/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.blur.store.blockcache_v2;

import java.util.Map.Entry;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.apache.blur.log.Log;
import org.apache.blur.log.LogFactory;
import org.apache.blur.store.blockcache_v2.BaseCache.STORE;
import org.apache.blur.store.blockcache_v2.cachevalue.ByteArrayCacheValue;
import org.apache.blur.store.blockcache_v2.cachevalue.UnsafeAllocateCacheValue;

public class SimpleCacheValueBufferPool extends BaseCacheValueBufferPool {

  private static final Log LOG = LogFactory.getLog(SimpleCacheValueBufferPool.class);

  private final ConcurrentMap<Integer, BlockingQueue<CacheValue>> _cacheValuePool = new ConcurrentHashMap<Integer, BlockingQueue<CacheValue>>();
  private final int _queueDepth;

  public SimpleCacheValueBufferPool(STORE store, int queueDepth) {
    super(store);
    _queueDepth = queueDepth;
  }

  public CacheValue getCacheValue(int cacheBlockSize) {
    BlockingQueue<CacheValue> blockingQueue = getPool(cacheBlockSize);
    CacheValue cacheValue = blockingQueue.poll();
    if (cacheValue == null) {
      _created.mark();
      return createCacheValue(cacheBlockSize);
    }
    _reused.mark();
    return cacheValue;
  }

  private BlockingQueue<CacheValue> getPool(int cacheBlockSize) {
    BlockingQueue<CacheValue> blockingQueue = _cacheValuePool.get(cacheBlockSize);
    if (blockingQueue == null) {
      blockingQueue = buildNewBlockQueue(cacheBlockSize);
    }
    return blockingQueue;
  }

  private BlockingQueue<CacheValue> buildNewBlockQueue(int cacheBlockSize) {
    LOG.info("Allocating new ArrayBlockingQueue with capacity [{0}]", _queueDepth);
    BlockingQueue<CacheValue> value = new ArrayBlockingQueue<CacheValue>(_queueDepth);
    _cacheValuePool.putIfAbsent(cacheBlockSize, value);
    return _cacheValuePool.get(cacheBlockSize);
  }

  private CacheValue createCacheValue(int cacheBlockSize) {
    switch (_store) {
    case ON_HEAP:
      return new ByteArrayCacheValue(cacheBlockSize);
    case OFF_HEAP:
      return new UnsafeAllocateCacheValue(cacheBlockSize);
    default:
      throw new RuntimeException("Unknown type [" + _store + "]");
    }
  }

  public void returnToPool(CacheValue cacheValue) {
    if (cacheValue == null || cacheValue.isEvicted()) {
      return;
    }
    try {
      BlockingQueue<CacheValue> blockingQueue = getPool(cacheValue.length());
      if (!blockingQueue.offer(cacheValue)) {
        _detroyed.mark();
        cacheValue.release();
      }
    } catch (EvictionException e) {
      return;
    }
  }

  @Override
  public void close() {
    for (Entry<Integer, BlockingQueue<CacheValue>> e : _cacheValuePool.entrySet()) {
      BlockingQueue<CacheValue> queue = _cacheValuePool.remove(e.getKey());
      for (CacheValue cacheValue : queue) {
        cacheValue.release();
      }
    }
  }
}