using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace FileWatcher
{
    public partial class DateWeek : Form
    {
        public DateWeek()
        {
            InitializeComponent();
        }

        private void DateWeek_Load(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            int year, year1, year2, month1, month2, day1, day2, week, sum = 0;

            int[] days = new int[] { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

            int i;
            if (textBox1.Text.Length != 4)
            {
                MessageBox.Show("请输入格式如2040，年2位，周数2位");
                return;
            }
            Console.Write("年：");
            year = int.Parse(textBox1.Text.Substring(0, 2));
            Console.Write("周次：");
            week = int.Parse(textBox1.Text.Substring(2, 2));

            if (year < 0)
            {
                Console.WriteLine("年份错误，必须大于等于0");
                return;
            }

            if (week < 1 || week > 54)
            {
                Console.WriteLine("周次错误，必须位于 1 .. 53 之间");
                return;
            }
            sum += 7 * (week - 1);
            //修正总天数
            switch (DateTime.Parse(year + "-1-1").DayOfWeek)
            {
                case DayOfWeek.Tuesday:
                    {
                        sum -= 1;
                        break;
                    }
                case DayOfWeek.Wednesday:
                    {
                        sum -= 2;
                        break;
                    }
                case DayOfWeek.Thursday:
                    {
                        sum -= 3;
                        break;
                    }
                case DayOfWeek.Friday:
                    {
                        sum -= 4;
                        break;
                    }
                case DayOfWeek.Saturday:
                    {
                        sum -= 5;
                        break;
                    }
                case DayOfWeek.Sunday:
                    {
                        sum -= 6;
                        break;
                    }
                default:
                    break;
            }

            if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0))
            {
                days[1] = 29;
            }

            for (i = 0; i < days.Length; i++)
            {
                if (sum >= days[i])
                {
                    sum -= days[i];
                }
                else
                {
                    break;
                }
            }

            year1 = year;

            month1 = i + 1;

            day1 = sum + 1;

            //修改开始日期

            if (day1 < 1)
            {
                day1 += days[11];
                month1 = 12;
                year1--;
            }

            year2 = year1;
            month2 = month1;
            day2 = day1 + 6;

            if (day2 > days[month1 - 1])

            {
                day2 -= days[month1 - 1];
                month2++;
                if (month2 > 12)
                {
                    month2 = 1;
                    year2++;
                }
            }
            label1.Text = year + "年第" + week + "周 : " + year1 + "年" + month1 + "月" + day1 + "日 ~ " + year2 + "年" + month2 + "月" + day2 + "日";
        }
    }
}