/*
    * 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.collect;
  
  import com.google.common.base.Function;
  import com.google.common.primitives.Ints;
  
  import junit.framework.TestCase;
  
  import java.util.List;
  import java.util.Random;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.ConcurrentSkipListMap;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.atomic.AtomicInteger;
  
  /**
   * Basher test for {@link ConcurrentHashMultiset}: start a bunch of threads, have each of them
   * do operations at random. Each thread keeps track of the per-key deltas that it's directly
   * responsible for; after all threads have completed, we sum the per-key deltas and compare to the
   * existing multiset values.
   *
   * @author mike nonemacher
   */
  
  public class ConcurrentHashMultisetBasherTest extends TestCase {
  
    public void testAddAndRemove_ConcurrentHashMap() throws Exception {
      testAddAndRemove(new ConcurrentHashMap<String, AtomicInteger>());
    }
  
    public void testAddAndRemove_ConcurrentSkipListMap() throws Exception {
      testAddAndRemove(new ConcurrentSkipListMap<String, AtomicInteger>());
    }
  
    public void testAddAndRemove_MapMakerMap() throws Exception {
      MapMaker mapMaker = new MapMaker();
      // force MapMaker to use its own MapMakerInternalMap
      mapMaker.useCustomMap = true;
      testAddAndRemove(mapMaker.<String, AtomicInteger>makeMap());
    }
  
    private void testAddAndRemove(ConcurrentMap<String, AtomicInteger> map)
        throws ExecutionException, InterruptedException {
  
      final ConcurrentHashMultiset<String> multiset = new ConcurrentHashMultiset<String>(map);
      int nThreads = 20;
      int tasksPerThread = 10;
      int nTasks = nThreads * tasksPerThread;
      ExecutorService pool = Executors.newFixedThreadPool(nThreads);
      ImmutableList<String> keys = ImmutableList.of("a", "b", "c");
      try {
        List<Future<int[]>> futures = Lists.newArrayListWithExpectedSize(nTasks);
        for (int i = 0; i < nTasks; i++) {
          futures.add(pool.submit(new MutateTask(multiset, keys)));
        }
  
        int[] deltas = new int[3];
        for (Future<int[]> future : futures) {
          int[] taskDeltas = future.get();
          for (int i = 0; i < deltas.length; i++) {
            deltas[i] += taskDeltas[i];
          }
        }
  
        List<Integer> actualCounts = Lists.transform(keys,
            new Function<String, Integer>() {
              @Override public Integer apply(String key) {
                return multiset.count(key);
              }
            });
        assertEquals("Counts not as expected", Ints.asList(deltas), actualCounts);
      } finally {
        pool.shutdownNow();
      }
  
      // Since we have access to the backing map, verify that there are no zeroes in the map
      for (AtomicInteger value : map.values()) {
        assertTrue("map should not contain a zero", value.get() != 0);
      }
   }
 
   private static class MutateTask implements Callable<int[]> {
     private final ConcurrentHashMultiset<String> multiset;
     private final ImmutableList<String> keys;
     private final Random random = new Random();
 
     private MutateTask(ConcurrentHashMultiset<String> multiset, ImmutableList<String> keys) {
       this.multiset = multiset;
       this.keys = keys;
     }
 
     @Override public int[] call() throws Exception {
       int iterations = 100000;
       int nKeys = keys.size();
       int[] deltas = new int[nKeys];
       Operation[] operations = Operation.values();
       for (int i = 0; i < iterations; i++) {
         int keyIndex = random.nextInt(nKeys);
         String key = keys.get(keyIndex);
         Operation op = operations[random.nextInt(operations.length)];
         switch (op) {
           case ADD: {
             int delta = random.nextInt(10);
             multiset.add(key, delta);
             deltas[keyIndex] += delta;
             break;
           }
           case SET_COUNT: {
             int newValue = random.nextInt(3);
             int oldValue = multiset.setCount(key, newValue);
             deltas[keyIndex] += (newValue - oldValue);
             break;
           }
           case SET_COUNT_IF: {
             int newValue = random.nextInt(3);
             int oldValue = multiset.count(key);
             if (multiset.setCount(key, oldValue, newValue)) {
               deltas[keyIndex] += (newValue - oldValue);
             }
             break;
           }
           case REMOVE: {
             int delta = random.nextInt(6);  // [0, 5]
             int oldValue = multiset.remove(key, delta);
             deltas[keyIndex] -= Math.min(delta, oldValue);
             break;
           }
           case REMOVE_EXACTLY: {
             int delta = random.nextInt(5);  // [0, 4]
             if (multiset.removeExactly(key, delta)) {
               deltas[keyIndex] -= delta;
             }
             break;
           }
         }
       }
       return deltas;
     }
 
     private enum Operation {
       ADD,
       SET_COUNT,
       SET_COUNT_IF,
       REMOVE,
       REMOVE_EXACTLY,
       ;
     }
   }
 }