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/*
 * Copyright (c) 1997, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package jakarta.resource.spi.work;

/**
 * This interface models a WorkManager which provides a facility
 * to submit Work instances for execution. This frees the user
 * from having to create Java™ threads directly to do work. Further, this
 * allows efficient pooling of thread resources and more control over thread
 * usage.
 *
 * The various stages in Work processing are:
 * 
 *  work submit: A Work instance is being submitted for 
 * execution. The Work instance could either be accepted or 
 * rejected with a WorkRejectedException set to an appropriate
 * error code. 
 *
 *  work accepted: The submitted Work instance has been 
 * accepted. The accepted Work instance could either start 
 * execution or could be rejected again with a 
 * WorkRejectedException set to an appropriate error code.
 * There is no guarantee on when the  execution would start unless a start 
 * timeout duration is specified. When a start timeout is specified, the 
 * Work execution must be started within the specified  
 * duration (not a  real-time guarantee), failing which a 
 * WorkRejectedException set to an error code 
 * (WorkRejected.TIMED_OUT) is thrown. 
 *
 *  work rejected: The Work instance has  been rejected. 
 * The Work instance could be rejected during Work
 * submittal  or after the Work instance has been accepted 
 * (but before Work instance starts execution). The rejection could be due 
 * to internal factors or start timeout expiration. A 
 * WorkRejectedException with an appropriate error code 
 * (indicates the reason) is thrown in both cases. 
 *
 *  work started: The execution of the Work 
 * instance has started. This means that a thread
 * has been allocated for its execution. But this  
 * does not guarantee that the allocated thread has been scheduled to run 
 * on a CPU resource. Once execution is started, the allocated thread 
 * sets up an appropriate execution context (transaction , security, etc)
 * and calls Work.run(). Note, any exception thrown during execution context
 * setup or Work.run() leads to completion of processing. 
 *
 *  work completed: The execution of the Work has been 
 * completed. The execution could complete with or without an exception.
 * The WorkManager catches any exception thrown during 
 * Work processing (which includes execution context setup), 
 * and wraps it with a WorkCompletedException. 
 * 
 *
 * @version 1.0
 * @author  Ram Jeyaraman
 */
public interface WorkManager {

    /**
     * A constant to indicate timeout duration. A zero timeout value indicates
     * an action be performed immediately. The WorkManager implementation
     * must timeout the action as soon as possible.
     */
    long IMMEDIATE = 0L;

    /**
     * A constant to indicate timeout duration. A maximum timeout value 
     * indicates that an action be performed arbitrarily without any time 
     * constraint.
     */
    long INDEFINITE = Long.MAX_VALUE;

    /**
     * A constant to indicate an unknown start delay duration or other unknown
     * values.
     */
    long UNKNOWN = -1;

    /**
     * Accepts a Work instance for processing. This call
     * blocks until the Work instance completes execution.
     * There is no guarantee on when the accepted Work 
     * instance would start execution ie., there is no time constraint 
     * to start execution. (that is, startTimeout=INDEFINITE)
     *
     * @param work The unit of work to be done.  
     * Could be long or short-lived.
     *
     * @throws WorkRejectedException indicates that a 
     * Work instance has been rejected from further processing.
     * This can occur due to internal factors.
     *
     * @throws WorkCompletedException indicates that a
     * Work instance has completed execution with an exception.
     */
    void doWork(Work work) // startTimeout = INDEFINITE
	throws WorkException;

    /**
     * Accepts a Work instance for processing. This call
     * blocks until the Work instance completes execution.
     *
     * @param work The unit of work to be done.  
     * Could be long or short-lived.
     *
     * @param startTimeout a time duration (in milliseconds) 
     * within which the execution of the Work instance must
     * start. Otherwise, the Work instance is rejected with a
     * WorkRejectedException set to an appropriate error code 
     * (WorkRejectedException.TIMED_OUT). Note, this
     * does not offer real-time guarantees.
     *
     * @param execContext an object containing the execution
     * context with which the submitted Work instance must
     * be executed.
     *
     * @param workListener an object which would be notified
     * when the various Work processing events (work accepted, 
     * work rejected, work started, work completed) occur.
     *
     * @throws WorkRejectedException indicates that a 
     * Work instance has been rejected from further processing.
     * This can occur due to internal factors or start timeout expiration.
     *
     * @throws WorkCompletedException indicates that a
     * Work instance has completed execution with an exception.
     */
    void doWork(Work work, long startTimeout, 
            ExecutionContext execContext, WorkListener workListener) 
	throws WorkException;

