/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.collections4.functors;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.IOException;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.Serializable;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  
  import org.apache.commons.collections4.Factory;
  import org.apache.commons.collections4.FunctorException;
  
  /**
   * Factory implementation that creates a new instance each time based on a prototype.
   * <p>
   * <b>WARNING:</b> from v4.1 onwards {@link Factory} instances returned by
   * {@link #prototypeFactory(Object)} will <b>not</b> be serializable anymore in order
   * to prevent potential remote code execution exploits. Please refer to
   * <a href="https://issues.apache.org/jira/browse/COLLECTIONS-580">COLLECTIONS-580</a>
   * for more details.
   * </p>
   *
   * @since 3.0
   */
  public class PrototypeFactory {
  
      // PrototypeCloneFactory
      /**
       * PrototypeCloneFactory creates objects by copying a prototype using the clone method.
       */
      static class PrototypeCloneFactory<T> implements Factory<T> {
  
          /** The object to clone each time */
          private final T iPrototype;
          /** The method used to clone */
          private transient Method iCloneMethod;
  
          /**
           * Constructor to store prototype.
           */
          private PrototypeCloneFactory(final T prototype, final Method method) {
              iPrototype = prototype;
              iCloneMethod = method;
          }
  
          /**
           * Creates an object by calling the clone method.
           *
           * @return the new object
           */
          @Override
          @SuppressWarnings("unchecked")
          public T create() {
              // needed for post-serialization
              if (iCloneMethod == null) {
                  findCloneMethod();
              }
  
              try {
                  return (T) iCloneMethod.invoke(iPrototype, (Object[]) null);
              } catch (final IllegalAccessException ex) {
                  throw new FunctorException("PrototypeCloneFactory: Clone method must be public", ex);
              } catch (final InvocationTargetException ex) {
                  throw new FunctorException("PrototypeCloneFactory: Clone method threw an exception", ex);
              }
          }
  
          /**
           * Find the Clone method for the class specified.
           */
          private void findCloneMethod() {
              try {
                  iCloneMethod = iPrototype.getClass().getMethod("clone", (Class[]) null);
              } catch (final NoSuchMethodException ex) {
                  throw new IllegalArgumentException("PrototypeCloneFactory: The clone method must exist and be public ");
              }
          }
      }
  
      // PrototypeSerializationFactory
      /**
      * PrototypeSerializationFactory creates objects by cloning a prototype using serialization.
      */
     static class PrototypeSerializationFactory<T extends Serializable> implements Factory<T> {
 
         /** The object to clone via serialization each time */
         private final T iPrototype;
 
         /**
          * Constructor to store prototype
          */
         private PrototypeSerializationFactory(final T prototype) {
             iPrototype = prototype;
         }
 
         /**
          * Creates an object using serialization.
          *
          * @return the new object
          */
         @Override
         @SuppressWarnings("unchecked")
         public T create() {
             final ByteArrayOutputStream baos = new ByteArrayOutputStream(512);
             ByteArrayInputStream bais = null;
             try {
                 final ObjectOutputStream out = new ObjectOutputStream(baos);
                 out.writeObject(iPrototype);
 
                 bais = new ByteArrayInputStream(baos.toByteArray());
                 final ObjectInputStream in = new ObjectInputStream(bais);
                 return (T) in.readObject();
 
             } catch (final ClassNotFoundException | IOException ex) {
                 throw new FunctorException(ex);
             } finally {
                 try {
                     if (bais != null) {
                         bais.close();
                     }
                 } catch (final IOException ex) { //NOPMD
                     // ignore
                 }
                 try {
                     baos.close();
                 } catch (final IOException ex) { //NOPMD
                     // ignore
                 }
             }
         }
     }
 
     /**
      * Factory method that performs validation.
      * <p>
      * Creates a Factory that will return a clone of the same prototype object
      * each time the factory is used. The prototype will be cloned using one of these
      * techniques (in order):
      * </p>
      *
      * <ul>
      * <li>public clone method</li>
      * <li>public copy constructor</li>
      * <li>serialization clone</li>
      * </ul>
      *
      * @param <T>  the type the factory creates
      * @param prototype  the object to clone each time in the factory
      * @return the {@code prototype} factory, or a {@link ConstantFactory#NULL_INSTANCE} if
      * the {@code prototype} is {@code null}
      * @throws IllegalArgumentException if the prototype cannot be cloned
      */
     @SuppressWarnings("unchecked")
     public static <T> Factory<T> prototypeFactory(final T prototype) {
         if (prototype == null) {
             return ConstantFactory.<T>constantFactory(null);
         }
         try {
             final Method method = prototype.getClass().getMethod("clone", (Class[]) null);
             return new PrototypeCloneFactory<>(prototype, method);
 
         } catch (final NoSuchMethodException ex) {
             try {
                 prototype.getClass().getConstructor(prototype.getClass());
                 return new InstantiateFactory<>(
                     (Class<T>) prototype.getClass(),
                     new Class<?>[] { prototype.getClass() },
                     new Object[] { prototype });
             } catch (final NoSuchMethodException ex2) {
                 if (prototype instanceof Serializable) {
                     return (Factory<T>) new PrototypeSerializationFactory<>((Serializable) prototype);
                 }
             }
         }
         throw new IllegalArgumentException("The prototype must be cloneable via a public clone method");
     }
 
     /**
      * Restricted constructor.
      */
     private PrototypeFactory() {
     }
 
 }