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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.
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package org.apache.commons.collections4.functors;

import java.io.Serializable;
import java.util.Map;

import org.apache.commons.collections4.Predicate;
import org.apache.commons.collections4.Transformer;

Transformer implementation calls the transformer whose predicate returns true,
like a switch statement.
Since:
3.0/**
 * Transformer implementation calls the transformer whose predicate returns true,
 * like a switch statement.
 *
 * @since 3.0
 */
public class SwitchTransformer<I, O> implements Transformer<I, O>, Serializable {

    
Serial version UID /** Serial version UID */
    private static final long serialVersionUID = -6404460890903469332L;

    
The tests to consider /** The tests to consider */
    private final Predicate<? super I>[] iPredicates;
    
The matching transformers to call /** The matching transformers to call */
    private final Transformer<? super I, ? extends O>[] iTransformers;
    
The default transformer to call if no tests match /** The default transformer to call if no tests match */
    private final Transformer<? super I, ? extends O> iDefault;

    
Factory method that performs validation and copies the parameter arrays.
Params:
predicates –  array of predicates, cloned, no nulls
transformers –  matching array of transformers, cloned, no nulls
defaultTransformer –  the transformer to use if no match, null means return null
Type parameters:
<I> –  the input type
<O> –  the output type
Throws:
NullPointerException – if array is null
NullPointerException – if any element in the array is null
Returns:
the chained transformer/**
     * Factory method that performs validation and copies the parameter arrays.
     *
     * @param <I>  the input type
     * @param <O>  the output type
     * @param predicates  array of predicates, cloned, no nulls
     * @param transformers  matching array of transformers, cloned, no nulls
     * @param defaultTransformer  the transformer to use if no match, null means return null
     * @return the <code>chained</code> transformer
     * @throws NullPointerException if array is null
     * @throws NullPointerException if any element in the array is null
     */
    @SuppressWarnings("unchecked")
    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) {
        FunctorUtils.validate(predicates);
        FunctorUtils.validate(transformers);
        if (predicates.length != transformers.length) {
            throw new IllegalArgumentException("The predicate and transformer arrays must be the same size");
        }
        if (predicates.length == 0) {
            return (Transformer<I, O>) (defaultTransformer == null ? ConstantTransformer.<I, O>nullTransformer() :
                                                                     defaultTransformer);
        }
        return new SwitchTransformer<>(predicates, transformers, defaultTransformer);
    }

    
Create a new Transformer that calls one of the transformers depending
on the predicates.

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. The ordering is that of the iterator() method on the entryset
collection of the map.
Params:
map –  a map of predicates to transformers
Type parameters:
<I> –  the input type
<O> –  the output type
Throws:
NullPointerException – if the map is null
NullPointerException – if any transformer in the map is null
ClassCastException –  if the map elements are of the wrong type
Returns:
the switch transformer/**
     * 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. 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 map  a map of predicates to transformers
     * @return the <code>switch</code> 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
     */
    @SuppressWarnings("unchecked")
    public static <I, O> Transformer<I, O> switchTransformer(
            final Map<? extends Predicate<? super I>, ? extends Transformer<? super I, ? extends O>> map) {

        if (map == null) {
            throw new NullPointerException("The predicate and transformer map must not be null");
        }
        if (map.size() == 0) {
            return ConstantTransformer.<I, O>nullTransformer();
        }
        // convert to array like this to guarantee iterator() ordering
        final Transformer<? super I, ? extends O> defaultTransformer = map.remove(null);
        final int size = map.size();
        if (size == 0) {
            return (Transformer<I, O>) (defaultTransformer == null ? ConstantTransformer.<I, O>nullTransformer() :
                                                                     defaultTransformer);
        }
        final Transformer<? super I, ? extends O>[] transformers = new Transformer[size];
        final Predicate<? super I>[] preds = new Predicate[size];
        int i = 0;
        for (final Map.Entry<? extends Predicate<? super I>,
                             ? extends Transformer<? super I, ? extends O>> entry : map.entrySet()) {
            preds[i] = entry.getKey();
            transformers[i] = entry.getValue();
            i++;
        }
        return new SwitchTransformer<>(false, preds, transformers, defaultTransformer);
    }

    
Hidden constructor for the use by the static factory methods.
Params:
clone –  if true the input arguments will be cloned
predicates –  array of predicates, no nulls
transformers –  matching array of transformers, no nulls
defaultTransformer –  the transformer to use if no match, null means return null/**
     * Hidden constructor for the use by the static factory methods.
     *
     * @param clone  if {@code true} the input arguments will be cloned
     * @param predicates  array of predicates, no nulls
     * @param transformers  matching array of transformers, no nulls
     * @param defaultTransformer  the transformer to use if no match, null means return null
     */
    @SuppressWarnings("unchecked")
    private SwitchTransformer(final boolean clone, final Predicate<? super I>[] predicates,
                             final Transformer<? super I, ? extends O>[] transformers,
                             final Transformer<? super I, ? extends O> defaultTransformer) {
        super();
        iPredicates = clone ? FunctorUtils.copy(predicates) : predicates;
        iTransformers = clone ? FunctorUtils.copy(transformers) : transformers;
        iDefault = (Transformer<? super I, ? extends O>) (defaultTransformer == null ?
                ConstantTransformer.<I, O>nullTransformer() : defaultTransformer);
    }

    
Constructor that performs no validation.
Use switchTransformer if you want that.
Params:
predicates –  array of predicates, cloned, no nulls
transformers –  matching array of transformers, cloned, no nulls
defaultTransformer –  the transformer to use if no match, null means return null/**
     * Constructor that performs no validation.
     * Use <code>switchTransformer</code> if you want that.
     *
     * @param predicates  array of predicates, cloned, no nulls
     * @param transformers  matching array of transformers, cloned, no nulls
     * @param defaultTransformer  the transformer to use if no match, null means return null
     */
    public SwitchTransformer(final Predicate<? super I>[] predicates,
            final Transformer<? super I, ? extends O>[] transformers,
            final Transformer<? super I, ? extends O> defaultTransformer) {
        this(true, predicates, transformers, defaultTransformer);
    }

    
Transforms the input to result by calling the transformer whose matching
predicate returns true.
Params:
input –  the input object to transform
Returns:
the transformed result/**
     * Transforms the input to result by calling the transformer whose matching
     * predicate returns true.
     *
     * @param input  the input object to transform
     * @return the transformed result
     */
    @Override
    public O transform(final I input) {
        for (int i = 0; i < iPredicates.length; i++) {
            if (iPredicates[i].evaluate(input) == true) {
                return iTransformers[i].transform(input);
            }
        }
        return iDefault.transform(input);
    }

    
Gets the predicates.
Returns:
a copy of the predicates
Since:
3.1/**
     * Gets the predicates.
     *
     * @return a copy of the predicates
     * @since 3.1
     */
    public Predicate<? super I>[] getPredicates() {
        return FunctorUtils.<I>copy(iPredicates);
    }

    
Gets the transformers.
Returns:
a copy of the transformers
Since:
3.1/**
     * Gets the transformers.
     *
     * @return a copy of the transformers
     * @since 3.1
     */
    public Transformer<? super I, ? extends O>[] getTransformers() {
        return FunctorUtils.<I, O>copy(iTransformers);
    }

    
Gets the default transformer.
Returns:
the default transformer
Since:
3.1/**
     * Gets the default transformer.
     *
     * @return the default transformer
     * @since 3.1
     */
    public Transformer<? super I, ? extends O> getDefaultTransformer() {
        return iDefault;
    }

}