/*
 * Copyright 2004,2005 The Apache Software Foundation.
 *
 * 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.apache.axiom.om.impl.llom;

import org.apache.axiom.om.OMAttribute;
import org.apache.axiom.om.OMComment;
import org.apache.axiom.om.OMDocument;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.OMNamespace;
import org.apache.axiom.om.OMNode;
import org.apache.axiom.om.OMText;
import org.apache.axiom.om.OMXMLParserWrapper;
import org.apache.axiom.om.impl.EmptyOMLocation;
import org.apache.axiom.om.impl.exception.OMStreamingException;

import javax.xml.namespace.NamespaceContext;
import javax.xml.namespace.QName;
import javax.xml.stream.Location;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import java.util.Iterator;
import java.util.Stack;

/**
 * Note  - This class also implements the streaming constants interface
 * to get access to the StAX constants
 */
public class OMStAXWrapper implements XMLStreamReader, XMLStreamConstants {
    /**
     * Field navigator
     */
    private OMNavigator navigator;

    /**
     * Field builder
     */
    private OMXMLParserWrapper builder;

    /**
     * Field parser
     */
    private XMLStreamReader parser;

    /**
     * Field rootNode
     */
    private OMNode rootNode;

    /**
     * Field isFirst
     */
    private boolean isFirst = true;

    // Navigable means the output should be taken from the navigator.
    // As soon as the navigator returns a null navigable will be reset
    // to false and the subsequent events will be taken from the builder
    // or the parser directly.

    /**
     * Field NAVIGABLE
     */
    private static final short NAVIGABLE = 0;
    private static final short SWITCH_AT_NEXT = 1;
    private static final short COMPLETED = 2;
    private static final short SWITCHED = 3;
    private static final short DOCUMENT_COMPLETE = 4;


    /**
     * Field state
     */
    private short state;

    /**
     * Field currentEvent
     * Default set to START_DOCUMENT
     */
    private int currentEvent = START_DOCUMENT;

    // SwitchingAllowed is set to false by default.
    // This means that unless the user explicitly states
    // that he wants things not to be cached, everything will
    // be cached.

    /**
     * Field switchingAllowed
     */
    boolean switchingAllowed = false;

    /**
     * Field elementStack
     */
    private Stack elementStack = new Stack();

    // keeps the next event. The parser actually keeps one step ahead to
    // detect the end of navigation. (at the end of the stream the navigator
    // returns a null

    /**
     * Field nextNode
     */
    private OMNode nextNode = null;

    // holder for the current node. Needs this to generate events from the current node

    /**
     * Field currentNode
     */
    private OMNode currentNode = null;

    // needs this to refer to the last known node

    /**
     * Field lastNode
     */
    private OMNode lastNode = null;

    /**
     * Track depth to ensure we stop generating events when we are done with the root node.  
     */
    int depth = 0;

    private boolean needToThrowEndDocument = false;

    /**
     * Method setAllowSwitching.
     *
     * @param b
     */
    public void setAllowSwitching(boolean b) {
        this.switchingAllowed = b;
    }

    /**
     * Method isAllowSwitching.
     *
     * @return Returns boolean.
     */
    public boolean isAllowSwitching() {
        return switchingAllowed;
    }

    /**
     * When constructing the OMStaxWrapper, the creator must produce the
     * builder (an instance of the OMXMLparserWrapper of the input) and the
     * Element Node to start parsing. The wrapper will parse(proceed) until
     * the end of the given element. Hence care should be taken to pass the
     * root element if the entire document is needed.
     *
     * @param builder
     * @param startNode
     */
    public OMStAXWrapper(OMXMLParserWrapper builder, OMElement startNode) {
        this(builder, startNode, false);
    }

    /**
     * Constructor OMStAXWrapper.
     *
     * @param builder
     * @param startNode
     * @param cache
     */
    public OMStAXWrapper(OMXMLParserWrapper builder, OMElement startNode,
                         boolean cache) {

