import {
    Box,
    Button,
    Container,
    Paper,
    TextField,
    Typography,
    LinearProgress,
    InputAdornment,
    IconButton
} from '@mui/material'
import { useState } from 'react'
import { useNavigate } from 'react-router-dom'
import api from '../lib/api'
import Visibility from '@mui/icons-material/Visibility'
import VisibilityOff from '@mui/icons-material/VisibilityOff'

export default function Signup() {
    const [email, setEmail] = useState('')
    const [emailError, setEmailError] = useState('')
    const [emailStatus, setEmailStatus] = useState<'available' | 'duplicate' | ''>('')

    const [password, setPassword] = useState('')
    const [confirmPassword, setConfirmPassword] = useState('')
    const [error, setError] = useState('')
    const [strengthScore, setStrengthScore] = useState(0)
    const [strengthLabel, setStrengthLabel] = useState<'약함' | '보통' | '강함' | ''>('')

    const [showPassword, setShowPassword] = useState(false)
    const navigate = useNavigate()

    const analyzePassword = (pw: string) => {
        let score = 0
        if (/[a-z]/.test(pw)) score++
        if (/[A-Z]/.test(pw)) score++
        if (/\d/.test(pw)) score++
        if (/[^A-Za-z0-9]/.test(pw)) score++
        if (pw.length >= 10) score++

        setStrengthScore(score)

        if (score <= 2) setStrengthLabel('약함')
        else if (score <= 4) setStrengthLabel('보통')
        else setStrengthLabel('강함')
    }

    const validatePassword = (pw: string) => {
        const regex = /^(?=.*[A-Za-z])(?=.*\d).{6,20}$/
        return regex.test(pw)
    }

    const validateEmailFormat = (value: string) => {
        const regex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
        return regex.test(value)
    }

    const checkEmailDuplicate = async (value: string) => {
        if (!validateEmailFormat(value)) {
            setEmailError('유효한 이메일 형식을 입력해주세요.')
            setEmailStatus('')
            return
        }

        try {
            const res = await api.get(`/auth/check-email?email=${value}`)
            if (res.data.available === false) {
                setEmailError('이미 존재하는 이메일입니다.')
                setEmailStatus('duplicate')
            } else {
                setEmailError('')
                setEmailStatus('available')
            }
        } catch (err: any) {
            setEmailError('서버 오류로 이메일 확인 실패')
            setEmailStatus('')
        }
    }

    const handleSignup = async () => {
        setError('')

        if (!validateEmailFormat(email)) {
            setError('유효한 이메일 형식을 입력해주세요.')
            return
        }

        if (!validatePassword(password)) {
            setError('비밀번호는 영문자+숫자를 포함한 6~20자여야 합니다.')
            return
        }

        if (password !== confirmPassword) {
            setError('비밀번호가 일치하지 않습니다.')
            return
        }

        try {
            await api.post('/users/', {
                email,
                password,
            })
            navigate('/login')
        } catch (err: any) {
            setError('회원가입 실패: 이미 존재하는 이메일이거나 서버 오류입니다.')
        }
    }

    return (
        <Container maxWidth="xs">
            <Paper elevation={3} sx={{ p: 4, mt: 8 }}>
                <Typography variant="h5" align="center" gutterBottom>
                    회원가입
                </Typography>

                <Box component="form" noValidate sx={{ display: 'flex', flexDirection: 'column', gap: 2 }}>
                    <TextField
                        label="이메일"
                        type="email"
                        fullWidth
                        value={email}
                        onChange={(e) => setEmail(e.target.value)}
                        onKeyUp={(e) => {
                            if (e.key === 'Enter') handleSignup()
                            else checkEmailDuplicate(email)
                        }}
                        error={!!emailError}
                        helperText={emailError || (emailStatus === 'available' ? '사용 가능한 이메일입니다.' : ' ')}
                    />

                    <TextField
                        label="비밀번호"
                        type={showPassword ? 'text' : 'password'}
                        fullWidth
                        value={password}
                        onChange={(e) => {
                            const pw = e.target.value
                            setPassword(pw)
                            analyzePassword(pw)
                        }}
                        onKeyUp={(e) => e.key === 'Enter' && handleSignup()}
                        helperText="영문자+숫자 포함 6~20자, 특수문자 허용"
                        InputProps={{
                            endAdornment: (
                                <InputAdornment position="end">
                                    <IconButton onClick={() => setShowPassword(!showPassword)} edge="end">
                                        {showPassword ? <VisibilityOff /> : <Visibility />}
                                    </IconButton>
                                </InputAdornment>
                            ),
                        }}
                    />

                    {strengthLabel && (
                        <Box>
                            <Typography variant="body2" gutterBottom>
                                비밀번호 강도: {strengthLabel}
                            </Typography>
                            <LinearProgress
                                variant="determinate"
                                value={(strengthScore / 5) * 100}
                                sx={{
                                    height: 10,
                                    borderRadius: 5,
                                    backgroundColor: '#555',
                                    '& .MuiLinearProgress-bar': {
                                        backgroundColor:
                                            strengthLabel === '강함' ? '#4caf50' :
                                                strengthLabel === '보통' ? '#ff9800' :
                                                    '#f44336',
                                    },
                                }}
                            />
                        </Box>
                    )}

                    <TextField
                        label="비밀번호 확인"
                        type="password"
                        fullWidth
                        value={confirmPassword}
                        onChange={(e) => setConfirmPassword(e.target.value)}
                        onKeyUp={(e) => e.key === 'Enter' && handleSignup()}
                    />

                    <Button variant="contained" onClick={handleSignup} disabled={!!emailError}>
                        회원가입
                    </Button>

                    {error && <Typography color="error">{error}</Typography>}
                </Box>
            </Paper>
        </Container>
    )
}