/*
 * Copyright 2002-2020 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.io.buffer;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.function.Predicate;

import reactor.core.publisher.Flux;

Custom List to collect data buffers with and enforce a limit on the total number of bytes buffered. For use with "collect" or other buffering operators in declarative APIs, e.g. Flux. 
Adding elements increases the byte count and if the limit is exceeded, DataBufferLimitException is raised. clear() resets the count. Remove and set are not supported. 
Note: This class does not automatically release the buffers it contains. It is usually preferable to use hooks such as doOnDiscard.doOnDiscard that also take care of cancel and error signals, or otherwise releaseAndClear() can be used. 
Author:
Rossen Stoyanchev
Since:
5.1.11/**
 * Custom {@link List} to collect data buffers with and enforce a
 * limit on the total number of bytes buffered. For use with "collect" or
 * other buffering operators in declarative APIs, e.g. {@link Flux}.
 *
 * <p>Adding elements increases the byte count and if the limit is exceeded,
 * {@link DataBufferLimitException} is raised.  {@link #clear()} resets the
 * count. Remove and set are not supported.
 *
 * <p><strong>Note:</strong> This class does not automatically release the
 * buffers it contains. It is usually preferable to use hooks such as
 * {@link Flux#doOnDiscard} that also take care of cancel and error signals,
 * or otherwise {@link #releaseAndClear()} can be used.
 *
 * @author Rossen Stoyanchev
 * @since 5.1.11
 */
@SuppressWarnings("serial")
public class LimitedDataBufferList extends ArrayList<DataBuffer> {

	private final int maxByteCount;

	private int byteCount;


	public LimitedDataBufferList(int maxByteCount) {
		this.maxByteCount = maxByteCount;
	}


	@Override
	public boolean add(DataBuffer buffer) {
		updateCount(buffer.readableByteCount());
		return super.add(buffer);
	}

	@Override
	public void add(int index, DataBuffer buffer) {
		super.add(index, buffer);
		updateCount(buffer.readableByteCount());
	}

	@Override
	public boolean addAll(Collection<? extends DataBuffer> collection) {
		boolean result = super.addAll(collection);
		collection.forEach(buffer -> updateCount(buffer.readableByteCount()));
		return result;
	}

	@Override
	public boolean addAll(int index, Collection<? extends DataBuffer> collection) {
		boolean result = super.addAll(index, collection);
		collection.forEach(buffer -> updateCount(buffer.readableByteCount()));
		return result;
	}

	private void updateCount(int bytesToAdd) {
		if (this.maxByteCount < 0) {
			return;
		}
		if (bytesToAdd > Integer.MAX_VALUE - this.byteCount) {
			raiseLimitException();
		}
		else {
			this.byteCount += bytesToAdd;
			if (this.byteCount > this.maxByteCount) {
				raiseLimitException();
			}
		}
	}

	private void raiseLimitException() {
		// Do not release here, it's likely down via doOnDiscard..
		throw new DataBufferLimitException(
				"Exceeded limit on max bytes to buffer : " + this.maxByteCount);
	}

	@Override
	public DataBuffer remove(int index) {
		throw new UnsupportedOperationException();
	}

	@Override
	public boolean remove(Object o) {
		throw new UnsupportedOperationException();
	}

	@Override
	protected void removeRange(int fromIndex, int toIndex) {
		throw new UnsupportedOperationException();
	}

	@Override
	public boolean removeAll(Collection<?> c) {
		throw new UnsupportedOperationException();
	}

	@Override
	public boolean removeIf(Predicate<? super DataBuffer> filter) {
		throw new UnsupportedOperationException();
	}

	@Override
	public DataBuffer set(int index, DataBuffer element) {
		throw new UnsupportedOperationException();
	}

	@Override
	public void clear() {
		this.byteCount = 0;
		super.clear();
	}

	
Shortcut to release all data buffers and then clear(). /**
	 * Shortcut to {@link DataBufferUtils#release release} all data buffers and
	 * then {@link #clear()}.
	 */
	public void releaseAndClear() {
		forEach(buf -> {
			try {
				DataBufferUtils.release(buf);
			}
			catch (Throwable ex) {
				// Keep going..
			}
		});
		clear();
	}

}