/*
    * 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.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  import java.util.NoSuchElementException;
  import java.util.Set;
  
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  /**
   * Test class for PermutationIterator.
   */
  public class PermutationIteratorTest extends AbstractIteratorTest<List<Character>> {
  
      @SuppressWarnings("boxing") // OK in test code
      protected Character[] testArray = { 'A', 'B', 'C' };
      protected List<Character> testList;
  
      @Override
      public PermutationIterator<Character> makeEmptyIterator() {
          return new PermutationIterator<>(new ArrayList<>());
      }
  
      @Override
      public PermutationIterator<Character> makeObject() {
          return new PermutationIterator<>(testList);
      }
  
      @BeforeEach
      public void setUp() {
          testList = new ArrayList<>();
          testList.addAll(Arrays.asList(testArray));
      }
  
      @Override
      public boolean supportsEmptyIterator() {
          return false;
      }
  
      @Override
      public boolean supportsRemove() {
          return false;
      }
  
      @Test
      public void testEmptyCollection() {
          final PermutationIterator<Character> it = makeEmptyIterator();
          // there is one permutation for an empty set: 0! = 1
          assertTrue(it.hasNext());
  
          final List<Character> nextPermutation = it.next();
          assertEquals(0, nextPermutation.size());
  
          assertFalse(it.hasNext());
      }
  
      @Test
      public void testPermutationException() {
          final List<List<Character>> resultsList = new ArrayList<>();
  
          final PermutationIterator<Character> it = makeObject();
          while (it.hasNext()) {
              final List<Character> permutation = it.next();
              resultsList.add(permutation);
          }
          //asking for another permutation should throw an exception
          assertThrows(NoSuchElementException.class, () -> it.next());
      }
  
      /**
       * test checking that all the permutations are returned
       */
      @Test
      @SuppressWarnings("boxing") // OK in test code
     public void testPermutationExhaustivity() {
         final List<Character> perm1 = new ArrayList<>();
         final List<Character> perm2 = new ArrayList<>();
         final List<Character> perm3 = new ArrayList<>();
         final List<Character> perm4 = new ArrayList<>();
         final List<Character> perm5 = new ArrayList<>();
         final List<Character> perm6 = new ArrayList<>();
 
         perm1.add('A');
         perm2.add('A');
         perm3.add('B');
         perm4.add('B');
         perm5.add('C');
         perm6.add('C');
 
         perm1.add('B');
         perm2.add('C');
         perm3.add('A');
         perm4.add('C');
         perm5.add('A');
         perm6.add('B');
 
         perm1.add('C');
         perm2.add('B');
         perm3.add('C');
         perm4.add('A');
         perm5.add('B');
         perm6.add('A');
 
         final List<List<Character>> results = new ArrayList<>();
 
         final PermutationIterator<Character> it = makeObject();
         while (it.hasNext()) {
             final List<Character> next = it.next();
             results.add(next);
         }
         //3! permutation for 3 elements
         assertEquals(6, results.size());
         assertTrue(results.contains(perm1));
         assertTrue(results.contains(perm2));
         assertTrue(results.contains(perm3));
         assertTrue(results.contains(perm4));
         assertTrue(results.contains(perm5));
         assertTrue(results.contains(perm6));
     }
 
     @Test
     @SuppressWarnings("boxing") // OK in test code
     public void testPermutationResultSize() {
         int factorial = 1;
         for (int i = 0; i < 8; i++, factorial *= i) {
             final List<Integer> list = new ArrayList<>();
             for (int j = 0; j < i; j++) {
                 list.add(j);
             }
             final Iterator<List<Integer>> it = new PermutationIterator<>(list);
             int count = 0;
             while (it.hasNext()) {
                 it.next();
                 count++;
             }
             assertEquals(factorial, count);
         }
     }
 
     /**
      * test checking that all the permutations are returned only once.
      */
     @Test
     public void testPermutationUnicity() {
         final List<List<Character>> resultsList = new ArrayList<>();
         final Set<List<Character>> resultsSet = new HashSet<>();
 
         final PermutationIterator<Character> it = makeObject();
         while (it.hasNext()) {
             final List<Character> permutation = it.next();
             resultsList.add(permutation);
             resultsSet.add(permutation);
         }
         //3! permutation for 3 elements
         assertEquals(6, resultsList.size());
         assertEquals(6, resultsSet.size());
     }
 
     @Test
     public void testPermutatorHasMore() {
         final PermutationIterator<Character> it = makeObject();
         for (int i = 0; i < 6; i++) {
             assertTrue(it.hasNext());
             it.next();
         }
         assertFalse(it.hasNext());
     }
 
 }