/*
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.imagepipeline.memory;

import com.facebook.common.internal.Preconditions;
import com.facebook.common.internal.VisibleForTesting;
import com.facebook.common.memory.MemoryTrimmableRegistry;
import com.facebook.common.references.CloseableReference;
import com.facebook.common.references.ResourceReleaser;

import java.util.Map;

import javax.annotation.concurrent.ThreadSafe;

/**
 * A special byte-array pool designed to minimize allocations.
 *
 * <p>The length of each bucket's free list is capped at the number of threads using the pool.
 * <p>The free list of each bucket uses {@link OOMSoftReference}s.
 */
@ThreadSafe
public class FlexByteArrayPool {

  private final ResourceReleaser<byte[]> mResourceReleaser;
  @VisibleForTesting final SoftRefByteArrayPool mDelegatePool;

  public FlexByteArrayPool(
      MemoryTrimmableRegistry memoryTrimmableRegistry,
      PoolParams params) {
    Preconditions.checkArgument(params.maxNumThreads > 0);
    mDelegatePool = new SoftRefByteArrayPool(
        memoryTrimmableRegistry,
        params,
        NoOpPoolStatsTracker.getInstance());
    mResourceReleaser = new ResourceReleaser<byte[]>() {
      @Override
      public void release(byte[] unused) {
        FlexByteArrayPool.this.release(unused);
      }
    };
  }

  public CloseableReference<byte[]> get(int size) {
    return CloseableReference.of(mDelegatePool.get(size), mResourceReleaser);
  }

  public void release(byte[] value) {
    mDelegatePool.release(value);
  }

  public Map<String, Integer> getStats() {
    return mDelegatePool.getStats();
  }

  public int getMinBufferSize() {
    return mDelegatePool.getMinBufferSize();
  }

  @VisibleForTesting static class SoftRefByteArrayPool extends GenericByteArrayPool {
    public SoftRefByteArrayPool(
        MemoryTrimmableRegistry memoryTrimmableRegistry,
        PoolParams poolParams,
        PoolStatsTracker poolStatsTracker) {
      super(memoryTrimmableRegistry, poolParams, poolStatsTracker);
    }

    @Override
    Bucket<byte[]> newBucket(int bucketedSize) {
      return new OOMSoftReferenceBucket<>(
          getSizeInBytes(bucketedSize),
          mPoolParams.maxNumThreads,
          0);
    }
  }
}