/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   *  Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *
 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
 *      and/or other materials provided with the distribution.
 *
 *   *  Neither the name of the University of Southampton nor the names of its
 *      contributors may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.openimaj.util.filter;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

import org.openimaj.util.array.ArrayIterator;
import org.openimaj.util.function.Predicate;

/**
 * Utilities for filtering collections by applying a {@link Predicate}.
 * 
 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
 */
public class FilterUtils {
        private FilterUtils() {
        }

        /**
         * Filter a collection, returning the accepted items in an {@link ArrayList}
         * .
         * 
         * @see Predicate#test(Object)
         * 
         * @param <T>
         *            type of object being filtered
         * @param <Q>
         *            type of object accepted by the filter
         * @param in
         *            input collection
         * @param filter
         *            the filter
         * @return the list of accepted items
         */
        public static <T, Q extends T> ArrayList<Q> filter(final Collection<Q> in, final Predicate<T> filter) {
                final ArrayList<Q> out = new ArrayList<Q>();

                for (final Q item : in)
                        if (filter.test(item))
                                out.add(item);

                return out;
        }

        /**
         * Filter a collection, storing the accepted items in the given output
         * collection.
         * 
         * @see Predicate#test(Object)
         * 
         * @param <T>
         *            type of object being filtered
         * @param in
         *            input collection
         * @param out
         *            output collection
         * @param filter
         *            the filter
         * @return the list of accepted items
         */
        public static <T> Collection<T> filter(final Collection<? extends T> in, final Collection<T> out,
                        final Predicate<T> filter)
        {
                for (final T item : in)
                        if (filter.test(item))
                                out.add(item);

                return out;
        }

        /**
         * Create an iterator that filters items from the given {@link Iterable}.
         * 
         * @see Predicate#test(Object)
         * 
         * @param <T>
         *            type of object being filtered
         * @param iterable
         *            {@link Iterable} to filter
         * @param filter
         *            the filter
         * @return the list of accepted items
         */
        public static <T> Iterator<T> filteredIterator(final Iterable<? extends T> iterable, final Predicate<T> filter) {
                return filteredIterator(iterable.iterator(), filter);
        }

        /**
         * Create an iterator that filters items from the given {@link Iterator}.
         * 
         * @see Predicate#test(Object)
         * 
         * @param <T>
         *            type of object being filtered
         * @param iterator
         *            {@link Iterator} to filter
         * @param filter
         *            the filter
         * @return the list of accepted items
         */
        public static <T> Iterator<T> filteredIterator(final Iterator<? extends T> iterator, final Predicate<T> filter) {
                return new Iterator<T>() {
                        T next;

                        @Override
                        public boolean hasNext() {
                                if (next != null)
                                        return true;

                                if (!iterator.hasNext())
                                        return false;

                                while (iterator.hasNext()) {
                                        next = iterator.next();

                                        if (filter.test(next))
                                                return true;
                                }

                                return false;
                        }

                        @Override
                        public T next() {
                                if (next == null)
                                        hasNext();

                                final T ret = next;
                                next = null;
                                return ret;
                        }

                        @Override
                        public void remove() {
                                iterator.remove();
                        }
                };
        }

        /**
         * Create an iterator that filters items from the given array.
         * 
         * @see Predicate#test(Object)
         * 
         * @param <T>
         *            type of object being filtered
         * @param array
         *            to filter
         * @param filter
         *            the filter
         * @return the list of accepted items
         */
        public static <T> Iterator<T> filteredIterator(final T[] array, final Predicate<T> filter) {
                return filteredIterator(new ArrayIterator<T>(array), filter);
        }
}