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Integration between Micronaut and Kafka Messaging
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/*
 * Copyright 2017-2020 original 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 io.micronaut.configuration.kafka.bind;

import io.micronaut.core.convert.ArgumentConversionContext;
import io.micronaut.core.convert.ConversionService;
import io.micronaut.core.type.Argument;
import org.apache.kafka.clients.consumer.ConsumerRecord;

import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import java.util.function.Function;

/**
 * The default binder that binds the Kafka value for a ConsumerRecord.
 *
 * @param  The target generic type
 * @author Graeme Rocher
 * @since 1.0
 */
public class KafkaDefaultBinder implements ConsumerRecordBinder {

    private final Map, Object>> defaultResolver;

    /**
     * Default constructor.
     */
    public KafkaDefaultBinder() {
        this.defaultResolver = new HashMap<>();
        Function, Object> topicFunc = ConsumerRecord::topic;
        Function, Object> offsetFunc = ConsumerRecord::offset;
        Function, Object> partitionFunc = ConsumerRecord::partition;
        Function, Object> timestampFunc = ConsumerRecord::timestamp;
        this.defaultResolver.put(
                Argument.of(String.class, "topic"),
                topicFunc
        );
        this.defaultResolver.put(
                Argument.of(String.class, "topics"),
                topicFunc
        );
        this.defaultResolver.put(
                Argument.of(Long.class, "offset"),
                offsetFunc
        );
        this.defaultResolver.put(
                Argument.of(Long.class, "offsets"),
                offsetFunc
        );
        this.defaultResolver.put(
                Argument.of(Integer.class, "partition"),
                partitionFunc
        );
        this.defaultResolver.put(
                Argument.of(Integer.class, "partitions"),
                partitionFunc
        );
        this.defaultResolver.put(
                Argument.of(Long.class, "timestamp"),
                timestampFunc
        );
        this.defaultResolver.put(
                Argument.of(Long.class, "timestamps"),
                timestampFunc
        );

        this.defaultResolver.put(
                Argument.of(long.class, "offset"),
                offsetFunc
        );
        this.defaultResolver.put(
                Argument.of(long.class, "offsets"),
                offsetFunc
        );
        this.defaultResolver.put(
                Argument.of(int.class, "partition"),
                partitionFunc
        );
        this.defaultResolver.put(
                Argument.of(int.class, "partitions"),
                partitionFunc
        );
        this.defaultResolver.put(
                Argument.of(long.class, "timestamp"),
                timestampFunc
        );
        this.defaultResolver.put(
                Argument.of(long.class, "timestamps"),
                timestampFunc
        );
    }

    @Override
    public BindingResult bind(ArgumentConversionContext context, ConsumerRecord source) {
        Argument argument = context.getArgument();
        Function, Object> f = defaultResolver.get(argument);
        if (f != null) {
            Optional