/*
 * ============================================================================
 * GNU Lesser General Public License
 * ============================================================================
 *
 * JasperReports - Free Java report-generating library.
 * Copyright (C) 2001-2006 JasperSoft Corporation http://www.jaspersoft.com
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
 * 
 * JasperSoft Corporation
 * 303 Second Street, Suite 450 North
 * San Francisco, CA 94107
 * http://www.jaspersoft.com
 */

/*
 * Contributors:
 * Tim Thomas - tthomas48@users.sourceforge.net 
 */
package net.sf.jasperreports.engine.data;

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;

import javax.xml.transform.TransformerException;

import net.sf.jasperreports.engine.JRException;
import net.sf.jasperreports.engine.JRField;
import net.sf.jasperreports.engine.JRRewindableDataSource;
import net.sf.jasperreports.engine.design.JRDesignField;
import net.sf.jasperreports.engine.util.JRXmlUtils;

import org.apache.commons.beanutils.ConvertUtils;
import org.apache.xpath.CachedXPathAPI;
import org.apache.xpath.objects.XObject;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;

/**
 * XML data source implementation that allows to access the data from a xml
 * document using XPath expressions.
 * <p>
 * The data source is constructed around a node set (record set) selected
 * by an XPath expression from the xml document.
 * </p>
 * <p>
 * Each field can provide an additional XPath expresion that will be used to
 * select its value. This expression must be specified using the "fieldDescription"
 * element of the field. The expression is evaluated in the context of the current
 * node thus the expression should be relative to the current node.
 * </p>
 * <p>
 * To support subreports, sub data sources can be created. There are two different methods 
 * for creating sub data sources. The first one allows to create a sub data source rooted 
 * at the current node. The current node can be seen as a new document around which the 
 * sub data source is created. The second method allows to create a sub data source that
 * is rooted at the same document that is used by the data source but uses a different 
 * XPath select expression. 
 * </p>
 * <p>
 * Example:
 * <pre>
 * &lt;A&gt;
 * 	&lt;B id="0"&gt;
 * 		&lt;C&gt;
 * 		&lt;C&gt;
 * 	&lt;/B&gt;
 * 	&lt;B id="1"&gt;
 * 		&lt;C&gt;
 * 		&lt;C&gt;
 * 	&lt;/B&gt;
 * 	&lt;D id="3"&gt;
 * 		&lt;E&gt;
 * 		&lt;E&gt;
 * 	&lt;/D&gt;
 * &lt;/A&gt;
 * </pre>
 * <p>
 * Data source creation
 * <ul>
 * <li>new JRXmlDataSource(document, "/A/B") - creates a data source with two nodes of type /A/B
 * <li>new JRXmlDataSource(document, "/A/D") - creates a data source with two nodes of type /A/D
 * </ul>
 * Field selection
 * <ul>
 * <li>@id - will select the "id" attribute from the current node
 * <li>C - will select the value of the first node of type C under the current node. 
 * </ul>
 * Sub data source creation
 * <ul>
 * <li>"((net.sf.jasperreports.engine.data.JRXmlDataSource)$P{REPORT_DATA_SOURCE}).subDataSource("/B/C")
 * 	- in the context of the node B, creates a data source with elements of type /B/C
 * <li>"((net.sf.jasperreports.engine.data.JRXmlDataSource)$P{REPORT_DATA_SOURCE}).dataSource("/A/D")
 * 	- creates a data source with elements of type /A/D
 * </ul>
 * </p>
 * <p>
 * Generally the full power of XPath expression is available. As an example, "/A/B[@id > 0"] will select all the
 * nodes of type /A/B having the id greater than 0. 
 * You'll find a short XPath tutorial <a href="http://www.zvon.org/xxl/XPathTutorial/General/examples.html" target="_blank">here</a>.
 * 
 * </p>
 * <p>
 * Note on performance. Due to the fact that all the XPath expression are interpreted the
 * data source performance is not great. For the cases where more speed is required,
 * consider implementing a custom data source that directly accesses the Document through the DOM API. 
 * </p>
 * @author Peter Severin (peter_p_s@sourceforge.net, contact@jasperassistant.com)
 */
public class JRXmlDataSource implements JRRewindableDataSource {

	// the xml document
	private Document document;

	// the XPath select expression that gives the nodes to iterate
	private String selectExpression;

	// the node list
	private NodeList nodeList;

	// the node list length
	private int nodeListLength;
	
	// the current node
	private Node currentNode;

	// current node index
	private int currentNodeIndex = - 1;

	// XPath API fa?ade
	private CachedXPathAPI xpathAPI = new CachedXPathAPI();
	
	// -----------------------------------------------------------------
	// Constructors