        // create a navigator
        this.navigator = new OMNavigator(startNode);
        this.builder = builder;
        this.rootNode = startNode;
        if (rootNode != null && rootNode.getParent() != null && rootNode.getParent() instanceof OMDocument) {
            needToThrowEndDocument = true;
        }

        // initaite the next and current nodes
        // Note -  navigator is written in such a way that it first
        // returns the starting node at the first call to it
        currentNode = navigator.next();
        updateNextNode();
        switchingAllowed = !cache;
    }

    /**
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getPrefix()
     */
    public String getPrefix() {
        String returnStr = null;
        if (parser != null) {
            returnStr = parser.getPrefix();
        } else {
            if ((currentEvent == START_ELEMENT)
                    || (currentEvent == END_ELEMENT)) {
                OMNamespace ns = ((OMElement) lastNode).getNamespace();
                returnStr = (ns == null)
                        ? null
                        : ns.getPrefix();
            }
        }
        return returnStr;
    }

    /**
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getNamespaceURI()
     */
    public String getNamespaceURI() {
        String returnStr = null;
        if (parser != null) {
            returnStr = parser.getNamespaceURI();
        } else {
            if ((currentEvent == START_ELEMENT)
                    || (currentEvent == END_ELEMENT)
                    || (currentEvent == NAMESPACE)) {
                OMNamespace ns = ((OMElement) lastNode).getNamespace();
                returnStr = (ns == null)
                        ? null
                        : ns.getName();
            }
        }
        return returnStr;
    }

    /**
     * @return Returns boolean.
     * @see javax.xml.stream.XMLStreamReader#hasName()
     */
    public boolean hasName() {
        if (parser != null) {
            return parser.hasName();
        } else {
            return ((currentEvent == START_ELEMENT)
                    || (currentEvent == END_ELEMENT));
        }
    }

    /**
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getLocalName()
     */
    public String getLocalName() {
        String returnStr = null;
        if (parser != null) {
            returnStr = parser.getLocalName();
        } else {
            if ((currentEvent == START_ELEMENT)
                    || (currentEvent == END_ELEMENT)
                    || (currentEvent == ENTITY_REFERENCE)) {
                returnStr = ((OMElement) lastNode).getLocalName();
            }
        }
        return returnStr;
    }

    /**
     * @return Returns QName.
     * @see javax.xml.stream.XMLStreamReader#getName()
     */
    public QName getName() {
        QName returnName = null;
        if (parser != null) {
            returnName = parser.getName();
        } else {
            if ((currentEvent == START_ELEMENT)
                    || (currentEvent == END_ELEMENT)) {
                returnName = getQName((OMElement) lastNode);
            }
        }
        return returnName;
    }

    /**
     * @return Returns boolean.
     * @see javax.xml.stream.XMLStreamReader#hasText()
     */
    public boolean hasText() {
        return ((currentEvent == CHARACTERS) || (currentEvent == DTD)
                || (currentEvent == ENTITY_REFERENCE)
                || (currentEvent == COMMENT) || (currentEvent == SPACE));
    }

    /**
     * @return Returns int.
     * @see javax.xml.stream.XMLStreamReader#getTextLength()
     */
    public int getTextLength() {
        int returnLength = 0;
        if (parser != null) {
            returnLength = parser.getTextLength();
        } else {
            OMText textNode = (OMText) lastNode;
            returnLength = textNode.getText().length();
        }
        return returnLength;
    }

    /**
     * @return Returns int.
     * @see javax.xml.stream.XMLStreamReader#getTextStart()
     */
    public int getTextStart() {
        int returnLength = 0;
        if (parser != null) {
            returnLength = parser.getTextStart();
        }

        // Note - this has no relevant method in the OM
        return returnLength;
    }

