ParticipantExtensionPoint.java

/*******************************************************************************
 * Copyright (c) 2000, 2008 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.ltk.core.refactoring.participants;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import org.eclipse.core.expressions.EvaluationContext;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Platform;

import org.eclipse.ltk.core.refactoring.RefactoringStatus;
import org.eclipse.ltk.internal.core.refactoring.Messages;
import org.eclipse.ltk.internal.core.refactoring.ParticipantDescriptor;
import org.eclipse.ltk.internal.core.refactoring.RefactoringCoreMessages;
import org.eclipse.ltk.internal.core.refactoring.RefactoringCorePlugin;

/**
 * A {@link ParticipantExtensionPoint} is used to manage contributions of participants.
 *
 * <p>
 * This class is not intended to be subclassed by clients.
 * </p>
 *
 * @since 3.4
 *
 * @noextend This class is not intended to be subclassed by clients.
 */
public class ParticipantExtensionPoint {

	private String fParticipantID;
	private List fParticipants;
	private Class fParticipantClass;
	private String fPluginId;

	/**
	 * Creates a {@link ParticipantExtensionPoint}.
	 *
	 * @param pluginId the ID of the plug-in defining the extension point
	 * @param participantId the name of the extension point
	 * @param clazz the type of the class that contributors must provide
	 */
	public ParticipantExtensionPoint(String pluginId, String participantId, Class clazz) {
		Assert.isNotNull(participantId);
		fParticipantID= participantId;
		fParticipantClass= clazz;
		fPluginId= pluginId;
	}

	/**
	 * Returns all participants for a given element.
	 *
	 * @param status a refactoring status to report status if problems occurred while
	 *  loading the participants
	 * @param processor the processor that will own the participants
	 * @param element the element to be copied or a corresponding descriptor
	 * @param arguments the arguments for the participants
	 * @param filter a participant filter to exclude certain participants, or <code>null</code>
	 *  if no filtering is desired
	 * @param affectedNatures an array of project natures affected by the refactoring
	 * @param shared a list of shared participants
	 *
	 * @return an array of participants
	 */
	public RefactoringParticipant[] getParticipants(RefactoringStatus status, RefactoringProcessor processor, Object element, RefactoringArguments arguments, IParticipantDescriptorFilter filter, String[] affectedNatures, SharableParticipants shared) {
		if (fParticipants == null)
			init();

		EvaluationContext evalContext= createEvaluationContext(processor, element, affectedNatures);
		List result= new ArrayList();
		for (Iterator iter= fParticipants.iterator(); iter.hasNext();) {
			ParticipantDescriptor descriptor= (ParticipantDescriptor)iter.next();
			if (!descriptor.isEnabled()) {
				iter.remove();
			} else {
				try {
					RefactoringStatus filterStatus= new RefactoringStatus();
					if (descriptor.matches(evalContext, filter, filterStatus)) {
						RefactoringParticipant participant= shared.get(descriptor);
						if (participant != null) {
							((ISharableParticipant)participant).addElement(element, arguments);
						} else {
							participant= descriptor.createParticipant();
							if (fParticipantClass.isInstance(participant)) {
								if (participant.initialize(processor, element, arguments)) {
									participant.setDescriptor(descriptor);
									result.add(participant);
									if (participant instanceof ISharableParticipant)
										shared.put(descriptor, participant);
								}
							} else {
								status.addError(Messages.format(
									RefactoringCoreMessages.ParticipantExtensionPoint_participant_removed,
									descriptor.getName()));
								RefactoringCorePlugin.logErrorMessage(
									Messages.format(
										RefactoringCoreMessages.ParticipantExtensionPoint_wrong_type,
										new String[] {descriptor.getName(), fParticipantClass.getName()}));
								iter.remove();
							}
						}
					} else {
						status.merge(filterStatus);
					}
				} catch (CoreException e) {
					logMalfunctioningParticipant(status, descriptor, e);
					iter.remove();
				} catch (RuntimeException e) {
					logMalfunctioningParticipant(status, descriptor, e);
					iter.remove();
				}
			}
		}

		return (RefactoringParticipant[])result.toArray(new RefactoringParticipant[result.size()]);
	}

	private void logMalfunctioningParticipant(RefactoringStatus status, ParticipantDescriptor descriptor, Throwable e) {
		status.addError(Messages.format(
			RefactoringCoreMessages.ParticipantExtensionPoint_participant_removed,
			descriptor.getName()));
		RefactoringCorePlugin.logRemovedParticipant(descriptor, e);
	}

	private void init() {
		IExtensionRegistry registry= Platform.getExtensionRegistry();
		IConfigurationElement[] ces= registry.getConfigurationElementsFor(fPluginId, fParticipantID);
		fParticipants= new ArrayList(ces.length);
		for (int i= 0; i < ces.length; i++) {
			ParticipantDescriptor descriptor= new ParticipantDescriptor(ces[i]);
			IStatus status= descriptor.checkSyntax();
			switch (status.getSeverity()) {
				case IStatus.ERROR:
					RefactoringCorePlugin.log(status);
					break;
				case IStatus.WARNING:
				case IStatus.INFO:
					RefactoringCorePlugin.log(status);
					fParticipants.add(descriptor);
					break;
				default:
					fParticipants.add(descriptor);
			}
		}
	}

	//---- Helper methods ------------------------------------------------------------------

	private static EvaluationContext createEvaluationContext(RefactoringProcessor processor, Object element, String[] affectedNatures) {
		EvaluationContext result= new EvaluationContext(null, element);
		result.addVariable("element", element); //$NON-NLS-1$
		result.addVariable("affectedNatures", Arrays.asList(affectedNatures)); //$NON-NLS-1$
		result.addVariable("processorIdentifier", processor.getIdentifier()); //$NON-NLS-1$
		return result;
	}
}