/*
    * 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 static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.collect.CollectPreconditions.checkNonnegative;
  
  import com.google.caliper.BeforeExperiment;
  import com.google.caliper.Benchmark;
  import com.google.caliper.Param;
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.primitives.Ints;
  import com.google.common.util.concurrent.ThreadFactoryBuilder;
  
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Random;
  import java.util.Set;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  
  import javax.annotation.Nullable;
  
  /**
   * Benchmarks for {@link ConcurrentHashMultiset}.
   *
   * @author mike nonemacher
   */
  public class ConcurrentHashMultisetBenchmark {
    @Param({"1", "2", "4", "8"}) int threads;
    @Param({"3", "30", "300"}) int size;
    @Param MultisetSupplier implSupplier;
  
    private Multiset<Integer> multiset;
    private ImmutableList<Integer> keys;
    private ExecutorService threadPool;
  
    @BeforeExperiment void setUp() throws Exception {
      multiset = implSupplier.get();
      ImmutableList.Builder<Integer> builder = ImmutableList.builder();
      for (int i = 0; i < size; i++) {
        builder.add(i);
      }
      keys = builder.build();
      threadPool =
          Executors.newFixedThreadPool(threads, new ThreadFactoryBuilder().setDaemon(true).build());
    }
  
    @Benchmark long add(final int reps) throws ExecutionException, InterruptedException {
      return doMultithreadedLoop(
          new Callable<Long>() {
            @Override public Long call() {
              return runAddSingleThread(reps);
            }
          });
    }
  
    @Benchmark long addRemove(final int reps) throws ExecutionException, InterruptedException {
      return doMultithreadedLoop(
          new Callable<Long>() {
            @Override public Long call() {
              return runAddRemoveSingleThread(reps);
            }
          });
    }
  
    private long doMultithreadedLoop(Callable<Long> task)
        throws InterruptedException, ExecutionException {
  
      List<Future<Long>> futures = Lists.newArrayListWithCapacity(threads);
      for (int i = 0; i < threads; i++) {
        futures.add(threadPool.submit(task));
      }
      long total = 0;
      for (Future<Long> future : futures) {
        total += future.get();
      }
      return total;
    }
 
   private long runAddSingleThread(int reps) {
     Random random = new Random();
     int nKeys = keys.size();
     long blah = 0;
     for (int i = 0; i < reps; i++) {
       Integer key = keys.get(random.nextInt(nKeys));
       int delta = random.nextInt(5);
       blah += delta;
       multiset.add(key, delta);
     }
     return blah;
   }
 
   private long runAddRemoveSingleThread(int reps) {
     Random random = new Random();
     int nKeys = keys.size();
     long blah = 0;
     for (int i = 0; i < reps; i++) {
       Integer key = keys.get(random.nextInt(nKeys));
       // This range is [-5, 4] - slight negative bias so we often hit zero, which brings the
       // auto-removal of zeroes into play.
       int delta = random.nextInt(10) - 5;
       blah += delta;
       if (delta >= 0) {
         multiset.add(key, delta);
       } else {
         multiset.remove(key, -delta);
       }
     }
     return blah;
   }
 
   private enum MultisetSupplier {
     CONCURRENT_HASH_MULTISET() {
       @Override Multiset<Integer> get() {
         return ConcurrentHashMultiset.create();
       }
     },
     BOXED_ATOMIC_REPLACE() {
       @Override Multiset<Integer> get() {
         return OldConcurrentHashMultiset.create();
       }
     },
     SYNCHRONIZED_MULTISET() {
       @Override Multiset<Integer> get() {
         return Synchronized.multiset(HashMultiset.<Integer>create(), null);
       }
     },
     ;
 
     abstract Multiset<Integer> get();
   }
 
   /**
    * Duplication of the old version of ConcurrentHashMultiset (with some unused stuff removed, like
    * serialization code) which used a map with boxed integers for the values.
    */
   private static final class OldConcurrentHashMultiset<E> extends AbstractMultiset<E> {
     /** The number of occurrences of each element. */
     private final transient ConcurrentMap<E, Integer> countMap;
 
     /**
      * Creates a new, empty {@code OldConcurrentHashMultiset} using the default
      * initial capacity, load factor, and concurrency settings.
      */
     public static <E> OldConcurrentHashMultiset<E> create() {
       return new OldConcurrentHashMultiset<E>(new ConcurrentHashMap<E, Integer>());
     }
 
     @VisibleForTesting OldConcurrentHashMultiset(ConcurrentMap<E, Integer> countMap) {
       checkArgument(countMap.isEmpty());
       this.countMap = countMap;
     }
 
     // Query Operations
 
     /**
      * Returns the number of occurrences of {@code element} in this multiset.
      *
      * @param element the element to look for
      * @return the nonnegative number of occurrences of the element
      */
     @Override public int count(@Nullable Object element) {
       try {
         return unbox(countMap.get(element));
       } catch (NullPointerException e) {
         return 0;
       } catch (ClassCastException e) {
         return 0;
       }
     }
 
