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.state.internals;
  
  import org.apache.kafka.clients.consumer.ConsumerRecord;
  import org.apache.kafka.common.serialization.Serializer;
  import org.apache.kafka.common.utils.Bytes;
  import org.apache.kafka.streams.KeyValue;
  import org.apache.kafka.streams.StreamsConfig;
  import org.apache.kafka.streams.processor.StateStore;
  import org.apache.kafka.streams.processor.StateStoreContext;
  import org.apache.kafka.streams.processor.internals.ChangelogRecordDeserializationHelper;
  import org.apache.kafka.streams.processor.internals.RecordBatchingStateRestoreCallback;
  import org.apache.kafka.streams.query.Position;
  import org.apache.kafka.streams.query.PositionBound;
  import org.apache.kafka.streams.query.Query;
  import org.apache.kafka.streams.query.QueryConfig;
  import org.apache.kafka.streams.query.QueryResult;
  import org.apache.kafka.streams.state.KeyValueIterator;
  import org.apache.kafka.streams.state.KeyValueStore;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Iterator;
  import java.util.List;
  import java.util.NavigableMap;
  import java.util.NoSuchElementException;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.TreeSet;
  
  import static org.apache.kafka.streams.StreamsConfig.InternalConfig.IQ_CONSISTENCY_OFFSET_VECTOR_ENABLED;
  
  public class InMemoryKeyValueStore implements KeyValueStore<Bytes, byte[]> {
  
      private static final Logger LOG = LoggerFactory.getLogger(InMemoryKeyValueStore.class);
  
      private final String name;
      private final NavigableMap<Bytes, byte[]> map = new TreeMap<>();
      private final Position position = Position.emptyPosition();
      private volatile boolean open = false;
      private StateStoreContext context;
  
      public InMemoryKeyValueStore(final String name) {
          this.name = name;
      }
  
      @Override
      public String name() {
          return name;
      }
  
      @Override
      public void init(final StateStoreContext stateStoreContext,
                       final StateStore root) {
          if (root != null) {
              final boolean consistencyEnabled = StreamsConfig.InternalConfig.getBoolean(
                  stateStoreContext.appConfigs(),
                  IQ_CONSISTENCY_OFFSET_VECTOR_ENABLED,
                  false
              );
              // register the store
              open = true;
  
              stateStoreContext.register(
                  root,
                  (RecordBatchingStateRestoreCallback) records -> {
                      synchronized (position) {
                          for (final ConsumerRecord<byte[], byte[]> record : records) {
                              put(Bytes.wrap(record.key()), record.value());
                              ChangelogRecordDeserializationHelper.applyChecksAndUpdatePosition(
                                  record,
                                  consistencyEnabled,
                                  position
                              );
                          }
                      }
                  }
              );
          }
  
          open = true;
          this.context = stateStoreContext;
      }
  
      @Override
      public boolean persistent() {
          return false;
      }
  
      @Override
      public boolean isOpen() {
          return open;
      }
  
      @Override
      public Position getPosition() {
          return position;
      }
  
      @Override
      public <R> QueryResult<R> query(final Query<R> query,
                                      final PositionBound positionBound,
                                      final QueryConfig config) {
  
          return StoreQueryUtils.handleBasicQueries(
              query,
              positionBound,
              config,
              this,
              position,
              context
          );
      }
  
      @Override
      public synchronized byte[] get(final Bytes key) {
          return map.get(key);
      }
  
      @Override
      public synchronized void put(final Bytes key, final byte[] value) {
          putInternal(key, value);
      }
  
      @Override
      public synchronized byte[] putIfAbsent(final Bytes key, final byte[] value) {
          final byte[] originalValue = get(key);
          if (originalValue == null) {
              put(key, value);
          }
          return originalValue;
      }
  
      // the unlocked implementation of put method, to avoid multiple lock/unlock cost in `putAll` method
      private void putInternal(final Bytes key, final byte[] value) {
          synchronized (position) {
              if (value == null) {
                  map.remove(key);
              } else {
                  map.put(key, value);
              }
  
              StoreQueryUtils.updatePosition(position, context);
          }
      }
  
      @Override
      public synchronized void putAll(final List<KeyValue<Bytes, byte[]>> entries) {
          for (final KeyValue<Bytes, byte[]> entry : entries) {
              putInternal(entry.key, entry.value);
          }
      }
  
