/*
 * 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:
 *
 *   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 io.netty.buffer;

import io.netty.util.Recycler.Handle;
import io.netty.util.ReferenceCounted;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;

Abstract base class for derived ByteBuf implementations. /**
 * Abstract base class for derived {@link ByteBuf} implementations.
 */
abstract class AbstractPooledDerivedByteBuf extends AbstractReferenceCountedByteBuf {

    private final Handle<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.
/**
     * 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 = (Handle<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.
            setRefCnt(1);

            @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.recycle(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 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 ReferenceCounted referenceCountDelegate;

        PooledNonRetainedDuplicateByteBuf(ReferenceCounted referenceCountDelegate, AbstractByteBuf buffer) {
            super(buffer);
            this.referenceCountDelegate = referenceCountDelegate;
        }

        @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 ReferenceCounted referenceCountDelegate;

        PooledNonRetainedSlicedByteBuf(ReferenceCounted referenceCountDelegate,
                                       AbstractByteBuf buffer, int index, int length) {
            super(buffer, index, length);
            this.referenceCountDelegate = referenceCountDelegate;
        }

        @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);
        }
    }
}