/*
 * @(#)ResolutionSyntax.java	1.4 01/12/03
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */


package javax.print.attribute;

import java.io.Serializable;

/**
 * Class ResolutionSyntax is an abstract base class providing the common 
 * implementation of all attributes denoting a printer resolution. 
 * <P>
 * A resolution attribute's value consists of two items, the cross feed 
 * direction resolution and the feed direction resolution. A resolution 
 * attribute may be constructed by supplying the two values and indicating the 
 * units in which the values are measured. Methods are provided to return a 
 * resolution attribute's values, indicating the units in which the values are 
 * to be returned. The two most common resolution units are dots per inch (dpi) 
 * and dots per centimeter (dpcm), and exported constants {@link #DPI 
 * <CODE>DPI</CODE>} and {@link #DPCM <CODE>DPCM</CODE>} are provided for 
 * indicating those units. 
 * <P>
 * Once constructed, a resolution attribute's value is immutable. 
 * <P>
 * <B>Design</B>
 * <P>
 * A resolution attribute's cross feed direction resolution and feed direction 
 * resolution values are stored internally using units of dots per 100 inches 
 * (dphi). Storing the values in dphi rather than, say, metric units allows 
 * precise integer arithmetic conversions between dpi and dphi and between dpcm 
 * and dphi: 1 dpi = 100 dphi, 1 dpcm = 254 dphi. Thus, the values can be stored 
 * into and retrieved back from a resolution attribute in either units with no 
 * loss of precision. This would not be guaranteed if a floating point 
 * representation were used. However, roundoff error will in general occur if a 
 * resolution attribute's values are created in one units and retrieved in 
 * different units; for example, 600 dpi will be rounded to 236 dpcm, whereas 
 * the true value (to five figures) is 236.22 dpcm. 
 * <P>
 * Storing the values internally in common units of dphi lets two resolution 
 * attributes be compared without regard to the units in which they were 
 * created; for example, 300 dpcm will compare equal to 762 dpi, as they both 
 * are stored as 76200 dphi. In particular, a lookup service can 
 * match resolution attributes based on equality of their serialized 
 * representations regardless of the units in which they were created. Again, 
 * using integers for internal storage allows precise equality comparisons to be 
 * done, which would not be guaranteed if a floating point representation were 
 * used. 
 * <P>
 * The exported constant {@link #DPI <CODE>DPI</CODE>} is actually the 
 * conversion factor by which to multiply a value in dpi to get the value in 
 * dphi. Likewise, the exported constant {@link #DPCM <CODE>DPCM</CODE>} is the 
 * conversion factor by which to multiply a value in dpcm to get the value in 
 * dphi. A client can specify a resolution value in units other than dpi or dpcm 
 * by supplying its own conversion factor. However, since the internal units of 
 * dphi was chosen with supporting only the external units of dpi and dpcm in 
 * mind, there is no guarantee that the conversion factor for the client's units 
 * will be an exact integer. If the conversion factor isn't an exact integer, 
 * resolution values in the client's units won't be stored precisely. 
 * <P>
 *
 * @author  David Mendenhall
 * @author  Alan Kaminsky
 */
public abstract class ResolutionSyntax implements Serializable, Cloneable {

    /**
     * Cross feed direction resolution in units of dots per 100 inches (dphi).
     * @serial
     */
    private int crossFeedResolution;

    /**
     * Feed direction resolution in units of dots per 100 inches (dphi).
     * @serial
     */
    private int feedResolution;

    /**
     * Value to indicate units of dots per inch (dpi). It is actually the 
     * conversion factor by which to multiply dpi to yield dphi (100). 
     */
    public static final int DPI = 100;

    /**
     * Value to indicate units of dots per centimeter (dpcm). It is actually 
     * the conversion factor by which to multiply dpcm to yield dphi (254). 
     */
    public static final int DPCM = 254;


    /**
     * Construct a new resolution attribute from the given items.
     *
     * @param  crossFeedResolution
     *     Cross feed direction resolution.
     * @param  feedResolution
     *     Feed direction resolution.
     * @param units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or
     * {@link    #DPCM <CODE>DPCM</CODE>}. 
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>crossFeedResolution</CODE> < 
     *     1 or <CODE>feedResolution</CODE> < 1 or <CODE>units</CODE> < 1. 
     */
    public ResolutionSyntax(int crossFeedResolution, int feedResolution,
			    int units) {

	if (crossFeedResolution < 1) {
	    throw new IllegalArgumentException("crossFeedResolution is < 1");
	}
	if (feedResolution < 1) {
		throw new IllegalArgumentException("feedResolution is < 1");
	}
	if (units < 1) {
		throw new IllegalArgumentException("units is < 1");
	}

	this.crossFeedResolution = crossFeedResolution * units;
	this.feedResolution = feedResolution * units;
    }

    /**
     * Convert a value from dphi to some other units. The result is rounded to 
     * the nearest integer. 
     *
     * @param  dphi
     *     Value (dphi) to convert.
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or
     * {@link     #DPCM <CODE>DPCM</CODE>}. 
     *
     * @return  The value of <CODE>dphi</CODE> converted to the desired units.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1. 
     */
    private static int convertFromDphi(int dphi, int units) {
	if (units < 1) {
	    throw new IllegalArgumentException(": units is < 1");
	}
	int round = units / 2;
	return (dphi + round) / units;
    }
    
    /**
     * Get this resolution attribute's resolution values in the given units.
     * The values are rounded to the nearest integer. 
     *
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or
     * {@link   #DPCM <CODE>DPCM</CODE>}. 
     *
     * @return  A two-element array with the cross feed direction resolution
     *          at index 0 and the feed direction resolution at index 1. 
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1. 
     */
    public int[] getResolution(int units) {
	return new int[] { getCrossFeedResolution(units),
			       getFeedResolution(units)
			       };
    }

