/*
    * Copyright 2015 Data Archiving and Networked Services (an institute of
    * Koninklijke Nederlandse Akademie van Wetenschappen), King's College London,
    * Georg-August-Universitaet Goettingen Stiftung Oeffentlichen Rechts
    *
    * Licensed under the EUPL, Version 1.1 or – as soon they will be approved by
    * the European Commission - subsequent versions of the EUPL (the "Licence");
    * You may not use this work except in compliance with the Licence.
    * You may obtain a copy of the Licence at:
   *
   * https://joinup.ec.europa.eu/software/page/eupl
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the Licence is distributed on an "AS IS" basis,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the Licence for the specific language governing
   * permissions and limitations under the Licence.
   */
  
  package eu.ehri.project.acl;
  
  import com.tinkerpop.blueprints.Vertex;
  import eu.ehri.project.definitions.Entities;
  import eu.ehri.project.models.Group;
  import eu.ehri.project.models.PermissionGrant;
  import eu.ehri.project.models.base.Accessor;
  import eu.ehri.project.models.base.Entity;
  
  import java.util.Collections;
  
  /**
   * Implementation of an anonymous user singleton.
   */
  public enum AnonymousAccessor implements Accessor {
  
      INSTANCE;
  
      /**
       * Obtain the shared instance of the Anonymous Accessor.
       * There Can Be Only One.
       */
      public static Accessor getInstance() {
          return INSTANCE;
      }
  
      @Override
      public <T extends Entity> T as(Class<T> cls) {
          throw new UnsupportedOperationException();
      }
  
      @Override
      public boolean isAdmin() {
          return false;
      }
  
      @Override
      public boolean isAnonymous() {
          return true;
      }
  
      @Override
      public String getId() {
          return Group.ANONYMOUS_GROUP_IDENTIFIER;
      }
  
      @Override
      public String getType() {
          return Entities.GROUP;
      }
  
      @Override
      public Vertex asVertex() {
          return null;
      }
  
      @Override
      public String getIdentifier() {
          return Group.ANONYMOUS_GROUP_IDENTIFIER;
      }
  
      @Override
      public Iterable<Accessor> getParents() {
          return Collections.emptyList();
      }
  
      @Override
      public Iterable<Accessor> getAllParents() {
          return Collections.emptyList();
      }
  
      @Override
      public Iterable<PermissionGrant> getPermissionGrants() {
          return Collections.emptyList();
      }
  
      @Override
      public void addPermissionGrant(PermissionGrant grant) {
          throw new UnsupportedOperationException();
      }
 
     @Override
     public <T> T getProperty(String key) {
         return null;
     }
 
     @Override
     public <T> T getProperty(Enum<?> key) {
         return null;
     }
 
     @Override
     public java.util.Set<String> getPropertyKeys() {
         return Collections.emptySet();
     }
 }