/*
 * Copyright 2005-2016 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.ArrayList;
import java.util.List;
import java.util.Map;
import javax.xml.namespace.QName;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.DOMException;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import org.springframework.xml.namespace.SimpleNamespaceContext;

/**
 * JAXP 1.3-specific factory creating {@link XPathExpression} objects.
 *
 * @author Arjen Poutsma
 * @author Greg Turnquist
 * @see #createXPathExpression(String)
 * @since 1.0.0
 */
abstract class Jaxp13XPathExpressionFactory {

	private static XPathFactory xpathFactory = XPathFactory.newInstance();

	/**
	 * Creates a JAXP 1.3 {@code XPathExpression} from the given string expression.
	 *
	 * @param expression the XPath expression
	 * @return the compiled {@code XPathExpression}
	 * @throws XPathParseException when the given expression cannot be parsed
	 */
	static XPathExpression createXPathExpression(String expression) {
		try {
			XPath xpath = createXPath();
			javax.xml.xpath.XPathExpression xpathExpression = xpath.compile(expression);
			return new Jaxp13XPathExpression(xpathExpression, expression);
		}
		catch (XPathExpressionException ex) {
			throw new org.springframework.xml.xpath.XPathParseException(
					"Could not compile [" + expression + "] to a XPathExpression: " + ex.getMessage(), ex);
		}
	}

	/**
	 * Creates a JAXP 1.3 {@code XPathExpression} from the given string expression and namespaces.
	 *
	 * @param expression the XPath expression
	 * @param namespaces the namespaces
	 * @return the compiled {@code XPathExpression}
	 * @throws XPathParseException when the given expression cannot be parsed
	 */
	public static XPathExpression createXPathExpression(String expression, Map<String, String> namespaces) {
		try {
			XPath xpath = createXPath();
			SimpleNamespaceContext namespaceContext = new SimpleNamespaceContext();
			namespaceContext.setBindings(namespaces);
			xpath.setNamespaceContext(namespaceContext);
			javax.xml.xpath.XPathExpression xpathExpression = xpath.compile(expression);
			return new Jaxp13XPathExpression(xpathExpression, expression);
		}
		catch (XPathExpressionException ex) {
			throw new org.springframework.xml.xpath.XPathParseException(
					"Could not compile [" + expression + "] to a XPathExpression: " + ex.getMessage(), ex);
		}
	}

	private static synchronized XPath createXPath() {
		return xpathFactory.newXPath();
	}


	/** JAXP 1.3 implementation of the {@code XPathExpression} interface. */
	private static class Jaxp13XPathExpression implements XPathExpression {

		private final javax.xml.xpath.XPathExpression xpathExpression;
		private final String expression;

		private Jaxp13XPathExpression(javax.xml.xpath.XPathExpression xpathExpression, String expression) {
			this.xpathExpression = xpathExpression;
			this.expression = expression;
		}

		@Override
		public String toString() {
			return expression;
		}

		@Override
		public String evaluateAsString(Node node) {
			return (String) evaluate(node, XPathConstants.STRING);
		}

		@Override
		public List<Node> evaluateAsNodeList(Node node) {
			NodeList nodeList = (NodeList) evaluate(node, XPathConstants.NODESET);
			return toNodeList(nodeList);
		}

		private Object evaluate(Node node, QName returnType) {
			try {
				// XPathExpression is not thread-safe
				synchronized (xpathExpression) {
					return xpathExpression.evaluate(node, returnType);
				}
			}
			catch (XPathExpressionException ex) {
				throw new XPathException("Could not evaluate XPath expression:" + ex.getMessage(), ex);
			}
		}

		private List<Node> toNodeList(NodeList nodeList) {
			List<Node> result = new ArrayList<Node>(nodeList.getLength());
			for (int i = 0; i < nodeList.getLength(); i++) {
				result.add(nodeList.item(i));
			}
			return result;
		}

		@Override
		public double evaluateAsNumber(Node node) {
			return (Double) evaluate(node, XPathConstants.NUMBER);
		}

		@Override
		public boolean evaluateAsBoolean(Node node) {
			return (Boolean) evaluate(node, XPathConstants.BOOLEAN);
		}

		@Override
		public Node evaluateAsNode(Node node) {
			return (Node) evaluate(node, XPathConstants.NODE);
		}

		@Override
		public <T> T evaluateAsObject(Node node, NodeMapper<T> nodeMapper) throws XPathException {
			Node result = (Node) evaluate(node, XPathConstants.NODE);
			if (result != null) {
				try {
					return nodeMapper.mapNode(result, 0);
				}
				catch (DOMException ex) {
					throw new XPathException("Mapping resulted in DOMException", ex);
				}
			}
			else {
				return null;
			}
		}

		@Override
		public <T> List<T> evaluate(Node node, NodeMapper<T> nodeMapper) throws XPathException {
			NodeList nodes = (NodeList) evaluate(node, XPathConstants.NODESET);
			List<T> results = new ArrayList<T>(nodes.getLength());
			for (int i = 0; i < nodes.getLength(); i++) {
				try {
					results.add(nodeMapper.mapNode(nodes.item(i), i));
				}
				catch (DOMException ex) {
					throw new XPathException("Mapping resulted in DOMException", ex);
				}
			}
			return results;
		}
	}

}