/*******************************************************************************
 * 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;
import org.eclipse.core.expressions.Expression;

/**
 * An instance of this interface is an activity 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 an activity
 * 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. A client may get an <code>IActivity</code> handle that is
 * currently undefined ({@link #isDefined()} equals <code>false</code>) and
 * listen for it to become defined.
 * </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 IActivity extends Comparable<IActivity> {

	/**
	 * Registers an instance of <code>IActivityListener</code> to listen for changes
	 * to properties of this instance.
	 *
	 * @param activityListener 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 addActivityListener(IActivityListener activityListener);

	/**
	 * Returns the set of activity requirement bindings for this instance.
	 * <p>
	 * This method will return all activity requirement 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 activity requirement 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>IActivityRequirementBinding</code>.
	 * @see IActivityRequirementBinding
	 */
	Set<IActivityRequirementBinding> getActivityRequirementBindings();

	/**
	 * Returns the set of activity pattern bindings for this instance.
	 * <p>
	 * This method will return all activity pattern 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 activity pattern 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>IActivityPatternBinding</code>.
	 * @see IActivityPatternBinding
	 */
	Set<IActivityPatternBinding> getActivityPatternBindings();

	/**
	 * 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. A defined activity may have
	 * a name, description and bindings (both pattern and relational).
	 * <p>
	 * Notification is sent to all registered listeners if this property changes.
	 * </p>
	 *
	 * @return <code>true</code>, iff this instance is defined.
	 */
	boolean isDefined();

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

	/**
	 * Returns whether or not this instance should be enabled by default.
	 *
	 * @return <code>true</code>, iff this instance should be enabled by default.
	 * @throws NotDefinedException if this instance is not defined.
	 * @since 3.1
	 */
	boolean isDefaultEnabled() throws NotDefinedException;

	/**
	 * Removes an instance of <code>IActivityListener</code> listening for changes
	 * to properties of this instance.
	 *
	 * @param activityListener 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 removeActivityListener(IActivityListener activityListener);

	/**
	 * Return an expression used to enable and disable this activity. If the
	 * expression is not <code>null</code>, this activity will be entirely
	 * controlled by the expression state.
	 *
	 * @return The core expression, or <code>null</code>
	 * @since 3.4
	 */
	Expression getExpression();
}
