/*
 * Copyright 2005-2014 the original author or authors.
 *
 * 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 org.springframework.xml.xpath;

import java.util.Map;
import javax.xml.transform.Source;
import javax.xml.transform.TransformerException;
import javax.xml.transform.dom.DOMResult;

import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

import org.springframework.xml.transform.TransformerObjectSupport;

/**
 * Abstract base class for implementations of {@link XPathOperations}. Contains a namespaces property.
 *
 * @author Arjen Poutsma
 * @since 1.0.0
 */
public abstract class AbstractXPathTemplate extends TransformerObjectSupport implements XPathOperations {

	private Map<String, String> namespaces;

	/** Returns namespaces used in the XPath expression. */
	public Map<String, String> getNamespaces() {
		return namespaces;
	}

	/** Sets namespaces used in the XPath expression. Maps prefixes to namespaces. */
	public void setNamespaces(Map<String, String> namespaces) {
		this.namespaces = namespaces;
	}

	@Override
	public final void evaluate(String expression, Source context, NodeCallbackHandler callbackHandler)
			throws XPathException {
		evaluate(expression, context, new NodeCallbackHandlerNodeMapper(callbackHandler));
	}

	/** Static inner class that adapts a {@link NodeCallbackHandler} to the interface of {@link NodeMapper}. */
	private static class NodeCallbackHandlerNodeMapper implements NodeMapper<Object> {

		private final NodeCallbackHandler callbackHandler;

		public NodeCallbackHandlerNodeMapper(NodeCallbackHandler callbackHandler) {
			this.callbackHandler = callbackHandler;
		}

		@Override
		public Object mapNode(Node node, int nodeNum) throws DOMException {
			callbackHandler.processNode(node);
			return null;
		}
	}

	/**
	 * Returns the root element of the given source.
	 *
	 * @param source the source to get the root element from
	 * @return the root element
	 */
	protected Element getRootElement(Source source) throws TransformerException {
		DOMResult domResult = new DOMResult();
		transform(source, domResult);
		Document document = (Document) domResult.getNode();
		return document.getDocumentElement();
	}

}