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/*
 * -\-\-
 * Spotify Apollo Testing Helpers
 * --
 * Copyright (C) 2013 - 2015 Spotify AB
 * --
 * 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.spotify.apollo.test.experimental;

import com.google.common.collect.ForwardingDeque;

import java.util.ArrayDeque;
import java.util.Deque;

import static com.google.common.base.Preconditions.checkArgument;

class SynchronizedRingBuffer extends ForwardingDeque {

  private final int capacity;
  private final ArrayDeque deque;

  public volatile int count;

  public SynchronizedRingBuffer(final int capacity) {
    checkArgument((capacity & capacity - 1) == 0, "capacity must be a power of 2");

    this.capacity = capacity;
    deque = new ArrayDeque<>(capacity);
  }

  @Override
  protected Deque delegate() {
    return deque;
  }

  public synchronized T[] copy(T[] into) {
    return deque.toArray(into);
  }

  @Override
  public synchronized boolean add(T element) {
    if (count >= capacity) {
      poll();
    } else {
      count++;
    }
    return super.add(element);
  }

  @Override
  public synchronized boolean offer(T o) {
    if (count >= capacity) {
      poll();
    } else {
      count++;
    }
    return super.offer(o);
  }

  @Override
  public synchronized void addFirst(T t) {
    if (count >= capacity) {
      poll();
    } else {
      count++;
    }
    super.addFirst(t);
  }
}