HourMinute.java

package org.frasermccrossan.ltc;

import java.util.Calendar;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/* a very simple time representation class since we don't really want the sophistication
 * of Calendar; really just acts as a return value of a regexp-parsed time
 */

public class HourMinute {
	
	public static final int AM = 0;
	public static final int PM = 2;
	public static final int NO_AMPM = -1;
	
	static final int DAY_MINUTES = 24 * 60;
	static final int HALF_DAY_MINUTES = DAY_MINUTES / 2;
	
	public int minsAfterMidnight; // absolute number of minutes after midnight
	
	/* this needs to match the following forms and extract the hour, minutes and am/pmage:
	 * "12:04"
	 * "12:04 [AP]"
	 * :12:04:08 [AP]"
	 */
	static final Pattern TIME_PATTERN = Pattern.compile("(\\d{1,2}):(\\d{2})(:\\d{2})? ?([AP])?");
	
	public int hour = -1;
	public int minute;
	public int am_pm = NO_AMPM;
	
	HourMinute(Calendar reference, String textTime) {
		Matcher m = TIME_PATTERN.matcher(textTime);
		if (m.find()) {
			hour=Integer.valueOf(m.group(1));
			if (hour == 12) { hour = 0; } // makes calculations easier
			minute = Integer.valueOf(m.group(2));
			String am_pm_s = m.group(4);
			if (am_pm_s != null) {
				am_pm_s = am_pm_s.toLowerCase();
				if (am_pm_s.equals("p")) {
					am_pm = PM;
					hour += 12; // we fixed the hour values above, so 12 is zero
				}
				else {
					am_pm = AM;
				}
			}
			minsAfterMidnight = hour * 60 + minute;
			if (!hasAmPm()) {
				/* no am/pm indicator, assume it's within 12 hours of now and take a best guess,
				 * then correct the hour value
				 */
				int ref12Hour = reference.get(Calendar.HOUR); // 12-hour hour of reference
				int refMinute = reference.get(Calendar.MINUTE); // minute of reference
				if (ref12Hour == 12) { ref12Hour = 0; } // easier calculation
				int refMinutes12 = ref12Hour * 60 + refMinute;
				int ref24hour = reference.get(Calendar.HOUR_OF_DAY);
				int refMinutes24 = ref24hour * 60 + refMinute;
				if (minsAfterMidnight >= refMinutes12) {
					/* the 12-hour time hour is greater than the reference 12-hour, assume it's
					 * *after* the reference time in the same 12-hour segment
					 */
					minsAfterMidnight = refMinutes24 + (minsAfterMidnight - refMinutes12);
				}
				else {
					/* otherwise, the 12-hour time is less than the reference, so it's 
					 * in the "other" 12 hour segment
					 */
					if (refMinutes24 >= HALF_DAY_MINUTES) {
						// reference is second half of day, so time we seek is after midnight, in the early hours
						// we need do nothing
					}
					else {
						// reference is first half of day, so time we seek is afternoon
						minsAfterMidnight += HALF_DAY_MINUTES;
					}
				}
				hour = minsAfterMidnight / 60;
				minute = minsAfterMidnight % 60;
			}
			//Log.d("HourMinute", String.format("orig %s hour %d min %d", textTime, hour, minute));
		}
	}
	
	public boolean isValid() {
		return hour >= 0;
	}
	
	public Boolean hasAmPm() {
		return am_pm != NO_AMPM;
	}

	int timeDiff(Calendar reference) {
		if (isValid()) {
			/* the minsAfterMidnight value here should now be correct whether we had
			 * an AM/PM time or not, so the calculation is simple
			 */
			int refMinsAfterMidnight = reference.get(Calendar.HOUR_OF_DAY) * 60 + reference.get(Calendar.MINUTE);
			int diff = minsAfterMidnight - refMinsAfterMidnight;
			if (diff >= 0) {
				return diff;
			}
			else {
				return DAY_MINUTES + diff;
			}
		}
		else {
			return Prediction.VERY_FAR_AWAY;
		}
	}
	
}