package com.earth2me.essentials.utils;

import static com.earth2me.essentials.I18n.tl;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.regex.Matcher;
import java.util.regex.Pattern;


public class DateUtil
{
	public static long parseDateDiff(String time, boolean future) throws Exception
	{
		Pattern timePattern = Pattern.compile("(?:([0-9]+)\\s*y[a-z]*[,\\s]*)?" + "(?:([0-9]+)\\s*mo[a-z]*[,\\s]*)?" + "(?:([0-9]+)\\s*w[a-z]*[,\\s]*)?" + "(?:([0-9]+)\\s*d[a-z]*[,\\s]*)?" + "(?:([0-9]+)\\s*h[a-z]*[,\\s]*)?" + "(?:([0-9]+)\\s*m[a-z]*[,\\s]*)?" + "(?:([0-9]+)\\s*(?:s[a-z]*)?)?", Pattern.CASE_INSENSITIVE);
		Matcher m = timePattern.matcher(time);
		int years = 0;
		int months = 0;
		int weeks = 0;
		int days = 0;
		int hours = 0;
		int minutes = 0;
		int seconds = 0;
		boolean found = false;
		while (m.find())
		{
			if (m.group() == null || m.group().isEmpty())
			{
				continue;
			}
			for (int i = 0; i < m.groupCount(); i++)
			{
				if (m.group(i) != null && !m.group(i).isEmpty())
				{
					found = true;
					break;
				}
			}
			if (found)
			{
				if (m.group(1) != null && !m.group(1).isEmpty())
				{
					years = Integer.parseInt(m.group(1));
				}
				if (m.group(2) != null && !m.group(2).isEmpty())
				{
					months = Integer.parseInt(m.group(2));
				}
				if (m.group(3) != null && !m.group(3).isEmpty())
				{
					weeks = Integer.parseInt(m.group(3));
				}
				if (m.group(4) != null && !m.group(4).isEmpty())
				{
					days = Integer.parseInt(m.group(4));
				}
				if (m.group(5) != null && !m.group(5).isEmpty())
				{
					hours = Integer.parseInt(m.group(5));
				}
				if (m.group(6) != null && !m.group(6).isEmpty())
				{
					minutes = Integer.parseInt(m.group(6));
				}
				if (m.group(7) != null && !m.group(7).isEmpty())
				{
					seconds = Integer.parseInt(m.group(7));
				}
				break;
			}
		}
		if (!found)
		{
			throw new Exception(tl("illegalDate"));
		}
		Calendar c = new GregorianCalendar();
		if (years > 0)
		{
			c.add(Calendar.YEAR, years * (future ? 1 : -1));
		}
		if (months > 0)
		{
			c.add(Calendar.MONTH, months * (future ? 1 : -1));
		}
		if (weeks > 0)
		{
			c.add(Calendar.WEEK_OF_YEAR, weeks * (future ? 1 : -1));
		}
		if (days > 0)
		{
			c.add(Calendar.DAY_OF_MONTH, days * (future ? 1 : -1));
		}
		if (hours > 0)
		{
			c.add(Calendar.HOUR_OF_DAY, hours * (future ? 1 : -1));
		}
		if (minutes > 0)
		{
			c.add(Calendar.MINUTE, minutes * (future ? 1 : -1));
		}
		if (seconds > 0)
		{
			c.add(Calendar.SECOND, seconds * (future ? 1 : -1));
		}
		Calendar max = new GregorianCalendar();
		max.add(Calendar.YEAR, 10);
		if (c.after(max))
		{
			return max.getTimeInMillis();
		}
		return c.getTimeInMillis();
	}

	static int dateDiff(int type, Calendar fromDate, Calendar toDate, boolean future)
	{
		int diff = 0;
		long savedDate = fromDate.getTimeInMillis();
		while ((future && !fromDate.after(toDate)) || (!future && !fromDate.before(toDate)))
		{
			savedDate = fromDate.getTimeInMillis();
			fromDate.add(type, future ? 1 : -1);
			diff++;
		}
		diff--;
		fromDate.setTimeInMillis(savedDate);
		return diff;
	}

	public static String formatDateDiff(long date)
	{
		Calendar c = new GregorianCalendar();
		c.setTimeInMillis(date);
		Calendar now = new GregorianCalendar();
		return DateUtil.formatDateDiff(now, c);
	}

	public static String formatDateDiff(Calendar fromDate, Calendar toDate)
	{
		boolean future = false;
		if (toDate.equals(fromDate))
		{
			return tl("now");
		}
		if (toDate.after(fromDate))
		{
			future = true;
		}
		StringBuilder sb = new StringBuilder();
		int[] types = new int[]
		{
			Calendar.YEAR, Calendar.MONTH, Calendar.DAY_OF_MONTH, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND
		};
		String[] names = new String[]
		{
			tl("year"), tl("years"), tl("month"), tl("months"), tl("day"), tl("days"), tl("hour"), tl("hours"), tl("minute"), tl("minutes"), tl("second"), tl("seconds")
		};
		int accuracy = 0;
		for (int i = 0; i < types.length; i++)
		{
			if (accuracy > 2)
			{
				break;
			}
			int diff = dateDiff(types[i], fromDate, toDate, future);
			if (diff > 0)
			{
				accuracy++;
				sb.append(" ").append(diff).append(" ").append(names[i * 2 + (diff > 1 ? 1 : 0)]);
			}
		}
		if (sb.length() == 0)
		{
			return "now";
		}
		return sb.toString().trim();
	}
}