//
// $Id: CssBackgroundPosition.java,v 1.5 2005-09-14 15:14:31 ylafon Exp $
// From Philippe Le Hegaret (Philippe.Le_Hegaret@sophia.inria.fr)
//
// (c) COPYRIGHT MIT and INRIA, 1997.
// Please first read the full copyright statement in file COPYRIGHT.html
package org.w3c.css.properties.css1;

import org.w3c.css.parser.CssStyle;
import org.w3c.css.util.ApplContext;
import org.w3c.css.util.InvalidParamException;
import org.w3c.css.values.CssExpression;
import org.w3c.css.values.CssIdent;
import org.w3c.css.values.CssLength;
import org.w3c.css.values.CssNumber;
//import org.w3c.css.values.CssNumber;
import org.w3c.css.values.CssOperator;
import org.w3c.css.values.CssPercentage;
import org.w3c.css.values.CssValue;

/**
 *   <H4>
 *     &nbsp;&nbsp; 'background-position'
 *   </H4>
 *   <P>
 *   <EM>Value:</EM> [&lt;percentage&gt; | &lt;length&gt;]{1,2} | [top | center
 *   | bottom] || [left | center | right]<BR>
 *   <EM>Initial:</EM> 0% 0%<BR>
 *   <EM>Applies to:</EM> block-level and replaced elements<BR>
 *   <EM>Inherited:</EM> no<BR>
 *   <EM>Percentage values:</EM> refer to the size of the element itself<BR>
 *   <P> If a background image has been specified, the value of
 *   'background-position' specifies its initial position.
 *   <P> With a value pair of '0% 0%', the upper left corner of the image is
 *   placed in the upper left corner of the box that surrounds the content of
 *   the element (i.e., not the box that surrounds the padding, border or
 *   margin). A value pair of '100% 100%' places the lower right corner of the
 *   image in the lower right corner of the element. With a value pair of '14%
 *   84%', the point 14% across and 84% down the image is to be placed at the
 *   point 14% across and 84% down the element.
 *   <P> With a value pair of '2cm 2cm', the upper left corner of the image is
 *   placed 2cm to the right and 2cm below the upper left corner of the element.
 *   <P> If only one percentage or length value is given, it sets the horizontal
 *   position only, the vertical position will be 50%. If two values are given,
 *   the horizontal position comes first. Combinations of length and percentage
 *   values are allowed, e.g. '50% 2cm'. Negative positions are allowed.
 *   <P> One can also use keyword values to indicate the position of the
 *   background image. Keywords cannot be combined with percentage values, or
 *   length values.  The possible combinations of keywords and their
 *   interpretations are as follows:

 *   <UL>
 *     <LI>
 *       'top left' and 'left top' both mean the same as '0% 0%'.
 *     <LI>
 *       'top', 'top center' and 'center top' mean the same as '50% 0%'.
 *     <LI>
 *       'right top' and 'top right' mean the same as '100% 0%'.
 *     <LI>
 *       'left', 'left center' and 'center left' mean the same as '0% 50%'.
 *     <LI>
 *       'center' and 'center center' mean the same as '50% 50%'.
 *     <LI>
 *       'right', 'right center' and 'center right' mean the same as '100% 50%'.
 *     <LI>
 *       'bottom left' and 'left bottom' mean the same as '0% 100%'.
 *     <LI>
 *       'bottom', 'bottom center' and 'center bottom' mean the same as '50% 100%'.
 *     <LI>
 *       'bottom right' and 'right bottom' mean the same as '100% 100%'.
 *   </UL>
 *   <P>
 *   examples:
 *   <PRE>
 *   BODY { background: url(banner.jpeg) right top }    / * 100%   0% * /
 *   BODY { background: url(banner.jpeg) top center }   / *  50%   0% * /
 *   BODY { background: url(banner.jpeg) center }       / *  50%  50% * /
 *   BODY { background: url(banner.jpeg) bottom }       / *  50% 100% * /
 *  </PRE>
 *   <P>
 *   If the background image is fixed with regard to the canvas (see the
 *   'background-attachment' property above), the image is placed relative to
 *   the canvas instead of the element. E.g.:
 *   <PRE>
 *   BODY {
 *     background-image: url(logo.png);
 *     background-attachment: fixed;
 *     background-position: 100% 100%;
 *   }
 *  </PRE>
 *   <P>
 *   In the example above, the image is placed in the lower right corner of the
 *   canvas.
 * @version $Revision: 1.5 $
 * @see CssBackgroundAttachment
 */
public class CssBackgroundPosition extends CssProperty
implements CssBackgroundConstants, CssOperator {

