/**

 * Alt2XML

 * Copyright © 2014 František Kučera (frantovo.cz)

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program. If not, see <http://www.gnu.org/licenses/>.

 */

package cz.frantovo.alt2xml.out.xpath;

import cz.frantovo.alt2xml.out.AbstractDOMAction;

import cz.frantovo.alt2xml.out.ActionContext;

import cz.frantovo.alt2xml.out.OutputActionException;

import java.io.PrintWriter;

import javax.xml.transform.dom.DOMResult;

import javax.xml.xpath.XPath;

import javax.xml.xpath.XPathExpression;

import javax.xml.xpath.XPathExpressionException;

import javax.xml.xpath.XPathFactory;

/**

 *

 * @author Ing. František Kučera (frantovo.cz)

 */

public class XPathAction extends AbstractDOMAction {

	private final XPathFactory xpathFactory;

	private final XPath xpath;

	private final String expressionString;

	private final XPathExpression xpathExpression;

	public XPathAction(ActionContext actionContext) throws OutputActionException {

		super(actionContext);

		xpathFactory = XPathFactory.newInstance();

		xpath = xpathFactory.newXPath();

		if (!actionContext.getActionProperties().isEmpty()) {

			xpath.setXPathVariableResolver(new PropertiesVariableResolver(actionContext.getActionProperties()));

		}

		if (getActionContext().getActionData().size() == 1) {

			expressionString = getActionContext().getActionData().get(0);

			try {

				xpathExpression = xpath.compile(expressionString);

			} catch (XPathExpressionException e) {

				throw new OutputActionException("Unable to compile XPath: " + expressionString, e);

			}

		} else {

			throw new OutputActionException("Please specify the XPath expression as action data");

		}

	}

	@Override

	public void run(DOMResult domResult) throws OutputActionException {

		try {

			String result = xpathExpression.evaluate(domResult.getNode());

			try (PrintWriter out = new PrintWriter(getActionContext().getOutputStream())) {

				out.println(result);

			}

		} catch (XPathExpressionException e) {

			throw new OutputActionException("Unable to evaluate XPath: " + xpathExpression, e);

		}

	}

}