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/*******************************************************************************
 * Copyright 2011 LibGDX.
 * Mario Zechner 
 * Nathan Sweet 
 *
 * 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 dorkbox.util.collections;

import java.util.Iterator;

/** Interface used to select items within an iterator against a predicate.
 * @author Xoppa */
public interface Predicate {

	/** @return true if the item matches the criteria and should be included in the iterator's items */
	boolean evaluate (T arg0);

	public class PredicateIterator implements Iterator {
		public Iterator iterator;
		public Predicate predicate;
		public boolean end = false;
		public boolean peeked = false;
		public T next = null;

		public PredicateIterator (final Iterable iterable, final Predicate predicate) {
			this(iterable.iterator(), predicate);
		}

		public PredicateIterator (final Iterator iterator, final Predicate predicate) {
			set(iterator, predicate);
		}

		public void set (final Iterable iterable, final Predicate predicate) {
			set(iterable.iterator(), predicate);
		}

		public void set (final Iterator iterator, final Predicate predicate) {
			this.iterator = iterator;
			this.predicate = predicate;
			end = peeked = false;
			next = null;
		}

		@Override
		public boolean hasNext () {
			if (end) return false;
			if (next != null) return true;
			peeked = true;
			while (iterator.hasNext()) {
				final T n = iterator.next();
				if (predicate.evaluate(n)) {
					next = n;
					return true;
				}
			}
			end = true;
			return false;
		}

		@Override
		public T next () {
			if (next == null && !hasNext()) return null;
			final T result = next;
			next = null;
			peeked = false;
			return result;
		}

		@Override
		public void remove () {
			if (peeked) throw new RuntimeException("Cannot remove between a call to hasNext() and next().");
			iterator.remove();
		}
	}

	public static class PredicateIterable implements Iterable {
		public Iterable iterable;
		public Predicate predicate;
		public PredicateIterator iterator = null;

		public PredicateIterable (Iterable iterable, Predicate predicate) {
			set(iterable, predicate);
		}

		public void set (Iterable iterable, Predicate predicate) {
			this.iterable = iterable;
			this.predicate = predicate;
		}

		/** Returns an iterator. Note that the same iterator instance is returned each time this method is called. Use the
		 * {@link Predicate.PredicateIterator} constructor for nested or multithreaded iteration. */
		@Override
		public Iterator iterator () {
			if (iterator == null)
				iterator = new PredicateIterator(iterable.iterator(), predicate);
			else
				iterator.set(iterable.iterator(), predicate);
			return iterator;
		}
	}
}