/*
    * 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.maven.buildcache.hash;
  
  import java.nio.ByteBuffer;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * ThreadLocalBuffer
   */
  public class ThreadLocalBuffer {
  
      private static final ConcurrentMap<CloseableBuffer, Boolean> LOCALS = new ConcurrentHashMap<>();
  
      public static ByteBuffer get(ThreadLocal<CloseableBuffer> local, int capacity) {
          final CloseableBuffer buffer = local.get();
          if (buffer == null) {
              return create(local, capacity);
          }
  
          if (capacity(buffer) < capacity) {
              close(buffer);
              return create(local, capacity * 2);
          }
  
          return clear(buffer);
      }
  
      @Override
      public void finalize() {
          for (CloseableBuffer buffer : LOCALS.keySet()) {
              buffer.close();
          }
      }
  
      private static ByteBuffer create(ThreadLocal<CloseableBuffer> local, int capacity) {
          final CloseableBuffer buffer = CloseableBuffer.directBuffer(capacity);
          local.set(buffer);
          LOCALS.put(buffer, false);
          return buffer.getBuffer();
      }
  
      private static int capacity(CloseableBuffer buffer) {
          return buffer.getBuffer().capacity();
      }
  
      private static ByteBuffer clear(CloseableBuffer buffer) {
          return (ByteBuffer) buffer.getBuffer().clear();
      }
  
      private static void close(CloseableBuffer buffer) {
          LOCALS.remove(buffer);
          buffer.close();
      }
  
      private ThreadLocalBuffer() {}
  }