/*
    * Copyright 2021 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty5.buffer.api.bytebuffer;
  
  import io.netty5.buffer.api.AllocationType;
  import io.netty5.buffer.api.AllocatorControl;
  import io.netty5.buffer.api.Buffer;
  import io.netty5.buffer.api.Drop;
  import io.netty5.buffer.api.MemoryManager;
  import io.netty5.buffer.api.StandardAllocationTypes;
  import io.netty5.buffer.api.internal.Statics;
  import io.netty5.buffer.api.internal.WrappingAllocation;
  
  import java.nio.ByteBuffer;
  import java.util.function.Function;
  
  import static io.netty5.buffer.api.internal.Statics.bbslice;
  import static io.netty5.buffer.api.internal.Statics.convert;
  
  /**
   * This memory manager produces and manages {@link Buffer} instances that are backed by NIO {@link ByteBuffer}
   * instances.
   * <p>
   * Memory managers are normally not used directly.
   * Instead, you likely want to use the {@link io.netty5.buffer.api.DefaultBufferAllocators}, or the static methods on
   * {@link io.netty5.buffer.api.BufferAllocator}.
   */
  public final class ByteBufferMemoryManager implements MemoryManager {
      @Override
      public Buffer allocateShared(AllocatorControl allocatorControl, long size,
                                   Function<Drop<Buffer>, Drop<Buffer>> dropDecorator,
                                   AllocationType allocationType) {
          int capacity = Math.toIntExact(size);
          final ByteBuffer buffer;
          if (allocationType == StandardAllocationTypes.OFF_HEAP) {
              buffer = ByteBuffer.allocateDirect(capacity);
          } else if (allocationType == StandardAllocationTypes.ON_HEAP) {
              buffer = ByteBuffer.allocate(capacity);
          } else if (allocationType instanceof WrappingAllocation) {
              buffer = ByteBuffer.wrap(((WrappingAllocation) allocationType).getArray());
          } else {
              throw new IllegalArgumentException("Unknown allocation type: " + allocationType);
          }
          return createBuffer(buffer, allocatorControl, dropDecorator.apply(drop()));
      }
  
      @Override
      public Buffer allocateConstChild(Buffer readOnlyConstParent) {
          NioBuffer buf = (NioBuffer) readOnlyConstParent;
          return buf.newConstChild();
      }
  
      private static Drop<Buffer> drop() {
          return Statics.NO_OP_DROP;
      }
  
      @Override
      public Object unwrapRecoverableMemory(Buffer buf) {
          return ((NioBuffer) buf).recoverable();
      }
  
      @Override
      public Buffer recoverMemory(AllocatorControl allocatorControl, Object recoverableMemory, Drop<Buffer> drop) {
          ByteBuffer memory = (ByteBuffer) recoverableMemory;
          return createBuffer(memory, allocatorControl, drop);
      }
  
      private static NioBuffer createBuffer(ByteBuffer memory, AllocatorControl allocatorControl, Drop<Buffer> drop) {
          Drop<NioBuffer> concreteDrop = convert(drop);
          NioBuffer nioBuffer = new NioBuffer(memory, memory, allocatorControl, concreteDrop);
          concreteDrop.attach(nioBuffer);
          return nioBuffer;
      }
  
      @Override
      public Object sliceMemory(Object memory, int offset, int length) {
          var buffer = (ByteBuffer) memory;
          return bbslice(buffer, offset, length);
      }
  
      @Override
      public void clearMemory(Object memory) {
          ByteBuffer buffer = (ByteBuffer) memory;
          Statics.setMemory(buffer, buffer.capacity(), (byte) 0);
      }
  
     @Override
     public String implementationName() {
         return "ByteBuffer";
     }
 }