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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 org.apache.flink.runtime.state.gemini.engine.page.bmap;

import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.core.memory.DataOutputViewStreamWrapper;

import java.nio.ByteBuffer;
import java.util.Comparator;

/**
 * GComparatorBytesImpl for Gemini, use bytes comparator.
 */
public class GComparatorBytesImpl implements GComparator {
	private static final int DEFAULT_REUSED_LEN = 100;
	private final Comparator jdkComparator;
	private final TypeSerializer typeSerializer;
	private final ThreadLocal reusedBytes;

	public GComparatorBytesImpl(Comparator jdkComparator, TypeSerializer typeSerializer) {
		this(jdkComparator, typeSerializer, DEFAULT_REUSED_LEN);
	}

	public GComparatorBytesImpl(Comparator jdkComparator, TypeSerializer typeSerializer, int reusedLen) {
		this.jdkComparator = jdkComparator;
		this.typeSerializer = typeSerializer;
		this.reusedBytes = ThreadLocal.withInitial(() -> new byte[reusedLen]);
	}

	@Override
	public int compare(BinaryKey left, BinaryKey right) {
		return ByteBufferUtils.compareTo(left.getBb(),
			left.getKeyOffset(),
			left.getKeyLen(),
			right.getBb(),
			right.getKeyOffset(),
			right.getKeyLen());
	}

	@Override
	public int compare(K left, K right) {
		return this.jdkComparator.compare(left, right);
	}

	@Override
	public int compare(K left, BinaryKey right) {
		//NOTICE: be careful to use GComparatorBytesImpl, especially in the case of MapSplit.
		//this is only best effort to use GComparatorBytesImpl to improve performance.
		//in some case such as String, compare(K, BinaryKey) could be opposite withe compare(K,K).
		//for this reason, we keep compare(K, BinaryKey) same with compare(BinaryKey, BinaryKey).
		try {
			byte[] reusedBB = reusedBytes.get();
			GByteArrayOutputStreamWithPos outputStreamForValue = new GByteArrayOutputStreamWithPos(reusedBB);
			DataOutputViewStreamWrapper outputViewForValue = new DataOutputViewStreamWrapper(outputStreamForValue);
			int offset1 = 0;
			typeSerializer.serialize(left, outputViewForValue);
			int len1 = outputStreamForValue.getPosition();
			ByteBuffer bb = ByteBuffer.wrap(outputStreamForValue.getBuf());
			if (len1 > reusedBB.length) {
				reusedBytes.set(outputStreamForValue.getBuf());
			}

			return ByteBufferUtils.compareTo(bb, offset1, len1, right.getBb(), right.getKeyOffset(), right.getKeyLen());
		} catch (Exception e) {
			throw new RuntimeException(e);
		}
	}

	@Override
	public Comparator getJDKCompactor() {
		return this.jdkComparator;
	}

	@Override
	public Comparator getJDKBinaryCompactor() {
		return GComparatorBytesImpl.this::compare;
	}

	@VisibleForTesting
	ThreadLocal getReusedBytes() {
		return reusedBytes;
	}
}