/**
    * This file Copyright (c) 2018 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.ui.contentapp.observation;
  
  import info.magnolia.ui.api.ioc.UiContextScoped;
  import info.magnolia.ui.datasource.jcr.JcrDatasourceDefinition;
  import info.magnolia.ui.framework.ioc.Destructible;
  import info.magnolia.ui.observation.DatasourceObservation;
  
  import java.util.Set;
  import java.util.function.Consumer;
  import java.util.stream.Stream;
  
  import javax.inject.Inject;
  import javax.jcr.observation.Event;
  
  import org.apache.commons.lang3.StringUtils;
  
  import com.google.common.collect.Sets;
  import com.machinezoo.noexception.Exceptions;
  import com.vaadin.shared.Registration;
  import com.vaadin.ui.UI;
  
  /**
   * JCR Observation utility wrapper to be used within UI framework.
   */
  @UiContextScoped
  public class JcrDataSourceObservation implements DatasourceObservation, Destructible {
  
      private final JcrDatasourceDefinition datasourceDefinition;
      private final JcrObservation jcrObservation;
      private final Set<Registration> registrations = Sets.newConcurrentHashSet();
      private final UI ui;
  
      @Inject
      JcrDataSourceObservation(JcrDatasourceDefinition datasourceDefinition, JcrObservation jcrObservation, UI ui) {
          this.datasourceDefinition = datasourceDefinition;
          this.jcrObservation = jcrObservation;
          this.ui = ui;
      }
  
      @Override
      public Registration register(Runnable action) {
          Consumer<Stream<Event>> consumer = events -> {
              if (!ui.isAttached()) {
                  destroy();
                  return;
              }
  
              boolean applicableEventPresent = events
                      .map(Exceptions.wrap().function(Event::getPath))
                      .map(path -> StringUtils.substringBeforeLast(path, "/") + "/")
                      .anyMatch(path -> StringUtils.startsWith(path, this.datasourceDefinition.getRootPath()));
  
              if (applicableEventPresent) {
                  if (ui.isAttached()) {
                      ui.access(() -> {
                          action.run();
                          ui.push();
                      });
                  }
              }
          };
  
          this.jcrObservation.register(consumer, datasourceDefinition.getWorkspace());
  
          Registration observationRegistration = new Registration() {
              @Override
             public void remove() {
                 jcrObservation.unregister(consumer, datasourceDefinition.getWorkspace());
                 registrations.remove(this);
             }
         };
         registrations.add(observationRegistration);
 
         return observationRegistration;
     }
 
     @Override
     public void destroy() {
         registrations.forEach(Registration::remove);
     }
 }