSlot index={1} />
                                                                <InputOTPSlot index={2} />
                                                                <InputOTPSlot index={3} />
                                                                <InputOTPSlot index={4} />
                                                                <InputOTPSlot index={5} />
                                                            </InputOTPGroup>
                                                        </InputOTP>
                                                    </div>
                                                </div>
                                            </div>

                                            <Button
                                                type="submit"
                                                className="w-full"
                                                variant="samsung"
                                                disabled={isLoading || mfaToken.length !== 6}
                                            >
                                                {isLoading ? '인증 중...' : '인증 완료'}
                                            </Button>
                                        </form>

                                        {/* 도움말 */}
                                        <div className="bg-yellow-50 p-3 rounded-lg border border-yellow-200">
                                            <div className="flex">
                                                <div className="flex-shrink-0">
                                                    ⚠️
                                                </div>
                                                <div className="ml-2">
                                                    <h4 className="text-xs font-medium text-yellow-800">
                                                        인증번호를 받지 못하셨나요?
                                                    </h4>
                                                    <div className="mt-1 text-xs text-yellow-700">
                                                        <ul className="list-disc list-inside space-y-1">
                                                            <li>전화번호가 올바른지 확인해주세요</li>
                                                            <li>스팸 메시지함을 확인해주세요</li>
                                                            <li>잠시 후 재전송 버튼을 이용해주세요</li>
                                                        </ul>
                                                    </div>
                                                </div>
                                            </div>
                                        </div>
                                    </div>
                                )}

                                {/* 비밀번호 재설정 다이얼로그 */}
                                {showForgotPassword && !showMfaForm && (
                                    <div className="fixed inset-0 bg-black bg-opacity-50 flex items-center justify-center z-50">
                                        <div className="bg-white rounded-lg p-6 w-full max-w-md mx-4">
                                            <div className="flex justify-between items-center mb-4">
                                                <h3 className="text-lg font-semibold">비밀번호 재설정</h3>
                                                <button
                                                    onClick={() => {
                                                        setShowForgotPassword(false);
                                                    }}
                                                    className="text-gray-400 hover:text-gray-600"
                                                >
                                                    ✕
                                                </button>
                                            </div>
                                            <form action={passwordResetAction} className="space-y-4">
                                                <div>
                                                    <p className="text-sm text-gray-600 mb-3">
                                                        가입하신 이메일 주소를 입력하시면 비밀번호 재설정 링크를 보내드립니다.
                                                    </p>
                                                    <Input
                                                        name="email"
                                                        type="email"
                                                        placeholder="이메일 주소"
                                                        required
                                                    />
                                                </div>
                                                <div className="flex gap-2">
                                                    <Button
                                                        type="button"
                                                        variant="outline"
                                                        className="flex-1"
                                                        onClick={() => {
                                                            setShowForgotPassword(false);
                                                        }}
                                                    >
                                                        취소
                                                    </Button>
                                                    <Button
                                                        type="submit"
                                                        className="flex-1"
                                                    >
                                                        재설정 링크 전송
                                                    </Button>
                                                </div>
                                            </form>
                                        </div>
                                    </div>
                                )}

                                {/* Language Selector - MFA 화면에서는 숨김 */}
                                {!showMfaForm && (
                                    <div className="text-center text-sm mx-auto">
                                        <DropdownMenu>
                                            <DropdownMenuTrigger asChild>
                                                <Button variant="ghost" className="flex items-center gap-2">
                                                    <GlobeIcon className="h-4 w-4" />
                                                    <span>{currentLanguageText}</span>
                                                    <ChevronDownIcon className="h-4 w-4" />
                                                </Button>
                                            </DropdownMenuTrigger>
                                            <DropdownMenuContent align="end">
                                                <DropdownMenuRadioGroup
                                                    value={i18n.language}
                                                    onValueChange={(value) => handleChangeLanguage(value)}
                                                >
                                                    <DropdownMenuRadioItem value="en">
                                                        {t('languages.english')}
                                                    </DropdownMenuRadioItem>
                                                    <DropdownMenuRadioItem value="ko">
                                                        {t('languages.korean')}
                                                    </DropdownMenuRadioItem>
                                                </DropdownMenuRadioGroup>
                                            </DropdownMenuContent>
                                        </DropdownMenu>
                                    </div>
                                )}
                            </div>
                        </div>

                        {/* Terms - MFA 화면에서는 숨김 */}
                        {!showMfaForm && (
                            <div className="text-balance text-center text-xs text-muted-foreground [&_a]:underline [&_a]:underline-offset-4 hover:[&_a]:text-primary">
                                {t("agreement")}{" "}
                                <Link
                                    href={`/${lng}/privacy`}  // 개인정보처리방침만 남김
                                    className="underline underline-offset-4 hover:text-primary"
                                >
                                    {t("privacyPolicy")}
                                </Link>
                            </div>
                        )}
                    </div>
                </div>
            </div>

            {/* Right BG 이미지 영역 */}
            <div className="relative hidden h-full flex-col p-10 text-white dark:border-r md:flex">
                <div className="absolute inset-0">
                    <Image
                        src="/images/02.jpg"
                        alt="Background image"
                        fill
                        priority
                        sizes="(max-width: 1024px) 100vw, 50vw"
                        className="object-cover"
                    />
                </div>
                <div className="relative z-10 mt-auto">
                    <blockquote className="space-y-2">
                        <p className="text-sm">&ldquo;{t("blockquote")}&rdquo;</p>
                    </blockquote>
                </div>
            </div>
        </div>
    )
}