    /**
     * @param i
     * @param chars
     * @param i1
     * @param i2
     * @return Returns int.
     * @throws XMLStreamException
     * @see javax.xml.stream.XMLStreamReader#getTextCharacters(int, char[], int, int)
     */
    public int getTextCharacters(int i, char[] chars, int i1, int i2)
            throws XMLStreamException {
        int returnLength = 0;
        if (parser != null) {
            try {
                returnLength = parser.getTextCharacters(i, chars, i1, i2);
            } catch (XMLStreamException e) {
                throw new OMStreamingException(e);
            }
        } else {
            if (hasText()) {
                OMText textNode = (OMText) lastNode;
                String str = textNode.getText();
                str.getChars(i, i + i2, chars, i1);
            }
        }
        return returnLength;
    }

    /**
     * @return Returns char[].
     * @see javax.xml.stream.XMLStreamReader#getTextCharacters()
     */
    public char[] getTextCharacters() {
        char[] returnArray = null;
        if (parser != null) {
            returnArray = parser.getTextCharacters();
        } else {
            if (hasText()) {
                OMText textNode = (OMText) lastNode;
                String str = textNode.getText();
                returnArray = str.toCharArray();
            }
        }
        return returnArray;
    }

    /**
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getText()
     */
    public String getText() {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getText();
        } else {
            if (hasText()) {
                if (lastNode instanceof OMText) {
                    returnString = ((OMText) lastNode).getText();
                } else if (lastNode instanceof OMComment) {
                    returnString = ((OMComment) lastNode).getValue();
                }
            }
        }
        return returnString;
    }

    /**
     * @return Returns int.
     * @see javax.xml.stream.XMLStreamReader#getEventType()
     */

    // todo this should be improved
    public int getEventType() {
        return currentEvent;
    }

    /**
     * @param i
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getNamespaceURI
     */
    public String getNamespaceURI(int i) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getNamespaceURI(i);
        } else {
            if (isStartElement() || isEndElement()
                    || (currentEvent == NAMESPACE)) {
                OMNamespace ns = (OMNamespace) getItemFromIterator(
                        ((OMElement) lastNode).getAllDeclaredNamespaces(), i);
                returnString = (ns == null)
                        ? null
                        : ns.getName();
            }
        }
        return returnString;
    }

    /**
     * @param i
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getNamespacePrefix
     */
    public String getNamespacePrefix(int i) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getNamespacePrefix(i);
        } else {
            if (isStartElement() || isEndElement()
                    || (currentEvent == NAMESPACE)) {
                OMNamespace ns = (OMNamespace) getItemFromIterator(
                        ((OMElement) lastNode).getAllDeclaredNamespaces(), i);
                returnString = (ns == null)
                        ? null
                        : ns.getPrefix();
            }
        }
        return returnString;
    }

    /**
     * @return Returns int.
     * @see javax.xml.stream.XMLStreamReader#getNamespaceCount()
     */
    public int getNamespaceCount() {
        int returnCount = 0;
        if (parser != null) {
            returnCount = parser.getNamespaceCount();
        } else {
            if (isStartElement() || isEndElement()
                    || (currentEvent == NAMESPACE)) {
                returnCount =
                        getCount(
                                ((OMElement) lastNode).getAllDeclaredNamespaces());
            }
        }
        return returnCount;
    }

    /**
     * @param i
     * @return Returns boolean.
     * @see javax.xml.stream.XMLStreamReader#isAttributeSpecified
     */
    public boolean isAttributeSpecified(int i) {
        boolean returnValue = false;
        if (parser != null) {
            returnValue = parser.isAttributeSpecified(i);
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {

                // theres nothing to be returned here
            } else {
                throw new IllegalStateException(
                        "attribute type accessed in illegal event!");
            }
        }
        return returnValue;
    }

    /**
     * @param i
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getAttributeValue
     */
    public String getAttributeValue(int i) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getAttributeValue(i);
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {
                OMAttribute attrib = getAttribute((OMElement) lastNode, i);
                if (attrib != null) {
                    returnString = attrib.getAttributeValue();
                }
            } else {
                throw new IllegalStateException(
                        "attribute type accessed in illegal event!");
            }
        }
        return returnString;
    }

    /**
     * @param i
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getAttributeType
     */
    public String getAttributeType(int i) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getAttributeType(i);
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {

