/*
 * Copyright (c) 2003-2004 Christopher Lenz and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     Christopher Lenz - initial API and implementation
 * 
 * $Id: CssDoubleClickStrategy.java,v 1.1 2004-09-02 18:11:48 jsurfer Exp $
 */

package net.sourceforge.phpeclipse.css.ui.internal.text;

import net.sourceforge.phpeclipse.css.core.internal.text.CssTextUtils;
import net.sourceforge.phpeclipse.css.ui.CssUI;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ITextDoubleClickStrategy;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.source.ICharacterPairMatcher;
import org.eclipse.jface.util.Assert;

/**
 * Strategy for selecting CSS identifiers on double click in the editor.
 * 
 * This strategy implements selection of CSS identifiers on double click inside
 * an identifier, as well as selection of blocks delimited by square brackets,
 * curly braces and parenthesis when the user double clicks directly after
 * either the opening or the closing delimiter.
 */
public class CssDoubleClickStrategy implements ITextDoubleClickStrategy {

	// Instance Variables ------------------------------------------------------

	/**
	 * The pair matcher used to select ranges delimited by matching pairs of
	 * braces, brackets and parenthesis.
	 */
	private ICharacterPairMatcher pairMatcher = new CssPairMatcher();

	// ITextDoubleClickStrategy Implementation ---------------------------------

	/*
	 * @see ITextDoubleClickStrategy#doubleClicked(ITextViewer)
	 */
	public void doubleClicked(ITextViewer viewer) {
		IDocument document = viewer.getDocument();
		if (document.getLength() == 0) {
			return;   
		}
		int offset = viewer.getSelectedRange().x;
		Assert.isLegal(offset >= 0,
			"Double click offset may not be negative"); //$NON-NLS-1$
		Assert.isLegal(offset <= document.getLength(),
			"Double click offset out of range"); //$NON-NLS-1$
		IRegion region = pairMatcher.match(document, offset);
		if ((region != null) && (region.getLength() >= 2)) {
			viewer.setSelectedRange(region.getOffset() + 1,
				region.getLength() - 2);
		} else {
			try {
				region = getSurroundingIdentifier(document, offset);
				if (region != null) {
					viewer.setSelectedRange(
						region.getOffset(), region.getLength());
				}
			} catch (BadLocationException e) {
				CssUI.log("Failed to get surrounding " + //$NON-NLS-1$
					"word for double click selection"); //$NON-NLS-1$
			}
		}
	}

	// Private Methods ---------------------------------------------------------

	/**
	 * Returns the region that delimits the identifier surrounding the given
	 * offset into the document. If no identifier is found at the specified
	 * offset, this method returns <code>null</code>.
	 * 
	 * @param doc the document
	 * @param offset the zero-based offset into the document
	 * @return the region covered by the identifier, or <code>null</code> if no
	 *         identifier was found at that offset
	 */
	private IRegion getSurroundingIdentifier(IDocument doc, int offset)
		throws BadLocationException {
		IRegion retVal = null;
		int length = doc.getLength();
		offset = Math.min(offset, length - 1);
		if (CssTextUtils.isCssIdentifierPart(doc.getChar(offset))) {
			int start = offset;
			while (start > 0) {
				if (!CssTextUtils.isCssIdentifierPart(doc.getChar(start - 1))) {
					break;
				}
				start--;
			}
			int end = offset;
			while (end < (length - 1)) {
				if (!CssTextUtils.isCssIdentifierPart(doc.getChar(end + 1))) {
					break;
				}
				end++;
			}
			retVal = new Region(start, end - start + 1);
		}
		return retVal;
	}

}