Metrics.java

/*
    GNU General Public License
    CacheWolf is a software for PocketPC, Win and Linux that
    enables paperless caching.
    It supports the sites geocaching.com and opencaching.de

    Copyright (C) 2006  CacheWolf development team
	See http://www.cachewolf.de/ for more information.
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; version 2 of the License.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
package CacheWolf.utils;

/**
 * @author Engywuck
 *
 */
public final class Metrics {

    /** Constant for use of metric units */
    public static final int METRIC = 1;
    /** Constant for use of imperial units */
    public static final int IMPERIAL = 2;

    public static final int KILOMETER = 10;
    public static final int METER = 11;

    public static final int MILES = 20;
    public static final int YARDS = 21;
    public static final int FEET = 22;

    private static final double FCT_MILE2KILOMETER = 1.609344;
    private static final double FCT_MILE2YARD = 1760;
    private static final double FCT_MILE2FOOT = 5280;

    /**
     * Converts values from one to another unit.
     * 
     * @param value
     *            Value to convert
     * @param sourceUnit
     *            Constant from class Metrics to represent unit in which <code>value</code> is
     *            meant.
     * @param targetUnit
     *            Constant from class Metrics to represent the unit in which <code>value</code>
     *            has to be transformed
     * @return The new converted value
     * @throws UnsupportedOperationException
     *             when the conversion between the two units is not programmed.
     */
    public static final double convertUnit(double value, int sourceUnit, int targetUnit) {
	/*
	 * Strategy: For each metrical system we define a standard unit: km and mi. In a first step
	 * any input value is converted to the standard unit in its system Then (if required) the
	 * standard units are converted between the systems. Last step: The converted unit is
	 * converted to the target unit (which is in the same metrical system).
	 */

	double result = Double.NaN;
	if (sourceUnit == targetUnit) {
	    result = value;
	} else {
	    double stdValue;
	    int sourceStdUnit = getMetricSystemStdUnit(sourceUnit);
	    int targetStdUnit = getMetricSystemStdUnit(targetUnit);
	    switch (sourceUnit) {
	    case KILOMETER:
	    case MILES:
		stdValue = value;
		break;
	    case METER:
		stdValue = value / 1000.0;
		break;
	    case YARDS:
		stdValue = value / FCT_MILE2YARD;
		break;
	    case FEET:
		stdValue = value / FCT_MILE2FOOT;
		break;
	    default:
		throw new UnsupportedOperationException("Cannot convert unit" + getUnit(sourceUnit));
	    }

	    // Convert between standard units of imperial systems
	    if (sourceStdUnit == KILOMETER && targetStdUnit == MILES) {
		stdValue = stdValue / FCT_MILE2KILOMETER;
	    } else if (sourceStdUnit == MILES && targetStdUnit == KILOMETER) {
		stdValue = stdValue * FCT_MILE2KILOMETER;
	    }

	    // Convert to unit from standard unit
	    switch (targetUnit) {
	    case KILOMETER:
	    case MILES:
		result = stdValue;
		break;
	    case METER:
		result = stdValue * 1000.0;
		break;
	    case YARDS:
		result = stdValue * FCT_MILE2YARD;
		break;
	    case FEET:
		result = stdValue * FCT_MILE2FOOT;
		break;
	    default:
		throw new UnsupportedOperationException("Cannot convert unit" + getUnit(targetUnit));
	    }
	}
	return result;
    }

    public static final String getUnit(int unit) {
	String result = null;
	switch (unit) {
	case KILOMETER:
	    result = "km";
	    break;
	case METER:
	    result = "m";
	    break;
	case MILES:
	    result = "mi.";
	    break;
	case YARDS:
	    result = "yd.";
	    break;
	case FEET:
	    result = "ft.";
	    break;
	default:
	    throw new UnsupportedOperationException("Unknown unit: " + String.valueOf(unit));
	}
	return result;
    }

    /**
     * Returns the constant for the metric systems standard unit (km or mi.) a given unit belongs to.
     * @param unit Unit to examine
     * @return Constant of the standard unit
     */
    private static int getMetricSystemStdUnit(int unit) {
	switch (unit) {
	case KILOMETER:
	case METER:
	    return KILOMETER;
	case MILES:
	case YARDS:
	case FEET:
	    return MILES;
	default:
	    throw new UnsupportedOperationException("Unknown unit: " + String.valueOf(unit));
	}
    }
}