                // todo implement this
            } else {
                throw new IllegalStateException(
                        "attribute type accessed in illegal event!");
            }
        }
        return returnString;
    }

    /**
     * @param i
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getAttributePrefix
     */
    public String getAttributePrefix(int i) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getAttributePrefix(i);
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {
                OMAttribute attrib = getAttribute((OMElement) lastNode, i);
                if (attrib != null) {
                    OMNamespace nameSpace = attrib.getNamespace();
                    if (nameSpace != null) {
                        returnString = nameSpace.getPrefix();
                    }
                }
            } else {
                throw new IllegalStateException(
                        "attribute prefix accessed in illegal event!");
            }
        }
        return returnString;
    }

    /**
     * @param i
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getAttributeLocalName
     */
    public String getAttributeLocalName(int i) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getAttributeLocalName(i);
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {
                OMAttribute attrib = getAttribute((OMElement) lastNode, i);
                if (attrib != null) {
                    returnString = attrib.getLocalName();
                }
            } else {
                throw new IllegalStateException(
                        "attribute localName accessed in illegal event!");
            }
        }
        return returnString;
    }

    /**
     * @param i
     * @return Returns String.
     * @see javax.xml.stream.XMLStreamReader#getAttributeNamespace
     */
    public String getAttributeNamespace(int i) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getAttributeNamespace(i);
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {
                OMAttribute attrib = getAttribute((OMElement) lastNode, i);
                if (attrib != null) {
                    OMNamespace nameSpace = attrib.getNamespace();
                    if (nameSpace != null) {
                        returnString = nameSpace.getName();
                    }
                }
            } else {
                throw new IllegalStateException(
                        "attribute nameSpace accessed in illegal event!");
            }
        }
        return returnString;
    }

    /**
     * @param i
     * @return Returns QName.
     * @see javax.xml.stream.XMLStreamReader#getAttributeName
     */
    public QName getAttributeName(int i) {
        QName returnQName = null;
        if (parser != null) {
            returnQName = parser.getAttributeName(i);
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {
                returnQName = getAttribute((OMElement) lastNode, i).getQName();
            } else {
                throw new IllegalStateException(
                        "attribute count accessed in illegal event!");
            }
        }
        return returnQName;
    }

    /**
     * @return Returns int.
     * @see javax.xml.stream.XMLStreamReader#getAttributeCount
     */
    public int getAttributeCount() {
        int returnCount = 0;
        if (parser != null) {
            returnCount = parser.getAttributeCount();
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {
                OMElement elt = (OMElement) lastNode;
                returnCount = getCount(elt.getAllAttributes());
            } else {
                throw new IllegalStateException(
                        "attribute count accessed in illegal event (" +
                                currentEvent + ")!");
            }
        }
        return returnCount;
    }

    // todo

    /**
     * Method getAttributeValue.
     *
     * @param s
     * @param s1
     * @return Returns String.
     */
    public String getAttributeValue(String s, String s1) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getAttributeValue(s, s1);
        } else {
            if (isStartElement() || (currentEvent == ATTRIBUTE)) {
                QName qname = new QName(s, s1);
                OMAttribute attrib = ((OMElement) lastNode).getAttribute(qname);
                if (attrib != null) {
                    returnString = attrib.getAttributeValue();
                }
            } else {
                throw new IllegalStateException(
                        "attribute type accessed in illegal event!");
            }
        }
        return returnString;
    }

    /**
     * Method isWhiteSpace.
     *
     * @return Returns boolean.
     */
    public boolean isWhiteSpace() {
        boolean b;
        if (parser != null) {
            b = parser.isWhiteSpace();
        } else {
            b = (currentEvent == SPACE);
        }
        return b;
    }

    /**
     * Method isCharacters.
     *
     * @return Returns boolean.
     */
    public boolean isCharacters() {
        boolean b;
        if (parser != null) {
            b = parser.isCharacters();
        } else {
            b = (currentEvent == CHARACTERS);
        }
        return b;
    }