	/**
	 * Creates the data source by parsing the xml document from the given file.
	 * The data source will contain exactly one record consisting of the document node itself.
	 * 
	 * @param document the document
	 * @throws JRException if the data source cannot be created
	 */
	public JRXmlDataSource(Document document) throws JRException {
		this(document, ".");
	}

	/**
	 * Creates the data source by parsing the xml document from the given file.
	 * An additional XPath expression specifies the select criteria that produces the 
	 * nodes (records) for the data source.
	 * 
	 * @param document the document
	 * @param selectExpression the XPath select expression
	 * @throws JRException if the data source cannot be created
	 */
	public JRXmlDataSource(Document document, String selectExpression)
			throws JRException {
		this.document = document;
		this.selectExpression = selectExpression;
		moveFirst();
	}


	/**
	 * Creates the data source by parsing the xml document from the given input stream.
	 *  
	 * @param in the input stream
	 * @see JRXmlDataSource#JRXmlDataSource(Document) 
	 */
	public JRXmlDataSource(InputStream in) throws JRException {
		this(in, ".");
	}

	/**
	 * Creates the data source by parsing the xml document from the given input stream.
	 * 
	 * @see JRXmlDataSource#JRXmlDataSource(InputStream) 
	 * @see JRXmlDataSource#JRXmlDataSource(Document, String) 
	 */
	public JRXmlDataSource(InputStream in, String selectExpression)
			throws JRException {
		this(JRXmlUtils.parse(new InputSource(in)), selectExpression);
	}

	/**
	 * Creates the data source by parsing the xml document from the given system identifier (URI).
	 * <p>If the system identifier is a URL, it must be full resolved.</p>
	 * 
	 * @param uri the system identifier
	 * @see JRXmlDataSource#JRXmlDataSource(Document) 
	 */
	public JRXmlDataSource(String uri) throws JRException {
		this(uri, ".");
	}

	/**
	 * Creates the data source by parsing the xml document from the given system identifier (URI).
	 * 
	 * @see JRXmlDataSource#JRXmlDataSource(String) 
	 * @see JRXmlDataSource#JRXmlDataSource(Document, String) 
	 */
	public JRXmlDataSource(String uri, String selectExpression)
			throws JRException {
		this(JRXmlUtils.parse(uri), selectExpression);
	}

	/**
	 * Creates the data source by parsing the xml document from the given file.
	 * 
	 * @param file the file
	 * @see JRXmlDataSource#JRXmlDataSource(Document) 
	 */
	public JRXmlDataSource(File file) throws JRException {
		this(file, ".");
	}

	/**
	 * Creates the data source by parsing the xml document from the given file.
	 * 
	 * @see JRXmlDataSource#JRXmlDataSource(File) 
	 * @see JRXmlDataSource#JRXmlDataSource(Document, String) 
	 */
	public JRXmlDataSource(File file, String selectExpression)
			throws JRException {
		this(JRXmlUtils.parse(file), selectExpression);
	}
	
	// -----------------------------------------------------------------
	// Implementation
	
	/*
	 * (non-Javadoc)
	 * 
	 * @see net.sf.jasperreports.engine.JRRewindableDataSource#moveFirst()
	 */
	public void moveFirst() throws JRException {
		if (document == null)
			throw new JRException("document cannot be not null");
		if (selectExpression == null)
			throw new JRException("selectExpression cannot be not null");

		try {
			currentNode = null;
			currentNodeIndex = -1;
			nodeListLength = 0;
			nodeList = xpathAPI.selectNodeList(document,
					selectExpression);
			nodeListLength = nodeList.getLength();
		} catch (TransformerException e) {
			throw new JRException("XPath selection failed. Expression: "
					+ selectExpression, e);
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see net.sf.jasperreports.engine.JRDataSource#next()
	 */
	public boolean next() {
		if(currentNodeIndex == nodeListLength - 1)
			return false;

		currentNode = nodeList.item(++ currentNodeIndex);
		return true;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see net.sf.jasperreports.engine.JRDataSource#getFieldValue(net.sf.jasperreports.engine.JRField)
	 */
	public Object getFieldValue(JRField jrField) throws JRException {
		if(currentNode == null)
			return null;
		
		String expression = jrField.getDescription();
		if (expression == null || expression.length() == 0)
			return null;

		Object value = null;
		
