// 日历状态管理
class CalendarApp {
    constructor() {
        this.currentDate = new Date();
        this.markedDates = this.loadData();
        this.init();
    }

    init() {
        this.renderCalendar();
        this.bindEvents();
    }

    // 获取月份的第一天是星期几（0=周日, 1=周一...）
    getFirstDayOfMonth(date) {
        const firstDay = new Date(date.getFullYear(), date.getMonth(), 1);
        return firstDay.getDay();
    }

    // 获取月份的天数
    getDaysInMonth(date) {
        return new Date(date.getFullYear(), date.getMonth() + 1, 0).getDate();
    }

    // 格式化日期为 YYYY-MM-DD
    formatDate(date) {
        const year = date.getFullYear();
        const month = String(date.getMonth() + 1).padStart(2, '0');
        const day = String(date.getDate()).padStart(2, '0');
        return `${year}-${month}-${day}`;
    }

    // 检查是否为今天
    isToday(date) {
        const today = new Date();
        return date.getDate() === today.getDate() &&
               date.getMonth() === today.getMonth() &&
               date.getFullYear() === today.getFullYear();
    }

    // 获取日期标记状态
    getDateStatus(date) {
        const dateStr = this.formatDate(date);
        return this.markedDates[dateStr] || 'none';
    }

    // 切换日期标记状态
    toggleDateStatus(date) {
        const dateStr = this.formatDate(date);
        const currentStatus = this.markedDates[dateStr] || 'none';
        
        // 状态循环: none -> completed -> partial -> none
        let newStatus;
        switch (currentStatus) {
            case 'none':
                newStatus = 'completed';
                break;
            case 'completed':
                newStatus = 'partial';
                break;
            case 'partial':
                newStatus = 'none';
                break;
            default:
                newStatus = 'none';
        }

        if (newStatus === 'none') {
            delete this.markedDates[dateStr];
        } else {
            this.markedDates[dateStr] = newStatus;
        }

        this.saveData();
        this.renderCalendar();
    }

    // 渲染日历
    renderCalendar() {
        const calendar = document.getElementById('calendar');
        calendar.innerHTML = '';

        // 星期标题
        const weekdays = ['日', '一', '二', '三', '四', '五', '六'];
        weekdays.forEach(day => {
            const weekdayEl = document.createElement('div');
            weekdayEl.className = 'weekday';
            weekdayEl.textContent = day;
            calendar.appendChild(weekdayEl);
        });

        // 更新月份显示
        const monthNames = ['一月', '二月', '三月', '四月', '五月', '六月', 
                           '七月', '八月', '九月', '十月', '十一月', '十二月'];
        const monthDisplay = document.getElementById('currentMonth');
        monthDisplay.textContent = `${this.currentDate.getFullYear()}年 ${monthNames[this.currentDate.getMonth()]}`;

        // 获取月份信息
        const firstDay = this.getFirstDayOfMonth(this.currentDate);
        const daysInMonth = this.getDaysInMonth(this.currentDate);
        const today = new Date();

        // 添加上个月的日期（填充空白）
        const prevMonth = new Date(this.currentDate.getFullYear(), this.currentDate.getMonth() - 1, 0);
        const daysInPrevMonth = prevMonth.getDate();
        
        for (let i = firstDay - 1; i >= 0; i--) {
            const day = daysInPrevMonth - i;
            const date = new Date(this.currentDate.getFullYear(), this.currentDate.getMonth() - 1, day);
            this.createDayElement(calendar, date, day, true);
        }

        // 添加当前月的日期
        for (let day = 1; day <= daysInMonth; day++) {
            const date = new Date(this.currentDate.getFullYear(), this.currentDate.getMonth(), day);
            this.createDayElement(calendar, date, day, false);
        }

        // 添加下个月的日期（填充到完整周）
        const totalCells = calendar.children.length - 7; // 减去星期标题
        const remainingCells = 42 - totalCells; // 6行 x 7列 = 42
        for (let day = 1; day <= remainingCells; day++) {
            const date = new Date(this.currentDate.getFullYear(), this.currentDate.getMonth() + 1, day);
            this.createDayElement(calendar, date, day, true);
        }
    }

    // 创建日期元素
    createDayElement(container, date, dayNumber, isOtherMonth) {
        const dayEl = document.createElement('div');
        dayEl.className = 'day';
        
        if (isOtherMonth) {
            dayEl.classList.add('other-month');
        }
        
        if (this.isToday(date)) {
            dayEl.classList.add('today');
        }

        const status = this.getDateStatus(date);
        if (status !== 'none') {
            dayEl.classList.add(status);
        }

        const dayNumberEl = document.createElement('div');
        dayNumberEl.className = 'day-number';
        dayNumberEl.textContent = dayNumber;
        dayEl.appendChild(dayNumberEl);

        if (status !== 'none') {
            const markEl = document.createElement('div');
            markEl.className = 'day-mark';
            markEl.textContent = status === 'completed' ? '✓' : '○';
            dayEl.appendChild(markEl);
        }

        // 添加点击事件
        dayEl.addEventListener('click', () => {
            if (!isOtherMonth) {
                this.toggleDateStatus(date);
            }
        });

        container.appendChild(dayEl);
    }

    // 绑定事件
    bindEvents() {
        document.getElementById('prevMonth').addEventListener('click', () => {
            this.currentDate.setMonth(this.currentDate.getMonth() - 1);
            this.renderCalendar();
        });

        document.getElementById('nextMonth').addEventListener('click', () => {
            this.currentDate.setMonth(this.currentDate.getMonth() + 1);
            this.renderCalendar();
        });

        document.getElementById('todayBtn').addEventListener('click', () => {
            this.currentDate = new Date();
            this.renderCalendar();
        });
    }

    // 保存数据到 localStorage
    saveData() {
        try {
            localStorage.setItem('calendarMarkedDates', JSON.stringify(this.markedDates));
        } catch (e) {
            console.error('保存数据失败:', e);
        }
    }

    // 从 localStorage 加载数据
    loadData() {
        try {
            const data = localStorage.getItem('calendarMarkedDates');
            return data ? JSON.parse(data) : {};
        } catch (e) {
            console.error('加载数据失败:', e);
            return {};
        }
    }
}

// 初始化应用
document.addEventListener('DOMContentLoaded', () => {
    new CalendarApp();
});