org.eclipse.emf.emfstore.server.model.edit/src/org/eclipse/emf/emfstore/server/model/provider/CustomOperationLabelProviderManager.java

/*******************************************************************************
 * Copyright 2011 Chair for Applied Software Engineering,
 * Technische Universitaet Muenchen.
 * All rights reserved. This program and the accompanying materials
 * are made available under the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 ******************************************************************************/
package org.eclipse.emf.emfstore.server.model.provider;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.emf.emfstore.common.IDisposable;
import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionElement;
import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionPoint;
import org.eclipse.emf.emfstore.common.extensionpoint.ExtensionPointException;
import org.eclipse.emf.emfstore.common.model.util.ModelUtil;
import org.eclipse.emf.emfstore.server.model.versioning.operations.AbstractOperation;

/**
 * Class for managing customLabelProvider for specified operations.
 * 
 * @author Michael Kagel
 * @author emueller
 */
public final class CustomOperationLabelProviderManager implements IDisposable {

	/**
	 * Initializes the singleton instance statically.
	 */
	private static class SingletonHolder {
		public static final CustomOperationLabelProviderManager INSTANCE = new CustomOperationLabelProviderManager();
	}

	/**
	 * Returns the singleton instance.
	 * 
	 * @return The DragSourcePlaceHolder instance
	 */
	public static CustomOperationLabelProviderManager getInstance() {
		return SingletonHolder.INSTANCE;
	}

	private List<AbstractOperationCustomLabelProvider> list;

	/**
	 * Constructor.
	 */
	private CustomOperationLabelProviderManager() {
		list = new ArrayList<AbstractOperationCustomLabelProvider>();
		collectExtensions();
	}

	/**
	 * Provides a customLabelProvider for a specified operation.
	 * 
	 * @param operation
	 *            for which the method should provide a customLabelProvider.
	 * @return The customLabelProvider for the given operation or null if there
	 *         is no customLabelProvider.
	 */
	public AbstractOperationCustomLabelProvider getCustomLabelProvider(
			AbstractOperation operation) {

		AbstractOperationCustomLabelProvider highestVisualizer = null;

		int highestNumber = 0;
		int currentRenderState = 0;

		for (AbstractOperationCustomLabelProvider changePackageVisualizer : list) {
			currentRenderState = changePackageVisualizer.canRender(operation);
			// Take the highest provider
			if (currentRenderState > highestNumber) {
				highestNumber = currentRenderState;
				highestVisualizer = changePackageVisualizer;
			}
		}

		return highestVisualizer;
	}

	private void collectExtensions() {
		for (ExtensionElement element : new ExtensionPoint(
				"org.eclipse.emf.emfstore.server.model.edit.customOperationLabelProvider",
				true).getExtensionElements()) {
			try {
				AbstractOperationCustomLabelProvider provider = element
						.getClass("class",
								AbstractOperationCustomLabelProvider.class);
				list.add(provider);
			} catch (ExtensionPointException e) {
				ModelUtil
						.logException(
								"Exception occured while initializing custom label provider extensions!",
								e);
			}
		}
	}

	/**
	 * 
	 * {@inheritDoc}
	 * 
	 * @see org.eclipse.emf.emfstore.common.IDisposable#dispose()
	 */
	public void dispose() {
		list = null;
	}
}