/*
    * 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
    *
    *      https://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;
  
  import java.util.Collection;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Objects;
  
  import org.apache.commons.collections4.functors.ChainedTransformer;
  import org.apache.commons.collections4.functors.CloneTransformer;
  import org.apache.commons.collections4.functors.ClosureTransformer;
  import org.apache.commons.collections4.functors.ConstantTransformer;
  import org.apache.commons.collections4.functors.EqualPredicate;
  import org.apache.commons.collections4.functors.ExceptionTransformer;
  import org.apache.commons.collections4.functors.FactoryTransformer;
  import org.apache.commons.collections4.functors.IfTransformer;
  import org.apache.commons.collections4.functors.InstantiateTransformer;
  import org.apache.commons.collections4.functors.InvokerTransformer;
  import org.apache.commons.collections4.functors.MapTransformer;
  import org.apache.commons.collections4.functors.NOPTransformer;
  import org.apache.commons.collections4.functors.PredicateTransformer;
  import org.apache.commons.collections4.functors.StringValueTransformer;
  import org.apache.commons.collections4.functors.SwitchTransformer;
  
  /**
   * {@code TransformerUtils} provides reference implementations and
   * utilities for the Transformer functor interface. The supplied transformers are:
   * <ul>
   * <li>Invoker - returns the result of a method call on the input object</li>
   * <li>Clone - returns a clone of the input object</li>
   * <li>Constant - always returns the same object</li>
   * <li>Closure - performs a Closure and returns the input object</li>
   * <li>Predicate - returns the result of the predicate as a Boolean</li>
   * <li>Factory - returns a new object from a factory</li>
   * <li>Chained - chains two or more transformers together</li>
   * <li>If - calls one transformer or another based on a predicate</li>
   * <li>Switch - calls one transformer based on one or more predicates</li>
   * <li>SwitchMap - calls one transformer looked up from a Map</li>
   * <li>Instantiate - the Class input object is instantiated</li>
   * <li>Map - returns an object from a supplied Map</li>
   * <li>Null - always returns null</li>
   * <li>NOP - returns the input object, which should be immutable</li>
   * <li>Exception - always throws an exception</li>
   * <li>StringValue - returns a {@link String} representation of the input object</li>
   * </ul>
   * <p>
   * Since v4.1 only transformers which are considered to be safe are
   * Serializable. Transformers considered to be unsafe for serialization are:
   * </p>
   * <ul>
   * <li>Invoker</li>
   * <li>Clone</li>
   * <li>Instantiate</li>
   * </ul>
   *
   * @since 3.0
   */
  public class TransformerUtils {
  
      /**
       * Creates a Transformer that calls a Closure each time the transformer is used.
       * The transformer returns the input object.
       *
       * @param <T>  the input/output type
       * @param closure  The closure to run each time in the transformer, not null
       * @return The transformer
       * @throws NullPointerException if the closure is null
       * @see ClosureTransformer
       */
      public static <T> Transformer<T, T> asTransformer(final Closure<? super T> closure) {
          return ClosureTransformer.closureTransformer(closure);
      }
  
      /**
       * Creates a Transformer that calls a Factory each time the transformer is used.
       * The transformer will return the value returned by the factory.
       *
       * @param <I>  the input type
       * @param <O>  the output type
       * @param factory  The factory to run each time in the transformer, not null
       * @return The transformer
       * @throws NullPointerException if the factory is null
       * @see FactoryTransformer
       */
     public static <I, O> Transformer<I, O> asTransformer(final Factory<? extends O> factory) {
         return FactoryTransformer.factoryTransformer(factory);
     }
 
     /**
      * Creates a Transformer that calls a Predicate each time the transformer is used.
      * The transformer will return either {@link Boolean#TRUE} or {@link Boolean#FALSE}.
      *
      * @param <T>  the input type
      * @param predicate  The predicate to run each time in the transformer, not null
      * @return The transformer
      * @throws NullPointerException if the predicate is null
      * @see PredicateTransformer
      */
     public static <T> Transformer<T, Boolean> asTransformer(final Predicate<? super T> predicate) {
         return PredicateTransformer.predicateTransformer(predicate);
     }
 
