/*
    * 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
    * https://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.hipparchus.util;
  
  import org.junit.jupiter.api.Test;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertNotEquals;
  import static org.junit.jupiter.api.Assertions.assertNotNull;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  /**
   * Test for {@link Pair}.
   */
  class PairTest {
  
      @Test
      void testAccessor() {
          final Pair<Integer, Double> p = new Pair<>(Integer.valueOf(1), Double.valueOf(2));
          assertEquals(Integer.valueOf(1), p.getKey());
          assertEquals(2, p.getValue().doubleValue(), Math.ulp(1d));
      }
  
      @Test
      void testAccessor2() {
          final Pair<Integer, Double> p = new Pair<>(Integer.valueOf(1), Double.valueOf(2));
  
          // Check that both APIs refer to the same data.
  
          assertTrue(p.getFirst() == p.getKey());
          assertTrue(p.getSecond() == p.getValue());
      }
  
      @Test
      void testEquals() {
          Pair<Integer, Double> p1 = new Pair<>(null, null);
          assertNotEquals(null, p1);
  
          Pair<Integer, Double> p2 = new Pair<>(null, null);
          assertEquals(p1, p2);
  
          p1 = new Pair<>(Integer.valueOf(1), Double.valueOf(2));
          assertNotEquals(p1, p2);
  
          p2 = new Pair<>(Integer.valueOf(1), Double.valueOf(2));
          assertEquals(p1, p2);
  
          Pair<Integer, Float> p3 = new Pair<>(Integer.valueOf(1), Float.valueOf(2));
          assertNotEquals(p1, p3);
      }
  
      @Test
      void testHashCode() {
          final MyInteger m1 = new MyInteger(1);
          final MyInteger m2 = new MyInteger(1);
  
          final Pair<MyInteger, MyInteger> p1 = new Pair<>(m1, m1);
          final Pair<MyInteger, MyInteger> p2 = new Pair<>(m2, m2);
          // Same contents, same hash code.
          assertEquals(p1.hashCode(), p2.hashCode());
  
          // Different contents, different hash codes.
          m2.set(2);
          assertFalse(p1.hashCode() == p2.hashCode());
      }
  
      @Test
      void testToString() {
          assertEquals("[null, null]", new Pair<>(null, null).toString());
          assertEquals("[foo, 3]", new Pair<>("foo", 3).toString());
      }
  
      @Test
      void testCreate() {
          final Pair<String, Integer> p1 = Pair.create("foo", 3);
          assertNotNull(p1);
          final Pair<String, Integer> p2 = new Pair<>("foo", 3);
          assertEquals(p2, p1);
      }
  
      /**
       * A mutable integer.
       */
      private static class MyInteger {
          private int i;
  
          public MyInteger(int i) {
             this.i = i;
         }
 
         public void set(int i) {
             this.i = i;
         }
 
         @Override
         public boolean equals(Object o) {
             if (!(o instanceof MyInteger)) {
                 return false;
             } else {
                 return i == ((MyInteger) o).i;
             }
         }
 
         @Override
         public int hashCode() {
             return i;
         }
     }
 }