TagChecker.java

/**
 * Modification from original by Gist Labs, LLC (http://gistlabs.com)
 * 
 * Copyright (c) 2009-2012, Christer Sandberg
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 */

package com.gistlabs.mechanize.util.css_query;

import java.util.Collection;
import java.util.LinkedHashSet;

import se.fishtank.css.selectors.NodeSelectorException;
import se.fishtank.css.selectors.Selector;
import se.fishtank.css.util.Assert;


public class TagChecker<Node> extends AbstractChecker<Node> {

	/** The selector to check against. */
	protected final Selector selector;
	
	/** Is this the initial part of a group of tag checkers? */
	protected final boolean initialPart;

	/** The set of nodes to check. */
	protected Collection<Node> nodes;

	/** The result of the checks. */
	protected Collection<Node> result;

	/**
	 * Create a new instance.
	 * 
	 * @param selector The selector to check against.
	 */
	public TagChecker(final NodeHelper<Node> helper, final Selector selector, boolean initialPart) {
		super(helper);
		Assert.notNull(selector, "selector is null!");
		this.selector = selector;
		this.initialPart = initialPart;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public Collection<Node> check(final Collection<Node> nodes) {
		Assert.notNull(nodes, "nodes is null!");
		this.nodes = nodes;

		result = new LinkedHashSet<Node>();
		switch (selector.getCombinator()) {
		case DESCENDANT:
			addDescendantElements();
			break;
		case CHILD:
			addChildElements();
			break;
		case ADJACENT_SIBLING:
			addAdjacentSiblingElements();
			break;
		case GENERAL_SIBLING:
			addGeneralSiblingElements();
			break;
		}

		return result;
	}

	/**
	 * Add descendant elements.
	 * 
	 * @see <a href="http://www.w3.org/TR/css3-selectors/#descendant-combinators">Descendant combinator</a>
	 * 
	 * @throws NodeSelectorException If one of the nodes have an illegal type.
	 */
	private void addDescendantElements() {
		for (Node node : nodes) {
			Collection<Node> nodes = new LinkedHashSet<Node>();

			if (initialPart) {
				nodes.add(node);
			}
			
			nodes.addAll(helper.getDescendentNodes(node));

			for(Node n : nodes)
				if (matchTag(n))
					result.add(n);
		}
	}

	/**
	 * Add child elements.
	 * 
	 * @see <a href="http://www.w3.org/TR/css3-selectors/#child-combinators">Child combinators</a>
	 */
	private void addChildElements() {
		for (Node node : nodes) {
			Collection<? extends Node> childNodes = helper.getChildNodes(node);
			for (Node child : childNodes)
				if (matchTag(child))
					result.add(child);
		}
	}

	private boolean matchTag(final Node child) {
		String tag = selector.getTagName();
		return helper.nameMatches(child, tag);
	}

	/**
	 * Add adjacent sibling elements.
	 * 
	 * @see <a href="http://www.w3.org/TR/css3-selectors/#adjacent-sibling-combinators">Adjacent sibling combinator</a>
	 */
	private void addAdjacentSiblingElements() {
		for (Node node : nodes) {
			Node n = helper.getNextSibling(node);
			if (n != null)
				if (matchTag(n))
					result.add(n);
		}
	}

	/**
	 * Add general sibling elements.
	 * 
	 * @see <a href="http://www.w3.org/TR/css3-selectors/#general-sibling-combinators">General sibling combinator</a>
	 */
	private void addGeneralSiblingElements() {
		for (Node node : nodes) {
			Node n = helper.getNextSibling(node);
			while (n != null) {
				String tag = selector.getTagName();
				if (helper.nameMatches(n, tag))
					result.add(n);

				n = helper.getNextSibling(n);
			}
		}
	}
}