content: /*
   * 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.kafka.streams.kstream.internals;
  
  import org.apache.kafka.common.metrics.Sensor;
  import org.apache.kafka.streams.kstream.Reducer;
  import org.apache.kafka.streams.processor.api.ContextualProcessor;
  import org.apache.kafka.streams.processor.api.Processor;
  import org.apache.kafka.streams.processor.api.ProcessorContext;
  import org.apache.kafka.streams.processor.api.Record;
  import org.apache.kafka.streams.processor.api.RecordMetadata;
  import org.apache.kafka.streams.processor.internals.StoreFactory;
  import org.apache.kafka.streams.processor.internals.StoreFactory.FactoryWrappingStoreBuilder;
  import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
  import org.apache.kafka.streams.state.StoreBuilder;
  import org.apache.kafka.streams.state.ValueAndTimestamp;
  import org.apache.kafka.streams.state.internals.KeyValueStoreWrapper;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Collections;
  import java.util.Set;
  
  import static org.apache.kafka.streams.processor.internals.metrics.TaskMetrics.droppedRecordsSensor;
  import static org.apache.kafka.streams.state.ValueAndTimestamp.getValueOrNull;
  import static org.apache.kafka.streams.state.VersionedKeyValueStore.PUT_RETURN_CODE_NOT_PUT;
  import static org.apache.kafka.streams.state.internals.KeyValueStoreWrapper.PUT_RETURN_CODE_IS_LATEST;
  
  public class KStreamReduce<K, V> implements KStreamAggProcessorSupplier<K, V, K, V> {
  
      private static final Logger LOG = LoggerFactory.getLogger(KStreamReduce.class);
  
      private final String storeName;
      private final StoreFactory storeFactory;
      private final Reducer<V> reducer;
  
      private boolean sendOldValues = false;
  
      KStreamReduce(final StoreFactory storeFactory, final Reducer<V> reducer) {
          this.storeFactory = storeFactory;
          this.storeName = storeFactory.storeName();
          this.reducer = reducer;
      }
  
      @Override
      public Set<StoreBuilder<?>> stores() {
          return Collections.singleton(new FactoryWrappingStoreBuilder<>(storeFactory));
      }
  
  
      @Override
      public Processor<K, V, K, Change<V>> get() {
          return new KStreamReduceProcessor();
      }
  
      @Override
      public void enableSendingOldValues() {
          sendOldValues = true;
      }
  
  
      private class KStreamReduceProcessor extends ContextualProcessor<K, V, K, Change<V>> {
          private KeyValueStoreWrapper<K, V> store;
          private TimestampedTupleForwarder<K, V> tupleForwarder;
          private Sensor droppedRecordsSensor;
  
          @Override
          public void init(final ProcessorContext<K, Change<V>> context) {
              super.init(context);
              droppedRecordsSensor = droppedRecordsSensor(
                  Thread.currentThread().getName(),
                  context.taskId().toString(),
                  (StreamsMetricsImpl) context.metrics()
              );
              store = new KeyValueStoreWrapper<>(context, storeName);
              tupleForwarder = new TimestampedTupleForwarder<>(
                  store.store(),
                  context,
                  new TimestampedCacheFlushListener<>(context),
                  sendOldValues);
          }
  
          @Override
          public void process(final Record<K, V> record) {
              // If the key or value is null we don't need to proceed
              if (record.key() == null || record.value() == null) {
                  if (context().recordMetadata().isPresent()) {
                      final RecordMetadata recordMetadata = context().recordMetadata().get();
                      LOG.warn(
                          "Skipping record due to null key or value. "
                              + "topic=[{}] partition=[{}] offset=[{}]",
                          recordMetadata.topic(), recordMetadata.partition(), recordMetadata.offset()
                      );
                  } else {
                      LOG.warn(
                          "Skipping record due to null key. Topic, partition, and offset not known."
                      );
                  }
                  droppedRecordsSensor.record();
                  return;
              }
  
              final ValueAndTimestamp<V> oldAggAndTimestamp = store.get(record.key());
              final V oldAgg = getValueOrNull(oldAggAndTimestamp);
  
              final V newAgg;
              final long newTimestamp;
  
              if (oldAgg == null) {
                  newAgg = record.value();
                  newTimestamp = record.timestamp();
              } else {
                  newAgg = reducer.apply(oldAgg, record.value());
                  newTimestamp = Math.max(record.timestamp(), oldAggAndTimestamp.timestamp());
              }
  
              final long putReturnCode = store.put(record.key(), newAgg, newTimestamp);
              // if not put to store, do not forward downstream either
              if (putReturnCode != PUT_RETURN_CODE_NOT_PUT) {
                  tupleForwarder.maybeForward(
                      record.withValue(new Change<>(newAgg, sendOldValues ? oldAgg : null, putReturnCode == PUT_RETURN_CODE_IS_LATEST))
                          .withTimestamp(newTimestamp));
              }
          }
      }
  
      @Override
      public KTableValueGetterSupplier<K, V> view() {
          return new KTableValueGetterSupplier<K, V>() {
  
              public KTableValueGetter<K, V> get() {
                  return new KStreamReduceValueGetter();
              }
  
              @Override
              public String[] storeNames() {
                  return new String[]{storeName};
              }
          };
      }
  
  
      private class KStreamReduceValueGetter implements KTableValueGetter<K, V> {
          private KeyValueStoreWrapper<K, V> store;
  
          @Override
          public void init(final ProcessorContext<?, ?> context) {
              store = new KeyValueStoreWrapper<>(context, storeName);
          }
  
          @Override
          public ValueAndTimestamp<V> get(final K key) {
              return store.get(key);
          }
  
          @Override
          public ValueAndTimestamp<V> get(final K key, final long asOfTimestamp) {
              return store.get(key, asOfTimestamp);
          }
  
          @Override
          public boolean isVersioned() {
              return store.isVersionedStore();
          }
      }
  }
  