    CssValue first;
    CssValue second;

    /**
     * Create a new CssBackgroundPosition
     */
    public CssBackgroundPosition() {
	first = DefaultValue0;
	second = DefaultValue0;
    }

    /**
     * Creates a new CssBackgroundPosition
     *
     * @param expression The expression for this property
     * @exception InvalidParamException Values are incorrect
     */
    public CssBackgroundPosition(ApplContext ac, CssExpression expression,
	    boolean check) throws InvalidParamException {

	if(check && expression.getCount() > 2) {
	    throw new InvalidParamException("unrecognize", ac);
	}

	setByUser();
	CssValue val = expression.getValue();
	char op  = expression.getOperator();

	if (op != SPACE)
	    throw new  InvalidParamException("operator",
		    ((new Character(op)).toString()),
		    ac);

	if (val.equals(inherit)) {
	    if(expression.getCount() > 1) {
		throw new InvalidParamException("unrecognize", ac);
	    }
	    first = inherit;
	    second = inherit;
	    expression.next();
	    return;
	}

	CssValue next = expression.getNextValue();

	if(val instanceof CssIdent) {
	    int index1 = IndexOfIdent((String) val.get());
	    if(index1 == -1) {
		throw new InvalidParamException("value", val, "background-position", ac);
	    }
	    // two keywords
	    if(next instanceof CssIdent) {
		int index2 = IndexOfIdent((String) next.get());
		if(index2 == -1 && check) {
		    throw new InvalidParamException("value", next, "background-position", ac);
		}
		// one is vertical, the other is vertical
		// or the two are 'center'
		if((isHorizontal(index1) && isVertical(index2)) ||
			(isHorizontal(index2) && isVertical(index1))) {
		    first = val;
		    second = next;
		}
		// both are horizontal or vertical but not 'center'
		else if(check){
		    throw new InvalidParamException("incompatible",
			    val, next, ac);
		}
		else {
		    first = val;
		}
	    }
	    // a keyword and a percentage/length
	    else if(next instanceof CssLength || next instanceof CssPercentage
		    || next instanceof CssNumber) {
		if(next instanceof CssNumber) {
		    next = ((CssNumber) next).getLength();
		}
		if(isHorizontal(index1)) {
		    first = val;
		    second = next;
		}
		// if the keyword is the first value, it can only be an
		// horizontal one
		else {
		    throw new InvalidParamException("incompatible",
			    val, next, ac);
		}
	    }
	    // only one value
	    else if(next == null) {
		first = val;
	    }
	    // the second value is invalid
	    else if(check) {
		throw new InvalidParamException("value", next,
			getPropertyName(), ac);
	    }
	    else {
		first = val;
	    }
	}
	else if(val instanceof CssLength || val instanceof CssPercentage ||
		val instanceof CssNumber) {
	    if(val instanceof CssNumber) {
		val = ((CssNumber) val).getLength();
	    }
	    // a percentage/length and an keyword
	    if(next instanceof CssIdent) {
		int index = IndexOfIdent((String) next.get());
		if(check && index == -1) {
		    throw new InvalidParamException("value", val, "background-position", ac);
		}
		// the keyword must be a vertical one
		if(isVertical(index)) {
		    first = val;
		    second = next;
		}
		else if(check) {
		    throw new InvalidParamException("incompatible",
			    val, next, ac);
		}
		else {
		    first = val;
		}
	    }
	    else if(next instanceof CssLength || next instanceof CssPercentage
		    || next instanceof CssNumber) {
		if(next instanceof CssNumber) {
		    next = ((CssNumber) next).getLength();
		}
		first = val;
		second = next;
	    }
	    else if(next == null || !check) {
		first = val;
	    }
	    else {
		throw new InvalidParamException("incompatible", val, next, ac);
	    }
	}
	else if(check){
	    throw new InvalidParamException("value", expression.getValue(),
		    getPropertyName(), ac);
	}

