/*
    * Copyright (C) 2011 The Guava Authors
    *
    * Licensed 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 com.google.common.testing;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.base.Equivalence;
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.Lists;
  
  import junit.framework.AssertionFailedError;
  
  import java.util.List;
  
  /**
   * Implementation helper for {@link EqualsTester} and {@link EquivalenceTester} that tests for
   * equivalence classes.
   *
   * @author Gregory Kick
   */
  @GwtCompatible
  final class RelationshipTester<T> {
  
    static class ItemReporter {
      String reportItem(Item<?> item) {
        return item.toString();
      }
    }
  
    /**
     * A word about using {@link Equivalence}, which automatically checks for {@code null} and
     * identical inputs: This sounds like it ought to be a problem here, since the goals of this class
     * include testing that {@code equals()} is reflexive and is tolerant of {@code null}. However,
     * there's no problem. The reason: {@link EqualsTester} tests {@code null} and identical inputs
     * directly against {@code equals()} rather than through the {@code Equivalence}.
     */
    private final Equivalence<? super T> equivalence;
    private final String relationshipName;
    private final String hashName;
    private final ItemReporter itemReporter;
    private final List<ImmutableList<T>> groups = Lists.newArrayList();
  
    RelationshipTester(Equivalence<? super T> equivalence, String relationshipName, String hashName,
        ItemReporter itemReporter) {
      this.equivalence = checkNotNull(equivalence);
      this.relationshipName = checkNotNull(relationshipName);
      this.hashName = checkNotNull(hashName);
      this.itemReporter = checkNotNull(itemReporter);
    }
  
    // TODO(cpovirk): should we reject null items, since the tests already check null automatically?
    public RelationshipTester<T> addRelatedGroup(Iterable<? extends T> group) {
      groups.add(ImmutableList.copyOf(group));
      return this;
    }
  
    public void test() {
      for (int groupNumber = 0; groupNumber < groups.size(); groupNumber++) {
        ImmutableList<T> group = groups.get(groupNumber);
        for (int itemNumber = 0; itemNumber < group.size(); itemNumber++) {
          // check related items in same group
          for (int relatedItemNumber = 0; relatedItemNumber < group.size(); relatedItemNumber++) {
            if (itemNumber != relatedItemNumber) {
              assertRelated(groupNumber, itemNumber, relatedItemNumber);
            }
          }
          // check unrelated items in all other groups
          for (int unrelatedGroupNumber = 0; unrelatedGroupNumber < groups.size();
              unrelatedGroupNumber++) {
            if (groupNumber != unrelatedGroupNumber) {
              ImmutableList<T> unrelatedGroup = groups.get(unrelatedGroupNumber);
              for (int unrelatedItemNumber = 0; unrelatedItemNumber < unrelatedGroup.size();
                  unrelatedItemNumber++) {
                assertUnrelated(groupNumber, itemNumber, unrelatedGroupNumber, unrelatedItemNumber);
              }
            }
          }
        }
      }
    }
  
    private void assertRelated(int groupNumber, int itemNumber, int relatedItemNumber) {
      Item<T> itemInfo = getItem(groupNumber, itemNumber);
      Item<T> relatedInfo = getItem(groupNumber, relatedItemNumber);
 
     T item = itemInfo.value;
     T related = relatedInfo.value;
     assertWithTemplate("$ITEM must be $RELATIONSHIP to $OTHER", itemInfo, relatedInfo,
         equivalence.equivalent(item, related));
     
     int itemHash = equivalence.hash(item);
     int relatedHash = equivalence.hash(related);
     assertWithTemplate("the $HASH (" + itemHash + ") of $ITEM must be equal to the $HASH ("
         + relatedHash + ") of $OTHER", itemInfo, relatedInfo, itemHash == relatedHash);
   }
 
   private void assertUnrelated(int groupNumber, int itemNumber, int unrelatedGroupNumber,
       int unrelatedItemNumber) {
     Item<T> itemInfo = getItem(groupNumber, itemNumber);
     Item<T> unrelatedInfo = getItem(unrelatedGroupNumber, unrelatedItemNumber);
 
     assertWithTemplate("$ITEM must not be $RELATIONSHIP to $OTHER", itemInfo, unrelatedInfo,
         !equivalence.equivalent(itemInfo.value, unrelatedInfo.value));
   }
 
   private void assertWithTemplate(String template, Item<T> item, Item<T> other, boolean condition) {
     if (!condition) {
       throw new AssertionFailedError(template
           .replace("$RELATIONSHIP", relationshipName)
           .replace("$HASH", hashName)
           .replace("$ITEM", itemReporter.reportItem(item))
           .replace("$OTHER", itemReporter.reportItem(other)));
     }
   }
 
   private Item<T> getItem(int groupNumber, int itemNumber) {
     return new Item<T>(groups.get(groupNumber).get(itemNumber), groupNumber, itemNumber);
   }
 
   static final class Item<T> {
     final T value;
     final int groupNumber;
     final int itemNumber;
 
     Item(T value, int groupNumber, int itemNumber) {
       this.value = value;
       this.groupNumber = groupNumber;
       this.itemNumber = itemNumber;
     }
 
     @Override public String toString() {
       return new StringBuilder()
           .append(value)
           .append(" [group ")
           .append(groupNumber + 1)
           .append(", item ")
           .append(itemNumber + 1)
           .append(']')
           .toString();
     }
   }
 }