/*
 * Data Hub Service (DHuS) - For Space data distribution.
 * Copyright (C) 2013,2014,2015 GAEL Systems
 *
 * This file is part of DHuS software sources.
 *
 * 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 should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package fr.gael.dhus.sync;

import java.util.Objects;

import fr.gael.dhus.database.object.SynchronizerConf;

/**
 * A Data synchronizer.
 *
 * Synchronizes this instance of DHuS with remote product sources.
 */
public abstract class Synchronizer
{
   /** A reference to the database object storing our configuration. */
   protected final SynchronizerConf syncConf;

   /**
    * Creates a new Synchronizer.
    * SubClasses of {@link Synchronizer} *MUST* have a public constructor with
    * one parameter of type {@link SynchronizerConf}.
    * @param sc a non null database object.
    */
   protected Synchronizer (SynchronizerConf sc)
   {
      Objects.requireNonNull (sc, "Parameter must not be null");
      this.syncConf = sc;
   }

   /**
    * Executes a synchronization pass and then returns.
    * Will be called by a RoundRobin scheduler to efficiently manage several
    * Synchronizers.
    *
    * @return true if there is more to synchronize.
    *
    * @throws InterruptedException If its thread has its {@code interrupted}
    *       flag set, this method must throw an {@link InterruptedException}
    *       immediately, abandoning the current synchronization pass.
    */
   public abstract boolean synchronize () throws InterruptedException;

   /**
    * Returns the configuration of this synchronizer.
    * @return the configuration of this synchronizer.
    */
   public SynchronizerConf getSynchronizerConf ()
   {
      return this.syncConf;
   }

   /**
    * Returns the identifier for this synchronizer.
    * This identifier will be used to identify a synchronizer.
    * @return a (local) unique identifier for this synchronizer.
    */
   public long getId ()
   {
      return syncConf.getId ();
   }

   /**
    * Returns the pace of the synchronization.
    * @return a cron expression.
    */
   public String getCronExpression ()
   {
      return syncConf.getCronExpression ();
   }

   @Override
   public boolean equals (Object obj)
   {
      if (obj == null || !(obj instanceof Synchronizer)) return false;
      Synchronizer asy = (Synchronizer)obj;
      return this.getId () == asy.getId ();
   }

   @Override
   public int hashCode ()
   {
      return Long.valueOf (this.getId ()).hashCode ();
   }
}