     /**
      * {@inheritDoc}
      *
      * <p>If the data in the multiset is modified by any other threads during this
      * method, it is undefined which (if any) of these modifications will be
      * reflected in the result.
      */
     @Override public int size() {
       long sum = 0L;
       for (Integer value : countMap.values()) {
         sum += value;
       }
       return Ints.saturatedCast(sum);
     }
 
     /*
     * Note: the superclass toArray() methods assume that size() gives a correct
     * answer, which ours does not.
     */
 
     @Override public Object[] toArray() {
       return snapshot().toArray();
     }
 
     @Override public <T> T[] toArray(T[] array) {
       return snapshot().toArray(array);
     }
 
     /*
     * We'd love to use 'new ArrayList(this)' or 'list.addAll(this)', but
     * either of these would recurse back to us again!
     */
     private List<E> snapshot() {
       List<E> list = Lists.newArrayListWithExpectedSize(size());
       for (Multiset.Entry<E> entry : entrySet()) {
         E element = entry.getElement();
         for (int i = entry.getCount(); i > 0; i--) {
           list.add(element);
         }
       }
       return list;
     }
 
     // Modification Operations
 
     /**
      * Adds a number of occurrences of the specified element to this multiset.
      *
      * @param element the element to add
      * @param occurrences the number of occurrences to add
      * @return the previous count of the element before the operation; possibly
      *     zero
      * @throws IllegalArgumentException if {@code occurrences} is negative, or if
      *     the resulting amount would exceed {@link Integer#MAX_VALUE}
      */
     @Override public int add(E element, int occurrences) {
       if (occurrences == 0) {
         return count(element);
       }
       checkArgument(occurrences > 0, "Invalid occurrences: %s", occurrences);
 
       while (true) {
         int current = count(element);
         if (current == 0) {
           if (countMap.putIfAbsent(element, occurrences) == null) {
             return 0;
           }
         } else {
           checkArgument(occurrences <= Integer.MAX_VALUE - current,
               "Overflow adding %s occurrences to a count of %s",
               occurrences, current);
           int next = current + occurrences;
           if (countMap.replace(element, current, next)) {
             return current;
           }
         }
         // If we're still here, there was a race, so just try again.
       }
     }
 
     /**
      * Removes a number of occurrences of the specified element from this
      * multiset. If the multiset contains fewer than this number of occurrences to
      * begin with, all occurrences will be removed.
      *
      * @param element the element whose occurrences should be removed
      * @param occurrences the number of occurrences of the element to remove
      * @return the count of the element before the operation; possibly zero
      * @throws IllegalArgumentException if {@code occurrences} is negative
      */
     @Override public int remove(@Nullable Object element, int occurrences) {
       if (occurrences == 0) {
         return count(element);
       }
       checkArgument(occurrences > 0, "Invalid occurrences: %s", occurrences);
 
       while (true) {
         int current = count(element);
         if (current == 0) {
           return 0;
         }
         if (occurrences >= current) {
           if (countMap.remove(element, current)) {
             return current;
           }
         } else {
           // We know it's an "E" because it already exists in the map.
           @SuppressWarnings("unchecked")
           E casted = (E) element;
 
           if (countMap.replace(casted, current, current - occurrences)) {
             return current;
           }
         }
         // If we're still here, there was a race, so just try again.
       }
     }
 
     /**
      * Removes <b>all</b> occurrences of the specified element from this multiset.
      * This method complements {@link Multiset#remove(Object)}, which removes only
      * one occurrence at a time.
      *
      * @param element the element whose occurrences should all be removed
      * @return the number of occurrences successfully removed, possibly zero
      */
     private int removeAllOccurrences(@Nullable Object element) {
       try {
         return unbox(countMap.remove(element));
       } catch (NullPointerException e) {
         return 0;
       } catch (ClassCastException e) {
         return 0;
       }
     }
 
     /**
      * Removes exactly the specified number of occurrences of {@code element}, or
      * makes no change if this is not possible.
      *
      * <p>This method, in contrast to {@link #remove(Object, int)}, has no effect
      * when the element count is smaller than {@code occurrences}.
      *
      * @param element the element to remove
      * @param occurrences the number of occurrences of {@code element} to remove
      * @return {@code true} if the removal was possible (including if {@code
      *     occurrences} is zero)
      */
     public boolean removeExactly(@Nullable Object element, int occurrences) {
       if (occurrences == 0) {
         return true;
       }
       checkArgument(occurrences > 0, "Invalid occurrences: %s", occurrences);
 
       while (true) {
         int current = count(element);
         if (occurrences > current) {
           return false;
         }
         if (occurrences == current) {
           if (countMap.remove(element, occurrences)) {
             return true;
           }
         } else {
           @SuppressWarnings("unchecked") // it's in the map, must be an "E"
               E casted = (E) element;
           if (countMap.replace(casted, current, current - occurrences)) {
             return true;
           }
         }
         // If we're still here, there was a race, so just try again.
       }
     }
 
