/*
 * #%L
 * ImageJ software for multidimensional image processing and analysis.
 * %%
 * Copyright (C) 2009 - 2013 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 * Institute of Molecular Cell Biology and Genetics.
 * %%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * The views and conclusions contained in the software and documentation are
 * those of the authors and should not be interpreted as representing official
 * policies, either expressed or implied, of any organization.
 * #L%
 */

package org.scijava.plugin;

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

import org.scijava.log.LogService;
import org.scijava.object.LazyObjects;
import org.scijava.object.ObjectService;

/**
 * Abstract base class for {@link SingletonService}s.
 * 
 * @author Curtis Rueden
 * @param <PT> Plugin type of the {@link SingletonPlugin}s being managed.
 */
public abstract class AbstractSingletonService<PT extends SingletonPlugin>
	extends AbstractPTService<PT> implements SingletonService<PT>
{

	@Parameter
	private LogService log;

	@Parameter
	private ObjectService objectService;

	// TODO: Listen for PluginsAddedEvent and PluginsRemovedEvent
	// and update the list of singletons accordingly.

	/** List of singleton plugin instances. */
	private List<PT> instances;

	// -- SingletonService methods --

	@Override
	public List<PT> getInstances() {
		if (instances == null) {
			createInstances();
		}
		return instances;
	}

	@Override
	public <P extends PT> P getInstance(final Class<P> pluginClass) {
		final List<P> objects = objectService.getObjects(pluginClass);
		return objects == null || objects.isEmpty() ? null : objects.get(0);
	}

	// -- Service methods --

	@Override
	public void initialize() {
		// add singleton instances to the object index... IN THE FUTURE!
		objectService.getIndex().addLater(new LazyObjects<Object>() {

			@Override
			public ArrayList<Object> get() {
				return new ArrayList<Object>(getInstances());
			}
		});
	}

	// -- Helper methods --

	private void createInstances() {
		instances =
			Collections.unmodifiableList(getPluginService().createInstancesOfType(
				getPluginType()));

		log.info("Found " + instances.size() + " " +
			getPluginType().getSimpleName() + " plugins.");

		// register singleton instances with the object service
		for (final PT instance : instances) {
			objectService.addObject(instance);
		}
	}

}

@@ -3424,16 +3424,32 @@
 bleList(
+filterInstances(
 getPlugi
@@ -3458,16 +3458,21 @@
 ervice()
+%0A%09%09%09%09
 .createI
@@ -3486,21 +3486,16 @@
 sOfType(
-%0A%09%09%09%09
 getPlugi
@@ -3503,16 +3503,17 @@
 Type()))
+)
 ;%0A%0A%09%09log
@@ -3746,14 +3746,14 @@
 e);%0A
-
 %09%09%7D%0A%09%7D%0A%0A
 %7D%0A
@@ -3750,10 +3750,240 @@
 %09%09%7D%0A%09%7D%0A%0A
+%09/**%0A%09 * Allows subclasses to exclude instances.%0A%09 * %0A%09 * @param list the initial list of instances%0A%09 * @return the filtered list of instances%0A%09 */%0A%09protected List%3C? extends PT%3E filterInstances(List%3CPT%3E list) %7B%0A%09%09return list;%0A%09%7D%0A%0A
 %7D%0A

Allow filtering instances before they become singletons