/*
 * 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.amoro.flink.read.internals;

import org.apache.flink.annotation.Internal;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.api.common.serialization.DeserializationSchema;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.connector.source.Boundedness;
import org.apache.flink.api.connector.source.Source;
import org.apache.flink.api.connector.source.SourceReader;
import org.apache.flink.api.connector.source.SourceReaderContext;
import org.apache.flink.api.connector.source.SplitEnumerator;
import org.apache.flink.api.connector.source.SplitEnumeratorContext;
import org.apache.flink.api.java.typeutils.ResultTypeQueryable;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.connector.base.source.reader.RecordsWithSplitIds;
import org.apache.flink.connector.base.source.reader.synchronization.FutureCompletingBlockingQueue;
import org.apache.flink.connector.kafka.source.KafkaSourceBuilder;
import org.apache.flink.connector.kafka.source.enumerator.KafkaSourceEnumState;
import org.apache.flink.connector.kafka.source.enumerator.KafkaSourceEnumStateSerializer;
import org.apache.flink.connector.kafka.source.enumerator.KafkaSourceEnumerator;
import org.apache.flink.connector.kafka.source.enumerator.initializer.OffsetsInitializer;
import org.apache.flink.connector.kafka.source.enumerator.subscriber.KafkaSubscriber;
import org.apache.flink.connector.kafka.source.metrics.KafkaSourceReaderMetrics;
import org.apache.flink.connector.kafka.source.reader.KafkaPartitionSplitReader;
import org.apache.flink.connector.kafka.source.reader.KafkaRecordEmitter;
import org.apache.flink.connector.kafka.source.reader.KafkaSourceReader;
import org.apache.flink.connector.kafka.source.reader.deserializer.KafkaRecordDeserializationSchema;
import org.apache.flink.connector.kafka.source.reader.fetcher.KafkaSourceFetcherManager;
import org.apache.flink.connector.kafka.source.split.KafkaPartitionSplit;
import org.apache.flink.connector.kafka.source.split.KafkaPartitionSplitSerializer;
import org.apache.flink.core.io.SimpleVersionedSerializer;
import org.apache.flink.metrics.MetricGroup;
import org.apache.flink.util.UserCodeClassLoader;
import org.apache.kafka.clients.consumer.ConsumerRecord;

import javax.annotation.Nullable;

import java.io.IOException;
import java.util.Collection;
import java.util.Properties;
import java.util.function.Consumer;
import java.util.function.Supplier;

/**
 * The Source implementation of Kafka. Please use a {@link KafkaSourceBuilder} to construct a {@link
 * KafkaSource}. The following example shows how to create a KafkaSource emitting records of <code>
 * String</code> type.
 *
 * <pre>{@code
 * KafkaSource<String> source = KafkaSource
 *     .<String>builder()
 *     .setBootstrapServers(KafkaSourceTestEnv.brokerConnectionStrings)
 *     .setGroupId("MyGroup")
 *     .setTopics(Arrays.asList(TOPIC1, TOPIC2))
 *     .setDeserializer(new TestingKafkaRecordDeserializationSchema())
 *     .setStartingOffsets(OffsetsInitializer.earliest())
 *     .build();
 * }</pre>
 *
 * @param <OUT> the output type of the source.
 */
@PublicEvolving
public class KafkaSource<OUT>
    implements Source<OUT, KafkaPartitionSplit, KafkaSourceEnumState>, ResultTypeQueryable<OUT> {
  private static final long serialVersionUID = -8755372893283732098L;
  // Users can choose only one of the following ways to specify the topics to consume from.
  private final KafkaSubscriber subscriber;
  // Users can specify the starting / stopping offset initializer.
  private final OffsetsInitializer startingOffsetsInitializer;
  private final OffsetsInitializer stoppingOffsetsInitializer;
  // Boundedness
  private final Boundedness boundedness;
  private final KafkaRecordDeserializationSchema<OUT> deserializationSchema;
  // The configurations.
  protected final Properties props;

  protected KafkaSource(
      KafkaSubscriber subscriber,
      OffsetsInitializer startingOffsetsInitializer,
      @Nullable OffsetsInitializer stoppingOffsetsInitializer,
      Boundedness boundedness,
      KafkaRecordDeserializationSchema<OUT> deserializationSchema,
      Properties props) {
    this.subscriber = subscriber;
    this.startingOffsetsInitializer = startingOffsetsInitializer;
    this.stoppingOffsetsInitializer = stoppingOffsetsInitializer;
    this.boundedness = boundedness;
    this.deserializationSchema = deserializationSchema;
    this.props = props;
  }

