/*=============================================================================#
 # Copyright (c) 2009, 2017 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.rj.servi;

import org.eclipse.core.runtime.CoreException;

import org.eclipse.statet.rj.services.RService;


/**
 * A RServi provides {@link RService R services} as background computing engine without an 
 * interactive R console. An RServi can be for example connected to a server side R engine or 
 * an R engine embedded in the local application.
 * <p>
 * How to receive an RServi instance depends on the application.
 * The RServi framework includes a server side RServi 
 * {@link org.eclipse.statet.rj.servi.node.RServiPool pool}
 * which can be used to provide RServi instances. To get a RServi instance
 * from such a pool which made available via RMI {@link org.eclipse.statet.rj.servi.pool.RServiUtil RServiUtil}
 * provides helper methods to request a RServi instance.</p>
 * <p>
 * In many applications it is sufficient to use an RServi for a direct 
 * sequence of executions, so that request, evaluations and closing can be
 * performed one after another in a single thread. If it is required to use
 * the RServi multiple times (e.g. a large data set should be reused),
 * the application must prevent concurrent access.</p>
 * <p>
 * A RServi instance must be closed if it is no longer used,
 * so that the R service consumer doesn't block the resources.
 * When using a RServi pool closing means that the RServi is returned
 * to the pool and can can be used by other consumers.</p>
 * <p>
 * After closing the RServi all resources created by it, R data objects and
 * files on the R host system are cleaned up. Client side R data objects and
 * files are not affected by the clean up. After calling this method,
 * the RServi instance can no longer be used; further function call will 
 * throw an exception.</p>
 * <p>
 * All common guidelines of {@link RService} should be taken into account.</p>
 * 
 * @since 0.1
 */
public interface RServi extends RService {
	
	
	/**
	 * Returns the current state of the RServi instance.
	 * <p>
	 * The RServi instance is usually closed by {@link #close()} or if a disconnection to the
	 * R engine was detected. The method does not actively test the connection.
	 * 
	 * @return <code>true</code> if the RServi instance is closed, otherwise <code>false</code>.
	 * @since 1.2
	 */
	boolean isClosed();
	
	/**
	 * Closes this RServi instance. An cleanup of resources created by this RServi
	 * is automatically performed.
	 * <p>
	 * See {@link RServi class comment} for detail.</p>
	 * <p>
	 * After calling the method the RServi instance is closed even if the method
	 * thrown an exception.</p>
	 * 
	 * @throws CoreException if the operation failed; the status
	 *     of the exception contains detail about the cause
	 */
	void close() throws CoreException;
	
}