/*
    * 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.collections.functors;
  
  import java.util.Collection;
  
  import org.apache.commons.collections.Closure;
  import org.apache.commons.collections.Predicate;
  import org.apache.commons.collections.Transformer;
  
  /**
   * Internal utilities for functors.
   *
   * @since 3.0
   * @version $Id: FunctorUtils.java 1435965 2013-01-20 21:13:18Z tn $
   */
  class FunctorUtils {
  
      /**
       * Restricted constructor.
       */
      private FunctorUtils() {
          super();
      }
  
      /**
       * Clone the predicates to ensure that the internal reference can't be messed with.
       * Due to the {@link Predicate#evaluate(T)} method, Predicate<? super T> is
       * able to be coerced to Predicate<T> without casting issues.
       *
       * @param predicates  the predicates to copy
       * @return the cloned predicates
       */
      @SuppressWarnings("unchecked")
      static <T> Predicate<T>[] copy(final Predicate<? super T>[] predicates) {
          if (predicates == null) {
              return null;
          }
          return (Predicate<T>[]) predicates.clone();
      }
  
      /**
       * A very simple method that coerces Predicate<? super T> to Predicate<T>.
       * Due to the {@link Predicate#evaluate(T)} method, Predicate<? super T> is
       * able to be coerced to Predicate<T> without casting issues.
       * <p>This method exists
       * simply as centralised documentation and atomic unchecked warning
       * suppression.
       *
       * @param <T> the type of object the returned predicate should "accept"
       * @param predicate the predicate to coerce.
       * @return the coerced predicate.
       */
      @SuppressWarnings("unchecked")
      static <T> Predicate<T> coerce(final Predicate<? super T> predicate){
          return (Predicate<T>) predicate;
      }
  
      /**
       * Validate the predicates to ensure that all is well.
       *
       * @param predicates  the predicates to validate
       */
      static void validate(final Predicate<?>[] predicates) {
          if (predicates == null) {
              throw new IllegalArgumentException("The predicate array must not be null");
          }
          for (int i = 0; i < predicates.length; i++) {
              if (predicates[i] == null) {
                  throw new IllegalArgumentException(
                          "The predicate array must not contain a null predicate, index " + i + " was null");
              }
          }
      }
  
      /**
       * Validate the predicates to ensure that all is well.
       *
       * @param predicates  the predicates to validate
       * @return predicate array
       */
      static <T> Predicate<T>[] validate(final Collection<? extends Predicate<T>> predicates) {
          if (predicates == null) {
              throw new IllegalArgumentException("The predicate collection must not be null");
          }
         // convert to array like this to guarantee iterator() ordering
         @SuppressWarnings("unchecked") // OK
         final
         Predicate<T>[] preds = new Predicate[predicates.size()];
         int i = 0;
         for (final Predicate<T> predicate : predicates) {
             preds[i] = predicate;
             if (preds[i] == null) {
                 throw new IllegalArgumentException(
                         "The predicate collection must not contain a null predicate, index " + i + " was null");
             }
             i++;
         }
         return preds;
     }
 
     /**
      * Clone the closures to ensure that the internal reference can't be messed with.
      *
      * @param closures  the closures to copy
      * @return the cloned closures
      */
     @SuppressWarnings("unchecked")
     static <E> Closure<E>[] copy(final Closure<? super E>[] closures) {
         if (closures == null) {
             return null;
         }
         return (Closure<E>[]) closures.clone();
     }
 
     /**
      * Validate the closures to ensure that all is well.
      *
      * @param closures  the closures to validate
      */
     static void validate(final Closure<?>[] closures) {
         if (closures == null) {
             throw new IllegalArgumentException("The closure array must not be null");
         }
         for (int i = 0; i < closures.length; i++) {
             if (closures[i] == null) {
                 throw new IllegalArgumentException(
                         "The closure array must not contain a null closure, index " + i + " was null");
             }
         }
     }
 
     /**
      * A very simple method that coerces Closure<? super T> to Closure<T>.
      * <p>This method exists
      * simply as centralised documentation and atomic unchecked warning
      * suppression.
      *
      * @param <T> the type of object the returned closure should "accept"
      * @param closure the closure to coerce.
      * @return the coerced closure.
      */
     @SuppressWarnings("unchecked")
     static <T> Closure<T> coerce(final Closure<? super T> closure){
         return (Closure<T>) closure;
     }
 
     /**
      * Copy method
      *
      * @param transformers  the transformers to copy
      * @return a clone of the transformers
      */
     @SuppressWarnings("unchecked")
     static <I, O> Transformer<I, O>[] copy(final Transformer<? super I, ? extends O>[] transformers) {
         if (transformers == null) {
             return null;
         }
         return (Transformer<I, O>[]) transformers.clone();
     }
 
     /**
      * Validate method
      *
      * @param transformers  the transformers to validate
      */
     static void validate(final Transformer<?, ?>[] transformers) {
         if (transformers == null) {
             throw new IllegalArgumentException("The transformer array must not be null");
         }
         for (int i = 0; i < transformers.length; i++) {
             if (transformers[i] == null) {
                 throw new IllegalArgumentException(
                     "The transformer array must not contain a null transformer, index " + i + " was null");
             }
         }
     }
 
     /**
      * A very simple method that coerces Transformer<? super I, ? extends O> to Transformer<I, O>.
      * <p>This method exists
      * simply as centralised documentation and atomic unchecked warning
      * suppression.
      *
      * @param <T> the type of object the returned transformer should "accept"
      * @param transformer the transformer to coerce.
      * @return the coerced transformer.
      */
     @SuppressWarnings("unchecked")
     static <I, O> Transformer<I, O> coerce(final Transformer<? super I, ? extends O> transformer) {
         return (Transformer<I, O>) transformer;
     }
 
 }