/*
 *    XMLConverter.java
 *    Copyright (C) 2002 New Zealand Digital Library, http://www.nzdl.org
 *
 *    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 2 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, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.greenstone.gsdl3.util;

// XML classes
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document; 
import org.w3c.dom.DocumentType; 
import org.w3c.dom.Element; 
import org.w3c.dom.Node; 
import org.w3c.dom.NodeList;
import org.w3c.dom.NamedNodeMap;
import org.xml.sax.InputSource;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.SAXParseException;
import org.apache.xerces.parsers.DOMParser;
import org.apache.xerces.dom.*; // for new Documents

// other java classes
import java.io.Reader;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.util.regex.*;

import org.apache.log4j.*;

// Apache Commons
import org.apache.commons.lang3.*;

import java.util.*;
import java.lang.reflect.*;

/** XMLConverter - utility class for greenstone
 *
 * parses XML Strings into Documents, converts Nodes to Strings
 * different parsers have different behaviour - can experiment in here
 * now we only use xerces
 *
 */
public class XMLConverter {

     static Logger logger = Logger.getLogger(org.greenstone.gsdl3.util.XMLConverter.class.getName());

    /** xerces parser */
    protected DOMParser parser = null;

    private static boolean outputEscaping = true;

     /** the no-args constructor */
    public XMLConverter() {
	try {
	    this.parser = new DOMParser();
	    this.parser.setFeature("http://xml.org/sax/features/validation", false);
	    // don't try and load external DTD - no need if we are not validating, and may cause connection errors if a proxy is not set up.
	    this.parser.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
	    // a performance test showed that having this on lead to increased 
	    // memory use for small-medium docs, and not much gain for large 
	    // docs.
	    // http://www.sosnoski.com/opensrc/xmlbench/conclusions.html
	    this.parser.setFeature("http://apache.org/xml/features/dom/defer-node-expansion", false);
		// add an errorhandler to the parser which will store useful a error message on encountering fatal errors, errors and warnings when parsing
		// this errormessage can then be converted to xhtml and displayed in a browser.
		this.parser.setErrorHandler(new ParseErrorHandler());
	} catch (Exception e) {
	    logger.error(e.getMessage());
	}
    }

    /** sets the entity resolver. pass in null to unset it */
    public void setEntityResolver(EntityResolver er) {
	this.parser.setEntityResolver(er);
    }

    /** Given a Node representing an Element or Document, will return the 
     * Element/docroot Element. Returns null if the Node was not an element. */
    public static Element nodeToElement(Node node)
    {
	if(node == null) {
	    return null;
	}
	short nodeType = node.getNodeType();

	if (nodeType == Node.DOCUMENT_NODE) {
		Document docNode = (Document)node;
		return docNode.getDocumentElement() ;
	}
	else if (nodeType == Node.ELEMENT_NODE) {
	    return (Element)node;
	}
	else {
	    String message = "Expecting Document or Element node type but got " 
		+ node.getNodeName() + "\nReturning null";
	    System.err.println(message);
	    logger.warn(message);
	    return null;
	}
    }

    /** returns a DOM Document */
    public Document getDOM(String in) {
	    
	try {
	    Reader reader = new StringReader(in);
	    InputSource xml_source = new InputSource(reader);
	    
	    this.parser.parse(xml_source);
	    Document doc = this.parser.getDocument();
	    
	    return doc;
	    
	} catch (Exception e) {
	    logger.error(e.getMessage());
	}
	return null;
    }
  
    /** returns a DOM Document */
    public Document getDOM(File in) {
	try {
	    FileReader reader = new FileReader(in);
	    InputSource xml_source = new InputSource(reader);
	    this.parser.parse(xml_source);
	    Document doc = this.parser.getDocument();
	    return doc;

	} catch (Exception e) {
	    logger.error(e.getMessage(), e);
	    
	}
	return null;
    }

    /** returns a DOM document */
    public Document getDOM(File in, String encoding) {
	try {
	    
