// pages/date-calc/date-calc.ts
Page({
  data: {
    currentTab: 0,
    startDate: '',
    startWeekday: '', // 新增：开始日期的星期
    endDate: '',
    days: 0, // 可以为空字符串以便清空输入框，但 input type number 会处理
    resultDate: '',
    resultWeekday: '',
    intervalDays: 0,
    intervalWeeks: 0,
    intervalRemainingDays: 0
  },

  onLoad() {
    const today = new Date();
    const dateStr = this.formatDate(today);
    this.setData({
      startDate: dateStr,
      endDate: dateStr,
      resultDate: dateStr,
      resultWeekday: this.getWeekday(today),
      startWeekday: this.getWeekday(today)
    });
  },

  switchTab(e: any) {
    this.setData({
      currentTab: parseFloat(e.currentTarget.dataset.index)
    });
    this.calculate(); // 切换时重新计算
  },

  bindDateChange(e: any) {
    const field = e.currentTarget.dataset.field;
    this.setData({
      [field]: e.detail.value
    });
    
    // 如果修改的是开始日期，同步更新星期显示
    if (field === 'startDate') {
        const d = new Date(e.detail.value);
        this.setData({ startWeekday: this.getWeekday(d) });
    }

    this.calculate();
  },

  bindDaysInput(e: any) {
    const val = e.detail.value;
    // 允许输入负号
    if (val === '-' || val === '') {
        this.setData({ days: val });
        return;
    }
    this.setData({
      days: parseInt(val)
    });
    this.calculate();
  },

  setDays(e: any) {
      const days = parseInt(e.currentTarget.dataset.days);
      this.setData({ days: days });
      this.calculate();
  },

  calculate() {
    if (this.data.currentTab === 0) {
      // 日期推算
      // 注意：直接使用 new Date('2023-10-01') 在 iOS 上可能不兼容，应替换为 '/'
      const start = new Date(this.data.startDate.replace(/-/g, '/'));
      // days 可能是字符串或数字
      const dayOffset = typeof(this.data.days) === 'number' ? this.data.days : parseInt(this.data.days || '0');
      
      const target = new Date(start.getTime() + dayOffset * 24 * 60 * 60 * 1000);
      
      this.setData({
        resultDate: this.formatDate(target),
        resultWeekday: this.getWeekday(target)
      });
    } else {
      // 日期通过 (Interval)
      const start = new Date(this.data.startDate.replace(/-/g, '/'));
      const end = new Date(this.data.endDate.replace(/-/g, '/'));
      const diffTime = Math.abs(end.getTime() - start.getTime());
      const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24)); 
      
      const weeks = Math.floor(diffDays / 7);
      const remainingDays = diffDays % 7;

      this.setData({
        intervalDays: diffDays,
        intervalWeeks: weeks,
        intervalRemainingDays: remainingDays
      });
    }
  },

  formatDate(date: Date): string {
    const y = date.getFullYear();
    const m = (date.getMonth() + 1).toString().padStart(2, '0');
    const d = date.getDate().toString().padStart(2, '0');
    return `${y}-${m}-${d}`;
  },

  getWeekday(date: Date): string {
    const days = ['周日', '周一', '周二', '周三', '周四', '周五', '周六'];
    return days[date.getDay()];
  }
})