/*
 * 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: CssPairMatcher.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 org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.source.ICharacterPairMatcher;
import org.eclipse.jface.util.Assert;

/**
 * 
 */
public class CssPairMatcher implements ICharacterPairMatcher {

	// Constants ---------------------------------------------------------------

	private static final char PAIRS[] = {
		'{', '}', '(', ')', '[', ']'
	};

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

	private IDocument document;

	private int offset;

	private int anchor;

	// ICharacterPairMatcher Implementation ------------------------------------

	/*
	 * @see ICharacterPairMatcher#clear
	 */
	public void clear() {
		document = null;
		offset = -1;
		anchor = 0;
	}

	/*
	 * @see ICharacterPairMatcher#dispose
	 */
	public void dispose() {
		document = null;
	}

	/*
	 * @see ICharacterPairMatcher#match
	 */
	public IRegion match(IDocument document, int offset) {
		Assert.isNotNull(document);
		Assert.isLegal(offset >= 0);
		this.document = document;
		this.offset = offset;

		IRegion retVal = null;
		try {
			retVal = matchPairsAt();
		} catch (BadLocationException e) {
			// ignore, there's probably no matching character to highlight
		}
		return retVal;
	}

	/*
	 * @see ICharacterPairMatcher#getAnchor
	 */
	public int getAnchor() {
		return anchor;
	}

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

	private boolean isClosingCharacter(char ch) {
		for (int i = 1; i < PAIRS.length; i += 2) {
			if (ch == PAIRS[i]) {
				return true;
			}
		}
		return false;
	}

	private boolean isOpeningCharacter(char ch) {
		for (int i = 0; i < PAIRS.length; i += 2) {
			if (ch == PAIRS[i]) {
				return true;
			}
		}
		return false;
	}

	private IRegion matchPairsAt() throws BadLocationException {
		int startPos = -1, endPos = -1;
		char prevChar = document.getChar(Math.max(offset - 1, 0));
		if (isOpeningCharacter(prevChar)) {
			startPos = offset - 1;
			if (startPos >= 0) {
				anchor = LEFT;
				endPos = CssTextUtils.findMatchingClosingPeer(
					document, startPos + 1, prevChar);
				if (endPos > -1) {
					return new Region(startPos, endPos - startPos + 1);
				}
			}
		}
		if (isClosingCharacter(prevChar)) {
			endPos = offset - 1;
			if (endPos >= 0) {
				anchor = RIGHT;
				startPos = CssTextUtils.findMatchingOpeningPeer(
					document, endPos - 1, prevChar);
				if (startPos > -1) {
					return new Region(startPos, endPos - startPos + 1);
				}
			}
		} 
		return null;
	}

}