package net.trajano.commons.testing;
   
   import java.util.concurrent.Callable;
   
   import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
   
   /**
    * This provides utility methods that ensure the {@link #equals(Object)} and
    * {@link #hashCode()} are implemented correctly.
   *
   * @author Archimedes Trajano
   */
  public final class EqualsTestUtil {
  
      /**
       * Builds two objects the same way and checks if they are equal.
       *
       * @param <T>
       *            type
       * @param objectBuilder
       *            object builder
       */
      public static <T> void assertEqualsImplementedCorrectly(final Callable<T> objectBuilder) {
  
          assertEqualsImplementedCorrectly(objectBuilder, objectBuilder);
      }
  
      /**
       * Builds two objects and ensures that they are equal.
       *
       * @param <T>
       *            type
       * @param objectBuilder1
       *            first object builder
       * @param objectBuilder2
       *            second object builder
       */
      public static <T> void assertEqualsImplementedCorrectly(final Callable<T> objectBuilder1,
              final Callable<T> objectBuilder2) {
  
          try {
              final T o1 = objectBuilder1.call();
              final T o2 = objectBuilder2.call();
              assertEqualsImplementedCorrectly(o1, o2);
          } catch (final Exception e) {
              throw new AssertionError(e);
          }
      }
  
      /**
       * Take two objects and ensure their are implemented correctly. Warnings are
       * suppressed as this block of code will do things that normal developers
       * are not supposed to do, but are needed to ensure that
       * {@link #equals(Object)} is implemented correctly.
       * <p>
       * The generic check is not put in to allow testing with different classes
       * </p>
       *
       * @param o1
       *            first object
       * @param o2
       *            second object
       */
      @SuppressWarnings("all")
      @SuppressFBWarnings()
      public static void assertEqualsImplementedCorrectly(final Object o1,
              final Object o2) {
  
          // symmetric
          if (!o1.equals(o2)) {
              throw new AssertionError("Expected " + o1 + " ==  " + o2);
          }
          if (!o2.equals(o1)) {
              throw new AssertionError("Expected " + o2 + " ==  " + o1);
          }
  
          // this == object tests
          if (!o1.equals(o1)) {
              throw new AssertionError("Expected " + o1 + " ==  " + o1);
          }
          if (!o2.equals(o2)) {
              throw new AssertionError("Expected " + o2 + " ==  " + o2);
          }
  
          // Different class checks
          if (o1.equals(new EqualsTestUtil())) {
              throw new AssertionError("Type of " + o1 + " does not match expected class");
          }
          if (o2.equals(new EqualsTestUtil())) {
              throw new AssertionError("Type of " + o2 + " does not match expected class");
          }
  
          // Null tests done poorly but will at least trigger the right paths.
  
          // CHECKSTYLE:OFF
          if (o1.equals(null)) {
              throw new AssertionError("Did not expect " + o1 + " == null");
          }
          if (o2.equals(null)) {
             throw new AssertionError("Did not expect " + o2 + " == null");
         }
         // CHECKSTYLE:ON
 
         // hash code validity
         if (o1.hashCode() != o2.hashCode()) {
             throw new AssertionError(String.format("Expected hash code of %s (%d) == %s (%d)", o1, o1.hashCode(), o2, o2.hashCode()));
         }
     }
 
     /**
      * Take a single object and ensure its equality is implemented correctly.
      *
      * @param <T>
      *            type
      * @param o
      *            object
      */
     public static <T> void assertEqualsImplementedCorrectly(final T o) {
 
         assertEqualsImplementedCorrectly(o, o);
     }
 
     /**
      * Prevent instantiation of utility class.
      */
     private EqualsTestUtil() {
 
     }
 }