	    InputStreamReader isr = new InputStreamReader(new FileInputStream(in), encoding);
	    InputSource xml_source = new InputSource(isr);
	    
	    this.parser.parse(xml_source);
	    Document doc = this.parser.getDocument();
	    
	    return doc;

	} catch (Exception e) {
	    logger.error(e.getMessage());
	}
	return null;
    }
    

    /** creates a new empty DOM Document */
    public static Document newDOM() {
	Document doc = new DocumentImpl(); 
	return doc;
    }
    
    /**
     * This method's parameters represent the parts of the Doctype of this
     * Document that is to be created.
     * For more info see 
     * http://xerces.apache.org/xerces-j/apiDocs/org/apache/xerces/dom/DocumentTypeImpl.html#DocumentTypeImpl(org.apache.xerces.dom.CoreDocumentImpl,%20java.lang.String)
     * 
     * */
    public static Document newDOM(String qualifiedName, String publicID, String systemID) {
    	// create empty DOM document
    	DocumentImpl docImpl = new DocumentImpl(); 
    	
    	// Need to use the document to create the docType for it
		DocumentType myDocType = new DocumentTypeImpl(docImpl, qualifiedName, publicID, systemID);
		
		// Although we have created the docType using the document, we need to still 
		// put it into the empty document we just created 
		try{
			docImpl.appendChild(myDocType);
		} catch(Exception e) {
			System.out.println("Could not append docType because: " + e) ;		
		}
		
		// return the document containing a DocType
		return docImpl;    	
    }

    /** returns the Node as a String */
    public static String getString(Node xmlNode)
    {
	outputEscaping = true;
	StringBuffer xmlRepresentation = new StringBuffer();
	getString(xmlNode, xmlRepresentation, 0, false);
	return xmlRepresentation.toString();
    }

    /** returns the node as a nicely formatted String - this introduces extra
     * text nodes if the String is read back in as a DOM, so should only be 
     * used for printing */
    public static String getPrettyString(Node xmlNode) {
	
	outputEscaping = true;
	StringBuffer xmlRepresentation = new StringBuffer();
	getString(xmlNode, xmlRepresentation, 0, true);
	return xmlRepresentation.toString();
    }

    /* For the purposes of logger.debug statements, where this is called and hence outputted,
	returns an empty string if debugging is not enabled */
    public static String getPrettyStringLogger(Node xmlNode, Logger log) {

	if(log.isDebugEnabled())
		return getPrettyString(xmlNode);
	
	return "";

    }

    private static void getString(Node xmlNode, StringBuffer xmlRepresentation, 
			     int depth, boolean pretty)
    {
	
	if (xmlNode == null) {
	    xmlRepresentation.append("<null>");
	    return;
	}

	short nodeType = xmlNode.getNodeType();
	String nodeName = xmlNode.getNodeName();

	if (nodeType == Node.DOCUMENT_NODE) {
	    Document xmlDocNode = (Document)xmlNode;
	    
	    //if (xmlDocNode.getDoctype() == null) {
		//System.err.println("Doctype is null.");
	    //}
	    //else {
		if (xmlDocNode.getDoctype() != null) {
		DocumentType dt = xmlDocNode.getDoctype();
		
		String name = dt.getName();
		String pid  = dt.getPublicId();
		String sid  = dt.getSystemId();
		
		// Use previously assigned name, not dt.getName() again
		String doctype_str = "<!DOCTYPE " + name + " PUBLIC \"" + pid + "\" \"" + sid + "\">\n";
		
		xmlRepresentation.append(doctype_str);
	    }
	    getString(xmlDocNode.getDocumentElement(), xmlRepresentation, depth, pretty);
	    return;
	}
	// Handle Element nodes
	if (nodeType == Node.ELEMENT_NODE) {
	    if (pretty) {
		xmlRepresentation.append("\n");
		for (int i = 0; i < depth; i++) {
		    xmlRepresentation.append("  ");
		}
	    }

