package org.msh.utils.date;

import org.jboss.seam.international.LocaleSelector;
import org.jboss.seam.international.Messages;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;

public class DateUtils {

	/**
	 * Return the number of days between two dates
	 * @param a initial date
	 * @param b ending date
	 * @return number of days
	 */
	public static int daysBetween(Date a, Date b)
	{
		int tempDifference = 0;
	    int difference = 0;
	    Calendar earlier = Calendar.getInstance();
	    Calendar later = Calendar.getInstance();
		 
	    if (a.compareTo(b) < 0)
	    {
	        earlier.setTime(a);
	        later.setTime(b);
	    }
	    else
	    {
	        earlier.setTime(b);
	        later.setTime(a);
	    }
		 
		while (earlier.get(Calendar.YEAR) != later.get(Calendar.YEAR))
		{
		    tempDifference = 365 * (later.get(Calendar.YEAR) - earlier.get(Calendar.YEAR));
		    difference += tempDifference;
		 
		    earlier.add(Calendar.DAY_OF_YEAR, tempDifference);
		}
		 
		if (earlier.get(Calendar.DAY_OF_YEAR) != later.get(Calendar.DAY_OF_YEAR))
		{
		    tempDifference = later.get(Calendar.DAY_OF_YEAR) - earlier.get(Calendar.DAY_OF_YEAR);
		    difference += tempDifference;
		 
		    earlier.add(Calendar.DAY_OF_YEAR, tempDifference);
		}
		 
		return difference;
	}


	/**
	 * Returns the dt parameter, incremented by <i>numDays</i> days
	 * @param dt
	 * @param days
	 * @return
	 */
	static public Date incDays(Date dt, int numDays) {
		Calendar c = Calendar.getInstance();
		c.setTime(dt);
		c.add(Calendar.DAY_OF_MONTH, numDays);

		// fix bug in java... when incrementing in 1 day the date oct 17,2009, the hour information were changed 
		c.set(Calendar.HOUR_OF_DAY, 0);
		
		return c.getTime();
	}

	
	/**
	 * Returns the dt parameter, incremented by <i>numMonths</i> months
	 * @param dt
	 * @param numMonths
	 * @return
	 */
	static public Date incMonths(Date dt, int numMonths) {
		Calendar c = Calendar.getInstance();
		c.setTime(dt);
		c.add(Calendar.MONTH, numMonths);
		return c.getTime();
	}
	
	
	/**
	 * Returns the dt parameter, incremented by <i>numMonths</i> months
	 * @param dt
	 * @param numMonths
	 * @return
	 */
	static public Date incYears(Date dt, int numYears) {
		Calendar c = Calendar.getInstance();
		c.setTime(dt);
		c.add(Calendar.YEAR, numYears);
		return c.getTime();
	}
	
	
	/**
	 * Increments a date <code>dt</code> in <code>numHours</code> hours
	 * @param dt
	 * @param numHours
	 * @return
	 */
	static public Date incHours(Date dt, int numHours) {
		Calendar c = Calendar.getInstance();
		c.setTime(dt);
		c.add(Calendar.HOUR_OF_DAY, numHours);
		return c.getTime();
	}
	
	/**
	 * Returns the year part of the date
	 * @param dt - Date
	 * @return - year of the date dt
	 */
	static public int yearOf(Date dt) {
		Calendar c = Calendar.getInstance();
		c.setTime(dt);
		return c.get(Calendar.YEAR);
	}
	
	
	/**
	 * Returns the month part of the date
	 * @param dt - Date
	 * @return - year of the given date
	 */
	static public int monthOf(Date dt) {
		Calendar c = Calendar.getInstance();
		c.setTime(dt);
		return c.get(Calendar.MONTH);
	}
	
	
	/**
	 * Returns the year part of the date
	 * @param dt - Date
	 * @return - year of the date dt
	 */
	static public int dayOf(Date dt) {
		Calendar c = Calendar.getInstance();
		c.setTime(dt);
		return c.get(Calendar.DAY_OF_MONTH);
	}
	
