/*
    * 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.assertAll;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  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.List;
  import java.util.NoSuchElementException;
  
  import org.junit.jupiter.api.Test;
  
  /**
   * Tests the LoopingListIterator class.
   */
  public class LoopingListIteratorTest {
  
      /**
       * Tests the add method.
       */
      @Test
      public void testAdd() {
          List<String> list = new ArrayList<>(Arrays.asList("b", "e", "f"));
          LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <b> e f
  
          loop.add("a");                      // <a> b e f
          assertEquals("b", loop.next());     // a <b> e f
          loop.reset();                       // <a> b e f
          assertEquals("a", loop.next());     // a <b> e f
          assertEquals("b", loop.next());     // a b <e> f
  
          loop.add("c");                      // a b c <e> f
          assertEquals("e", loop.next());     // a b c e <f>
          assertEquals("e", loop.previous()); // a b c <e> f
          assertEquals("c", loop.previous()); // a b <c> e f
          assertEquals("c", loop.next());     // a b c <e> f
  
          loop.add("d");                      // a b c d <e> f
          loop.reset();                       // <a> b c d e f
          assertEquals("a", loop.next());     // a <b> c d e f
          assertEquals("b", loop.next());     // a b <c> d e f
          assertEquals("c", loop.next());     // a b c <d> e f
          assertEquals("d", loop.next());     // a b c d <e> f
          assertEquals("e", loop.next());     // a b c d e <f>
          assertEquals("f", loop.next());     // <a> b c d e f
          assertEquals("a", loop.next());     // a <b> c d e f
  
          list = new ArrayList<>(Arrays.asList("b", "e", "f"));
          loop = new LoopingListIterator<>(list); // <b> e f
  
          loop.add("a");                      // a <b> e f
          assertEquals("a", loop.previous()); // a b e <f>
          loop.reset();                       // <a> b e f
          assertEquals("f", loop.previous()); // a b e <f>
          assertEquals("e", loop.previous()); // a b <e> f
  
          loop.add("d");                      // a b d <e> f
          assertEquals("d", loop.previous()); // a b <d> e f
  
          loop.add("c");                      // a b c <d> e f
          assertEquals("c", loop.previous()); // a b <c> d e f
  
          loop.reset();
          assertEquals("a", loop.next());     // a <b> c d e f
          assertEquals("b", loop.next());     // a b <c> d e f
          assertEquals("c", loop.next());     // a b c <d> e f
          assertEquals("d", loop.next());     // a b c d <e> f
          assertEquals("e", loop.next());     // a b c d e <f>
          assertEquals("f", loop.next());     // <a> b c d e f
          assertEquals("a", loop.next());     // a <b> c d e f
      }
  
      /**
       * Tests constructor exception.
       */
      @Test
      public void testConstructorEx() {
          assertThrows(NullPointerException.class, () -> new LoopingListIterator<>(null));
      }
  
     /**
      * Tests jogging back and forth between two elements, but not over
      * the begin/end boundary of the list.
      */
     @Test
     public void testJoggingNotOverBoundary() {
         final List<String> list = Arrays.asList("a", "b");
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <a> b
 
         // Try jogging back and forth between the elements, but not
         // over the begin/end boundary.
         loop.reset();
         assertEquals("a", loop.next());     // a <b>
         assertEquals("a", loop.previous()); // <a> b
         assertEquals("a", loop.next());     // a <b>
 
         assertEquals("b", loop.next());     // <a> b
         assertEquals("b", loop.previous()); // a <b>
         assertEquals("b", loop.next());     // <a> b
     }
 
     /**
      * Tests jogging back and forth between two elements over the
      * begin/end boundary of the list.
      */
     @Test
     public void testJoggingOverBoundary() {
         final List<String> list = Arrays.asList("a", "b");
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <a> b
 
         // Try jogging back and forth between the elements, but not
         // over the begin/end boundary.
         assertEquals("b", loop.previous()); // a <b>
         assertEquals("b", loop.next());     // <a> b
         assertEquals("b", loop.previous()); // a <b>
 
         assertEquals("a", loop.previous()); // <a> b
         assertEquals("a", loop.next());     // a <b>
         assertEquals("a", loop.previous()); // <a> b
     }
 
     /**
      * Tests whether an empty looping list iterator works.
      */
     @Test
     public void testLooping0() {
         final List<Object> list = new ArrayList<>();
         final LoopingListIterator<Object> loop = new LoopingListIterator<>(list);
         assertFalse(loop.hasNext());
         assertFalse(loop.hasPrevious());
         assertAll(
                 () -> assertThrows(NoSuchElementException.class, () -> loop.next()),
                 () -> assertThrows(NoSuchElementException.class, () -> loop.previous())
         );
     }
 
     /**
      * Tests whether a looping list iterator works on a list with only
      * one element.
      */
     @Test
     public void testLooping1() {
         final List<String> list = Arrays.asList("a");
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <a>
 
         assertTrue(loop.hasNext());
         assertEquals("a", loop.next());     // <a>
 
         assertTrue(loop.hasNext());
         assertEquals("a", loop.next());     // <a>
 
         assertTrue(loop.hasNext());
         assertEquals("a", loop.next());     // <a>
 
         assertTrue(loop.hasPrevious());
         assertEquals("a", loop.previous()); // <a>
 
         assertTrue(loop.hasPrevious());
         assertEquals("a", loop.previous()); // <a>
 
         assertTrue(loop.hasPrevious());
         assertEquals("a", loop.previous()); // <a>
     }
 
