/*******************************************************************************
 * 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 folding position for an XML comment
 */
public abstract class AbstractStructuredCommentFoldingPosition extends Position implements IProjectionPosition {

	/**
	 * Default constructor
	 * 
	 * @param offset the offset of the folding position
	 * @param length the length of the folidng position
	 */
	public AbstractStructuredCommentFoldingPosition(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 findFirstContent(document.get(offset, length));
	}

	/**
	 * @see org.eclipse.jface.text.source.projection.IProjectionPosition#computeProjectionRegions(org.eclipse.jface.text.IDocument)
	 */
	public IRegion[] computeProjectionRegions(IDocument document) throws BadLocationException {
		//get the content of the comment
		String content = document.get(offset, length);
		int contentStart = findFirstContent(content);
		
		//find the start line of the comment
		//find the end line of the comment
		//find the first line of text in the comment
		int startLineNum = document.getLineOfOffset(getStartOffset());
		IRegion startLine = document.getLineInformation(startLineNum);
		int endLineNum = document.getLineOfOffset(getEndOffset()) +1;
		IRegion endLine = document.getLineInformation(endLineNum);
		int captionLineNum = document.getLineOfOffset(getStartOffset() + contentStart);
		
		int foldOffset;			
		int foldEndOffset;
		
		synchronized (this) {
			foldOffset = startLine.getOffset();
			if(foldOffset < offset) {
				offset = foldOffset;
			}
		
			foldEndOffset = endLine.getOffset();
		
			if((foldEndOffset-offset) > length) {
				length = foldEndOffset-offset;
			}
		}
		
		//fold before the first line of text in the comment
		IRegion preRegion = null;
		IRegion postRegion = null;
		if(startLineNum < captionLineNum) {
			IRegion captionLine = document.getLineInformation(captionLineNum);
			preRegion = new Region(foldOffset, captionLine.getOffset()-foldOffset);
		}
		
		//fold after the first line of text in the comment
		if(captionLineNum < endLineNum) {
			int postRegionOffset = document.getLineOffset(captionLineNum+1);
			postRegion = new Region(postRegionOffset, foldEndOffset-postRegionOffset);
		}
		
		IRegion[] regions = null;
		if(preRegion != null && postRegion != null) {
			regions = new IRegion[] {preRegion, postRegion};
		} else if(preRegion != null) {
			regions = new IRegion[] {preRegion};
		} else if(postRegion != null) {
			regions = new IRegion[] {postRegion};
		}
		
		return regions;
	}
	
	/**
	 * Finds the offset of the first identifier part within <code>content</code>.
	 * Returns 0 if none is found.
	 *
	 * @param content the content to search
	 * @param prefixEnd the end of the prefix
	 * @return the first index of a unicode identifier part, or zero if none can
	 *         be found
	 */
	private int findFirstContent(final CharSequence content) {
		int lenght= content.length();
		for (int i= 0; i < lenght; i++) {
			if (Character.isUnicodeIdentifierPart(content.charAt(i)))
				return i;
		}
		return 0;
	}
	
	/**
	 * @return the start offset of the folding position
	 */
	protected abstract int getStartOffset();
	
	/**
	 * @return the end offset of the folding position
	 */
	protected abstract int getEndOffset();

}