/*******************************************************************************
 * Copyright (c) 2001, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Jens Lukowski/Innoopract - initial renaming/restructuring
 *     
 *******************************************************************************/
package org.eclipse.wst.xml.ui.internal.validation;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.osgi.util.NLS;
import org.eclipse.wst.sse.core.StructuredModelManager;
import org.eclipse.wst.sse.core.internal.provisional.IStructuredModel;
import org.eclipse.wst.sse.core.internal.provisional.text.IStructuredDocument;
import org.eclipse.wst.sse.core.internal.provisional.text.IStructuredDocumentRegion;
import org.eclipse.wst.sse.core.internal.provisional.text.ITextRegion;
import org.eclipse.wst.sse.core.internal.provisional.text.ITextRegionList;
import org.eclipse.wst.sse.ui.internal.reconcile.AbstractStructuredTextReconcilingStrategy;
import org.eclipse.wst.sse.ui.internal.reconcile.ReconcileAnnotationKey;
import org.eclipse.wst.sse.ui.internal.reconcile.TemporaryAnnotation;
import org.eclipse.wst.sse.ui.internal.reconcile.validator.AnnotationInfo;
import org.eclipse.wst.sse.ui.internal.reconcile.validator.ISourceValidator;
import org.eclipse.wst.sse.ui.internal.reconcile.validator.IncrementalReporter;
import org.eclipse.wst.validation.internal.core.ValidationException;
import org.eclipse.wst.validation.internal.operations.LocalizedMessage;
import org.eclipse.wst.validation.internal.provisional.core.IMessage;
import org.eclipse.wst.validation.internal.provisional.core.IReporter;
import org.eclipse.wst.validation.internal.provisional.core.IValidationContext;
import org.eclipse.wst.validation.internal.provisional.core.IValidator;
import org.eclipse.wst.xml.core.internal.provisional.document.IDOMNode;
import org.eclipse.wst.xml.core.internal.regions.DOMRegionContext;
import org.eclipse.wst.xml.ui.internal.Logger;
import org.eclipse.wst.xml.ui.internal.XMLUIMessages;
import org.eclipse.wst.xml.ui.internal.correction.ProblemIDsXML;
import org.w3c.dom.Node;

/**
 * Basic XML syntax checking step. Only used as ISourceValidator at the
 * momment
 * 
 * @author pavery
 */
public class MarkupValidator implements IValidator, ISourceValidator {
	private String DQUOTE = "\""; //$NON-NLS-1$

	protected String SEVERITY_ATTR_MISSING_VALUE = TemporaryAnnotation.ANNOT_ERROR;
	protected String SEVERITY_ATTR_NO_VALUE = TemporaryAnnotation.ANNOT_ERROR;
	// severities for the problems discoverable by this reconciler; possibly
	// user configurable later
	protected String SEVERITY_GENERIC_ILLFORMED_SYNTAX = TemporaryAnnotation.ANNOT_WARNING;
	protected String SEVERITY_STRUCTURE = TemporaryAnnotation.ANNOT_ERROR;
	protected String SEVERITY_SYNTAX_ERROR = TemporaryAnnotation.ANNOT_ERROR;
	// used for attribute quote checking
	private String SQUOTE = "'"; //$NON-NLS-1$

	private IDocument fDocument;

	private void addAttributeError(String messageText, String attributeValueText, int start, int length, int problemId, IStructuredDocumentRegion sdRegion, IReporter reporter) {

		if (sdRegion.isDeleted()) {
			return;
		}

		int lineNo = getLineNumber(start);
		LocalizedMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
		message.setOffset(start);
		message.setLength(length);
		message.setLineNo(lineNo);

		AnnotationInfo info = new AnnotationInfo(message, problemId, attributeValueText);
		((IncrementalReporter) reporter).addAnnotationInfo(this, info);
	}

	private void checkAttributesInEndTag(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {

		if (structuredDocumentRegion.isDeleted()) {
			return;
		}

		ITextRegionList textRegions = structuredDocumentRegion.getRegions();
		int errorCount = 0;
		int start = structuredDocumentRegion.getEndOffset();
		int end = structuredDocumentRegion.getEndOffset();
		for (int i = 0; (i < textRegions.size()) && (errorCount < AbstractStructuredTextReconcilingStrategy.ELEMENT_ERROR_LIMIT) && !structuredDocumentRegion.isDeleted(); i++) {
			ITextRegion textRegion = textRegions.get(i);
			if ((textRegion.getType() == DOMRegionContext.XML_TAG_ATTRIBUTE_NAME) || (textRegion.getType() == DOMRegionContext.XML_TAG_ATTRIBUTE_EQUALS) || (textRegion.getType() == DOMRegionContext.XML_TAG_ATTRIBUTE_VALUE)) {
				if (start > structuredDocumentRegion.getStartOffset(textRegion)) {
					start = structuredDocumentRegion.getStartOffset(textRegion);
				}
				end = structuredDocumentRegion.getEndOffset(textRegion);
				errorCount++;
			}
		}
		// create one error for all attributes in the end tag
		if (errorCount > 0) {
			// Position p = new Position(start, end - start);
			String messageText = XMLUIMessages.End_tag_has_attributes;
			LocalizedMessage message = new LocalizedMessage(IMessage.NORMAL_SEVERITY, messageText);
			message.setOffset(start);
			message.setLength(end - start);
			message.setLineNo(getLineNumber(start));

			AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.AttrsInEndTag, null);
			((IncrementalReporter) reporter).addAnnotationInfo(this, info);
		}
	}


	private void checkClosingBracket(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {

		if (structuredDocumentRegion.isDeleted()) {
			return;
		}

		ITextRegionList regions = structuredDocumentRegion.getRegions();
		ITextRegion r = null;
		boolean closed = false;
		for (int i = 0; (i < regions.size()) && !structuredDocumentRegion.isDeleted(); i++) {
			r = regions.get(i);
			if ((r.getType() == DOMRegionContext.XML_TAG_CLOSE) || (r.getType() == DOMRegionContext.XML_EMPTY_TAG_CLOSE)) {
				closed = true;
			}
		}
		if (!closed) {

			String messageText = XMLUIMessages.ReconcileStepForMarkup_6;

			int start = structuredDocumentRegion.getStartOffset();
			int length = structuredDocumentRegion.getText().trim().length();
			int lineNo = getLineNumber(start);

			LocalizedMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
			message.setOffset(start);
			message.setLength(length);
			message.setLineNo(lineNo);

			AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.MissingClosingBracket, null);
			((IncrementalReporter) reporter).addAnnotationInfo(this, info);
		}
	}

	private void checkEmptyTag(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {

		if (structuredDocumentRegion.isDeleted()) {
			return;
		}

		// navigate to name
		ITextRegionList regions = structuredDocumentRegion.getRegions();
		if (regions.size() == 2) {
			// missing name region
			if ((regions.get(0).getType() == DOMRegionContext.XML_TAG_OPEN) && (regions.get(1).getType() == DOMRegionContext.XML_TAG_CLOSE)) {
				String messageText = XMLUIMessages.ReconcileStepForMarkup_3;
				int start = structuredDocumentRegion.getStartOffset();
				int length = structuredDocumentRegion.getLength();
				int lineNo = getLineNumber(start);

				LocalizedMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
				message.setOffset(start);
				message.setLength(length);
				message.setLineNo(lineNo);

				AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.EmptyTag, null);
				((IncrementalReporter) reporter).addAnnotationInfo(this, info);
			}
		}
	}

	private int getLineNumber(int start) {
		int lineNo = -1;
		try {
			lineNo = getDocument().getLineOfOffset(start);
		}
		catch (BadLocationException e) {
			Logger.logException(e);
		}
		return lineNo;
	}

	private void checkForAttributeValue(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {

		if (structuredDocumentRegion.isDeleted()) {
			return;
		}

		// check for attributes without a value
		// track the attribute/equals/value sequence using a state of 0, 1 ,2
		// representing the name, =, and value, respectively
		int attrState = 0;
		ITextRegionList textRegions = structuredDocumentRegion.getRegions();
		// ReconcileAnnotationKey key = createKey(structuredDocumentRegion,
		// getScope());

		int errorCount = 0;
		for (int i = 0; (i < textRegions.size()) && (errorCount < AbstractStructuredTextReconcilingStrategy.ELEMENT_ERROR_LIMIT); i++) {
			ITextRegion textRegion = textRegions.get(i);
			if ((textRegion.getType() == DOMRegionContext.XML_TAG_ATTRIBUTE_NAME) || isTagCloseTextRegion(textRegion)) {
				// dangling name and '='
				if ((attrState == 2) && (i >= 2)) {
					// create annotation
					ITextRegion nameRegion = textRegions.get(i - 2);
					Object[] args = {structuredDocumentRegion.getText(nameRegion)};
					String messageText = NLS.bind(XMLUIMessages.Attribute__is_missing_a_value, args);

					int start = structuredDocumentRegion.getStartOffset(nameRegion);
					int end = structuredDocumentRegion.getEndOffset();
					int lineNo = getLineNumber(start);
					int textLength = structuredDocumentRegion.getText(nameRegion).trim().length();

					LocalizedMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
					message.setOffset(start);
					message.setLength(textLength);
					message.setLineNo(lineNo);

					// quick fix info
					ITextRegion equalsRegion = textRegions.get(i - 2 + 1);
					int insertOffset = structuredDocumentRegion.getTextEndOffset(equalsRegion) - end;
					Object[] additionalFixInfo = {structuredDocumentRegion.getText(nameRegion), new Integer(insertOffset)};

					AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.MissingAttrValue, additionalFixInfo);

					((IncrementalReporter) reporter).addAnnotationInfo(this, info);

					// annotation.setAdditionalFixInfo(additionalFixInfo);
					// results.add(annotation);
					errorCount++;
				}
				// name but no '=' (XML only)
				else if ((attrState == 1) && (i >= 1)) {
					// create annotation
					ITextRegion previousRegion = textRegions.get(i - 1);
					Object[] args = {structuredDocumentRegion.getText(previousRegion)};
					String messageText = NLS.bind(XMLUIMessages.Attribute__has_no_value, args);
					int start = structuredDocumentRegion.getStartOffset(previousRegion);
					int textLength = structuredDocumentRegion.getText(previousRegion).trim().length();
					int lineNo = getLineNumber(start);

					LocalizedMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
					message.setOffset(start);
					message.setLength(textLength);
					message.setLineNo(lineNo);

					AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.NoAttrValue, structuredDocumentRegion.getText(previousRegion));

					((IncrementalReporter) reporter).addAnnotationInfo(this, info);

					errorCount++;
				}
				attrState = 1;
			}
			else if (textRegion.getType() == DOMRegionContext.XML_TAG_ATTRIBUTE_EQUALS) {
				attrState = 2;
			}
			else if (textRegion.getType() == DOMRegionContext.XML_TAG_ATTRIBUTE_VALUE) {
				attrState = 0;
			}
		}

	}

	private void checkForSpaceBeforeName(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {

		if (structuredDocumentRegion.isDeleted()) {
			return;
		}

		String sdRegionText = structuredDocumentRegion.getFullText();
		if (sdRegionText.startsWith(" ")) { //$NON-NLS-1$
			IStructuredDocumentRegion prev = structuredDocumentRegion.getPrevious();
			if (prev != null) {
				// this is possibly the case of "< tag"
				if ((prev.getRegions().size() == 1) && isStartTag(prev)) {
					// add the error for preceding space in tag name
					String messageText = XMLUIMessages.ReconcileStepForMarkup_2;
					int start = structuredDocumentRegion.getStartOffset();
					// find length of whitespace
					int length = sdRegionText.trim().equals("") ? sdRegionText.length() : sdRegionText.indexOf(sdRegionText.trim()); //$NON-NLS-1$

					LocalizedMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
					message.setOffset(start);
					message.setLength(length);
					message.setLineNo(getLineNumber(start));

					AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.SpacesBeforeTagName, null);
					((IncrementalReporter) reporter).addAnnotationInfo(this, info);
				}
			}
		}
	}

	private void checkNoNamespaceInPI(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {

		if (structuredDocumentRegion.isDeleted()) {
			return;
		}

		// navigate to name
		ITextRegionList regions = structuredDocumentRegion.getRegions();
		ITextRegion r = null;
		int errorCount = 0;
		for (int i = 0; (i < regions.size()) && (errorCount < AbstractStructuredTextReconcilingStrategy.ELEMENT_ERROR_LIMIT) && !structuredDocumentRegion.isDeleted(); i++) {
			r = regions.get(i);
			if (r.getType() == DOMRegionContext.XML_TAG_NAME) {
				String piText = structuredDocumentRegion.getText(r);
				int index = piText.indexOf(":"); //$NON-NLS-1$
				if (index != -1) {
					String messageText = XMLUIMessages.ReconcileStepForMarkup_4;
					int start = structuredDocumentRegion.getStartOffset(r) + index;
					int length = piText.trim().length() - index;

					LocalizedMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
					message.setOffset(start);
					message.setLength(length);
					message.setLineNo(getLineNumber(start));

					AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.NamespaceInPI, null);
					((IncrementalReporter) reporter).addAnnotationInfo(this, info);

					errorCount++;
				}
			}
		}
	}

	private void checkQuotesForAttributeValues(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {
		ITextRegionList regions = structuredDocumentRegion.getRegions();
		ITextRegion r = null;
		String attrValueText = ""; //$NON-NLS-1$
		int errorCount = 0;
		for (int i = 0; (i < regions.size()) && (errorCount < AbstractStructuredTextReconcilingStrategy.ELEMENT_ERROR_LIMIT); i++) {
			r = regions.get(i);
			if (r.getType() != DOMRegionContext.XML_TAG_ATTRIBUTE_VALUE) {
				continue;
			}

			attrValueText = structuredDocumentRegion.getText(r);
			// attribute value includes quotes in the string
			// split up attribute value on quotes
			/*
			 * WORKAROUND till
			 * http://dev.icu-project.org/cgi-bin/icu-bugs/incoming?findid=5207
			 * is fixed. (Also see BUG143628)
			 */

			java.util.StringTokenizer st = new java.util.StringTokenizer(attrValueText, "\"'", true); //$NON-NLS-1$
			int size = st.countTokens();
			// get the pieces of the attribute value
			String one = "", two = ""; //$NON-NLS-1$ //$NON-NLS-2$
			if (size > 0) {
				one = st.nextToken();
			}
			if (size > 1) {
				two = st.nextToken();
			}
			if (size > 2) {
				// should be handled by parsing...
				// as in we can't have an attribute value like: <element
				// attr="a"b"c"/>
				// and <element attr='a"b"c' /> is legal
				continue;
			}


			if (size == 1) {
				if (one.equals(DQUOTE) || one.equals(SQUOTE)) {
					// missing closing quote
					String message = XMLUIMessages.ReconcileStepForMarkup_0;
					addAttributeError(message, attrValueText, structuredDocumentRegion.getStartOffset(r), attrValueText.trim().length(), ProblemIDsXML.Unclassified, structuredDocumentRegion, reporter);
					errorCount++;
				}
				else {
					// missing both
					String message = XMLUIMessages.ReconcileStepForMarkup_1;
					addAttributeError(message, attrValueText, structuredDocumentRegion.getStartOffset(r), attrValueText.trim().length(), ProblemIDsXML.AttrValueNotQuoted, structuredDocumentRegion, reporter);
					errorCount++;
				}
			}
			else if (size == 2) {
				if ((one.equals(SQUOTE) && !two.equals(SQUOTE)) || (one.equals(DQUOTE) && !two.equals(DQUOTE))) {
					// missing closing quote
					String message = XMLUIMessages.ReconcileStepForMarkup_0;
					addAttributeError(message, attrValueText, structuredDocumentRegion.getStartOffset(r), attrValueText.trim().length(), ProblemIDsXML.Unclassified, structuredDocumentRegion, reporter);
					errorCount++;
				}
			}
		}
		// end of region for loop
	}

	private void checkStartEndTagPairs(IStructuredDocumentRegion sdRegion, IReporter reporter) {

		if (sdRegion.isDeleted()) {
			return;
		}

		// check start/end tag pairs
		IDOMNode xmlNode = getXMLNode(sdRegion);

		if (xmlNode == null) {
			return;
		}

		boolean selfClosed = false;
		String tagName = null;
		int length = 0;

		if (xmlNode.isContainer()) {
			IStructuredDocumentRegion endRegion = xmlNode.getEndStructuredDocumentRegion();
			if (endRegion == null) {
				IStructuredDocumentRegion startRegion = xmlNode.getStartStructuredDocumentRegion();
				if (!startRegion.isDeleted()) {
					// analyze the tag (check self closing)
					ITextRegionList regions = startRegion.getRegions();
					ITextRegion r = null;
					for (int i = 0; i < regions.size(); i++) {
						r = regions.get(i);
						if ((r.getType() == DOMRegionContext.XML_TAG_OPEN) || (r.getType() == DOMRegionContext.XML_TAG_CLOSE)) {
							length++;
						}
						else if (r.getType() == DOMRegionContext.XML_TAG_NAME) {
							tagName = sdRegion.getText(r);
							length += tagName.length();
						}
						else if (r.getType() == DOMRegionContext.XML_EMPTY_TAG_CLOSE) {
							selfClosed = true;
						}
					}

					if (!selfClosed && (tagName != null)) {
						Object[] args = {tagName};
						String messageText = NLS.bind(XMLUIMessages.Missing_end_tag_, args);

						int start = sdRegion.getStart();
						int lineNumber = getLineNumber(start);