     /**
      * Tests whether a looping list iterator works on a list with two
      * elements.
      */
     @Test
     public void testLooping2() {
         final List<String> list = Arrays.asList("a", "b");
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <a> b
 
         assertTrue(loop.hasNext());
         assertEquals("a", loop.next());     // a <b>
 
         assertTrue(loop.hasNext());
         assertEquals("b", loop.next());     // <a> b
 
         assertTrue(loop.hasNext());
         assertEquals("a", loop.next());     // a <b>
 
         // Reset the iterator and try using previous.
         loop.reset();                       // <a> b
 
         assertTrue(loop.hasPrevious());
         assertEquals("b", loop.previous()); // a <b>
 
         assertTrue(loop.hasPrevious());
         assertEquals("a", loop.previous()); // <a> b
 
         assertTrue(loop.hasPrevious());
         assertEquals("b", loop.previous()); // a <b>
     }
 
     /**
      * Tests nextIndex and previousIndex.
      */
     @Test
     public void testNextAndPreviousIndex() {
         final List<String> list = Arrays.asList("a", "b", "c");
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <a> b c
 
         assertEquals(0, loop.nextIndex());
         assertEquals(2, loop.previousIndex());
 
         assertEquals("a", loop.next());        // a <b> c
         assertEquals(1, loop.nextIndex());
         assertEquals(0, loop.previousIndex());
 
         assertEquals("a", loop.previous());    // <a> b c
         assertEquals(0, loop.nextIndex());
         assertEquals(2, loop.previousIndex());
 
         assertEquals("c", loop.previous());    // a b <c>
         assertEquals(2, loop.nextIndex());
         assertEquals(1, loop.previousIndex());
 
         assertEquals("b", loop.previous());    // a <b> c
         assertEquals(1, loop.nextIndex());
         assertEquals(0, loop.previousIndex());
 
         assertEquals("a", loop.previous());    // <a> b c
         assertEquals(0, loop.nextIndex());
         assertEquals(2, loop.previousIndex());
     }
 
     /**
      * Tests removing an element from a wrapped ArrayList.
      */
     @Test
     public void testRemovingElementsAndIteratingBackwards() {
         final List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <a> b c
 
         assertTrue(loop.hasPrevious());
         assertEquals("c", loop.previous()); // a b <c>
         loop.remove();                      // <a> b
         assertEquals(2, list.size());
 
         assertTrue(loop.hasPrevious());
         assertEquals("b", loop.previous()); // a <b>
         loop.remove();                      // <a>
         assertEquals(1, list.size());
 
         assertTrue(loop.hasPrevious());
         assertEquals("a", loop.previous()); // <a>
         loop.remove();                      // ---
         assertEquals(0, list.size());
 
         assertFalse(loop.hasPrevious());
 
         assertThrows(NoSuchElementException.class, () -> loop.previous());
     }
 
     /**
      * Tests removing an element from a wrapped ArrayList.
      */
     @Test
     public void testRemovingElementsAndIteratingForward() {
         final List<String> list = new ArrayList<>(Arrays.asList("a", "b", "c"));
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <a> b c
 
         assertTrue(loop.hasNext());
         assertEquals("a", loop.next()); // a <b> c
         loop.remove();                  // <b> c
         assertEquals(2, list.size());
 
         assertTrue(loop.hasNext());
         assertEquals("b", loop.next()); // b <c>
         loop.remove();                  // <c>
         assertEquals(1, list.size());
 
         assertTrue(loop.hasNext());
         assertEquals("c", loop.next()); // <c>
         loop.remove();                  // ---
         assertEquals(0, list.size());
 
         assertFalse(loop.hasNext());
 
         assertThrows(NoSuchElementException.class, () -> loop.next());
     }
 
     /**
      * Tests the reset method.
      */
     @Test
     public void testReset() {
         final List<String> list = Arrays.asList("a", "b", "c");
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <a> b c
 
         assertEquals("a", loop.next()); // a <b> c
         assertEquals("b", loop.next()); // a b <c>
         loop.reset();                   // <a> b c
         assertEquals("a", loop.next()); // a <b> c
         loop.reset();                   // <a> b c
         assertEquals("a", loop.next()); // a <b> c
         assertEquals("b", loop.next()); // a b <c>
         assertEquals("c", loop.next()); // <a> b c
         loop.reset();                   // <a> b c
 
         assertEquals("c", loop.previous()); // a b <c>
         assertEquals("b", loop.previous()); // a <b> c
         loop.reset();                       // <a> b c
         assertEquals("c", loop.previous()); // a b <c>
         loop.reset();                       // <a> b c
         assertEquals("c", loop.previous()); // a b <c>
         assertEquals("b", loop.previous()); // a <b> c
         assertEquals("a", loop.previous()); // <a> b c
     }
 
     /**
      * Tests using the set method to change elements.
      */
     @Test
     public void testSet() {
         final List<String> list = Arrays.asList("q", "r", "z");
         final LoopingListIterator<String> loop = new LoopingListIterator<>(list); // <q> r z
 
         assertEquals("z", loop.previous()); // q r <z>
         loop.set("c");                      // q r <c>
 
         loop.reset();                       // <q> r c
         assertEquals("q", loop.next());     // q <r> c
         loop.set("a");                      // a <r> c
 
         assertEquals("r", loop.next());     // a r <c>
         loop.set("b");                      // a b <c>
 
         loop.reset();                       // <a> b c
         assertEquals("a", loop.next());     // a <b> c
         assertEquals("b", loop.next());     // a b <c>
         assertEquals("c", loop.next());     // <a> b c
     }
 
 }