    /**
     * Method isEndElement.
     *
     * @return Returns boolean.
     */
    public boolean isEndElement() {
        boolean b;
        if (parser != null) {
            b = parser.isEndElement();
        } else {
            b = (currentEvent == END_ELEMENT);
        }
        return b;
    }

    /**
     * @param i
     * @param s
     * @param s1
     * @throws XMLStreamException
     * @see javax.xml.stream.XMLStreamReader#require(int, String, String)
     */
    public void require(int i, String s, String s1) throws XMLStreamException {
        throw new XMLStreamException();
    }

    /**
     * Method isStartElement.
     *
     * @return Returns boolean.
     */
    public boolean isStartElement() {
        boolean b;
        if (parser != null) {
            b = parser.isStartElement();
        } else {
            b = (currentEvent == START_ELEMENT);
        }
        return b;
    }

    /**
     * Method getNamespaceURI.
     *
     * @param s
     * @return Returns String.
     */
    public String getNamespaceURI(String s) {
        String returnString = null;
        if (parser != null) {
            returnString = parser.getNamespaceURI(s);
        } else {
            if (isStartElement() || isEndElement()
                    || (currentEvent == NAMESPACE)) {

                // Nothing to do here! How to get the namespacace references
            }
        }
        return returnString;
    }

    /**
     * Method close.
     *
     * @throws XMLStreamException
     */
    public void close() throws XMLStreamException {

        // this doesnot mean anything with respect to the OM
        if (parser != null) {
            parser.close();
        }
    }

    /**
     * Method hasNext.
     *
     * @return Returns boolean.
     * @throws XMLStreamException
     */
    public boolean hasNext() throws XMLStreamException {
        if(needToThrowEndDocument){
            return !(state == DOCUMENT_COMPLETE);
        } else {
            return (state != COMPLETED && currentEvent != END_DOCUMENT);
        }
    }

    /**
     * Returns the next tag.
     *
     * @return Returns int.
     * @throws org.apache.axiom.om.impl.exception.OMStreamingException
     *
     * @throws XMLStreamException
     */
    public int nextTag() throws XMLStreamException {
        int eventType = next();
        while((eventType == XMLStreamConstants.CHARACTERS && isWhiteSpace()) // skip whitespace
            || (eventType == XMLStreamConstants.CDATA && isWhiteSpace()) // skip whitespace
            || eventType == XMLStreamConstants.SPACE
            || eventType == XMLStreamConstants.PROCESSING_INSTRUCTION
            || eventType == XMLStreamConstants.COMMENT) {
            eventType = next();
         }
         if (eventType != XMLStreamConstants.START_ELEMENT && eventType != XMLStreamConstants.END_ELEMENT) {
             throw new XMLStreamException("expected start or end tag", getLocation());
         }
         return eventType;    
    }
    
    /**
     * @return Returns String.
     * @throws XMLStreamException
     * @see javax.xml.stream.XMLStreamReader#getElementText()
     */
    public String getElementText() throws XMLStreamException {
        if (parser != null) {
            try {
                return parser.getElementText();
            } catch (XMLStreamException e) {
                throw new OMStreamingException(e);
            }
        } else {
            if (currentNode.getType() == OMNode.ELEMENT_NODE) {
                return ((OMElement)currentNode).getText();
            }else if (currentNode.getType() == OMNode.TEXT_NODE){
                 return ((OMText)currentNode).getText();
            }
        }
        return "";
    }

    /**
     * Method next.
     *
     * @return Returns int.
     * @throws XMLStreamException
     */
    public int next() throws XMLStreamException {
        switch (state) {
            case DOCUMENT_COMPLETE:
                throw new XMLStreamException("End of the document reached");
            case COMPLETED:
                state = DOCUMENT_COMPLETE;
                currentEvent = END_DOCUMENT;
                break;
            case SWITCH_AT_NEXT:
                state = SWITCHED;

