/**
 * 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 CACHE_TTL = 30 * 60 * 1000; // 30분

    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();

        var cached = getCache(currentYear, currentMonth);
        if (cached !== null) {
            buildGrid(cached);
        } else {
            // 즉시 빈 그리드 렌더링 (체감 속도 향상)
            buildGrid([]);
            calBody.classList.add('loading');
            fetchBookedDates(currentYear, currentMonth, function(dates) {
                setCache(currentYear, currentMonth, dates);
                buildGrid(dates);
                calBody.classList.remove('loading');
                prefetchAdjacent();
            });
        }
    }

    function prefetchAdjacent() {
        var nextM = currentMonth + 1, nextY = currentYear;
        if (nextM > 12) { nextM = 1; nextY++; }
        if (getCache(nextY, nextM) === null) {
            fetchBookedDates(nextY, nextM, function(dates) {
                setCache(nextY, nextM, dates);
            });
        }
    }

    // --- localStorage 캐싱 ---
    function cacheKey(y, m) { return 'mingle_cal_' + y + '_' + m; }

    function getCache(y, m) {
        try {
            var raw = localStorage.getItem(cacheKey(y, m));
            if (!raw) return null;
            var obj = JSON.parse(raw);
            if (Date.now() - obj.ts > CACHE_TTL) {
                localStorage.removeItem(cacheKey(y, m));
                return null;
            }
            return obj.dates;
        } catch (e) { return null; }
    }

    function setCache(y, m, dates) {
        try {
            localStorage.setItem(cacheKey(y, m), JSON.stringify({ dates: dates, ts: Date.now() }));
        } catch (e) { /* quota exceeded 등 무시 */ }
    }

    // --- 제목 업데이트 ---
    function updateTitle() {
        var lang = (window.i18n && window.i18n.currentLang) || 'ko';
        var monthNames = {
            ko: ['1월','2월','3월','4월','5월','6월','7월','8월','9월','10월','11월','12월'],
            en: ['January','February','March','April','May','June','July','August','September','October','November','December'],
            ja: ['1月','2月','3月','4月','5月','6月','7月','8月','9月','10月','11月','12月'],
            zh: ['1月','2月','3月','4月','5月','6月','7月','8月','9月','10月','11月','12月']
        };
        var names = monthNames[lang] || monthNames.ko;
        if (lang === 'en') {
            calTitle.textContent = names[currentMonth - 1] + ' ' + currentYear;
        } else if (lang === 'ja' || lang === 'zh') {
            calTitle.textContent = currentYear + '年 ' + names[currentMonth - 1];
        } else {
            calTitle.textContent = currentYear + '년 ' + names[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);
    }

    document.addEventListener('langChanged', function() { updateTitle(); });

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