# CancellableCallable.java

    /*
    ** Module   : CancellableCallable.java
    ** Abstract : Cancellable callable.
    **
    ** Copyright (c) 2025, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------Description----------------------------------
    ** 001 GBB 20250122 Created initial version.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
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    **
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    **
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    **
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    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.util.appserver;

    import java.util.concurrent.*;
    import java.util.concurrent.atomic.*;
    import java.util.function.*;

    /** Cancellable callable. */
    abstract class CancellableCallable<V>
    implements Callable<V>
    {
       /** The MSA task that is running as part of the callable. */
       private MultiSessionAppserver.MsaTask task;

       /** Thread-safe flag indicating if the MSA task is running. */
       private final AtomicBoolean isRunning = new AtomicBoolean(false);

       /** Thread-safe flag indicating if the MSA task is cancelled. */
       private final AtomicBoolean isCancelled = new AtomicBoolean(false);

       /** The Future for a nested task that is currently running and can be cancelled. */
       private Future currentlyRunningFuture;

       /** The cause for the cancel of the callable. */
       private CancelCause cancelCause;

       /**
        * Sends STOP by cancelling the task and interrupting the running thread.
        *
        * @param    cancelCause
        *           The cause for the cancel.
        */
       void sendStop(CancelCause cancelCause)
       {
          Thread executorThread = getExecutorThread();
          if (executorThread != null)
          {
             this.cancelCause = cancelCause;
             isCancelled.set(true);
             executorThread.interrupt();
          }
       }

       /**
        * Cancels the Future for the currently running task, excluding the MSA task itself. Used for
        * requestWaitTimeout.
        *
        * @param    cancelCause
        *           The cause for the cancel.
        */
       void cancel(CancelCause cancelCause)
       {
          this.cancelCause = cancelCause;
          isCancelled.set(true);
          if (currentlyRunningFuture != null)
          {
             currentlyRunningFuture.cancel(true);
          }
       }

       /**
        * Sets the Future for the currently running nested task.
        *
        * @param    future
        *           The Future for the currently running nested task.
        */
       void setCurrentlyRunningFuture(Future future)
       {
          this.currentlyRunningFuture = future;
       }

       /**
        * Returns <code>true</code> if the MSA task is cancelled, <code>false</code> otherwise.
        *
        * @return   See above.
        */
       boolean isCancelled()
       {
          return isCancelled.get();
       }

       /**
        * Returns the cause of the cancel, <code>null</code> when the callable is not cancelled.
        *
        * @return   See above.
        */
       CancelCause getCancelCause()
       {
          return cancelCause;
       }

       /**
        * Returns <code>true</code> if the MSA task is running, <code>false</code> otherwise.
        *
        * @return   See above.
        */
       boolean isRunning()
       {
          return isRunning.get();
       }

       /**
        * Returns a thread-safe flag indicating if the MSA task is cancelled.
        *
        * @return   See above.
        */
       AtomicBoolean getCancelledSupplier()
       {
          return isCancelled;
       }

       /**
        * Returns a thread-safe flag indicating if the MSA task is running.
        *
        * @return   See above.
        */
       AtomicBoolean getIsRunningSupplier()
       {
          return isRunning;
       }

       /**
        * Returns a new Function that can be used to set the MSA task.
        *
        * @return   See above.
        */
       Function<MultiSessionAppserver.MsaTask, Void> getTaskReceiver()
       {
          return msaTask ->
          {
             this.task = msaTask;
             return null;
          };
       }

       /**
        * Returns the Thread on which the executor is running the MSA task, <code>null</code> if the MSA
        * task hasn't started running.
        *
        * @return   See above.
        */
       private Thread getExecutorThread()
       {
          return task == null ? null : task.getRunningThread();
       }
    }