    /**
     * Returns this resolution attribute's cross feed direction resolution in 
     * the given units. The value is rounded to the nearest integer. 
     *
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or
     * {@link  #DPCM <CODE>DPCM</CODE>}. 
     *
     * @return  Cross feed direction resolution.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1. 
     */
    public int getCrossFeedResolution(int units) {
	return convertFromDphi (crossFeedResolution, units);
    }

    /**
     * Returns this resolution attribute's feed direction resolution in the 
     * given units. The value is rounded to the nearest integer. 
     *
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or {@link 
     *     #DPCM <CODE>DPCM</CODE>}. 
     *
     * @return  Feed direction resolution.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1. 
     */
    public int getFeedResolution(int units) {
	return convertFromDphi (feedResolution, units);
    }
    
    /**
     * Returns a string version of this resolution attribute in the given units. 
     * The string takes the form <CODE>"<I>C</I>x<I>F</I> <I>U</I>"</CODE>, 
     * where <I>C</I> is the cross feed direction resolution, <I>F</I> is the 
     * feed direction resolution, and <I>U</I> is the units name. The values are 
     * rounded to the nearest integer. 
     *
     * @param  units
     *     Unit conversion factor, e.g. {@link #DPI <CODE>DPI</CODE>} or {@link 
     *     #DPCM <CODE>DPCM</CODE>}. 
     * @param  unitsName
     *     Units name string, e.g. <CODE>"dpi"</CODE> or <CODE>"dpcm"</CODE>. If 
     *     null, no units name is appended to the result. 
     *
     * @return  String version of this resolution attribute.
     *
     * @exception  IllegalArgumentException
     *     (unchecked exception) Thrown if <CODE>units</CODE> < 1. 
     */
    public String toString(int units, String unitsName) {
	StringBuffer result = new StringBuffer();
	result.append(getCrossFeedResolution (units));
	result.append('x');
	result.append(getFeedResolution (units));
	if (unitsName != null) {
	    result.append (' ');
	    result.append (unitsName);
	}
	return result.toString();
    }

    
    /**
     * Determine whether this resolution attribute's value is less than or 
     * equal to the given resolution attribute's value. This is true if all
     * of the following conditions are true: 
     * <UL>
     * <LI>
     * This attribute's cross feed direction resolution is less than or equal to 
     * the <CODE>other</CODE> attribute's cross feed direction resolution.
     * <LI>
     * This attribute's feed direction resolution is less than or equal to the 
     * <CODE>other</CODE> attribute's feed direction resolution. 
     * </UL>
     *
     * @param  other  Resolution attribute to compare with.
     *
     * @return  True if this resolution attribute is less than or equal to the
     *          <CODE>other</CODE> resolution attribute, false otherwise.
     *
     * @exception  NullPointerException
     *     (unchecked exception) Thrown if <CODE>other</CODE> is null.
     */
    public boolean lessThanOrEquals(ResolutionSyntax other) {
	return (this.crossFeedResolution <= other.crossFeedResolution &&
		this.feedResolution <= other.feedResolution);
    }


    /**
     * Returns whether this resolution attribute is equivalent to the passed in 
     * object. To be equivalent, all of the following conditions must be true: 
     * <OL TYPE=1>
     * <LI>
     * <CODE>object</CODE> is not null.
     * <LI>
     * <CODE>object</CODE> is an instance of class ResolutionSyntax.
     * <LI>
     * This attribute's cross feed direction resolution is equal to 
     * <CODE>object</CODE>'s cross feed direction resolution. 
     * <LI>
     * This attribute's feed direction resolution is equal to
     * <CODE>object</CODE>'s feed direction resolution. 
     * </OL>
     *
     * @param  object  Object to compare to.
     *
     * @return  True if <CODE>object</CODE> is equivalent to this resolution
     *          attribute, false otherwise. 
     */
    public boolean equals(Object object) {

	return(object != null &&
	       object instanceof ResolutionSyntax &&
	       this.crossFeedResolution ==
	       ((ResolutionSyntax) object).crossFeedResolution &&
	       this.feedResolution == 
	       ((ResolutionSyntax) object).feedResolution);
    }
    
    /**
     * Returns a hash code value for this resolution attribute.
     */
    public int hashCode() {
	return(((crossFeedResolution & 0x0000FFFF)) |
	       ((feedResolution      & 0x0000FFFF) << 16));
    }
    
    /**
     * Returns a string version of this resolution attribute. The string takes 
     * the form <CODE>"<I>C</I>x<I>F</I> dphi"</CODE>, where <I>C</I> is the 
     * cross feed direction resolution and <I>F</I> is the feed direction 
     * resolution. The values are reported in the internal units of dphi. 
     */
    public String toString() {
	StringBuffer result = new StringBuffer();
	result.append(crossFeedResolution);
	result.append('x');
	result.append(feedResolution);
	result.append(" dphi");
	return result.toString();
    }


    /**
     * Returns this resolution attribute's cross feed direction resolution in 
     * units of dphi. (For use in a subclass.)
     *
     * @return  Cross feed direction resolution.
     */
    protected int getCrossFeedResolutionDphi() {
	return crossFeedResolution;
    }

    /**
     * Returns this resolution attribute's feed direction resolution in units 
     * of dphi. (For use in a subclass.) 
     *
     * @return  Feed direction resolution.
     */
    protected int getFeedResolutionDphi() {
	return feedResolution;
    }

}