     /**
      * Create a new Transformer that calls each transformer in turn, passing the
      * result into the next transformer. The ordering is that of the iterator()
      * method on the collection.
      *
      * @param <T>  the input/output type
      * @param transformers  A collection of transformers to chain
      * @return The transformer
      * @throws NullPointerException if the transformers collection or any of the transformers is null
      * @see ChainedTransformer
      */
     public static <T> Transformer<T, T> chainedTransformer(
             final Collection<? extends Transformer<? super T, ? extends T>> transformers) {
         return ChainedTransformer.chainedTransformer(transformers);
     }
 
     /**
      * Create a new Transformer that calls each transformer in turn, passing the
      * result into the next transformer.
      *
      * @param <T>  the input/output type
      * @param transformers  An array of transformers to chain
      * @return The transformer
      * @throws NullPointerException if the transformers array or any of the transformers is null
      * @see ChainedTransformer
      */
     public static <T> Transformer<T, T> chainedTransformer(
             final Transformer<? super T, ? extends T>... transformers) {
         return ChainedTransformer.chainedTransformer(transformers);
     }
 
     /**
      * Gets a transformer that returns a clone of the input object.
      * The input object will be cloned using one of these techniques (in order):
      * <ul>
      * <li>public clone method</li>
      * <li>public copy constructor</li>
      * <li>serialization clone</li>
      * </ul>
      *
      * @param <T>  the input/output type
      * @return The transformer
      * @see CloneTransformer
      */
     public static <T> Transformer<T, T> cloneTransformer() {
         return CloneTransformer.cloneTransformer();
     }
 
     /**
      * Creates a Transformer that will return the same object each time the
      * transformer is used.
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param constantToReturn  The constant object to return each time in the transformer
      * @return The transformer.
      * @see ConstantTransformer
      */
     public static <I, O> Transformer<I, O> constantTransformer(final O constantToReturn) {
         return ConstantTransformer.constantTransformer(constantToReturn);
     }
 
     /**
      * Gets a transformer that always throws an exception.
      * This could be useful during testing as a placeholder.
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @return The transformer
      * @see ExceptionTransformer
      */
     public static <I, O> Transformer<I, O> exceptionTransformer() {
         return ExceptionTransformer.exceptionTransformer();
     }
 
     /**
      * Create a new Transformer that calls one of two transformers depending
      * on the specified predicate.
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param predicate  The predicate to switch on
      * @param trueTransformer  The transformer called if the predicate is true
      * @param falseTransformer  The transformer called if the predicate is false
      * @return The transformer
      * @throws NullPointerException if either the predicate or transformer is null
      * @see IfTransformer
      * @since 4.1
      */
     public static <I, O> Transformer<I, O> ifTransformer(final Predicate<? super I> predicate,
                                                          final Transformer<? super I, ? extends O> trueTransformer,
                                                          final Transformer<? super I, ? extends O> falseTransformer) {
         return IfTransformer.ifTransformer(predicate, trueTransformer, falseTransformer);
     }
 
     /**
      * Create a new Transformer that calls the transformer if the predicate is true,
      * otherwise the input object is returned unchanged.
      *
      * @param <T>  the input / output type
      * @param predicate  The predicate to switch on
      * @param trueTransformer  The transformer called if the predicate is true
      * @return The transformer
      * @throws NullPointerException if either the predicate or transformer is null
      * @see IfTransformer
      * @since 4.1
      */
     public static <T> Transformer<T, T> ifTransformer(final Predicate<? super T> predicate,
                                                       final Transformer<? super T, ? extends T> trueTransformer) {
         return IfTransformer.ifTransformer(predicate, trueTransformer);
     }
 
     /**
      * Gets a Transformer that expects an input Class object that it will instantiate.
      *
      * @param <T>  the output type
      * @return The transformer
      * @see InstantiateTransformer
      */
     public static <T> Transformer<Class<? extends T>, T> instantiateTransformer() {
         return InstantiateTransformer.instantiateTransformer();
     }
 
     /**
      * Creates a Transformer that expects an input Class object that it will
      * instantiate. The constructor used is determined by the arguments specified
      * to this method.
      *
      * @param <T>  the output type
      * @param paramTypes  parameter types for the constructor, can be null
      * @param args  The arguments to pass to the constructor, can be null
      * @return The transformer
      * @throws IllegalArgumentException if the paramTypes and args don't match
      * @see InstantiateTransformer
      */
     public static <T> Transformer<Class<? extends T>, T> instantiateTransformer(
             final Class<?>[] paramTypes, final Object[] args) {
         return InstantiateTransformer.instantiateTransformer(paramTypes, args);
     }
 