		Class valueClass = jrField.getValueClass();

		if(Object.class != valueClass) {
			String text = null;
			
			try {
				XObject list = xpathAPI.eval(currentNode, expression);
				if (list.getType() == XObject.CLASS_NODESET) {
					Node node = list.nodeset().nextNode();
					if (node != null) {
						text = getText(node);
					}
				} else {
					text = list.str();
				}
			} catch (TransformerException e) {
				throw new JRException("XPath selection failed. Expression: "
						+ expression, e);
			}
	
			if(text != null) {
				if(String.class == valueClass)
					value = text;
				else
					value = ConvertUtils.convert(text.trim(), valueClass);
			}
		}
		
		return value;
	}

	/**
	 * Creates a sub data source using the current node (record) as the root
	 * of the document. An additional XPath expression specifies the select criteria applied to
	 * this new document and that produces the nodes (records) for the data source.
	 * 
	 * @param selectExpr the XPath select expression
	 * @return the xml sub data source
	 * @throws JRException if the sub data source couldn't be created
	 * @see JRXmlDataSource#JRXmlDataSource(Document, String)
	 */
	public JRXmlDataSource subDataSource(String selectExpr)
			throws JRException {
		// create a new document from the current node
		Document doc = subDocument();
		return new JRXmlDataSource(doc, selectExpr);
	}

	/**
	 * Creates a sub data source using the current node (record) as the root
	 * of the document. The data source will contain exactly one record consisting 
	 * of the document node itself.
	 * 
	 * @return the xml sub data source
	 * @throws JRException if the data source cannot be created
	 * @see JRXmlDataSource#subDataSource(String)
	 * @see JRXmlDataSource#JRXmlDataSource(Document)
	 */
	public JRXmlDataSource subDataSource() throws JRException {
		return subDataSource(".");
	}

	
	/**
	 * Creates a document using the current node as root.
	 * 
	 * @return a document having the current node as root
	 * @throws JRException
	 */
	public Document subDocument() throws JRException
	{
		if(currentNode == null)
		{
			throw new JRException("No node available. Iterate or rewind the data source.");
		}
		
		// create a new document from the current node
		Document doc = JRXmlUtils.createDocument(currentNode);
		return doc;
	}
	
	
	/**
	 * Creates a sub data source using as root document the document used by "this" data source.
	 * An additional XPath expression specifies the select criteria applied to
	 * this document and that produces the nodes (records) for the data source.
	 * 
	 * @param selectExpr the XPath select expression
	 * @return the xml sub data source
	 * @throws JRException if the sub data source couldn't be created
	 * @see JRXmlDataSource#JRXmlDataSource(Document, String)
	 */
	public JRXmlDataSource dataSource(String selectExpr)
			throws JRException {
		return new JRXmlDataSource(document, selectExpr);
	}

	/**
	 * Creates a sub data source using as root document the document used by "this" data source.
	 * The data source will contain exactly one record consisting  of the document node itself.
	 * 
	 * @return the xml sub data source
	 * @throws JRException if the data source cannot be created
	 * @see JRXmlDataSource#dataSource(String)
	 * @see JRXmlDataSource#JRXmlDataSource(Document)
	 */
	public JRXmlDataSource dataSource() throws JRException {
		return dataSource(".");
	}

	/**
	 * Return the text that a node contains. This routine:
	 * <ul>
	 * <li>Ignores comments and processing instructions.
	 * <li>Concatenates TEXT nodes, CDATA nodes, and the results of recursively
	 * processing EntityRef nodes.
	 * <li>Ignores any element nodes in the sublist. (Other possible options
	 * are to recurse into element sublists or throw an exception.)
	 * </ul>
	 * 
	 * @param node a DOM node
	 * @return a String representing node contents or null
	 */
	public String getText(Node node) {
		if (!node.hasChildNodes())
			return node.getNodeValue();

		StringBuffer result = new StringBuffer();

		NodeList list = node.getChildNodes();
		for (int i = 0; i < list.getLength(); i++) {
			Node subnode = list.item(i);
			if (subnode.getNodeType() == Node.TEXT_NODE) {
				String value = subnode.getNodeValue();
				if(value != null)
					result.append(value);
			} else if (subnode.getNodeType() == Node.CDATA_SECTION_NODE) {
				String value = subnode.getNodeValue();
				if(value != null)
					result.append(value);
			} else if (subnode.getNodeType() == Node.ENTITY_REFERENCE_NODE) {
				// Recurse into the subtree for text
				// (and ignore comments)
				String value = getText(subnode);
				if(value != null)
					result.append(value);
			}
		}

		return result.toString();
	}
	
	public static void main(String[] args) throws Exception {
		JRXmlDataSource ds = new JRXmlDataSource(new FileInputStream("northwind.xml"), "/Northwind/Customers");
		JRDesignField field = new JRDesignField();
		field.setDescription("CustomerID");
		field.setValueClass(String.class);
		
		ds.next();
		String v = (String) ds.getFieldValue(field);
		System.out.println(field.getDescription() + "=" + v);
		
		JRXmlDataSource subDs = ds.dataSource("/Northwind/Orders");

		JRDesignField field1 = new JRDesignField();
		field1.setDescription("OrderID");
		field1.setValueClass(String.class);
		
		subDs.next();
		String v1 = (String) subDs.getFieldValue(field1);
		System.out.println(field1.getDescription() + "=" + v1);
		
	}
}