/*
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 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2017 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, Max Planck
 * Institute of Molecular Cell Biology and Genetics, University of
 * Konstanz, and KNIME GmbH.
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 *    this list of conditions and the following disclaimer.
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package org.scijava.plugin;

import java.util.List;

import org.scijava.service.Service;

/**
 * A service for managing a particular sort of {@link SciJavaPlugin}.
 * <p>
 * There are many kinds of services, but most of them share one common
 * characteristic: they provide API specific to a particular type of plugin. A
 * few examples:
 * </p>
 * <ul>
 * <li>The {@link org.scijava.command.CommandService} works with
 * {@link org.scijava.command.Command}s.</li>
 * <li>The {@link org.scijava.text.TextService} works with
 * {@link org.scijava.text.TextFormat}s.</li>
 * <li>The {@link org.scijava.platform.PlatformService} works with
 * {@link org.scijava.platform.Platform}s.</li>
 * </ul>
 * <p>
 * Most services fit this pattern in one way or another. When you wish to
 * provide a new extensibility point, you create a new type of
 * {@link SciJavaPlugin}, and a corresponding {@link PTService} for working with
 * it. Depending on the nature of your new plugin type, this service might be:
 * </p>
 * <ul>
 * <li>A {@link SingletonService}, such as
 * {@link org.scijava.platform.PlatformService}, which manages
 * {@link SingletonPlugin}s.</li>
 * <li>A {@link HandlerService}, such as {@link org.scijava.text.TextService},
 * which manages {@link HandlerPlugin}s.</li>
 * <li>A {@link WrapperService}, such as
 * {@link org.scijava.widget.WidgetService}, which manages
 * {@link WrapperPlugin}s.</li>
 * </ul>
 * <p>
 * It is named {@code PTService} rather than {@code PluginTypeService} or
 * similar to avoid confusion with A) the {@link PluginService} itself, and B)
 * any other service interface intended to define the API of a concrete service.
 * In contrast to such services, the {@code PTService} is a more general layer
 * in a type hierarchy intended to ease creation of services that fit its
 * pattern.
 * </p>
 * 
 * @author Curtis Rueden
 * @param <PT> Plugin type of the plugins being managed.
 * @see SingletonService
 * @see TypedService
 * @see WrapperService
 */
public interface PTService<PT extends SciJavaPlugin> extends Service {

	/**
	 * Gets the service responsible for discovering and managing this service's
	 * plugins.
	 */
	default PluginService pluginService() {
		return context().getService(PluginService.class);
	}

	/** Gets the type of plugins managed by this service. */
	Class<PT> getPluginType();

	/** Gets the plugins managed by this service. */
	default List<PluginInfo<PT>> getPlugins() {
		return pluginService().getPluginsOfType(getPluginType());
	}

	/** Creates an instance of the given plugin class. */
	default <P extends PT> P create(final Class<P> pluginClass) {
		final PluginInfo<PT> info =
			pluginService().getPlugin(pluginClass, getPluginType());
		@SuppressWarnings("unchecked")
		final P plugin = (P) pluginService().createInstance(info);
		return plugin;
	}

	// -- Deprecated methods --

	/** @deprecated Use {@link #pluginService()} instead. */
	@Deprecated
	default PluginService getPluginService() {
		return pluginService();
	}
}
