const identifierInput = document.getElementById('identifier');
const passwordField = document.getElementById('password-field');
const passwordInput = document.getElementById('password');
const inputHint = document.getElementById('input-hint');
const submitButton = document.getElementById('submit-button');
const loginForm = document.getElementById('login-form');
const statusText = document.getElementById('status-text');
const statusDisplay = document.getElementById('status-display');
const successPanel = document.getElementById('success-panel');
const successTitle = document.getElementById('success-title');
const successDescription = document.getElementById('success-description');

let currentMode = 'unknown'; // 'unknown', 'phone', 'employee'

function classifyInput(value) {
    const trimmed = value.trim();
    if (!trimmed) return 'unknown';

    // Check if it's strictly numeric (ignoring spaces or dashes for phone)
    const numericOnly = trimmed.replace(/[\s-]/g, '');
    if (/^\d+$/.test(numericOnly)) {
        return 'phone';
    }
    return 'employee';
}

function formatPhoneNumber(value) {
    const digits = value.replace(/\D/g, '').slice(0, 11);
    if (digits.length <= 3) return digits;
    if (digits.length <= 7) return `${digits.slice(0, 3)}-${digits.slice(3)}`;
    return `${digits.slice(0, 3)}-${digits.slice(3, 7)}-${digits.slice(7)}`;
}

function updateUI() {
    const value = identifierInput.value;
    const mode = classifyInput(value);
    currentMode = mode;

    if (mode === 'phone') {
        const formatted = formatPhoneNumber(value);
        if (identifierInput.value !== formatted) {
            identifierInput.value = formatted;
        }
        
        passwordField.classList.add('hidden');
        inputHint.textContent = '전화번호가 확인되었습니다. 인증링크 발송 흐름을 사용할 수 있습니다.';
        submitButton.textContent = '인증링크 발송';
        submitButton.disabled = value.replace(/\D/g, '').length < 10;
        statusText.textContent = '인증링크 발송 단계를 준비했습니다.';
    } else if (mode === 'employee') {
        passwordField.classList.remove('hidden');
        inputHint.textContent = 'ID 입력이 확인되었습니다. 비밀번호를 입력해 로그인하세요.';
        submitButton.textContent = '로그인';
        submitButton.disabled = passwordInput.value.trim().length === 0;
        statusText.textContent = '비밀번호 입력 단계를 노출했습니다.';
    } else {
        passwordField.classList.add('hidden');
        inputHint.textContent = '입력값에 따라 적절한 로그인 방식이 자동으로 선택됩니다.';
        submitButton.textContent = '로그인';
        submitButton.disabled = true;
        statusText.textContent = '입력값을 기다리는 초기 상태입니다.';
    }
}

identifierInput.addEventListener('input', updateUI);
passwordInput.addEventListener('input', updateUI);

loginForm.addEventListener('submit', async (e) => {
    e.preventDefault();
    
    const identifier = identifierInput.value;
    const password = passwordInput.value;
    
    submitButton.disabled = true;
    const originalBtnText = submitButton.textContent;
    submitButton.textContent = '처리 중...';
    
    try {
        let response;
        if (currentMode === 'phone') {
            response = await fetch('/api/send-link', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ phoneNumber: identifier.replace(/\D/g, '') })
            });
        } else {
            response = await fetch('/api/login', {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({ loginId: identifier, password: password })
            });
        }
        
        const result = await response.json();
        
        if (response.ok) {
            loginForm.classList.add('hidden');
            statusDisplay.classList.add('hidden');
            successPanel.classList.remove('hidden');
            
            successTitle.textContent = currentMode === 'phone' ? '인증링크 발송 완료' : '로그인 성공';
            successDescription.textContent = currentMode === 'phone' 
                ? `${identifier} 번호로 인증 링크를 보냈습니다.`
                : `${identifier} 계정으로 접속되었습니다.`;
        } else {
            alert(result.message || '오류가 발생했습니다.');
            submitButton.disabled = false;
            submitButton.textContent = originalBtnText;
        }
    } catch (error) {
        console.error('Request failed', error);
        alert('서버 통신에 실패했습니다.');
        submitButton.disabled = false;
        submitButton.textContent = originalBtnText;
    }
});