     /**
      * Gets a Transformer that invokes a method on the input object.
      * The method must have no parameters. If the input object is {@code null},
      * {@code null} is returned.
      *
      * <p>
      * For example, {@code TransformerUtils.invokerTransformer("getName");}
      * will call the {@code getName} method on the input object to
      * determine the transformer result.
      * </p>
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param methodName  The method name to call on the input object, may not be null
      * @return The transformer
      * @throws NullPointerException if the methodName is null.
      * @see InvokerTransformer
      */
     public static <I, O> Transformer<I, O> invokerTransformer(final String methodName) {
         return InvokerTransformer.invokerTransformer(methodName, null, null);
     }
 
     /**
      * Gets a Transformer that invokes a method on the input object.
      * The method parameters are specified. If the input object is {@code null},
      * {@code null} is returned.
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param methodName  The name of the method
      * @param paramTypes  The parameter types
      * @param args  The arguments
      * @return The transformer
      * @throws NullPointerException if the method name is null
      * @throws IllegalArgumentException if the paramTypes and args don't match
      * @see InvokerTransformer
      */
     public static <I, O> Transformer<I, O> invokerTransformer(final String methodName, final Class<?>[] paramTypes,
                                                               final Object[] args) {
         return InvokerTransformer.invokerTransformer(methodName, paramTypes, args);
     }
 
     /**
      * Creates a Transformer that uses the passed in Map to transform the input
      * object (as a simple lookup).
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param map  The map to use to transform the objects
      * @return The transformer, or {@link ConstantTransformer#nullTransformer()} if the
      *   {@code map} is {@code null}
      * @see MapTransformer
      */
     public static <I, O> Transformer<I, O> mapTransformer(final Map<? super I, ? extends O> map) {
         return MapTransformer.mapTransformer(map);
     }
 
     /**
      * Gets a transformer that returns the input object.
      * The input object should be immutable to maintain the
      * contract of Transformer (although this is not checked).
      *
      * @param <T>  the input/output type
      * @return The transformer
      * @see NOPTransformer
      */
     public static <T> Transformer<T, T> nopTransformer() {
         return NOPTransformer.nopTransformer();
     }
 
     /**
      * Gets a transformer that always returns null.
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @return The transformer
      * @see ConstantTransformer
      */
     public static <I, O> Transformer<I, O> nullTransformer() {
         return ConstantTransformer.nullTransformer();
     }
 
     /**
      * Gets a transformer that returns a {@link String}
      * representation of the input object. This is achieved via the
      * {@code toString} method, {@code null} returns 'null'.
      *
      * @param <T>  the input type
      * @return The transformer
      * @see StringValueTransformer
      */
     public static <T> Transformer<T, String> stringValueTransformer() {
         return StringValueTransformer.stringValueTransformer();
     }
 
     /**
      * Create a new Transformer that uses the input object as a key to find the
      * transformer to call.
      * <p>
      * The Map consists of object keys and Transformer values. A transformer
      * is called if the input object equals the key. If there is no match, the
      * default transformer is called. The default transformer is set in the map
      * using a null key. If no default is set, null will be returned in a default case.
      * </p>
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param objectsAndTransformers  A map of objects to transformers
      * @return The transformer
      * @throws NullPointerException if the map is null
      * @throws NullPointerException if any transformer in the map is null
      * @see SwitchTransformer
      */
     @SuppressWarnings("unchecked")
     public static <I, O> Transformer<I, O> switchMapTransformer(
             final Map<I, Transformer<I, O>> objectsAndTransformers) {
 
         Objects.requireNonNull(objectsAndTransformers, "objectsAndTransformers");
         // copy so the caller's map is not mutated
         final Map<I, Transformer<I, O>> objects = new LinkedHashMap<>(objectsAndTransformers);
         final Transformer<? super I, ? extends O> def = objects.remove(null);
         final int size = objects.size();
         final Transformer<? super I, ? extends O>[] trs = new Transformer[size];
         final Predicate<I>[] preds = new Predicate[size];
         int i = 0;
         for (final Map.Entry<I, Transformer<I, O>> entry : objects.entrySet()) {
             preds[i] = EqualPredicate.<I>equalPredicate(entry.getKey());
             trs[i++] = entry.getValue();
         }
         return switchTransformer(preds, trs, def);
     }
 
