package com.amap.api.location;

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

public class DateUtil{
    private static final long DAY_IN_MILLIS = 24 * 60 * 60 * 1000;

    /**
     * 入口
     * 校正gps时间
     * @param gpsTime 原始的gps时间
     * @return
     */public static long correctGpsTime(long gpsTime){
        if(Math.abs(gpsTime - System.currentTimeMillis()) > 365 * 24 * 60 * 60 * 1000) {
            return getNewGpsTime(gpsTime);
        } else {
            return gpsTime;
        }
    }

    /**
     * 获取新的GPS时间
     * @param gpsTime 原始的gps时间
     * @return
     */private static long getNewGpsTime(long gpsTime){
        //系统时间当前时间戳long sysTime = System.currentTimeMillis();

        //从GPS时间戳中获取当前0点到现在的毫秒数long millisSecondOfDayInGps = getMillisSecondOfDay(gpsTime);

        //newTime = 系统时间到当天零点毫秒数 +  gps 0点到现在的毫秒数long newTime = getDayInMillis(sysTime) + millisSecondOfDayInGps;

        //系统时间与计算出的gps时间差值long absTime = Math.abs(newTime - sysTime);

        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date(newTime));
        int hour = calendar.get(Calendar.HOUR_OF_DAY);

        //差值阈值, 23小时long diffMillisThreshold = 23 * 60 * 60 * 1000;

        //解决跨0点问题, 0点收到昨天23点的数据if (hour == 23 && absTime >= diffMillisThreshold) {
            //减去一天时间
            newTime -= DAY_IN_MILLIS;
        }

        //解决跨0点问题, 23点收到明天0点的数据if (hour == 0 && absTime >= diffMillisThreshold) {
            //加上一天时间
            newTime += DAY_IN_MILLIS;
        }
        return newTime;
    }

    /**
     * 从时间戳中获取当天0点到现在的毫秒数（只取时分秒）
     * @param time
     * @return
     */private static long getMillisSecondOfDay(long time){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date(time));
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        long newTime = calendar.getTimeInMillis();
        return (time - newTime);
    }

    /**
     * 从时间戳中获取从1970.1.1号到当天0点的毫秒数（只取年月日）
     * @param time
     * @return
     */private static long getDayInMillis(long time){
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date(time));
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        long newTime = calendar.getTimeInMillis();
        return newTime;
    }

}