tikhomirov@148: /*
tikhomirov@148:  * Copyright (c) 2011 TMate Software Ltd
tikhomirov@148:  *  
tikhomirov@148:  * This program is free software; you can redistribute it and/or modify
tikhomirov@148:  * it under the terms of the GNU General Public License as published by
tikhomirov@148:  * the Free Software Foundation; version 2 of the License.
tikhomirov@148:  *
tikhomirov@148:  * This program is distributed in the hope that it will be useful,
tikhomirov@148:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
tikhomirov@148:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
tikhomirov@148:  * GNU General Public License for more details.
tikhomirov@148:  *
tikhomirov@148:  * For information on how to redistribute this software under
tikhomirov@148:  * the terms of a license other than GNU General Public License
tikhomirov@148:  * contact TMate Software at support@hg4j.com
tikhomirov@148:  */
tikhomirov@148: package org.tmatesoft.hg.util;
tikhomirov@148: 
tikhomirov@148: /**
tikhomirov@148:  * Mix-in for objects that support cancellation. 
tikhomirov@148:  * 
tikhomirov@148:  * @author Artem Tikhomirov
tikhomirov@148:  * @author TMate Software Ltd.
tikhomirov@148:  */
tikhomirov@148: public interface CancelSupport {
tikhomirov@148: 
tikhomirov@148: 	/**
tikhomirov@148: 	 * This method is invoked to check if target had been brought to canceled state. Shall silently return if target is
tikhomirov@148: 	 * in regular state.
tikhomirov@148: 	 * @throws CancelledException when target internal state has been changed to canceled.
tikhomirov@148: 	 */
tikhomirov@148: 	void checkCancelled() throws CancelledException;
tikhomirov@148: 
tikhomirov@148: 
tikhomirov@148: 	// Yeah, this factory class looks silly now, but perhaps in the future I'll need wrappers for other cancellation sources?
tikhomirov@148: 	// just don't want to have general Utils class with methods like get() below
tikhomirov@148: 	static class Factory {
tikhomirov@148: 
tikhomirov@148: 		/**
tikhomirov@148: 		 * Obtain non-null cancel support object.
tikhomirov@148: 		 * 
tikhomirov@215: 		 * @param target any object (or <code>null</code>) that might have cancel support. For <code>null</code>, returns an instance than never cancels.
tikhomirov@148: 		 * @return target if it's capable checking cancellation status or no-op implementation that never cancels.
tikhomirov@148: 				 */
tikhomirov@148: 		public static CancelSupport get(Object target) {
tikhomirov@312: 			CancelSupport cs = get(target, null);
tikhomirov@312: 			if (cs != null) {
tikhomirov@312: 				return cs;
tikhomirov@312: 			}
tikhomirov@312: 			return new CancelSupport() {
tikhomirov@312: 				public void checkCancelled() {
tikhomirov@312: 				}
tikhomirov@312: 			};
tikhomirov@312: 		}
tikhomirov@312: 		
tikhomirov@312: 		public static CancelSupport get(Object target, CancelSupport defaultValue) {
tikhomirov@148: 			if (target instanceof  CancelSupport) {
tikhomirov@148: 				return (CancelSupport) target;
tikhomirov@148: 			}
tikhomirov@148: 			if (target instanceof Adaptable) {
tikhomirov@148: 				CancelSupport cs = ((Adaptable) target).getAdapter(CancelSupport.class);
tikhomirov@148: 				if (cs != null) {
tikhomirov@148: 					return cs;
tikhomirov@148: 				}
tikhomirov@148: 			}
tikhomirov@312: 			return defaultValue;
tikhomirov@148: 		}
tikhomirov@148: 	}
tikhomirov@215: 
tikhomirov@215: 	interface Target<T> {
tikhomirov@215: 		T set(CancelSupport cs);
tikhomirov@215: 	}
tikhomirov@148: }