     /**
      * Adds or removes occurrences of {@code element} such that the {@link #count}
      * of the element becomes {@code count}.
      *
      * @return the count of {@code element} in the multiset before this call
      * @throws IllegalArgumentException if {@code count} is negative
      */
     @Override public int setCount(E element, int count) {
       checkNonnegative(count, "count");
       return (count == 0)
           ? removeAllOccurrences(element)
           : unbox(countMap.put(element, count));
     }
 
     /**
      * Sets the number of occurrences of {@code element} to {@code newCount}, but
      * only if the count is currently {@code oldCount}. If {@code element} does
      * not appear in the multiset exactly {@code oldCount} times, no changes will
      * be made.
      *
      * @return {@code true} if the change was successful. This usually indicates
      *     that the multiset has been modified, but not always: in the case that
      *     {@code oldCount == newCount}, the method will return {@code true} if
      *     the condition was met.
      * @throws IllegalArgumentException if {@code oldCount} or {@code newCount} is
      *     negative
      */
     @Override public boolean setCount(E element, int oldCount, int newCount) {
       checkNonnegative(oldCount, "oldCount");
       checkNonnegative(newCount, "newCount");
       if (newCount == 0) {
         if (oldCount == 0) {
           // No change to make, but must return true if the element is not present
           return !countMap.containsKey(element);
         } else {
           return countMap.remove(element, oldCount);
         }
       }
       if (oldCount == 0) {
         return countMap.putIfAbsent(element, newCount) == null;
       }
       return countMap.replace(element, oldCount, newCount);
     }
 
     // Views
 
     @Override Set<E> createElementSet() {
       final Set<E> delegate = countMap.keySet();
       return new ForwardingSet<E>() {
         @Override protected Set<E> delegate() {
           return delegate;
         }
         @Override public boolean remove(Object object) {
           try {
             return delegate.remove(object);
           } catch (NullPointerException e) {
             return false;
           } catch (ClassCastException e) {
             return false;
           }
         }
       };
     }
 
     private transient EntrySet entrySet;
 
     @Override public Set<Multiset.Entry<E>> entrySet() {
       EntrySet result = entrySet;
       if (result == null) {
         entrySet = result = new EntrySet();
       }
       return result;
     }
 
     @Override int distinctElements() {
       return countMap.size();
     }
 
     @Override public boolean isEmpty() {
       return countMap.isEmpty();
     }
 
     @Override Iterator<Entry<E>> entryIterator() {
       final Iterator<Map.Entry<E, Integer>> backingIterator =
           countMap.entrySet().iterator();
       return new Iterator<Entry<E>>() {
         @Override public boolean hasNext() {
           return backingIterator.hasNext();
         }
 
         @Override public Multiset.Entry<E> next() {
           Map.Entry<E, Integer> backingEntry = backingIterator.next();
           return Multisets.immutableEntry(backingEntry.getKey(),
               backingEntry.getValue());
         }
 
         @Override public void remove() {
           backingIterator.remove();
         }
       };
     }
 
     @Override public void clear() {
       countMap.clear();
     }
 
     private class EntrySet extends AbstractMultiset<E>.EntrySet {
       @Override Multiset<E> multiset() {
         return OldConcurrentHashMultiset.this;
       }
 
       /*
       * Note: the superclass toArray() methods assume that size() gives a correct
       * answer, which ours does not.
       */
 
       @Override public Object[] toArray() {
         return snapshot().toArray();
       }
 
       @Override public <T> T[] toArray(T[] array) {
         return snapshot().toArray(array);
       }
 
       private List<Multiset.Entry<E>> snapshot() {
         List<Multiset.Entry<E>> list = Lists.newArrayListWithExpectedSize(size());
         // not Iterables.addAll(list, this), because that'll forward back here
         Iterators.addAll(list, iterator());
         return list;
       }
 
       @Override public boolean remove(Object object) {
         if (object instanceof Multiset.Entry) {
           Multiset.Entry<?> entry = (Multiset.Entry<?>) object;
           Object element = entry.getElement();
           int entryCount = entry.getCount();
           return countMap.remove(element, entryCount);
         }
         return false;
       }
 
       /**
        * The hash code is the same as countMap's, though the objects aren't equal.
        */
       @Override public int hashCode() {
         return countMap.hashCode();
       }
     }
 
     /**
      * We use a special form of unboxing that treats null as zero.
      */
     private static int unbox(@Nullable Integer i) {
       return (i == null) ? 0 : i;
     }
   }
 }