/*
    * Copyright 2016 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.netty.buffer;
  
  import io.netty.util.Recycler.EnhancedHandle;
  import io.netty.util.internal.ObjectPool.Handle;
  
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  
  /**
   * Abstract base class for derived {@link ByteBuf} implementations.
   */
  abstract class AbstractPooledDerivedByteBuf extends AbstractReferenceCountedByteBuf {
  
      private final EnhancedHandle<AbstractPooledDerivedByteBuf> recyclerHandle;
      private AbstractByteBuf rootParent;
      /**
       * Deallocations of a pooled derived buffer should always propagate through the entire chain of derived buffers.
       * This is because each pooled derived buffer maintains its own reference count and we should respect each one.
       * If deallocations cause a release of the "root parent" then then we may prematurely release the underlying
       * content before all the derived buffers have been released.
       */
      private ByteBuf parent;
  
      @SuppressWarnings("unchecked")
      AbstractPooledDerivedByteBuf(Handle<? extends AbstractPooledDerivedByteBuf> recyclerHandle) {
          super(0);
          this.recyclerHandle = (EnhancedHandle<AbstractPooledDerivedByteBuf>) recyclerHandle;
      }
  
      // Called from within SimpleLeakAwareByteBuf and AdvancedLeakAwareByteBuf.
      final void parent(ByteBuf newParent) {
          assert newParent instanceof SimpleLeakAwareByteBuf;
          parent = newParent;
      }
  
      @Override
      public final AbstractByteBuf unwrap() {
          return rootParent;
      }
  
      final <U extends AbstractPooledDerivedByteBuf> U init(
              AbstractByteBuf unwrapped, ByteBuf wrapped, int readerIndex, int writerIndex, int maxCapacity) {
          wrapped.retain(); // Retain up front to ensure the parent is accessible before doing more work.
          parent = wrapped;
          rootParent = unwrapped;
  
          try {
              maxCapacity(maxCapacity);
              setIndex0(readerIndex, writerIndex); // It is assumed the bounds checking is done by the caller.
              resetRefCnt();
  
              @SuppressWarnings("unchecked")
              final U castThis = (U) this;
              wrapped = null;
              return castThis;
          } finally {
              if (wrapped != null) {
                  parent = rootParent = null;
                  wrapped.release();
              }
          }
      }
  
      @Override
      protected final void deallocate() {
          // We need to first store a reference to the parent before recycle this instance. This is needed as
          // otherwise it is possible that the same AbstractPooledDerivedByteBuf is again obtained and init(...) is
          // called before we actually have a chance to call release(). This leads to call release() on the wrong parent.
          ByteBuf parent = this.parent;
          recyclerHandle.unguardedRecycle(this);
          parent.release();
      }
  
      @Override
      public final ByteBufAllocator alloc() {
          return unwrap().alloc();
      }
  
      @Override
      @Deprecated
      public final ByteOrder order() {
          return unwrap().order();
      }
 
     @Override
     public boolean isReadOnly() {
         return unwrap().isReadOnly();
     }
 
     @Override
     public final boolean isDirect() {
         return unwrap().isDirect();
     }
 
     @Override
     public boolean hasArray() {
         return unwrap().hasArray();
     }
 
     @Override
     public byte[] array() {
         return unwrap().array();
     }
 
     @Override
     public boolean hasMemoryAddress() {
         return unwrap().hasMemoryAddress();
     }
 
     @Override
     public boolean isContiguous() {
         return unwrap().isContiguous();
     }
 
     @Override
     public final int nioBufferCount() {
         return unwrap().nioBufferCount();
     }
 
     @Override
     public final ByteBuffer internalNioBuffer(int index, int length) {
         return nioBuffer(index, length);
     }
 
     @Override
     public final ByteBuf retainedSlice() {
         final int index = readerIndex();
         return retainedSlice(index, writerIndex() - index);
     }
 
     @Override
     public ByteBuf slice(int index, int length) {
         ensureAccessible();
         // All reference count methods should be inherited from this object (this is the "parent").
         return new PooledNonRetainedSlicedByteBuf(this, unwrap(), index, length);
     }
 
     final ByteBuf duplicate0() {
         ensureAccessible();
         // All reference count methods should be inherited from this object (this is the "parent").
         return new PooledNonRetainedDuplicateByteBuf(this, unwrap());
     }
 
     private static final class PooledNonRetainedDuplicateByteBuf extends UnpooledDuplicatedByteBuf {
         private final ByteBuf referenceCountDelegate;
 
