/*******************************************************************************
 * 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.typing;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.link.ILinkedModeListener;
import org.eclipse.jface.text.link.LinkedModeModel;
import org.eclipse.jface.text.link.LinkedModeUI;
import org.eclipse.jface.text.link.LinkedPosition;
import org.eclipse.jface.text.link.LinkedPositionGroup;
import org.eclipse.jface.text.link.LinkedModeUI.ExitFlags;
import org.eclipse.jface.text.link.LinkedModeUI.IExitPolicy;
import org.eclipse.jface.text.source.ISourceViewer;
import org.eclipse.swt.events.VerifyEvent;
import org.eclipse.swt.graphics.Point;
import org.eclipse.wst.sse.ui.internal.Logger;

abstract public class AbstractCharacterPairInserter {

	class ExitPolicy implements IExitPolicy {

		private char fExit;
		private char fEscape;
		private IDocument fDocument;

		public ExitPolicy(char exit, char escape, IDocument document) {
			fExit = exit;
			fEscape = escape;
			fDocument = document;
		}

		public ExitFlags doExit(LinkedModeModel model, VerifyEvent event, int offset, int length) {
			if(!isMasked(offset)) {
				if (event.character == fExit)
					return new ExitFlags(ILinkedModeListener.UPDATE_CARET, false);
			}
			return null;
		}

		private boolean isMasked(int offset) {
			try {
				return fEscape == fDocument.getChar(offset - 1);
			} catch (BadLocationException e) {
			}
			return false;
		}
	}

	/**
	 * Pair the character <code>c</code> in the source viewer <code>viewer</code>.
	 * Positions are linked before and after the inserted character.
	 * 
	 * @param viewer the source viewer to add the linked mode to
	 * @param c the character to pair with
	 * @return true if the character was successfully paired; false otherwise
	 */
	public boolean pair(final ISourceViewer viewer, final char c) {
		if (!shouldPair(viewer, c))
			return false;

		final char mc = getPair(c);
		final char[] chars = new char[2];
		chars[0] = c;
		chars[1] = mc;

		IDocument document = viewer.getDocument();

		final Point selection= viewer.getSelectedRange();
		final int offset= selection.x;
		final int length= selection.y;

		boolean paired = false;
		try {
			document.replace(offset, length, new String(chars));
			LinkedModeModel model = new LinkedModeModel();
			LinkedPositionGroup group = new LinkedPositionGroup();
			group.addPosition(new LinkedPosition(document, offset + 1, 0, LinkedPositionGroup.NO_STOP));
			model.addGroup(group);
			model.forceInstall();

			LinkedModeUI ui = new LinkedModeUI(model, viewer);
			ui.setCyclingMode(LinkedModeUI.CYCLE_NEVER);
			ui.setExitPosition(viewer, offset + 2, 0, Integer.MAX_VALUE);
			ui.setExitPolicy(new ExitPolicy(mc, getEscapeChar(c), document));
			ui.setSimpleMode(true);
			ui.enter();

			paired = true;
		} catch (BadLocationException e) {
			Logger.logException(e);
		}
		return paired;
	}

	/**
	 * Hook to evaluate if the character should be paired. Clients may override
	 * to evaluate the case.
	 * @param viewer the source viewer where the character would be paired
	 * @param c the character to pair
	 * @return true if the character should have its pair character inserted; false otherwise
	 */
	protected boolean shouldPair(ISourceViewer viewer, char c) {
		return true;
	}

	/**
	 * Can the character be paired by the inserter
	 * @param c the character of interest
	 * @return true if the character can be paired by the inserter; false otherwise
	 */
	abstract public boolean hasPair(char c);

	/**
	 * Get the paired character for <code>c</code>
	 * @param c the character to find the pair of
	 * @return the pair character
	 */
	abstract protected char getPair(char c);

	/**
	 * Gets the escape character for <code>c</code> in case <code>c</code> is to be used
	 * within the paired characters
	 * @param c the character to find the escape character of
	 * @return the escape character
	 */
	protected char getEscapeChar(char c) {
		return 0;
	}

	public void initialize() {
	}

	public void dispose() {
	}
}