import java.util.Calendar;
import java.util.Date;

/**
 * 时间日期相关操作工具
 * @author: Nemo
 * @date: 2018/3/23.
 */
public class DateTimeUtils {

    /**
     * 得到某日期在一个月中的天数
     * @param date
     * @return
     */
    public static int getDayOfMonth(Date date){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        int day = calendar.get(Calendar.DAY_OF_MONTH);
        return day;
    }

    /**
     * 得到下个月的当前号日期时间戳
     * 如果下个月的最大日期小于当前日期，那么则取下个月的最大日期作为测算日期，下下个月依旧按照这个月的日期来算
     * @param thisMonth
     */
    public static Date getNextMonth(Date thisMonth,int day){
        Calendar cal = Calendar.getInstance();
        cal.setTime(thisMonth);
        //月份加1
        cal.add(Calendar.MONTH, 1);
        cal.set(Calendar.YEAR,cal.get(Calendar.YEAR));

        //当前日期 < 需测算日期,则按这个月最大的日期来测算
        Date date=cal.getTime();
        int maxDay = getMaxDayByYearMonth(date);
        if(day > maxDay){
            cal.set(Calendar.DAY_OF_MONTH,maxDay);
        }else{
            cal.set(Calendar.DAY_OF_MONTH,day);
        }

        return cal.getTime();
    }

    /**
     * date2比date1多的天数
     * @param date1
     * @param date2
     * @return
     */
    public static int differentDays(Date date1,Date date2) {
        Calendar cal1 = Calendar.getInstance();
        cal1.setTime(date1);

        Calendar cal2 = Calendar.getInstance();
        cal2.setTime(date2);
        int day1= cal1.get(Calendar.DAY_OF_YEAR);
        int day2 = cal2.get(Calendar.DAY_OF_YEAR);

        int year1 = cal1.get(Calendar.YEAR);
        int year2 = cal2.get(Calendar.YEAR);
        //同一年
        if(year1 != year2) {
            int timeDistance = 0 ;
            for(int i = year1 ; i < year2 ; i ++) {
                //闰年
                if(i%4==0 && i%100!=0 || i%400==0)   {
                    timeDistance += 366;
                }
                else {
                    //不是闰年
                    timeDistance += 365;
                }
            }
            return timeDistance + (day2-day1) ;
        }
        else {
            //不同年
            return day2-day1;
        }
    }

    /**
     * 获得某个月最大天数
     * @param now 需要测算的当前时间
     * @return 某个月最大天数
     */
    public static int getMaxDayByYearMonth(Date now) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(now);
        return calendar.getActualMaximum(Calendar.DATE);
    }
}