/*
 * 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.util;

import org.apache.flink.util.TraversableOnceException;
import org.apache.flink.util.UnionIterator;
import org.junit.Test;

import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;

import static org.junit.Assert.*;

public class UnionIteratorTest {

	@Test
	public void testUnion() {
		try {
			UnionIterator<Integer> iter = new UnionIterator<>();

			// should succeed and be empty
			assertFalse(iter.iterator().hasNext());

			iter.clear();
			
			try {
				iter.iterator().next();
				fail("should fail with an exception");
			} catch (NoSuchElementException e) {
				// expected
			}

			iter.clear();
			iter.addList(Arrays.asList(1, 2, 3, 4, 5, 6, 7));
			iter.addList(Collections.<Integer>emptyList());
			iter.addList(Arrays.asList(8, 9, 10, 11));
			
			int val = 1;
			for (int i : iter) {
				assertEquals(val++, i);
			}
		}
		catch (Exception e) {
			e.printStackTrace();
			fail(e.getMessage());
		}
	}
	
	@Test
	public void testTraversableOnce() {
		try {
			UnionIterator<Integer> iter = new UnionIterator<>();
			
			// should succeed
			iter.iterator();
			
			// should fail
			try {
				iter.iterator();
				fail("should fail with an exception");
			} catch (TraversableOnceException e) {
				// expected
			}

			// should fail again
			try {
				iter.iterator();
				fail("should fail with an exception");
			} catch (TraversableOnceException e) {
				// expected
			}

			// reset the thing, keep it empty
			iter.clear();

			// should succeed
			iter.iterator();

			// should fail
			try {
				iter.iterator();
				fail("should fail with an exception");
			} catch (TraversableOnceException e) {
				// expected
			}

			// should fail again
			try {
				iter.iterator();
				fail("should fail with an exception");
			} catch (TraversableOnceException e) {
				// expected
			}

			// reset the thing, add some data
			iter.clear();
			iter.addList(Arrays.asList(1, 2, 3, 4, 5, 6, 7));
			
			// should succeed
			Iterator<Integer> ints = iter.iterator();
			assertNotNull(ints.next());
			assertNotNull(ints.next());
			assertNotNull(ints.next());
			
			// should fail if called in the middle of operations
			try {
				iter.iterator();
				fail("should fail with an exception");
			} catch (TraversableOnceException e) {
				// expected
			}

			// reset the thing, keep it empty
			iter.clear();

			// should succeed again
			assertFalse(iter.iterator().hasNext());
			
		}
		catch (Exception e) {
			e.printStackTrace();
			fail(e.getMessage());
		}
	}
}