                // load the parser
                try {
                    parser = (XMLStreamReader) builder.getParser();
                } catch (Exception e) {
                    throw new XMLStreamException("problem accessing the parser. " + e.getMessage(), e);
                }

                // We should throw an END_DOCUMENT
                if ((currentEvent == START_DOCUMENT) &&
                        (currentEvent == parser.getEventType())) {
                    currentEvent = parser.next();
                } else {
                    currentEvent = parser.getEventType();
                }

                updateCompleteStatus();
                break;
            case NAVIGABLE:
                currentEvent = generateEvents(currentNode);
                updateCompleteStatus();
                updateLastNode();
                break;
            case SWITCHED:
                if(parser.hasNext()) {
                    currentEvent = parser.next();
                }
                updateCompleteStatus();
                break;
            default :
                throw new OMStreamingException("unsuppported state!");
        }
        return currentEvent;
    }

    /**
     * Method getProperty.
     *
     * @param s
     * @return Returns Object.
     * @throws IllegalArgumentException
     */
    public Object getProperty(String s) throws IllegalArgumentException {
        throw new IllegalArgumentException();
    }

    /**
     * This is a very important method. It keeps the navigator one step ahead 
     * and pushes it one event ahead. If the nextNode is null then navigable is 
     * set to false. At the same time the parser and builder are set up for 
     * the upcoming event generation.
     *
     * @throws XMLStreamException
     */
    private void updateLastNode() throws XMLStreamException {
        lastNode = currentNode;
        currentNode = nextNode;
        try {
            updateNextNode();
        } catch (Exception e) {
            throw new XMLStreamException(e);
        }
    }

    /**
     * Method updateNextNode.
     */
    private void updateNextNode() {
        if (navigator.isNavigable()) {
            nextNode = navigator.next();
        } else {
            if (!switchingAllowed) {
                if (navigator.isCompleted()) {
                    nextNode = null;

                } else {
                    builder.next();
                    navigator.step();
                    nextNode = navigator.next();
                }
            } else {
                //at this point check whether the navigator is done
                //if the navigator is done then we are fine and can directly
                // jump to the complete state ?
               if (navigator.isCompleted()) {
                    nextNode = null;
               }else{
                // reset caching (the default is ON so it was not needed in the
                // earlier case!
                builder.setCache(false);
                state = SWITCH_AT_NEXT;
               }
            }
        }
    }

    /**
     * Method updateCompleteStatus.
     */
    private void updateCompleteStatus() {
        if (state == NAVIGABLE) {
            if (rootNode == currentNode) {
                if (isFirst) {
                    isFirst = false;
                } else {
                    state = COMPLETED;
                }
            }
        } else {
            if (state == SWITCHED) {
                if (currentEvent == START_ELEMENT) {
                    ++depth;
                } else if (currentEvent == END_ELEMENT) {
                    --depth;
                    if(depth < 0) {
                        state = COMPLETED;
                    }
                }
            }
            state = (currentEvent == END_DOCUMENT)
                    ? DOCUMENT_COMPLETE
                    : state;
        }
    }

    /**
     * Method getNamespaceContext.
     *
     * @return Returns NamespaceContext.
     */
    public NamespaceContext getNamespaceContext() {
        throw new UnsupportedOperationException();
    }

    /**
     * Method getEncoding.
     *
     * @return Returns String.
     */
    public String getEncoding() {
        return null;
    }

    /**
     * Method getLocation.
     *
     * @return Returns Location.
     */
    public Location getLocation() {
         return new EmptyOMLocation();
    }

    /**
     * Method getVersion.
     *
     * @return Returns String.
     */
    public String getVersion() {
        return "1.0"; //todo put the constant
    }


    /**
     * Method isStandalone.
     *
     * @return Returns boolean.
     */
    public boolean isStandalone() {
        return true;
    }

    /**
     * Method standaloneSet.
     *
     * @return Returns boolean.
     */
    public boolean standaloneSet() {
        return false;
    }

    /**
     * Method getCharacterEncodingScheme.
     *
     * @return Returns String.
     */
    public String getCharacterEncodingScheme() {
        return "utf-8";
    }

