/**

 * 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 java.util.Arrays;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

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;

import javax.xml.xpath.XPathVariableResolver;

/**

 *

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

 */

public class XPathAction extends AbstractDOMAction {

	public static final String PARAMETER_TYPED_PARAMETERS = "typed-parameters";

	public static final String PARAMETER_LINE_BREAK = "line-break";

	public static final String PARAMETER_ENVIRONMENT_VARIABLES = "environment-variables";

	private final boolean typedParameters;

	private final boolean lineBreak;

	private final boolean environmentVariables;

	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();

		final List<String> actionData = getActionContext().getActionData();

		if (actionData.size() < 1) {

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

		} else {

			typedParameters = Boolean.parseBoolean(actionContext.getActionProperties().getProperty(PARAMETER_TYPED_PARAMETERS));

			lineBreak = Boolean.parseBoolean(actionContext.getActionProperties().getProperty(PARAMETER_LINE_BREAK, Boolean.TRUE.toString()));

			environmentVariables = Boolean.parseBoolean(actionContext.getActionProperties().getProperty(PARAMETER_ENVIRONMENT_VARIABLES, Boolean.FALSE.toString()));

			Map<String, Object> xpathParameters = new HashMap<>();

			for (int i = 1; i < actionData.size(); i++) {

				String parameterName = actionData.get(i++);

				String parameterType = typedParameters ? actionData.get(i++) : PARAMETER_TYPE.STRING.name();

				Object parameterValue = parseParameterValue(parameterType, actionData.get(i));

				xpathParameters.put(parameterName, parameterValue);

			}

			XPathVariableResolver cliVariableResolver = new PropertiesVariableResolver(xpathParameters);

			XPathVariableResolver variableResolver = environmentVariables ? new CompoundVariableResolver(cliVariableResolver, new EnvironmentVariableResolver()) : cliVariableResolver;

			xpath.setXPathVariableResolver(variableResolver);

			expressionString = actionData.get(0);

			try {

				xpathExpression = xpath.compile(expressionString);

			} catch (XPathExpressionException e) {

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

			}

		}

	}

	private enum PARAMETER_TYPE {

		// TODO: wait for Java 8 widespread and rewrite with lambdas :-)

		STRING {

					@Override

					public Object parse(String value) {

						return value;

					}

				},

		BOOLEAN {

					@Override

					public Object parse(String value) {

						return Boolean.valueOf(value);

					}

				},

		INTEGER {

					@Override

					public Object parse(String value) {

						return Integer.parseInt(value);

					}

				},

		LONG {

					@Override

					public Object parse(String value) {

						return Long.parseLong(value);

					}

				},

		DOUBLE {

					@Override

					public Object parse(String value) {

						return Double.parseDouble(value);

					}

				};

		public abstract Object parse(String value);

	}

	private static Object parseParameterValue(String type, String value) throws OutputActionException {

		try {

			PARAMETER_TYPE parameterType = PARAMETER_TYPE.valueOf(type.toUpperCase());

			try {

				return parameterType.parse(value);

			} catch (IllegalArgumentException e) {

				throw new OutputActionException("Unable to parse value: „" + value + "“ as " + parameterType.name());

			}

		} catch (IllegalArgumentException e) {

			throw new OutputActionException(

					"Invalid XPath parameter type: „" + type

					+ "“. Possible values are: " + Arrays.toString(PARAMETER_TYPE.values())

					+ " and are case insensitive.",

					e);

		}

	}

	@Override

	public void run(DOMResult domResult) throws OutputActionException {

		try {

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

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

				out.print(result);

				if (lineBreak) {

					out.println();

				}

			}

		} catch (XPathExpressionException e) {

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

		}

	}

}