PseudoNthSpecifierChecker.java

package org.nate.internal.dom4j.cssselectors.internal;

import java.util.LinkedHashSet;
import java.util.Set;

import org.dom4j.Branch;
import org.nate.internal.dom4j.cssselectors.DOMHelper;

import se.fishtank.css.selectors.NodeSelectorException;
import se.fishtank.css.selectors.specifier.PseudoNthSpecifier;
import se.fishtank.css.util.Assert;
/**
 * Simple port of Christer Sandberg's CSS selectors to Dom4j (https://github.com/chrsan/css-selectors)
 */
public class PseudoNthSpecifierChecker implements NodeTraversalChecker {
    
    /** The {@code nth-*} pseudo-class specifier to check against. */
    private final PseudoNthSpecifier specifier;
    
    /** The set of nodes to check. */
    private Set<Branch> nodes;
    
    /** The result of the checks. */
    private Set<Branch> result;

	public PseudoNthSpecifierChecker(PseudoNthSpecifier specifier) {
        Assert.notNull(specifier, "specifier is null!");
        this.specifier = specifier;
	}

	@Override
	public Set<Branch> check(Set<Branch> nodes) throws NodeSelectorException {
        Assert.notNull(nodes, "nodes is null!");
        this.nodes = nodes;
        result = new LinkedHashSet<Branch>();
        String value = specifier.getValue();
        if ("nth-child".equals(value)) {
            getNthChild();
        } else if ("nth-last-child".equals(value)) {
            getNthLastChild();
        } else if ("nth-of-type".equals(value)) {
            getNthOfType();
        } else if ("nth-last-of-type".equals(value)) {
            getNthLastOfType();
        } else {
            throw new NodeSelectorException("Unknown pseudo nth class: " + value);
        }
        
        return result;
	}
    
    /**
     * Get the {@code :nth-child} elements.
     * 
     * @see <a href="http://www.w3.org/TR/css3-selectors/#nth-child-pseudo"><code>:nth-child</code> pseudo-class</a>
     */
    private void getNthChild() {
        for (Branch node : nodes) {
            int count = 1;
            Branch n = DOMHelper.getPreviousSiblingElement(node);
            while (n != null) {
                count++;
                n = DOMHelper.getPreviousSiblingElement(n);
            }
            
            if (specifier.isMatch(count)) {
                result.add(node);
            }
        }
    }
    
    /**
     * Get {@code :nth-last-child} elements.
     * 
     * @see <a href="http://www.w3.org/TR/css3-selectors/#nth-last-child-pseudo"><code>:nth-last-child</code> pseudo-class</a>
     */
    private void getNthLastChild() {
        for (Branch node : nodes) {
            int count = 1;
            Branch n = DOMHelper.getNextSiblingElement(node);
            while (n != null) {
                count++;
                n = DOMHelper.getNextSiblingElement(n);
            }
            
            if (specifier.isMatch(count)) {
                result.add(node);
            }
        }
    }
    
    /**
     * Get {@code :nth-of-type} elements.
     * 
     * @see <a href="http://www.w3.org/TR/css3-selectors/#nth-of-type-pseudo"><code>:nth-of-type</code> pseudo-class</a>
     */
    private void getNthOfType() {
        for (Branch node : nodes) {
            int count = 1;
            Branch n = DOMHelper.getPreviousSiblingElement(node);
            while (n != null) {
                if (n.getName().equals(node.getName())) {
                    count++;
                }
                
                n = DOMHelper.getPreviousSiblingElement(n);
            }
            
            if (specifier.isMatch(count)) {
                result.add(node);
            }
        }
    }
    
    /**
     * Get {@code nth-last-of-type} elements.
     * 
     * @see <a href="http://www.w3.org/TR/css3-selectors/#nth-last-of-type-pseudo"><code>:nth-last-of-type</code> pseudo-class</a>
     */
    private void getNthLastOfType() {
        for (Branch node : nodes) {
            int count = 1;
            Branch n = DOMHelper.getNextSiblingElement(node);
            while (n != null) {
                if (n.getName().equals(node.getName())) {
                    count++;
                }
                
                n = DOMHelper.getNextSiblingElement(n);
            }
            
            if (specifier.isMatch(count)) {
                result.add(node);
            }
        }
    }
    
}