    /**
     * Method getPITarget.
     *
     * @return Returns String.
     */
    public String getPITarget() {
        throw new UnsupportedOperationException();
    }

    /**
     * Method getPIData.
     *
     * @return Returns String.
     */
    public String getPIData() {
        throw new UnsupportedOperationException();
    }

    /*
     *
     * ################################################################
     * Generator methods for the OMNodes returned by the navigator
     * ################################################################
     *
     */

    /**
     * Method generateEvents.
     *
     * @param node
     * @return Returns int.
     */
    private int generateEvents(OMNode node) {
        int returnEvent = 0;
        int nodeType = node.getType();
        switch (nodeType) {
            case OMNode.ELEMENT_NODE:
                OMElement element = (OMElement) node;
                returnEvent = generateElementEvents(element);
                break;
            case OMNode.TEXT_NODE:
                returnEvent = generateTextEvents();
                break;
            case OMNode.COMMENT_NODE:
                returnEvent = generateCommentEvents();
                break;
            case OMNode.CDATA_SECTION_NODE:
                returnEvent = generateCdataEvents();
                break;
            default :
                break;    // just ignore any other nodes
        }
        return returnEvent;
    }

    /**
     * Method generateElementEvents.
     *
     * @param elt
     * @return Returns int.
     */
    private int generateElementEvents(OMElement elt) {
        int returnValue = START_ELEMENT;
        if (!elementStack.isEmpty() && elementStack.peek().equals(elt)) {
            returnValue = END_ELEMENT;
            elementStack.pop();
        } else {
            elementStack.push(elt);
        }
        return returnValue;
    }

    /**
     * Method generateTextEvents.
     *
     * @return Returns int.
     */
    private int generateTextEvents() {
        return CHARACTERS;
    }

    /**
     * Method generateCommentEvents
     *
     * @return Returns int.
     */
    private int generateCommentEvents() {
        return COMMENT;
    }

    /**
     * Method generateCdataEvents
     *
     * @return Returns int.
     */
    private int generateCdataEvents() {
        return CDATA;
    }

    /*
     * ####################################################################
     * Other helper methods
     * ####################################################################
     */

    /**
     * helper method getCount.
     *
     * @param it
     * @return Returns int.
     */
    private int getCount(Iterator it) {
        int count = 0;
        if (it != null) {
            while (it.hasNext()) {
                it.next();
                count++;
            }
        }
        return count;
    }

    /**
     * Helper method getItemFromIterator.
     *
     * @param it
     * @param index
     * @return Returns Object.
     */
    private Object getItemFromIterator(Iterator it, int index) {
        int count = 0;
        Object returnObject = null;
        boolean found = false;
        if (it != null) {
            while (it.hasNext()) {
                returnObject = it.next();
                if (index == count++) {
                    found = true;
                    break;
                }
            }
        }
        if (found) {
            return returnObject;
        } else {
            return null;
        }
    }

    /**
     * Helper method getQName.
     *
     * @param element
     * @return Returns QName.
     */
    private QName getQName(OMElement element) {
        QName returnName;
        OMNamespace ns = element.getNamespace();
        String localPart = element.getLocalName();
        if (ns != null) {
            String prefix = ns.getPrefix();
            String uri = ns.getName();
            if ((prefix == null) || prefix.equals("")) {
                returnName = new QName(uri, localPart);
            } else {
                returnName = new QName(uri, localPart, prefix);
            }
        } else {
            returnName = new QName(localPart);
        }
        return returnName;
    }

    /**
     * @param elt
     * @param index
     * @return Returns OMAttribute.
     */
    private OMAttribute getAttribute(OMElement elt, int index) {
        OMAttribute returnAttrib = null;
        if (elt != null) {
            returnAttrib =
                    (OMAttribute) getItemFromIterator(elt.getAllAttributes(),
                            index);
        }
        return returnAttrib;
    }

    public void setParser(XMLStreamReader parser) {
        this.parser = parser;
    }

}