						// SEVERITY_STRUCTURE == IMessage.HIGH_SEVERITY
						IMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
						message.setOffset(start);
						message.setLength(length);
						message.setLineNo(lineNumber);

						if (reporter instanceof IncrementalReporter) {

							Object[] additionalFixInfo = getStartEndFixInfo(xmlNode, tagName, r);

							AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.MissingEndTag, additionalFixInfo);
							// annotation.setAdditionalFixInfo(additionalFixInfo);
							((IncrementalReporter) reporter).addAnnotationInfo(this, info);
						}
						else {
							reporter.addMessage(this, message);
						}
					}
				}
			}

		}
	}

	private Object[] getStartEndFixInfo(IDOMNode xmlNode, String tagName, ITextRegion r) {
		// quick fix info
		String tagClose = "/>"; //$NON-NLS-1$
		int tagCloseOffset = xmlNode.getFirstStructuredDocumentRegion().getEndOffset();
		if ((r != null) && (r.getType() == DOMRegionContext.XML_TAG_CLOSE)) {
			tagClose = "/"; //$NON-NLS-1$
			tagCloseOffset--;
		}
		IDOMNode firstChild = (IDOMNode) xmlNode.getFirstChild();
		while ((firstChild != null) && (firstChild.getNodeType() == Node.TEXT_NODE)) {
			firstChild = (IDOMNode) firstChild.getNextSibling();
		}
		int endOffset = xmlNode.getEndOffset();
		int firstChildStartOffset = firstChild == null ? endOffset : firstChild.getStartOffset();
		Object[] additionalFixInfo = {tagName, tagClose, new Integer(tagCloseOffset), new Integer(xmlNode.getFirstStructuredDocumentRegion().getEndOffset()), // startTagEndOffset
					new Integer(firstChildStartOffset), // firstChildStartOffset
					new Integer(endOffset)}; // endOffset
		return additionalFixInfo;
	}

	private void checkStartingSpaceForPI(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {

		if (structuredDocumentRegion.isDeleted()) {
			return;
		}

		IStructuredDocumentRegion prev = structuredDocumentRegion.getPrevious();
		if ((prev != null) && !prev.isDeleted()) {
			String prevText = prev.getFullText();
			if ((prev.getType() == DOMRegionContext.XML_CONTENT) && prevText.endsWith(" ")) { //$NON-NLS-1$
				String messageText = XMLUIMessages.ReconcileStepForMarkup_5;
				int start = prev.getStartOffset();
				int length = prev.getLength();

				LocalizedMessage message = new LocalizedMessage(IMessage.HIGH_SEVERITY, messageText);
				message.setOffset(start);
				message.setLength(length);
				message.setLineNo(getLineNumber(start));

				AnnotationInfo info = new AnnotationInfo(message, ProblemIDsXML.SpacesBeforePI, null);
				((IncrementalReporter) reporter).addAnnotationInfo(this, info);

				// Position p = new Position(start, length);
				//				
				// ReconcileAnnotationKey key =
				// createKey(structuredDocumentRegion, getScope());
				// TemporaryAnnotation annotation = new TemporaryAnnotation(p,
				// SEVERITY_SYNTAX_ERROR, message, key,
				// ProblemIDsXML.SpacesBeforePI);
				// results.add(annotation);
			}
		}
	}

	public int getScope() {
		return ReconcileAnnotationKey.PARTIAL;
	}

	private IDOMNode getXMLNode(IStructuredDocumentRegion sdRegion) {

		if (sdRegion == null) {
			return null;
		}

		IStructuredModel xModel = null;
		IDOMNode xmlNode = null;
		// get/release models should always be in a try/finally block
		try {
			xModel = StructuredModelManager.getModelManager().getExistingModelForRead(getDocument());
			// xModel is sometime null, when closing editor, for example
			if (xModel != null) {
				xmlNode = (IDOMNode) xModel.getIndexedRegion(sdRegion.getStart());
			}
		}
		finally {
			if (xModel != null) {
				xModel.releaseFromRead();
			}
		}
		return xmlNode;
	}

	/**
	 * Determines whether the IStructuredDocumentRegion is a XML "end tag"
	 * since they're not allowed to have attribute ITextRegions
	 * 
	 * @param structuredDocumentRegion
	 */
	private boolean isEndTag(IStructuredDocumentRegion structuredDocumentRegion) {
		if ((structuredDocumentRegion == null) || structuredDocumentRegion.isDeleted()) {
			return false;
		}
		return structuredDocumentRegion.getFirstRegion().getType() == DOMRegionContext.XML_END_TAG_OPEN;
	}

