/*
    * Grapht, an open source dependency injector.
    * Copyright 2014-2015 various contributors (see CONTRIBUTORS.txt)
    * Copyright 2010-2014 Regents of the University of Minnesota
    *
    * This program is free software; you can redistribute it and/or modify
    * it under the terms of the GNU Lesser General Public License as
    * published by the Free Software Foundation; either version 2.1 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 General Public License for more
   * details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc., 51
   * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
   */
  package org.grouplens.grapht.reflect.internal;
  
  import org.grouplens.grapht.*;
  import org.grouplens.grapht.reflect.Desire;
  import org.grouplens.grapht.reflect.Satisfaction;
  import org.grouplens.grapht.reflect.SatisfactionVisitor;
  import org.grouplens.grapht.util.ClassProxy;
  import org.grouplens.grapht.util.Preconditions;
  import org.grouplens.grapht.util.Types;
  
  import javax.inject.Singleton;
  import java.io.InvalidObjectException;
  import java.io.ObjectInputStream;
  import java.io.ObjectStreamException;
  import java.io.Serializable;
  import java.lang.reflect.Type;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  
  /**
   * NullSatisfaction is a satisfaction that explicitly satisfies desires with the
   * <code>null</code> value.
   * 
   * @author <a href="http://grouplens.org">GroupLens Research</a>
   */
  public class
          NullSatisfaction implements Satisfaction, Serializable {
      private static final long serialVersionUID = -1L;
      private final transient Class<?> type;
      
      /**
       * Create a NullSatisfaction that uses <code>null</code> to satisfy the
       * given class type.
       * 
       * @param type The type to satisfy
       * @throws NullPointerException if type is null
       */
      public NullSatisfaction(Class<?> type) {
          Preconditions.notNull("type", type);
          this.type = Types.box(type);
      }
      
      @Override
      public CachePolicy getDefaultCachePolicy() {
          return (getErasedType().getAnnotation(Singleton.class) != null ? CachePolicy.MEMOIZE : CachePolicy.NO_PREFERENCE);
      }
      
      @Override
      public List<Desire> getDependencies() {
          return Collections.emptyList();
      }
  
      @Override
      public Type getType() {
          return type;
      }
  
      @Override
      public Class<?> getErasedType() {
          return type;
      }
  
      @Override
      public boolean hasInstance() {
          // Null satisfactions have instances, just null ones.
          return true;
      }
  
      @Override
      public <T> T visit(SatisfactionVisitor<T> visitor) {
          return visitor.visitNull();
      }
  
      @Override
      @SuppressWarnings({ "unchecked", "rawtypes" })
      public Instantiator makeInstantiator(Map<Desire,Instantiator> dependencies,
                                           LifecycleManager lm) {
          return Instantiators.ofNull(type);
      }
     
     @Override
     public boolean equals(Object o) {
         if (!(o instanceof NullSatisfaction)) {
             return false;
         }
         return ((NullSatisfaction) o).type.equals(type);
     }
     
     @Override
     public int hashCode() {
         return type.hashCode();
     }
     
     @Override
     public String toString() {
         return "Null(" + type.getSimpleName() + ")";
     }
 
     private Object writeReplace() {
         return new SerialProxy(type);
     }
 
     private void readObject(ObjectInputStream stream) throws ObjectStreamException {
         throw new InvalidObjectException("must use serialization proxy");
     }
 
     private static class SerialProxy implements Serializable {
         private static final long serialVersionUID = 1L;
 
         private final ClassProxy type;
 
         public SerialProxy(Class<?> cls) {
             type = ClassProxy.of(cls);
         }
 
         private Object readResolve() throws ObjectStreamException {
             try {
                 return new NullSatisfaction(type.resolve());
             } catch (ClassNotFoundException e) {
                 InvalidObjectException ex = new InvalidObjectException("cannot resolve " + type);
                 ex.initCause(e);
                 throw ex;
             }
         }
     }
 }