/*******************************************************************************
 * Copyright (c) 2000, 2018 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.ui.activities;

import java.util.Set;

/**
 * An instance of this interface is a category as defined by the extension point
 * <code>org.eclipse.ui.activities</code>.
 * <p>
 * An instance of this interface can be obtained from an instance of
 * <code>IActivityManager</code> for any identifier, whether or not a category
 * with that identifier is defined in the extension registry.
 * </p>
 * <p>
 * The handle-based nature of this API allows it to work well with runtime
 * plugin activation and deactivation, which can cause dynamic changes to the
 * extension registry.
 * </p>
 * <p>
 * This interface is not intended to be extended or implemented by clients.
 * </p>
 *
 * @since 3.0
 * @see IActivityManager
 * @noimplement This interface is not intended to be implemented by clients.
 */
public interface ICategory extends Comparable<ICategory> {

	/**
	 * Registers an instance of <code>ICategoryListener</code> to listen for changes
	 * to properties of this instance.
	 *
	 * @param categoryListener the instance to register. Must not be
	 *                         <code>null</code>. If an attempt is made to register
	 *                         an instance which is already registered with this
	 *                         instance, no operation is performed.
	 */
	void addCategoryListener(ICategoryListener categoryListener);

	/**
	 * Returns the set of category activity bindings for this instance.
	 * <p>
	 * This method will return all category activity bindings for this instance,
	 * whether or not this instance is defined.
	 * </p>
	 * <p>
	 * Notification is sent to all registered listeners if this property changes.
	 * </p>
	 *
	 * @return the set of category activity bindings. This set may be empty, but is
	 *         guaranteed not to be <code>null</code>. If this set is not empty, it
	 *         is guaranteed to only contain instances of
	 *         <code>ICategoryActivityBinding</code>.
	 * @see ICategoryActivityBinding
	 */
	Set<ICategoryActivityBinding> getCategoryActivityBindings();

	/**
	 * Returns the identifier of this instance.
	 *
	 * @return the identifier of this instance. Guaranteed not to be
	 *         <code>null</code>.
	 */
	String getId();

	/**
	 * Returns the name of this instance suitable for display to the user.
	 * <p>
	 * Notification is sent to all registered listeners if this property changes.
	 * </p>
	 *
	 * @return the name of this instance. Guaranteed not to be <code>null</code>.
	 * @throws NotDefinedException if this instance is not defined.
	 */
	String getName() throws NotDefinedException;

	/**
	 * Returns the description of this instance suitable for display to the user.
	 * <p>
	 * Notification is sent to all registered listeners if this property changes.
	 * </p>
	 *
	 * @return the description of this instance. Guaranteed not to be
	 *         <code>null</code>.
	 * @throws NotDefinedException if this instance is not defined.
	 */
	String getDescription() throws NotDefinedException;

	/**
	 * Returns whether or not this instance is defined.
	 * <p>
	 * Notification is sent to all registered listeners if this property changes.
	 * </p>
	 *
	 * @return <code>true</code>, iff this instance is defined.
	 */
	boolean isDefined();

	/**
	 * Removes an instance of <code>ICategoryListener</code> listening for changes
	 * to properties of this instance.
	 *
	 * @param categoryListener the instance to remove. Must not be
	 *                         <code>null</code>. If an attempt is made to remove an
	 *                         instance which is not already registered with this
	 *                         instance, no operation is performed.
	 */
	void removeCategoryListener(ICategoryListener categoryListener);
}
