# ForEach.java

    /*
     * Copyright (c) 2010, Rickard Öberg. All Rights Reserved.
     *
     * Licensed 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.qi4j.functional;

    import java.util.Iterator;

    /**
     * When using Iterables with map() and filter() the code often reads "in reverse", with the first item last in the code.
     * Example: Iterables.map(function,Iterables.filter(specification, iterable))
     * <p>
     * This ForEach class reverses that order and makes the code more readable, and allows easy application of visitors on iterables.
     * </p>
     * <p>
     * Example: forEach(iterable).filter(specification).map(function).visit(visitor)
     * </p>
     */
    public final class ForEach<T>
        implements Iterable<T>
    {
        public static <T> ForEach<T> forEach( Iterable<T> iterable )
        {
            return new ForEach<>( iterable );
        }

        private final Iterable<T> iterable;

        public ForEach( Iterable<T> iterable )
        {
            this.iterable = iterable;
        }

        @Override
        public Iterator<T> iterator()
        {
            return iterable.iterator();
        }

        public ForEach<T> filter( Specification<? super T> specification )
        {
            return new ForEach<>( Iterables.filter( specification, iterable ) );
        }

        public <TO> ForEach<TO> map( Function<? /* super T */, TO> function )
        {
            return new ForEach<>( Iterables.map( function, iterable ) );
        }

        public <TO> ForEach<TO> flatten()
        {
            Iterable<Iterable<TO>> original = iterable();
            Iterable<TO> iterable1 = Iterables.flattenIterables( original );
            return new ForEach<>( iterable1 );
        }

        @SuppressWarnings( "unchecked" )
        private <TO> Iterable<Iterable<TO>> iterable()
        {
            return (Iterable<Iterable<TO>>) iterable;
        }

        public T last()
        {
            T lastItem = null;
            for( T item : iterable )
            {
                lastItem = item;
            }
            return lastItem;
        }

        public <ThrowableType extends Throwable> boolean visit( final Visitor<T, ThrowableType> visitor )
            throws ThrowableType
        {
            for( T item : iterable )
            {
                if( !visitor.visit( item ) )
                {
                    return false;
                }
            }

            return true;
        }
    }