/*******************************************************************************
 * Copyright (c) 2000, 2008 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
 *******************************************************************************/
package org.eclipse.ui.examples.templateeditor.editors;

import org.eclipse.swt.custom.StyleRange;

import org.eclipse.core.runtime.Assert;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ITypedRegion;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.TextAttribute;
import org.eclipse.jface.text.TextPresentation;
import org.eclipse.jface.text.presentation.IPresentationDamager;
import org.eclipse.jface.text.presentation.IPresentationRepairer;

public class NonRuleBasedDamagerRepairer implements IPresentationDamager, IPresentationRepairer {

	/** The document this object works on */
	protected IDocument fDocument;
	/** The default text attribute if non is returned as data by the current token */
	protected TextAttribute fDefaultTextAttribute;

	/**
	 * Creates a new damager/repairer.
	 *
	 * @param defaultTextAttribute the default text attribute for all detected regions
	 */
	public NonRuleBasedDamagerRepairer(TextAttribute defaultTextAttribute) {
		Assert.isNotNull(defaultTextAttribute);
		fDefaultTextAttribute= defaultTextAttribute;
	}

	@Override
	public void setDocument(IDocument document) {
		fDocument= document;
	}

	/**
	 * Returns the end offset of the line that contains the specified offset or
	 * if the offset is inside a line delimiter, the end offset of the next
	 * line.
	 *
	 * @param offset the offset whose line end offset must be computed
	 * @return the line end offset for the given offset
	 * @exception BadLocationException if offset is invalid in the current document
	 */
	protected int endOfLineOf(int offset) throws BadLocationException {

		IRegion info= fDocument.getLineInformationOfOffset(offset);
		if (offset <= info.getOffset() + info.getLength())
			return info.getOffset() + info.getLength();

		int line= fDocument.getLineOfOffset(offset);
		try {
			info= fDocument.getLineInformation(line + 1);
			return info.getOffset() + info.getLength();
		} catch (BadLocationException x) {
			return fDocument.getLength();
		}
	}

	@Override
	public IRegion getDamageRegion(ITypedRegion partition, DocumentEvent event, boolean documentPartitioningChanged) {
		if (!documentPartitioningChanged) {
			try {

				IRegion info= fDocument.getLineInformationOfOffset(event.getOffset());
				int start= Math.max(partition.getOffset(), info.getOffset());
				int end= event.getOffset() + (event.getText() == null ? event.getLength() : event.getText().length());

				if (info.getOffset() <= end && end <= info.getOffset() + info.getLength()) {
					// optimize the case of the same line
					end= info.getOffset() + info.getLength();
				} else
					end= endOfLineOf(end);

				end= Math.min(partition.getOffset() + partition.getLength(), end);
				return new Region(start, end - start);

			} catch (BadLocationException x) {
			}
		}

		return partition;
	}

	@Override
	public void createPresentation(TextPresentation presentation, ITypedRegion region) {
		addRange(presentation, region.getOffset(), region.getLength(), fDefaultTextAttribute);
	}

	/**
	 * Adds style information to the given text presentation.
	 *
	 * @param presentation the text presentation to be extended
	 * @param offset the offset of the range to be styled
	 * @param length the length of the range to be styled
	 * @param attr the attribute describing the style of the range to be styled
	 */
	protected void addRange(TextPresentation presentation, int offset, int length, TextAttribute attr) {
		if (attr != null)
			presentation.addStyleRange(new StyleRange(offset, length, attr.getForeground(), attr.getBackground(), attr.getStyle()));
	}
}