	// we only move the cursor if we found valid values
	if(first != null) {
	    expression.next();
	}
	if(second != null) {
	    expression.next();
	}
    }

    public CssBackgroundPosition(ApplContext ac, CssExpression expression)
    throws InvalidParamException {
	this(ac, expression, false);
    }

    private boolean isHorizontal(int index) {
	return index == POSITION_LEFT || index == POSITION_RIGHT ||
	index == POSITION_CENTER;
    }

    private boolean isVertical(int index) {
	return index == POSITION_TOP || index == POSITION_BOTTOM ||
	index == POSITION_CENTER;
    }

    /**
     * Returns the value of this property
     */
    public Object get() {
	return first;
    }

    /**
     * Returns the name of this property
     */
    public String getPropertyName() {
	return "background-position";
    }

    /**
     * Returns the horizontal value of the position
     */
    public CssValue getHorizontalPosition() {
	return first;
    }

    /**
     * Returns the vertical value of the position
     */
    public CssValue getVerticalPosition() {
	return second;
    }

    /**
     * Returns true if this property is "softly" inherited
     * e.g. his value equals inherit
     */
    public boolean isSoftlyInherited() {
	return first == inherit;
    }

    /**
     * Returns a string representation of the object.
     */
    public String toString() {
	if (first == inherit) {
	    return inherit.toString();
	} else {
	    String ret = "";
	    if (first != null) {
		ret += first;
	    }
	    if (second != null) {
		if (!ret.equals("")) {
		    ret += " ";
		}
		ret += second;
	    }
	    return ret;
	}
    }
    /*
     private void getPercentageFromIdent(int horizontal, int vertical) {
     first = DefaultValue50;
     second = DefaultValue50;
     if (horizontal == POSITION_LEFT || vertical == POSITION_LEFT)
     first = DefaultValue0;
     if (horizontal == POSITION_RIGHT || vertical == POSITION_RIGHT)
     first = DefaultValue100;
     if (horizontal == POSITION_TOP || vertical == POSITION_TOP)
     second = DefaultValue0;
     if (horizontal == POSITION_BOTTOM || vertical == POSITION_BOTTOM)
     second = DefaultValue100;
     }
     */
    /**
     * Add this property to the CssStyle.
     *
     * @param style The CssStyle
     */
    public void addToStyle(ApplContext ac, CssStyle style) {
	CssBackground cssBackground = ((Css1Style) style).cssBackground;
	if (cssBackground.position != null)
	    style.addRedefinitionWarning(ac, this);
	cssBackground.position = this;
    }

    /**
     * Get this property in the style.
     *
     * @param style The style where the property is
     * @param resolve if true, resolve the style to find this property
     */
    public CssProperty getPropertyInStyle(CssStyle style, boolean resolve) {
	if (resolve) {
	    return ((Css1Style) style).getBackgroundPosition();
	} else {
	    return ((Css1Style) style).cssBackground.position;
	}
    }

    /**
     * Compares two properties for equality.
     *
     * @param value The other property.
     */
    public boolean equals(CssProperty property) {
	return ((property == null && first == null && second == null) ||
		(property instanceof CssBackgroundPosition &&
			first != null &&
			first.equals(((CssBackgroundPosition) property).first) &&
			second != null &&
			second.equals(((CssBackgroundPosition) property).second)));
    }

    /**
     * Is the value of this property is a default value.
     * It is used by all macro for the function <code>print</code>
     */
    public boolean isDefault() {
	return first != null && second != null &&
	first.equals(DefaultValue0) && second.equals(DefaultValue0);
    }

    private int IndexOfIdent(String ident) throws InvalidParamException {
	int hash = ident.hashCode();
	for (int i = 0; i < POSITION.length; i++)
	    if (hash_values[i] == hash)
		return i;

	return -1;
    }

    private static int[] hash_values;

//  private static int INVALID = -1;
    private static CssPercentage DefaultValue0 = new CssPercentage(0);
//  private static CssPercentage DefaultValue50 = new CssPercentage(50);
//  private static CssPercentage DefaultValue100 = new CssPercentage(100);

    static {
	hash_values = new int[POSITION.length];
	for (int i = 0; i < POSITION.length; i++)
	    hash_values[i] = POSITION[i].hashCode();
    }
}
