/**
 * 밍글 스튜디오 - 예약 현황 캘린더
 * Google Apps Script 프록시를 통해 캘린더 데이터를 가져와 표시
 */
(function() {
    'use strict';

    var APPS_SCRIPT_URL = 'https://script.google.com/macros/s/AKfycbwoaoSmEskbJod4gR5NjLnpWSkhIDUYaGBYk0y1Q865TzaJ4gctSrTOWXxRnVa7J9AASA/exec';

    var currentYear, currentMonth;
    var calTitle = document.getElementById('calTitle');
    var calBody = document.getElementById('calBody');
    var prevBtn = document.getElementById('prevMonth');
    var nextBtn = document.getElementById('nextMonth');

    function init() {
        var now = new Date();
        currentYear = now.getFullYear();
        currentMonth = now.getMonth() + 1;

        prevBtn.addEventListener('click', function() { changeMonth(-1); });
        nextBtn.addEventListener('click', function() { changeMonth(1); });

        renderCalendar();
    }

    function changeMonth(delta) {
        currentMonth += delta;
        if (currentMonth > 12) { currentMonth = 1; currentYear++; }
        else if (currentMonth < 1) { currentMonth = 12; currentYear--; }
        renderCalendar();
    }

    function renderCalendar() {
        updateTitle();

        // 매번 새로 불러오기
        buildGrid([]);
        showLoading();
        fetchBookedDates(currentYear, currentMonth, function(dates) {
            buildGrid(dates);
            hideLoading();
        });
    }

    function showLoading() {
        calBody.classList.add('loading');
        // 기존 오버레이 제거
        var existing = calBody.querySelector('.cal-loading-overlay');
        if (existing) existing.remove();

        var overlay = document.createElement('div');
        overlay.className = 'cal-loading-overlay';
        overlay.innerHTML = '<div class="loading-spinner"></div><span class="loading-text">불러오는 중...</span>';
        calBody.appendChild(overlay);
    }

    function hideLoading() {
        calBody.classList.remove('loading');
        var overlay = calBody.querySelector('.cal-loading-overlay');
        if (overlay) overlay.remove();
    }

    // --- 제목 업데이트 ---
    function updateTitle() {
        var monthNames = ['1월','2월','3월','4월','5월','6월','7월','8월','9월','10월','11월','12월'];
        calTitle.textContent = currentYear + '년 ' + monthNames[currentMonth - 1];
    }

    // --- API 호출 ---
    function fetchBookedDates(year, month, callback) {
        if (!APPS_SCRIPT_URL) { callback([]); return; }

        var url = APPS_SCRIPT_URL + '?year=' + year + '&month=' + month;
        fetch(url)
            .then(function(res) { return res.json(); })
            .then(function(data) { callback(data.bookedDates || []); })
            .catch(function() { callback([]); });
    }

    // --- 그리드 렌더링 ---
    function buildGrid(bookedDates) {
        calBody.innerHTML = '';

        var firstDay = new Date(currentYear, currentMonth - 1, 1).getDay();
        var daysInMonth = new Date(currentYear, currentMonth, 0).getDate();
        var today = new Date();
        var todayStr = today.getFullYear() + '-' +
            String(today.getMonth() + 1).padStart(2, '0') + '-' +
            String(today.getDate()).padStart(2, '0');

        var bookedSet = {};
        for (var b = 0; b < bookedDates.length; b++) {
            bookedSet[bookedDates[b]] = true;
        }

        var fragment = document.createDocumentFragment();

        for (var e = 0; e < firstDay; e++) {
            var emptyCell = document.createElement('div');
            emptyCell.className = 'cal-cell empty';
            fragment.appendChild(emptyCell);
        }

        for (var d = 1; d <= daysInMonth; d++) {
            var dateStr = currentYear + '-' +
                String(currentMonth).padStart(2, '0') + '-' +
                String(d).padStart(2, '0');

            var cell = document.createElement('div');
            cell.className = 'cal-cell';

            var dayNum = document.createElement('span');
            dayNum.className = 'day-num';
            dayNum.textContent = d;

            var cellDate = new Date(currentYear, currentMonth - 1, d);
            var isPast = cellDate < new Date(today.getFullYear(), today.getMonth(), today.getDate());

            if (dateStr === todayStr) {
                cell.classList.add('today');
            } else if (isPast) {
                cell.classList.add('past');
            } else if (bookedSet[dateStr]) {
                cell.classList.add('booked');
            } else {
                cell.classList.add('available');
            }

            cell.appendChild(dayNum);
            fragment.appendChild(cell);
        }

        calBody.appendChild(fragment);
    }

    if (document.readyState === 'loading') {
        document.addEventListener('DOMContentLoaded', init);
    } else {
        init();
    }
})();