package com.jsql.model.suspendable;
   
   import com.jsql.model.InjectionModel;
   import com.jsql.model.exception.JSqlException;
   import com.jsql.util.LogLevelUtil;
   import org.apache.logging.log4j.LogManager;
   import org.apache.logging.log4j.Logger;
   
   /**
   * A thread used to inject database ; stoppable and pausable.
   */
  public abstract class AbstractSuspendable {
      
      /**
       * Log4j logger sent to view.
       */
      private static final Logger LOGGER = LogManager.getRootLogger();
  
      /**
       * Make the action to stop if true.
       */
      private boolean isStopped = false;
      
      /**
       * Make the action to pause if true, else make it unpause.
       */
      private boolean isPaused = false;
  
      protected final InjectionModel injectionModel;
      
      protected AbstractSuspendable(InjectionModel injectionModel) {
          this.injectionModel = injectionModel;
      }
      
      /**
       * The pausable/stoppable action.
       */
      public abstract String run(Object... args) throws JSqlException;
  
      /**
       * Thread's states Pause and Stop are processed by this method.<br>
       * - Pause action in infinite loop if invoked while shouldPauseThread is set to true,<br>
       * - Return stop state.
       * @return Stop state
       */
      public synchronized boolean isSuspended() {
          // Make application loop until shouldPauseThread is set to false by another user action
          while (this.isPaused) {
              try {
                  this.wait();
              } catch (InterruptedException e) {
                  LOGGER.log(LogLevelUtil.IGNORE, e, e);
                  Thread.currentThread().interrupt();
              }
          }
          return this.isStopped || this.injectionModel.isStoppedByUser();  // Return true if stop requested, else return false
      }
      
      /**
       * Mark as stopped.
       */
      public void stop() {
          this.unpause();
          this.isStopped = true;
      }
      
      /**
       * Mark as paused.
       */
      public void pause() {
          this.isPaused = true;
      }
      
      /**
       * Mark as unpaused.
       */
      public void unpause() {
          this.isPaused = false;
          this.resume();  // Restart the action after unpause
      }
      
      /**
       * Return true if thread is paused, false otherwise.
       * @return Pause state
       */
      public boolean isPaused() {
          return this.isPaused;
      }
      
      /**
       * Wake threads.
       */
      public synchronized void resume() {
          this.notifyAll();
      }
  }