      @Override
      public synchronized <PS extends Serializer<P>, P> KeyValueIterator<Bytes, byte[]> prefixScan(final P prefix, final PS prefixKeySerializer) {
  
          final Bytes from = Bytes.wrap(prefixKeySerializer.serialize(null, prefix));
          final Bytes to = Bytes.increment(from);
  
          return new InMemoryKeyValueIterator(map.subMap(from, true, to, false).keySet(), true);
      }
  
      @Override
      public synchronized byte[] delete(final Bytes key) {
          return map.remove(key);
      }
  
      @Override
      public synchronized KeyValueIterator<Bytes, byte[]> range(final Bytes from, final Bytes to) {
          return range(from, to, true);
      }
  
      @Override
      public synchronized KeyValueIterator<Bytes, byte[]> reverseRange(final Bytes from, final Bytes to) {
          return range(from, to, false);
      }
  
      private KeyValueIterator<Bytes, byte[]> range(final Bytes from, final Bytes to, final boolean forward) {
          if (from == null && to == null) {
              return getKeyValueIterator(map.keySet(), forward);
          } else if (from == null) {
              return getKeyValueIterator(map.headMap(to, true).keySet(), forward);
          } else if (to == null) {
              return getKeyValueIterator(map.tailMap(from, true).keySet(), forward);
          } else if (from.compareTo(to) > 0) {
              LOG.warn("Returning empty iterator for fetch with invalid key range: from > to. " +
                      "This may be due to range arguments set in the wrong order, " +
                      "or serdes that don't preserve ordering when lexicographically comparing the serialized bytes. " +
                      "Note that the built-in numerical serdes do not follow this for negative numbers");
              return KeyValueIterators.emptyIterator();
          } else {
              return getKeyValueIterator(map.subMap(from, true, to, true).keySet(), forward);
          }
      }
  
      private KeyValueIterator<Bytes, byte[]> getKeyValueIterator(final Set<Bytes> rangeSet, final boolean forward) {
          return new InMemoryKeyValueIterator(rangeSet, forward);
      }
  
      @Override
      public synchronized KeyValueIterator<Bytes, byte[]> all() {
          return range(null, null);
      }
  
      @Override
      public synchronized KeyValueIterator<Bytes, byte[]> reverseAll() {
          return new InMemoryKeyValueIterator(map.keySet(), false);
      }
  
      @Override
      public long approximateNumEntries() {
          return map.size();
      }
  
      @Override
      public void flush() {
          // do-nothing since it is in-memory
      }
  
      @Override
      public void close() {
          map.clear();
          open = false;
      }
  
      private class InMemoryKeyValueIterator implements KeyValueIterator<Bytes, byte[]> {
          private final Iterator<Bytes> iter;
          private Bytes currentKey;
          private Boolean iteratorOpen = true;
  
          private InMemoryKeyValueIterator(final Set<Bytes> keySet, final boolean forward) {
              if (forward) {
                  this.iter = new TreeSet<>(keySet).iterator();
              } else {
                  this.iter = new TreeSet<>(keySet).descendingIterator();
              }
          }
  
          @Override
          public boolean hasNext() {
              if (!iteratorOpen) {
                  throw new IllegalStateException(String.format("Iterator for store %s has already been closed.", name));
              }
              if (currentKey != null) {
                  if (map.containsKey(currentKey)) {
                      return true;
                  } else {
                      currentKey = null;
                      return hasNext();
                  }
              }
              if (!iter.hasNext()) {
                  return false;
              }
              currentKey = iter.next();
              return hasNext();
          }
  
          @Override
          public KeyValue<Bytes, byte[]> next() {
              if (!hasNext()) {
                  throw new NoSuchElementException();
              }
              final KeyValue<Bytes, byte[]> ret = new KeyValue<>(currentKey, map.get(currentKey));
              currentKey = null;
              return ret;
          }
  
          @Override
          public void close() {
              iteratorOpen = false;
          }
  
          @Override
          public Bytes peekNextKey() {
              if (!hasNext()) {
                  throw new NoSuchElementException();
              }
              return currentKey;
          }
      }
  }
  