/*******************************************************************************
 * Copyright (c) 2009 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.wst.sse.ui.internal.projection;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.source.projection.IProjectionPosition;

/**
 * Represents a single folding position in an <code>IStructuredDocument</code>
 */
public abstract class AbstractStructuredFoldingPosition extends Position implements IProjectionPosition {
	
	/**
	 * Default constructor
	 * 
	 * @param offset the offset of the folding position
	 * @param length the length of the folidng position
	 */
	public AbstractStructuredFoldingPosition(int offset, int length) {
		super(offset, length);
	}
	
	/**
	 * @see org.eclipse.jface.text.source.projection.IProjectionPosition#computeCaptionOffset(org.eclipse.jface.text.IDocument)
	 */
	public int computeCaptionOffset(IDocument document) throws BadLocationException {
		
		return 0;
	}
	
	/**
	 * @see org.eclipse.jface.text.source.projection.IProjectionPosition#computeProjectionRegions(org.eclipse.jface.text.IDocument)
	 */
	public IRegion[] computeProjectionRegions(IDocument document) throws BadLocationException {
		
		int startLineNum = document.getLineOfOffset(getStartOffset()) + 1;
		IRegion startLine = document.getLineInformation(startLineNum);
		int endLineNum = document.getLineOfOffset(getEndOffset()) + 1;
		IRegion endLine = document.getLineInformation(endLineNum);
		
		int foldOffset;			
		int foldEndOffset;
		
		synchronized (this) {
			foldOffset = startLine.getOffset();
			if(foldOffset < offset) {
				offset = foldOffset;
			}
		
			foldEndOffset = endLine.getOffset();
		
			if((foldEndOffset-offset) > length) {
				length = foldEndOffset-offset;
			}
		}
		
		return new IRegion[] {new Region(foldOffset, foldEndOffset-foldOffset)};
	}
	
	/**
	 * @return the start offset of the folding position
	 */
	protected abstract int getStartOffset();
	
	/**
	 * @return the end offset of the folding position
	 */
	protected abstract int getEndOffset();
}