	    // Write opening tag
	    xmlRepresentation.append("<");
	    xmlRepresentation.append(nodeName);
	    
	    // Write the node attributes
	    NamedNodeMap nodeAttributes = xmlNode.getAttributes();
	    for (int i = 0; i < nodeAttributes.getLength(); i++) {
		Node attribute = nodeAttributes.item(i);
		xmlRepresentation.append(" ");
		xmlRepresentation.append(attribute.getNodeName());
		xmlRepresentation.append("=\"");
		xmlRepresentation.append(attribute.getNodeValue());
		xmlRepresentation.append("\"");
	    }

	    // If the node has no children, close the opening tag and return
	    if (xmlNode.hasChildNodes() == false) {
		// This produces somewhat ugly output, but it is necessary to compensate
		// for display bugs in Netscape. Firstly, the space is needed before the
		// closing bracket otherwise Netscape will ignore some tags (<br/>, for
		// example). Also, a newline character would be expected after the tag,
		// but this causes problems with the display of links (the link text
		// will contain a newline character, which is displayed badly).
		xmlRepresentation.append(" />");
		return;
	    }
	    
	    // Close the opening tag
	    xmlRepresentation.append(">");
	    
	    // Apply recursively to the children of this node
	    // hack for nodes next to text nodes - dont make them pretty
	    // this is needed for text inside a <pre> element - any new lines 
	    // or spaces around the span elements show up in the text
	    NodeList children = xmlNode.getChildNodes();
	    boolean do_pretty = pretty;
	    for (int i = 0; i < children.getLength(); i++) {
		if (children.item(i).getNodeType()==Node.TEXT_NODE) {
		    do_pretty=false; // if there is a text node amongst the children, do teh following nodes in non-pretty mode - hope this doesn't stuff up something else
		}
		getString(children.item(i), xmlRepresentation, depth + 1, do_pretty);
	    }
	    
	    // Write closing tag
	    if (pretty) {
		if (xmlRepresentation.charAt(xmlRepresentation.length()-1) == '\n') {
		    for (int i = 0; i < depth; i++)
			xmlRepresentation.append("  ");
		}
	    }
	    xmlRepresentation.append("</");
	    xmlRepresentation.append(nodeName);
	    xmlRepresentation.append(">");
	    if (pretty) {
		xmlRepresentation.append("\n");
	    }
	}
	
	// Handle Text nodes
	else if (nodeType == Node.TEXT_NODE) {
	    String text = xmlNode.getNodeValue();

	    // Perform output escaping, if required
	    // Apache Commons replace method is far superior to String.replaceAll - very fast!
	    if (outputEscaping) {

		text = StringUtils.replace(text, "&", "&amp;");
		text = StringUtils.replace(text, "<", "&lt;");
		text = StringUtils.replace(text, ">", "&gt;");
		text = StringUtils.replace(text, "'", "&apos;");
		text = StringUtils.replace(text, "\"", "&quot;");
	    }

	    // Remove any control-C characters
	    text = StringUtils.replace(text, "" + (char)3, "");

	    xmlRepresentation.append(text);
	}

	// Handle Processing Instruction nodes
	else if (nodeType == Node.PROCESSING_INSTRUCTION_NODE) {
	    if (nodeName.equals("javax.xml.transform.disable-output-escaping")) {
		outputEscaping = false;
	    }
	    else if (nodeName.equals("javax.xml.transform.enable-output-escaping")) {
		outputEscaping = true;
	    }
	    else {
		logger.warn("Unhandled processing instruction " + nodeName);
	    }
	}
	
	else if (nodeType == Node.COMMENT_NODE) {
	    String text = xmlNode.getNodeValue();
	    xmlRepresentation.append("<!-- ");
	    xmlRepresentation.append(text);
	    xmlRepresentation.append(" -->");
	}
	    