    /**
     * Accepts a Work instance for processing. This call
     * blocks until the Work instance starts execution
     * but not until its completion. There is no guarantee on when
     * the accepted Work instance would start
     * execution ie., there is no time constraint to start execution.
     * (that is, startTimeout=INDEFINITE)
     *
     * @param work The unit of work to be done.  
     * Could be long or short-lived.
     *
     * @return the time elapsed (in milliseconds) from Work
     * acceptance until start of execution. Note, this does not offer 
     * real-time guarantees. It is valid to return -1, if the actual start 
     * delay duration is unknown.
     *
     * @throws WorkRejectedException indicates that a 
     * Work instance has been rejected from further processing.
     * This can occur due to internal factors.
     */
    long startWork(Work work) // startTimeout = INDEFINITE
	throws WorkException;

    /**
     * Accepts a Work instance for processing. This call
     * blocks until the Work instance starts execution
     * but not until its completion. There is no guarantee on when
     * the accepted Work instance would start
     * execution ie., there is no time constraint to start execution.
     *
     * @param work The unit of work to be done.  
     * Could be long or short-lived.
     *
     * @param startTimeout a time duration (in milliseconds) 
     * within which the execution of the Work instance must
     * start. Otherwise, the Work instance is rejected with a
     * WorkRejectedException set to an appropriate error code 
     * (WorkRejectedException.TIMED_OUT). Note, this
     * does not offer real-time guarantees.
     *
     * @param execContext an object containing the execution
     * context with which the submitted Work instance must
     * be executed.
     *
     * @param workListener an object which would be notified
     * when the various Work processing events (work accepted, 
     * work rejected, work started, work completed) occur.
     *
     * @return the time elapsed (in milliseconds) from Work
     * acceptance until start of execution. Note, this does not offer 
     * real-time guarantees. It is valid to return -1, if the actual start 
     * delay duration is unknown.
     *
     * @throws WorkRejectedException indicates that a 
     * Work instance has been rejected from further processing.
     * This can occur due to internal factors or start timeout expiration.
     */
    long startWork(Work work, long startTimeout, 
            ExecutionContext execContext, WorkListener workListener) 
	throws WorkException;

    /**
     * Accepts a Work instance for processing. This call
     * does not block and returns immediately once a Work
     * instance has been accepted for processing. There is no guarantee
     * on when the submitted Work instance would start
     * execution ie., there is no time constraint to start execution.
     * (that is, startTimeout=INDEFINITE).
     *
     * @param work The unit of work to be done.  
     * Could be long or short-lived.
     *
     * @throws WorkRejectedException indicates that a 
     * Work instance has been rejected from further processing.
     * This can occur due to internal factors.
     */
    void scheduleWork(Work work) // startTimeout = INDEFINITE
	throws WorkException;

    /**
     * Accepts a Work instance for processing. This call
     * does not block and returns immediately once a Work
     * instance has been accepted for processing.
     *
     * @param work The unit of work to be done. 
     * Could be long or short-lived.
     *
     * @param startTimeout a time duration (in milliseconds) 
     * within which the execution of the Work instance must
     * start. Otherwise, the Work instance is rejected with a
     * WorkRejectedException set to an appropriate error code 
     * (WorkRejectedException.TIMED_OUT). Note, this
     * does not offer real-time guarantees.
     *
     * @param execContext an object containing the execution
     * context with which the submitted Work instance must
     * be executed.
     *
     * @param workListener an object which would be notified
     * when the various Work processing events (work accepted, 
     * work rejected, work started, work completed) occur.
     *
     * @throws WorkRejectedException indicates that a 
     * Work instance has been rejected from further processing.
     * This can occur due to internal factors.
     */
    void scheduleWork(Work work, long startTimeout, 
            ExecutionContext execContext, WorkListener workListener) 
	throws WorkException;
}