         PooledNonRetainedDuplicateByteBuf(ByteBuf referenceCountDelegate, AbstractByteBuf buffer) {
             super(buffer);
             this.referenceCountDelegate = referenceCountDelegate;
         }
 
         @Override
         boolean isAccessible0() {
             return referenceCountDelegate.isAccessible();
         }
 
         @Override
         int refCnt0() {
             return referenceCountDelegate.refCnt();
         }
 
         @Override
         ByteBuf retain0() {
             referenceCountDelegate.retain();
             return this;
         }
 
         @Override
         ByteBuf retain0(int increment) {
             referenceCountDelegate.retain(increment);
             return this;
         }
 
         @Override
         ByteBuf touch0() {
             referenceCountDelegate.touch();
             return this;
         }
 
         @Override
         ByteBuf touch0(Object hint) {
             referenceCountDelegate.touch(hint);
             return this;
         }
 
         @Override
         boolean release0() {
             return referenceCountDelegate.release();
         }
 
         @Override
         boolean release0(int decrement) {
             return referenceCountDelegate.release(decrement);
         }
 
         @Override
         public ByteBuf duplicate() {
             ensureAccessible();
             return new PooledNonRetainedDuplicateByteBuf(referenceCountDelegate, this);
         }
 
         @Override
         public ByteBuf retainedDuplicate() {
             return PooledDuplicatedByteBuf.newInstance(unwrap(), this, readerIndex(), writerIndex());
         }
 
         @Override
         public ByteBuf slice(int index, int length) {
             checkIndex(index, length);
             return new PooledNonRetainedSlicedByteBuf(referenceCountDelegate, unwrap(), index, length);
         }
 
         @Override
         public ByteBuf retainedSlice() {
             // Capacity is not allowed to change for a sliced ByteBuf, so length == capacity()
             return retainedSlice(readerIndex(), capacity());
         }
 
         @Override
         public ByteBuf retainedSlice(int index, int length) {
             return PooledSlicedByteBuf.newInstance(unwrap(), this, index, length);
         }
     }
 
     private static final class PooledNonRetainedSlicedByteBuf extends UnpooledSlicedByteBuf {
         private final ByteBuf referenceCountDelegate;
 
         PooledNonRetainedSlicedByteBuf(ByteBuf referenceCountDelegate,
                                        AbstractByteBuf buffer, int index, int length) {
             super(buffer, index, length);
             this.referenceCountDelegate = referenceCountDelegate;
         }
 
         @Override
         boolean isAccessible0() {
             return referenceCountDelegate.isAccessible();
         }
 
         @Override
         int refCnt0() {
             return referenceCountDelegate.refCnt();
         }
 
         @Override
         ByteBuf retain0() {
             referenceCountDelegate.retain();
             return this;
         }
 
         @Override
         ByteBuf retain0(int increment) {
             referenceCountDelegate.retain(increment);
             return this;
         }
 
         @Override
         ByteBuf touch0() {
             referenceCountDelegate.touch();
             return this;
         }
 
         @Override
         ByteBuf touch0(Object hint) {
             referenceCountDelegate.touch(hint);
             return this;
         }
 
         @Override
         boolean release0() {
             return referenceCountDelegate.release();
         }
 
         @Override
         boolean release0(int decrement) {
             return referenceCountDelegate.release(decrement);
         }
 
         @Override
         public ByteBuf duplicate() {
             ensureAccessible();
             return new PooledNonRetainedDuplicateByteBuf(referenceCountDelegate, unwrap())
                     .setIndex(idx(readerIndex()), idx(writerIndex()));
         }
 
         @Override
         public ByteBuf retainedDuplicate() {
             return PooledDuplicatedByteBuf.newInstance(unwrap(), this, idx(readerIndex()), idx(writerIndex()));
         }
 
         @Override
         public ByteBuf slice(int index, int length) {
             checkIndex(index, length);
             return new PooledNonRetainedSlicedByteBuf(referenceCountDelegate, unwrap(), idx(index), length);
         }
 
         @Override
         public ByteBuf retainedSlice() {
             // Capacity is not allowed to change for a sliced ByteBuf, so length == capacity()
             return retainedSlice(0, capacity());
         }
 
         @Override
         public ByteBuf retainedSlice(int index, int length) {
             return PooledSlicedByteBuf.newInstance(unwrap(), this, idx(index), length);
         }
     }
 }