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Provides the fluent Kafka Streams test framework.
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/*
 * MIT License
 *
 * Copyright (c) 2019 bakdata GmbH
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.bakdata.fluent_kafka_streams_tests;

import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.common.serialization.Serde;
import org.apache.kafka.streams.TestOutputTopic;
import org.apache.kafka.streams.TopologyTestDriver;
import org.apache.kafka.streams.test.TestRecord;

abstract class BaseOutput implements TestOutput {
    protected final TopologyTestDriver testDriver;
    protected final TestOutputTopic testOutputTopic;
    protected final String topic;
    protected final Serde keySerde;
    protected final Serde valueSerde;

    protected BaseOutput(final TopologyTestDriver testDriver, final String topic, final Serde keySerde,
            final Serde valueSerde) {
        this.testDriver = testDriver;
        this.topic = topic;
        this.keySerde = keySerde;
        this.valueSerde = valueSerde;

        this.testOutputTopic = this.testDriver
                .createOutputTopic(this.topic, this.keySerde.deserializer(), this.valueSerde.deserializer());
    }

    /**
     * Set new serde for this output.

     *
     * @param keySerde The serializer/deserializer to be used for the keys in the output.
     * @param valueSerde The serializer/deserializer to be used for the values in the output.
     */
    @Override
    public  TestOutput withSerde(final Serde keySerde, final Serde valueSerde) {
        return this.create(this.testDriver, this.topic, keySerde, valueSerde);
    }

    /**
     * Set new key serde for this output.

     */
    public  TestOutput withKeySerde(final Serde keySerde) {
        return this.withSerde(keySerde, this.valueSerde);
    }

    /**
     * Set new value serde for this output.

     */
    public  TestOutput withValueSerde(final Serde valueSerde) {
        return this.withSerde(this.keySerde, valueSerde);
    }

    /**
     * Reads the next record as creates an {@link Expectation} for it.

     *
     * @return An {@link Expectation} containing the next record from the output.

     */
    @Override
    public Expectation expectNextRecord() {
        return new Expectation<>(this.readOneRecord(), this);
    }

    /**
     * Reads the next record from the output and expects it to be the end of output.

     *
     * @return An {@link Expectation} containing the next record from the output.

     */
    @Override
    public Expectation expectNoMoreRecord() {
        return this.expectNextRecord().toBeEmpty();
    }

    /**
     * Interpret the output with {@link org.apache.kafka.streams.kstream.KTable} semantics (each key only once).

     * Note: once the first value of the stream has been read or the iterator has be called, you cannot switch between
     * the output types any more.

     */
    @Override
    public TestOutput asTable() {
        return new TableOutput<>(this.testDriver, this.topic, this.keySerde, this.valueSerde);
    }

    /**
     * Interpret the output with {@link org.apache.kafka.streams.kstream.KStream} semantics (each key multiple times)
     * .
 This is the default, there should usually be no need to call this method.
 Note: once the first value
     * of the stream has been read or the iterator has be called, you cannot switch between the output types any
     * more.

     */
    @Override
    public TestOutput asStream() {
        return new StreamOutput<>(this.testDriver, this.topic, this.keySerde, this.valueSerde);
    }

    // ==================
    // Non-public methods
    // ==================
    protected ProducerRecord readFromTestDriver() {
        // the Expectation implementation requires null if the topic is empty but outputTopic.readRecord() throws a
        // NoSuchElementException. Thus, we have to check beforehand.
        if (this.testOutputTopic.isEmpty()) {
            return null;
        }
        final TestRecord testRecord = this.testOutputTopic.readRecord();
        // partition is always 0, see TopologyTestDriver.PARTITION_ID
        return new ProducerRecord<>(this.topic, 0, testRecord.timestamp(), testRecord.key(), testRecord.value(),
                testRecord.getHeaders());
    }


    protected abstract  TestOutput create(TopologyTestDriver testDriver, String topic,
            Serde keySerde, Serde valueSerde);
}