package org.greenstone.core.util;


import java.io.*;
import java.net.*;
import java.util.*;
import org.apache.xerces.parsers.*;
import org.apache.xml.serialize.*;
import org.greenstone.core.DebugStream;
import org.w3c.dom.*;
import org.xml.sax.*;


/** This class is a static class containing useful XML functions */
public class XMLTools
{
    /** Remove all of the child nodes from a certain node. */
    static final public void clear(Node node)
    {
	while (node.hasChildNodes()) {
	    node.removeChild(node.getFirstChild());
	}
    }


    static public ArrayList getChildElementsByTagName(Element parent_element, String element_name)
    {
	ArrayList child_elements = new ArrayList();

	NodeList children_nodelist = parent_element.getChildNodes();
	for (int i = 0; i < children_nodelist.getLength(); i++) {
	    Node child_node = children_nodelist.item(i);
	    if (child_node.getNodeType() == Node.ELEMENT_NODE && child_node.getNodeName().equals(element_name)) {
		child_elements.add(child_node);
	    }
	}

	return child_elements;
    }


    static public String getElementTextValue(Element element)
    {
	// Find the first text node child
	NodeList children_nodelist = element.getChildNodes();
	for (int i = 0; i < children_nodelist.getLength(); i++) {
	    Node child_node = children_nodelist.item(i);
	    if (child_node.getNodeType() == Node.TEXT_NODE) {
		return child_node.getNodeValue();
	    }
	}

	// None found
	return "";
    }


    /** Method to retrieve the value of a given node.
     * @param element The <strong>Element</strong> whose value we wish to find.
     * Soon to be deprecated!
     */
    static final public String getValue(Node element) {
	// If we've been given a subject node first retrieve its value node.
	if(element.getNodeName().equals("Subject")) {
	    element = getNodeFromNamed(element, "Value");
	}
	// If we've got a value node, then reconstruct the text. Remember that DOM will split text over 256 characters into several text nodes
	if(element != null && element.hasChildNodes()) {
	    StringBuffer text_buffer = new StringBuffer();
	    NodeList text_nodes = element.getChildNodes();
	    for(int i = 0; i < text_nodes.getLength(); i++) {
		Node possible_text = text_nodes.item(i);
		if(possible_text.getNodeName().equals(StaticStrings.TEXT_NODE)) {
		    text_buffer.append(possible_text.getNodeValue());
		}
	    }
	    return text_buffer.toString();
	}
	return "";
    }


    /** Method to retrieve from the node given, a certain child node with the specified name.
     * @param parent The <strong>Node</strong> whose children should be searched.
     * @param name The required nodes name as a <strong>String</strong>.
     * @return The requested <strong>Node</strong> if it is found, <i>null</i> otherwise.
     * Soon to be deprecated!
     */ 
    static final public Node getNodeFromNamed(Node parent, String name) {
	Node child = null;
	for(Node i = parent.getFirstChild(); i != null && child == null; 
	    i = i.getNextSibling()) {
	    if(i.getNodeName().equals(name)) {
		child = i;
	    }
	}
	return child;
    }


    /** Parse an XML document from a given file */
    static public Document parseXMLFile(File xml_file)
    {
	// No file? No point trying!
	if (xml_file.exists() == false) {
	    return null;
	}

	try {
	    return parseXML(new FileInputStream(xml_file));
	}
	catch (Exception exception) {
	    DebugStream.printStackTrace(exception);
	    return null;
	}
    }


    /** Parse an XML document from a given input stream */
    static public Document parseXML(InputStream xml_input_stream)
    {
	Document document = null;

	try {
	    InputStreamReader isr = new InputStreamReader(xml_input_stream, "UTF-8");
	    Reader xml_reader = new BufferedReader(isr);
	    document = parseXML(xml_reader);
	    isr.close();
	    xml_input_stream.close();
	}
	catch (Exception exception) {
	    DebugStream.printStackTrace(exception);
	}

	return document;
    }


    /** Parse an XML document from a given reader */
    static public Document parseXML(Reader xml_reader)
    {
	Document document = null;

	try {
	    InputSource isc       = new InputSource(xml_reader);
	    DOMParser parser      = new DOMParser();
	    parser.setFeature("http://xml.org/sax/features/validation", false);
	    parser.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
	    // May or may not be ignored, the documentation for Xerces is contradictory. If it works then parsing -should- be faster.
	    parser.setFeature("http://apache.org/xml/features/dom/defer-node-expansion", true);
	    parser.setFeature("http://apache.org/xml/features/dom/include-ignorable-whitespace", false);
	    parser.parse(isc);
	    document = parser.getDocument();
	}
	catch (Exception exception) {
	    DebugStream.printStackTrace(exception);
	}

	return document;
    }


    /** Removes characters that are invalid in XML (see http://www.w3.org/TR/2000/REC-xml-20001006#charsets) */
    static public String removeInvalidCharacters(String text)
    {
	char[] safe_characters = new char[text.length()];
	int j = 0;

	char[] raw_characters = new char[text.length()];
	text.getChars(0, text.length(), raw_characters, 0);
	for (int i = 0; i < raw_characters.length; i++) {
	    char character = raw_characters[i];
	    if ((character >= 0x20 && character <= 0xD7FF) || character == 0x09 || character == 0x0A || character == 0x0D || (character >= 0xE000 && character <= 0xFFFD) || (character >= 0x10000 && character <= 0x10FFFF)) {
		safe_characters[j] = character;
		j++;
	    }
	}

	return new String(safe_characters, 0, j);
    }


    /** Set the #text node value of some element.
     * @param element the Element whose value we wish to set
     * @param value the new value for the element as a String
     * Soon to be deprecated!
     */
    static final public void setValue(Element element, String value) {
	// Remove any existing child node(s)
	clear(element);
	// Add new text node.
	if (value != null) {
	    element.appendChild(element.getOwnerDocument().createTextNode(value));
	}
    }


    /** Write an XML document to a given file */
    static public void writeXMLFile(File xml_file, Document document)
    {
	try {
	    OutputStream os = new FileOutputStream(xml_file);
	    // Create an output format for our document.
	    OutputFormat f = new OutputFormat(document);
	    f.setEncoding("UTF-8");
	    f.setIndenting(true);
	    f.setLineWidth(0); // Why isn't this working!
	    f.setPreserveSpace(false);
	    // Create the necessary writer stream for serialization.
	    OutputStreamWriter osw = new OutputStreamWriter(os, "UTF-8");
	    Writer w               = new BufferedWriter(osw);
	    // Generate a new serializer from the above.
	    XMLSerializer s        = new XMLSerializer(w, f);
	    s.asDOMSerializer();
	    // Finally serialize the document to file.
	    s.serialize(document);
	    // And close.
	    os.close();
	}
	catch (Exception exception) {
	    DebugStream.printStackTrace(exception);
	}
    }
}