	/**
	 * Return number of hours between 2 dates
	 * @param first
	 * @param second
	 * @return
	 */
	static public int hoursBetween(Date first, Date second) {
		 
		double milliElapsed = second.getTime() - first.getTime();
		double hoursElapsed = (milliElapsed / 3600F / 1000F);
		return Math.round((Math.round(hoursElapsed * 100F) / 100F));
	}

	
	/**
	 * Return the number of minutes between two dates
	 * @param dtIni initial date
	 * @param dtEnd end date
	 * @return minutes between dtIni and dtEnd
	 */
	static public int minutesBetween(Date dtIni, Date dtEnd) {
		return Math.round(DateUtils.secondsBetween(dtIni, dtEnd) / 60);
	}

	
	/**
	 * Return the number of seconds between two dates
	 * @param dtIni initial date
	 * @param dtEnd end date
	 * @return seconds between the two dates
	 */
	static public int secondsBetween(Date dtIni, Date dtEnd) {
		long milliElapsed = dtIni.getTime() - dtEnd.getTime();
		if (milliElapsed < 0)
			milliElapsed = -milliElapsed;
		return Math.round(milliElapsed / 1000);
	}
	
	
	/**
	 * Returns the number of months between 2 dates
	 * @param dt1
	 * @param dt2
	 * @return
	 */
	static public int monthsBetween(Date dt1, Date dt2) {
		if (dt1.after(dt2)) {
			Date aux = dt1;
			dt1 = dt2;
			dt2 = aux;
		}

		Calendar c1 = Calendar.getInstance();
		Calendar c2 = Calendar.getInstance();
		
		c1.setTime(dt1);
		c2.setTime(dt2);
		
		int y = c2.get(Calendar.YEAR) - c1.get(Calendar.YEAR);
		int m = (c2.get(Calendar.MONTH) + (y * 12)) - c1.get(Calendar.MONTH);
		
		if (c2.get(Calendar.DAY_OF_MONTH) < c1.get(Calendar.DAY_OF_MONTH))
			m--;
		
		return m;
	}

	/**
	 * Return the number of years between two dates
	 * @param dt1
	 * @param dt2
	 * @return
	 */
	public static int yearsBetween(Date dt1, Date dt2) {
		Calendar c1 = Calendar.getInstance();
		Calendar c2 = Calendar.getInstance();
		
		c1.setTime(dt1);
		c2.setTime(dt2);

		if (c1.compareTo(c2) > 0) {
			Calendar aux = c1;
			c1 = c2;
			c2 = aux;
		}
		int num = c2.get(Calendar.YEAR) - c1.get(Calendar.YEAR);
		
		if (num > 0) {
			if (c1.get(Calendar.DAY_OF_YEAR) > c2.get(Calendar.DAY_OF_YEAR))
				num--;
		}

		return num;
	}
	
	public static String FormatDateTime(String dateFormat, Date dt)
	{
		SimpleDateFormat f = new SimpleDateFormat(dateFormat);
		return f.format(dt);
	}
	
	/**
	 * Return the current date without time information
	 * @return
	 */
	public static Date getDate() {
		Calendar c = Calendar.getInstance();
		Calendar dtNow = Calendar.getInstance(); 
		c.clear();
		c.set(Calendar.YEAR, dtNow.get(Calendar.YEAR));
		c.set(Calendar.MONTH, dtNow.get(Calendar.MONTH));
		c.set(Calendar.DAY_OF_MONTH, dtNow.get(Calendar.DAY_OF_MONTH));
		return c.getTime();
	}

	/**
	 * Remove time information of a {@link Date} object
	 * @param dt date to remove time information
	 * @return {@link Date} instance without time information
	 */
	public static Date getDatePart(Date dt) {
		Calendar c = Calendar.getInstance();
		Calendar aux = Calendar.getInstance();
		aux.setTime(dt);
		c.clear();
		c.set(Calendar.YEAR, aux.get(Calendar.YEAR));
		c.set(Calendar.MONTH, aux.get(Calendar.MONTH));
		c.set(Calendar.DAY_OF_YEAR, aux.get(Calendar.DAY_OF_YEAR));
		
		return c.getTime();
	}

	
	/**
	 * Return the day of the week, starting in sun = 1
	 * @param dt Date to return the week day
	 * @return week day
	 */
	public static int dayOfWeek(Date dt) {
		Calendar c = Calendar.getInstance();
		return c.get(Calendar.DAY_OF_WEEK);
	}


