/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe 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 General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.util.concurrent.processing;
  
  import java.time.Instant;
  import java.util.concurrent.Callable;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Future;
  import java.util.function.Supplier;
  
  import org.mycore.common.MCRException;
  import org.mycore.common.processing.MCRProcessable;
  import org.mycore.common.processing.MCRProcessableStatus;
  import org.mycore.common.processing.MCRProcessableTask;
  import org.mycore.common.processing.MCRProgressable;
  import org.mycore.util.concurrent.MCRDecorator;
  import org.mycore.util.concurrent.MCRPrioritySupplier;
  
  /**
   * A processable supplier combines a {@link Supplier} and a {@link MCRProcessable}.
   * The supplier will be executed with the help of an {@link CompletableFuture}.
   * To get the future call {@link #getFuture()}.
   * 
   * @author Matthias Eichner
   *
   * @param <R> the result of the task
   */
  public class MCRProcessableSupplier<R> extends MCRProcessableTask<Callable<R>> implements Supplier<R> {
  
      protected CompletableFuture<R> future;
  
      /**
       * Creates a new {@link MCRProcessableSupplier} by the already committed task and its future.
       * 
       * @param task the task which should be executed
       * @param future the future
       * @return a new processable supplier
       */
      public static <T> MCRProcessableSupplier<T> of(Callable<T> task, CompletableFuture<T> future) {
          MCRProcessableSupplier<T> ps = new MCRProcessableSupplier<>(task);
          ps.future = future;
          return ps;
      }
  
      /**
       * Creates a new {@link MCRProcessableSupplier} by submitting the task to the executorService with
       * the given priority.
       * 
       * @param task the task to submit
       * @param executorService the executor service
       * @param priority the priority
       * @return a new processable supplier
       */
      public static <T> MCRProcessableSupplier<T> of(Callable<T> task, ExecutorService executorService,
          Integer priority) {
          MCRProcessableSupplier<T> ps = new MCRProcessableSupplier<>(task);
          ps.future = new MCRPrioritySupplier<>(ps, priority).runAsync(executorService);
          return ps;
      }
  
      /**
       * Private constructor, 
       * 
       * @param task the task itself
       */
      private MCRProcessableSupplier(Callable<R> task) {
          super(task);
      }
  
      /**
       * Gets the result of the task. Will usually be called by the executor service
       * and should not be executed directly.
       */
      @Override
      public R get() {
          try {
              this.setStatus(MCRProcessableStatus.processing);
              this.startTime = Instant.now();
              R result = getTask().call();
              this.setStatus(MCRProcessableStatus.successful);
              return result;
          } catch (InterruptedException exc) {
             this.error = exc;
             this.setStatus(MCRProcessableStatus.canceled);
             throw new MCRException(this.error);
         } catch (Exception exc) {
             this.error = exc;
             this.setStatus(MCRProcessableStatus.failed);
             throw new MCRException(this.error);
         }
     }
 
     /**
      * The future the task is assigned to.
      * 
      * @return the future
      */
     public CompletableFuture<R> getFuture() {
         return future;
     }
 
     /**
      * Returns true if this task completed. Completion may be due to normal termination,
      * an exception, or cancellation -- in all of these cases, this method will return true.
      *
      * @return true if this task completed
      */
     public boolean isFutureDone() {
         return future.isDone();
     }
 
     /**
      * Same as {@link Future#cancel(boolean)}.
      * 
      * @param mayInterruptIfRunning true if the thread executing this task should be interrupted;
      *      otherwise, in-progress tasks are allowed to complete
      * @return false if the task could not be cancelled, typically because it has already
      *      completed normally; true otherwise
      */
     public boolean cancel(boolean mayInterruptIfRunning) {
         return future.cancel(mayInterruptIfRunning);
     }
 
     /**
      * Returns an integer between 0-100 indicating the progress
      * of the processable. Can return null if the task is not started
      * yet or the task is not an instance of {@link MCRProgressable}.
      * 
      * @return the progress between 0-100 or null
      */
     @Override
     public Integer getProgress() {
         if (task instanceof MCRProgressable) {
             return ((MCRProgressable) task).getProgress();
         }
         return super.getProgress();
     }
 
     /**
      * Returns a human readable text indicating the state of the progress.
      * 
      * @return progress text
      */
     @Override
     public String getProgressText() {
         if (task instanceof MCRProgressable) {
             return ((MCRProgressable) task).getProgressText();
         }
         return super.getProgressText();
     }
 
     /**
      * Returns the name of this process. If no name is set
      * this returns the simplified class name of the task.
      * 
      * @return a human readable name of this processable task
      */
     @Override
     public String getName() {
         String name = super.getName();
         if (name == null) {
             return MCRDecorator.resolve(this.task).map(object -> {
                 if (object instanceof MCRProcessable) {
                     return ((MCRProcessable) object).getName();
                 }
                 return object.toString();
             }).orElse(this.task.toString());
         }
         return name;
     }
 
 }