/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed 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 org.springframework.core.codec;

import java.util.Map;

import org.reactivestreams.Publisher;
import reactor.core.publisher.Flux;

import org.springframework.core.ResolvableType;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.lang.Nullable;
import org.springframework.util.MimeType;
import org.springframework.util.MimeTypeUtils;

Simple pass-through decoder for DataBuffers. 
Note: The data buffers should be released via DataBufferUtils.release(DataBuffer) after they have been consumed. In addition, if using Flux or Mono operators such as flatMap, reduce, and others that prefetch, cache, and skip or filter out data items internally, please add doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release) to the composition chain to ensure cached data buffers are released prior to an error or cancellation signal. 
Author:
Arjen Poutsma, Rossen Stoyanchev
Since:
5.0/**
 * Simple pass-through decoder for {@link DataBuffer DataBuffers}.
 *
 * <p><strong>Note:</strong> The data buffers should be released via
 * {@link org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer)}
 * after they have been consumed. In addition, if using {@code Flux} or
 * {@code Mono} operators such as flatMap, reduce, and others that prefetch,
 * cache, and skip or filter out data items internally, please add
 * {@code doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release)} to the
 * composition chain to ensure cached data buffers are released prior to an
 * error or cancellation signal.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class DataBufferDecoder extends AbstractDataBufferDecoder<DataBuffer> {

	public DataBufferDecoder() {
		super(MimeTypeUtils.ALL);
	}


	@Override
	public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
		return (DataBuffer.class.isAssignableFrom(elementType.toClass()) &&
				super.canDecode(elementType, mimeType));
	}

	@Override
	public Flux<DataBuffer> decode(Publisher<DataBuffer> input, ResolvableType elementType,
			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

		return Flux.from(input);
	}

	@Override
	public DataBuffer decode(DataBuffer buffer, ResolvableType elementType,
			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

		if (logger.isDebugEnabled()) {
			logger.debug(Hints.getLogPrefix(hints) + "Read " + buffer.readableByteCount() + " bytes");
		}
		return buffer;
	}

}