/*
    * 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.commons.collections4.iterators;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertNull;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.NoSuchElementException;
  
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  /**
   * Tests the PeekingIterator.
   *
   * @param <E> the type of elements tested by this iterator.
   */
  public class PeekingIteratorTest<E> extends AbstractIteratorTest<E> {
  
      private final String[] testArray = { "a", "b", "c" };
  
      private List<E> testList;
  
      @Override
      public Iterator<E> makeEmptyIterator() {
          return PeekingIterator.peekingIterator(Collections.<E>emptyList().iterator());
      }
  
      @Override
      public PeekingIterator<E> makeObject() {
          return PeekingIterator.peekingIterator(testList.iterator());
      }
  
      @SuppressWarnings("unchecked")
      @BeforeEach
      protected void setUp() throws Exception {
          testList = new ArrayList<>(Arrays.asList((E[]) testArray));
      }
  
      @Override
      public boolean supportsRemove() {
          return true;
      }
  
      @Test
      public void testEmpty() {
          final Iterator<E> it = makeEmptyIterator();
          assertFalse(it.hasNext());
      }
  
      @Test
      public void testIllegalRemove() {
          final PeekingIterator<E> it = makeObject();
          it.next();
          it.remove(); // supported
  
          assertTrue(it.hasNext());
          assertEquals("b", it.peek());
  
          assertThrows(IllegalStateException.class, () -> it.remove());
      }
  
      @Test
      public void testIteratorExhausted() {
          final PeekingIterator<E> it = makeObject();
          it.next();
          it.next();
          it.next();
          assertFalse(it.hasNext());
          assertNull(it.peek());
  
          assertThrows(NoSuchElementException.class, () -> it.element());
      }
  
      @Test
      public void testMultiplePeek() {
          final PeekingIterator<E> it = makeObject();
         assertEquals("a", it.peek());
         assertEquals("a", it.peek());
         assertEquals("a", it.next());
         assertTrue(it.hasNext());
         assertEquals("b", it.peek());
         assertEquals("b", it.peek());
         assertEquals("b", it.next());
         assertTrue(it.hasNext());
         assertEquals("c", it.peek());
         assertEquals("c", it.peek());
         assertEquals("c", it.next());
         assertFalse(it.hasNext());
     }
 
     @Test
     @SuppressWarnings("unchecked")
     public void testSinglePeek() {
         final PeekingIterator<E> it = makeObject();
         assertEquals("a", it.peek());
         assertEquals("a", it.element());
         validate(it, (E[]) testArray);
     }
 
     private void validate(final Iterator<E> iter, final E... items) {
         for (final E x : items) {
             assertTrue(iter.hasNext());
             assertEquals(x, iter.next());
         }
         assertFalse(iter.hasNext());
     }
 
 }