	/**
	 * Calculate the day of the month according to the month, year, week in the month and weekday
	 * @param year
	 * @param month
	 * @param week
	 * @param weekday - 1 is the first day of the week and 7 is the last day of the week
	 * @return
	 */
	public static int calcMonthDay(int year, int month, int week, int weekday) {
		Calendar c = Calendar.getInstance();
		c.set(Calendar.YEAR, year);
		c.set(Calendar.MONTH, month);
		c.set(Calendar.DAY_OF_MONTH, 1);
		int wd = c.get(Calendar.DAY_OF_WEEK);
		
		wd = weekday - wd + 1;
		if (wd <= 0) {
			if (week == 1)
				return 1;
			wd += 7;
			week--;
		}
		
		if (week == 1)
			return wd;		
		
		int max = c.getActualMaximum(Calendar.DAY_OF_MONTH);
		int d = wd + (week - 1) * 7;
		if (d > max)
			return max;
		else return d;
	}


	/**
	 * Returns the number of days in a specific month/year
	 * @param year
	 * @param month
	 * @return number of days in the month/year
	 */
	public static int daysInAMonth(int year, int month) {
		Calendar c = Calendar.getInstance();
		c.clear();
		c.set(Calendar.MONTH, month);
		c.set(Calendar.YEAR, year);
		return c.getActualMaximum(Calendar.DAY_OF_MONTH);
	}


	/**
	 * Create a new instance of a Date class
	 * @param year
	 * @param month
	 * @param day
	 * @return date object
	 */
	public static Date newDate(int year, int month, int day) {
		Calendar c = Calendar.getInstance();
		c.clear();
		c.set(Calendar.YEAR, year);
		c.set(Calendar.MONTH, month);
		c.set(Calendar.DAY_OF_MONTH, day);
		return c.getTime();
	}
	

	public static String formatDate(Date dt, String format) {
		SimpleDateFormat f = new SimpleDateFormat(format);
		return f.format(dt);
	}

	
	/**
	 * Return the difference between two dates. The result is stored in an instance
	 * of {@link Calendar} class
	 * @param d1
	 * @param d2
	 * @return
	 */
	public static Calendar calcDifference(Date d1, Date d2) {
		Calendar c1 = Calendar.getInstance();
		Calendar c2 = Calendar.getInstance();
		c1.setTime(d1);
		c2.setTime(d2);

		long len = c1.getTimeInMillis() - c2.getTimeInMillis();
		if (len < 0)
			len = -len;
		
		c1.setTimeInMillis(len);
		return c1;
	}
	
	
	/**
	 * Check if a data has time information
	 * @param dt1
	 * @return
	 */
	public static boolean hasTimePart(Date dt1) {
		if (dt1 instanceof java.sql.Date)
			return false;

		Calendar c = Calendar.getInstance();
		return (c.get(Calendar.HOUR) > 0) || (c.get(Calendar.MINUTE) > 0) | (c.get(Calendar.SECOND) > 0) || (c.get(Calendar.MILLISECOND) > 0);
	}
	
	/**
	 * Returns a string formating the date on the format of a locale
	 * @param dt1
	 * @return
	 */
	public static String formatAsLocale(Date dt, boolean includeTime) {
		if(dt==null)
			return "";
		
		String patt = Messages.instance().get("locale.outputDatePattern");
		if (includeTime)
			patt += " HH:mm:ss";
		Locale locale = LocaleSelector.instance().getLocale();
		SimpleDateFormat df = new SimpleDateFormat(patt, locale);
		
		return df.format(dt);
	}
	
}