  @Override
  public Boundedness getBoundedness() {
    return this.boundedness;
  }

  @Internal
  @Override
  public SourceReader<OUT, KafkaPartitionSplit> createReader(SourceReaderContext readerContext)
      throws Exception {
    return createReader(readerContext, (ignore) -> {});
  }

  @VisibleForTesting
  SourceReader<OUT, KafkaPartitionSplit> createReader(
      SourceReaderContext readerContext, Consumer<Collection<String>> splitFinishedHook)
      throws Exception {
    FutureCompletingBlockingQueue<RecordsWithSplitIds<ConsumerRecord<byte[], byte[]>>>
        elementsQueue = new FutureCompletingBlockingQueue<>();
    deserializationSchema.open(
        new DeserializationSchema.InitializationContext() {
          @Override
          public MetricGroup getMetricGroup() {
            return readerContext.metricGroup().addGroup("deserializer");
          }

          @Override
          public UserCodeClassLoader getUserCodeClassLoader() {
            return readerContext.getUserCodeClassLoader();
          }
        });
    final KafkaSourceReaderMetrics kafkaSourceReaderMetrics =
        new KafkaSourceReaderMetrics(readerContext.metricGroup());

    Supplier<KafkaPartitionSplitReader> splitReaderSupplier =
        () -> new KafkaPartitionSplitReader(props, readerContext, kafkaSourceReaderMetrics);
    KafkaRecordEmitter<OUT> recordEmitter = new KafkaRecordEmitter<>(deserializationSchema);

    return new KafkaSourceReader<>(
        elementsQueue,
        new KafkaSourceFetcherManager(elementsQueue, splitReaderSupplier::get, splitFinishedHook),
        recordEmitter,
        toConfiguration(props),
        readerContext,
        kafkaSourceReaderMetrics);
  }

  @Internal
  @Override
  public SplitEnumerator<KafkaPartitionSplit, KafkaSourceEnumState> createEnumerator(
      SplitEnumeratorContext<KafkaPartitionSplit> enumContext) {
    return new KafkaSourceEnumerator(
        subscriber,
        startingOffsetsInitializer,
        stoppingOffsetsInitializer,
        props,
        enumContext,
        boundedness);
  }

  @Internal
  @Override
  public SplitEnumerator<KafkaPartitionSplit, KafkaSourceEnumState> restoreEnumerator(
      SplitEnumeratorContext<KafkaPartitionSplit> enumContext, KafkaSourceEnumState checkpoint)
      throws IOException {
    return new KafkaSourceEnumerator(
        subscriber,
        startingOffsetsInitializer,
        stoppingOffsetsInitializer,
        props,
        enumContext,
        boundedness,
        checkpoint);
  }

  @Internal
  @Override
  public SimpleVersionedSerializer<KafkaPartitionSplit> getSplitSerializer() {
    return new KafkaPartitionSplitSerializer();
  }

  @Internal
  @Override
  public SimpleVersionedSerializer<KafkaSourceEnumState> getEnumeratorCheckpointSerializer() {
    return new KafkaSourceEnumStateSerializer();
  }

  @Override
  public TypeInformation<OUT> getProducedType() {
    return deserializationSchema.getProducedType();
  }

  // ----------- private helper methods ---------------

  private Configuration toConfiguration(Properties props) {
    Configuration config = new Configuration();
    props.stringPropertyNames().forEach(key -> config.setString(key, props.getProperty(key)));
    return config;
  }

  @VisibleForTesting
  Configuration getConfiguration() {
    return toConfiguration(props);
  }
}