	/**
	 * Determines if the IStructuredDocumentRegion is an XML Processing
	 * Instruction
	 * 
	 * @param structuredDocumentRegion
	 * 
	 */
	private boolean isPI(IStructuredDocumentRegion structuredDocumentRegion) {
		if ((structuredDocumentRegion == null) || structuredDocumentRegion.isDeleted()) {
			return false;
		}
		return structuredDocumentRegion.getFirstRegion().getType() == DOMRegionContext.XML_PI_OPEN;
	}

	/**
	 * Determines whether the IStructuredDocumentRegion is a XML "start tag"
	 * since they need to be checked for proper XML attribute region sequences
	 * 
	 * @param structuredDocumentRegion
	 * 
	 */
	private boolean isStartTag(IStructuredDocumentRegion structuredDocumentRegion) {
		if ((structuredDocumentRegion == null) || structuredDocumentRegion.isDeleted()) {
			return false;
		}
		return structuredDocumentRegion.getFirstRegion().getType() == DOMRegionContext.XML_TAG_OPEN;
	}

	// Because we check the "proper" closing separately from attribute
	// sequencing, we need to know what's
	// an appropriate close.
	private boolean isTagCloseTextRegion(ITextRegion textRegion) {
		return (textRegion.getType() == DOMRegionContext.XML_TAG_CLOSE) || (textRegion.getType() == DOMRegionContext.XML_EMPTY_TAG_CLOSE);
	}

	/**
	 * Determines if the IStructuredDocumentRegion is XML Content
	 * 
	 * @param structuredDocumentRegion
	 * 
	 */
	private boolean isXMLContent(IStructuredDocumentRegion structuredDocumentRegion) {
		if ((structuredDocumentRegion == null) || structuredDocumentRegion.isDeleted()) {
			return false;
		}
		return structuredDocumentRegion.getFirstRegion().getType() == DOMRegionContext.XML_CONTENT;
	}

	private void setDocument(IDocument doc) {
		fDocument = doc;
	}

	private IDocument getDocument() {
		return fDocument;
	}

	public void connect(IDocument document) {
		setDocument(document);
	}

	public void disconnect(IDocument document) {
		setDocument(null);
	}

	public void validate(IRegion dirtyRegion, IValidationContext helper, IReporter reporter) {
		if (getDocument() == null) {
			return;
		}
		if (!(reporter instanceof IncrementalReporter)) {
			return;
		}
		if (!(getDocument() instanceof IStructuredDocument)) {
			return;
		}

		// remove old messages
		reporter.removeAllMessages(this);

		IStructuredDocumentRegion[] regions = ((IStructuredDocument) fDocument).getStructuredDocumentRegions(dirtyRegion.getOffset(), dirtyRegion.getLength());
		for (int i = 0; i < regions.length; i++) {
			validate(regions[i], reporter);
		}
	}

	public void validate(IStructuredDocumentRegion structuredDocumentRegion, IReporter reporter) {

		if (structuredDocumentRegion == null) {
			return;
		}

		if (isStartTag(structuredDocumentRegion)) {
			// check for attributes without a value
			checkForAttributeValue(structuredDocumentRegion, reporter);
			// check if started tag is ended
			checkStartEndTagPairs(structuredDocumentRegion, reporter);
			// check empty tag <>
			checkEmptyTag(structuredDocumentRegion, reporter);
			// check that each attribute has quotes
			checkQuotesForAttributeValues(structuredDocumentRegion, reporter);
			// check that the closing '>' is there
			checkClosingBracket(structuredDocumentRegion, reporter);
		}
		else if (isEndTag(structuredDocumentRegion)) {
			checkAttributesInEndTag(structuredDocumentRegion, reporter);
			// check that the closing '>' is there
			checkClosingBracket(structuredDocumentRegion, reporter);
		}
		else if (isPI(structuredDocumentRegion)) {
			// check validity of processing instruction
			checkStartingSpaceForPI(structuredDocumentRegion, reporter);
			checkNoNamespaceInPI(structuredDocumentRegion, reporter);
		}
		else if (isXMLContent(structuredDocumentRegion)) {
			checkForSpaceBeforeName(structuredDocumentRegion, reporter);
		}
	}

	public void cleanup(IReporter reporter) {
		// TODO Auto-generated method stub

	}

	public void validate(IValidationContext helper, IReporter reporter) throws ValidationException {
		// TODO Auto-generated method stub

	}
}