	    
	
	// A type of node that is not handled yet
	else {
	    logger.warn("Unknown node type: " + nodeType+" "+getNodeTypeString(nodeType));
	}

	return;
    }

    protected static String getNodeTypeString(short node_type) {

	String type = "";
	switch(node_type) {
	case Node.ATTRIBUTE_NODE: 
	    type="ATTRIBUTE_NODE";
	    break;
	case Node.CDATA_SECTION_NODE:
	    type="CDATA_SECTION_NODE";
	    break;
	case Node.COMMENT_NODE:
	    type="COMMENT_NODE";
	    break;
	case Node.DOCUMENT_FRAGMENT_NODE:
	    type="DOCUMENT_FRAGMENT_NODE";
	    break;
	case Node.DOCUMENT_NODE:
	    type="DOCUMENT_NODE";
	    break;
	case Node.DOCUMENT_TYPE_NODE:
	    type="DOCUMENT_TYPE_NODE";
	    break;
	case Node.ELEMENT_NODE:
	    type="ELEMENT_NODE";
	    break;
	case Node.ENTITY_NODE:
	    type="ENTITY_NODE";
	    break;
	case Node.ENTITY_REFERENCE_NODE:
	    type="ENTITY_REFERENCE_NODE";
	    break;
	case Node.NOTATION_NODE:
	    type="NOTATION_NODE";
	    break;
	case Node.PROCESSING_INSTRUCTION_NODE:
	    type="PROCESSING_INSTRUCTION_NODE";
	    break;
	case Node.TEXT_NODE:
	    type="TEXT_NODE";
	    break;
	default:
	    type="UNKNOWN";
	}

	return type;
    }
	
	// returns null if there no error occurred during parsing, or else returns the error message
	public String getParseErrorMessage() {
		ParseErrorHandler errorHandler = (ParseErrorHandler)this.parser.getErrorHandler();
		return errorHandler.getErrorMessage();
	}
	
	// Errorhandler for SAXParseExceptions that are errors, fatal errors or warnings. This class can be used to 
	// register a handler for any fatal errors, errors and warnings that may occur when parsing an xml file. The
	// errors are printed both to the greenstone.log and to the tomcat console (System.err), and the error message
	// is stored in the errorMessage variable so that it can be retrieved and be used to generate an xhtml error page.
	static public class ParseErrorHandler implements ErrorHandler {
		protected String errorMessage = null;
	
		//  Receive notification of a recoverable error.
		public void error(SAXParseException exception) {
			handleError("Error:\n", exception);
		}
        //   Receive notification of a non-recoverable error.
		public void fatalError(SAXParseException exception) {
			handleError("Fatal Error:\n", exception);
		}
		// Receive notification of a warning.
        public void warning(SAXParseException exception) {
			handleError("Warning:\n", exception);
        }
		
		public String toString(SAXParseException e) {
			String msg = e.getMessage();
			msg += "\nOn line(column): " + e.getLineNumber() + "(" + e.getColumnNumber() + ")";
			msg += (e.getPublicId() != null) ? ("\npublic ID: " + e.getPublicId()) : "\nNo public ID";
			msg += (e.getSystemId() != null) ? ("\nsystem ID: " + e.getSystemId()) : "\nNo system ID";
					
			return msg;
		}
		
		// clears the errorPage variable after first call to this method
		public String getErrorMessage() {
			String errMsg = this.errorMessage;
			if(this.errorMessage != null) {
				this.errorMessage = null;
			}
			return errMsg;
		}
		
		// sets the errorMessage member variable to the data stored in the exception
		// and writes the errorMessage to the logger and tomcat's System.err
		protected void handleError(String errorType, SAXParseException exception) {
			this.errorMessage = errorType + toString(exception); 
			System.err.println("\n****Error parsing xml:\n" + this.errorMessage + "\n****\n");
			logger.error(this.errorMessage);
		}
	}
}