/*
 * 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.flink.api.common.operators.util;

import org.apache.flink.api.common.typeutils.TypeComparator;
import org.apache.flink.api.common.typeutils.TypeSerializer;

import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * The KeyValueIterator returns a key and all values that belong to the key (share the same key).
 */
public final class ListKeyGroupedIterator<E> {

	private final List<E> input;

	private final TypeSerializer<E> serializer;  // != null if the elements should be copied
	
	private final TypeComparator<E> comparator;

	private ValuesIterator valuesIterator;

	private int currentPosition = 0;

	private E lookahead;
	
	private boolean done;

	/**
	 * Initializes the ListKeyGroupedIterator..
	 *
	 * @param input The list with the input elements.
	 * @param comparator The comparator for the data type iterated over.
	 */
	public ListKeyGroupedIterator(List<E> input, TypeSerializer<E> serializer, TypeComparator<E> comparator, boolean copy) {
		if (input == null || comparator == null) {
			throw new NullPointerException();
		}

		this.input = input;
		this.serializer = copy ? serializer : null;
		this.comparator = comparator;

		this.done = input.isEmpty() ? true : false;
	}

	/**
	 * Moves the iterator to the next key. This method may skip any values that have not yet been returned by the
	 * iterator created by the {@link #getValues()} method. Hence, if called multiple times it "removes" key groups.
	 *
	 * @return true, if the input iterator has an other group of records with the same key.
	 */
	public boolean nextKey() throws IOException {

		if (lookahead != null) {
			// common case: whole value-iterator was consumed and a new key group is available.
			this.comparator.setReference(this.lookahead);
			this.valuesIterator.next = this.lookahead;
			this.lookahead = null;
			return true;
		}

		// first element, empty/done, or the values iterator was not entirely consumed
		if (this.done) {
			return false;
		}

		if (this.valuesIterator != null) {
			// values was not entirely consumed. move to the next key
			// Required if user code / reduce() method did not read the whole value iterator.
			E next;
			while (true) {
				if ((next = this.input.get(currentPosition++)) != null) {
					if (!this.comparator.equalToReference(next)) {
						// the keys do not match, so we have a new group. store the current key
						this.comparator.setReference(next);
						this.valuesIterator.next = next;
						return true;
					}
				}
				else {
					// input exhausted
					this.valuesIterator.next = null;
					this.valuesIterator = null;
					this.done = true;
					return false;
				}
			}
		}
		else {
			// first element
			// get the next element
			E first = input.get(currentPosition++);
			if (first != null) {
				this.comparator.setReference(first);
				this.valuesIterator = new ValuesIterator(first, serializer);
				return true;
			}
			else {
				// empty input, set everything null
				this.done = true;
				return false;
			}
		}
	}

	private E advanceToNext() {
		if (currentPosition < input.size()) {
			E next = input.get(currentPosition++);
			if (comparator.equalToReference(next)) {
				// same key
				return next;
			} else {
				// moved to the next key, no more values here
				lookahead = next;
				return null;
			}
		}
		else {
			// backing iterator is consumed
			this.done = true;
			return null;
		}
	}

	/**
	 * Returns an iterator over all values that belong to the current key. The iterator is initially <code>null</code>
	 * (before the first call to {@link #nextKey()} and after all keys are consumed. In general, this method returns
	 * always a non-null value, if a previous call to {@link #nextKey()} return <code>true</code>.
	 *
	 * @return Iterator over all values that belong to the current key.
	 */
	public ValuesIterator getValues() {
		return this.valuesIterator;
	}

	// --------------------------------------------------------------------------------------------

	public final class ValuesIterator implements Iterator<E>, Iterable<E> {

		private E next;
		
		private final TypeSerializer<E> serializer;

		private ValuesIterator(E first, TypeSerializer<E> serializer) {
			this.next = first;
			this.serializer = serializer;
		}

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

		@Override
		public E next() {
			if (this.next != null) {
				E current = this.next;
				this.next = ListKeyGroupedIterator.this.advanceToNext();
				return serializer != null ? serializer.copy(current) : current;
			} else {
				throw new NoSuchElementException();
			}
		}

		@Override
		public void remove() {
			throw new UnsupportedOperationException();
		}

		@Override
		public Iterator<E> iterator() {
			return this;
		}

		public E getCurrent() {
			return next;
		}
	}
}

@@ -3053,16 +3053,50 @@
 %09%09%09%09if (
+currentPosition %3C input.size() && 
 (next = 

Fix IndexOutOfBoundsException in ListKeyGroupedIterator