     /**
      * Create a new Transformer that calls one of the transformers depending
      * on the predicates.
      * <p>
      * The Map consists of Predicate keys and Transformer values. A transformer
      * is called if its matching predicate returns true. Each predicate is evaluated
      * until one returns true. If no predicates evaluate to true, the default
      * transformer is called. The default transformer is set in the map with a
      * null key. If no default transformer is set, null will be returned in a default
      * case. The ordering is that of the iterator() method on the entryset collection
      * of the map.
      * </p>
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param predicatesAndTransformers  A map of predicates to transformers
      * @return The transformer
      * @throws NullPointerException if the map is null
      * @throws NullPointerException if any transformer in the map is null
      * @throws ClassCastException  if the map elements are of the wrong type
      * @see SwitchTransformer
      */
     public static <I, O> Transformer<I, O> switchTransformer(
             final Map<Predicate<I>, Transformer<I, O>> predicatesAndTransformers) {
         return SwitchTransformer.switchTransformer(predicatesAndTransformers);
     }
 
     /**
      * Create a new Transformer that calls one of two transformers depending
      * on the specified predicate.
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param predicate  The predicate to switch on
      * @param trueTransformer  The transformer called if the predicate is true
      * @param falseTransformer  The transformer called if the predicate is false
      * @return The transformer
      * @throws NullPointerException if either the predicate or transformer is null
      * @see SwitchTransformer
      * @deprecated as of 4.1, use {@link #ifTransformer(Predicate, Transformer, Transformer)}
      */
     @SuppressWarnings("unchecked")
     @Deprecated
     public static <I, O> Transformer<I, O> switchTransformer(final Predicate<? super I> predicate,
             final Transformer<? super I, ? extends O> trueTransformer,
             final Transformer<? super I, ? extends O> falseTransformer) {
         return SwitchTransformer.switchTransformer(new Predicate[] { predicate },
                                                    new Transformer[] { trueTransformer }, falseTransformer);
     }
 
     /**
      * Create a new Transformer that calls one of the transformers depending
      * on the predicates. The transformer at array location 0 is called if the
      * predicate at array location 0 returned true. Each predicate is evaluated
      * until one returns true. If no predicates evaluate to true, null is returned.
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param predicates  An array of predicates to check
      * @param transformers  An array of transformers to call
      * @return The transformer
      * @throws NullPointerException if either array is null
      * @throws NullPointerException if any element in the arrays is null
      * @throws IllegalArgumentException if the arrays have different sizes
      * @see SwitchTransformer
      */
     public static <I, O> Transformer<I, O> switchTransformer(final Predicate<? super I>[] predicates,
             final Transformer<? super I, ? extends O>[] transformers) {
         return SwitchTransformer.switchTransformer(predicates, transformers, null);
     }
 
     /**
      * Create a new Transformer that calls one of the transformers depending
      * on the predicates. The transformer at array location 0 is called if the
      * predicate at array location 0 returned true. Each predicate is evaluated
      * until one returns true. If no predicates evaluate to true, the default
      * transformer is called. If the default transformer is null, null is returned.
      *
      * @param <I>  the input type
      * @param <O>  the output type
      * @param predicates  An array of predicates to check
      * @param transformers  An array of transformers to call
      * @param defaultTransformer  The default to call if no predicate matches, null means return null
      * @return The transformer
      * @throws NullPointerException if either array is null
      * @throws NullPointerException if any element in the arrays is null
      * @throws IllegalArgumentException if the arrays have different sizes
      * @see SwitchTransformer
      */
     public static <I, O> Transformer<I, O> switchTransformer(final Predicate<? super I>[] predicates,
             final Transformer<? super I, ? extends O>[] transformers,
             final Transformer<? super I, ? extends O> defaultTransformer) {
         return SwitchTransformer.switchTransformer(predicates, transformers, defaultTransformer);
     }
 
     /**
      * This class is not normally instantiated.
      */
     private TransformerUtils() {
         // empty
     }
 
 }