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	/*
	* 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;

	import java.util.Collection;
	import java.util.Map;

	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</code> 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>Clone - returns a clone of the input object
	* <li>Constant - always returns the same object
	* <li>Closure - performs a Closure and returns the input object
	* <li>Predicate - returns the result of the predicate as a Boolean
	* <li>Factory - returns a new object from a factory
	* <li>Chained - chains two or more transformers together
	* <li>If - calls one transformer or another based on a predicate
	* <li>Switch - calls one transformer based on one or more predicates
	* <li>SwitchMap - calls one transformer looked up from a Map
	* <li>Instantiate - the Class input object is instantiated
	* <li>Map - returns an object from a supplied Map
	* <li>Null - always returns null
	* <li>NOP - returns the input object, which should be immutable
	* <li>Exception - always throws an exception
	* <li>StringValue - returns a <code>java.lang.String</code> representation of the input object
	* </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>Clone
	* <li>Instantiate
	* </ul>
	*
	* @since 3.0
	*/
	public class TransformerUtils {

	/**
	* This class is not normally instantiated.
	*/
	private TransformerUtils() {}

	/**
	* 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();
	}

	/**
	* 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 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 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);
	}

	/**
	* 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 Predicate each time the transformer is used.
	* The transformer will return either Boolean.TRUE or 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);
	}

	/**
	* 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);
	}

	/**
	* 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);
	}

	/**
	* 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 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);
	}

	/**
	* 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 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 the 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 the 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);
	}

	/**
	* 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.
	*
	* @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 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.
	*
	* @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) {

	if (objectsAndTransformers == null) {
	throw new NullPointerException("The object and transformer map must not be null");
	}
	final Transformer<? super I, ? extends O> def = objectsAndTransformers.remove(null);
	final int size = objectsAndTransformers.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 : objectsAndTransformers.entrySet()) {
	preds[i] = EqualPredicate.<I>equalPredicate(entry.getKey());
	trs[i++] = entry.getValue();
	}
	return TransformerUtils.switchTransformer(preds, trs, def);
	}

	/**
	* 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);
	}

	/**
	* 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 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");</code>
	* will call the <code>getName</code> 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);
	}

	/**
	* Gets a transformer that returns a <code>java.lang.String</code>
	* representation of the input object. This is achieved via the
	* <code>toString</code> method, <code>null</code> returns 'null'.
	*
	* @param <T> the input type
	* @return the transformer
	* @see StringValueTransformer
	*/
	public static <T> Transformer<T, String> stringValueTransformer() {
	return StringValueTransformer.stringValueTransformer();
	}

	}

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