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.common.serialization.Serializer;
  import org.apache.kafka.common.utils.Bytes;
  import org.apache.kafka.streams.KeyValue;
  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.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Iterator;
  import java.util.Map;
  import java.util.Objects;
  import java.util.TreeMap;
  
  public class MemoryNavigableLRUCache extends MemoryLRUCache {
  
      private static final Logger LOG = LoggerFactory.getLogger(MemoryNavigableLRUCache.class);
  
      public MemoryNavigableLRUCache(final String name, final int maxCacheSize) {
          super(name, maxCacheSize);
      }
  
      @Override
      public KeyValueIterator<Bytes, byte[]> range(final Bytes from, final Bytes to) {
          if (Objects.nonNull(from) && Objects.nonNull(to) && 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 {
              final TreeMap<Bytes, byte[]> treeMap = toTreeMap();
              final Iterator<Bytes> keys = getIterator(treeMap, from, to, true);
              return new DelegatingPeekingKeyValueIterator<>(name(),
                      new MemoryNavigableLRUCache.CacheIterator(keys, treeMap));
          }
      }
  
      @Override
      public KeyValueIterator<Bytes, byte[]> reverseRange(final Bytes from, final Bytes to) {
          if (Objects.nonNull(from) && Objects.nonNull(to) && 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 {
              final TreeMap<Bytes, byte[]> treeMap = toTreeMap();
              final Iterator<Bytes> keys = getIterator(treeMap, from, to, false);
              return new DelegatingPeekingKeyValueIterator<>(name(),
                      new MemoryNavigableLRUCache.CacheIterator(keys, treeMap));
          }
      }
  
      private Iterator<Bytes> getIterator(final TreeMap<Bytes, byte[]> treeMap, final Bytes from, final Bytes to, final boolean forward) {
          if (from == null && to == null) {
              return forward ? treeMap.navigableKeySet().iterator() : treeMap.navigableKeySet().descendingIterator();
          } else if (from == null) {
              return forward ? treeMap.navigableKeySet().headSet(to, true).iterator() : treeMap.navigableKeySet().headSet(to, true).descendingIterator();
          } else if (to == null) {
              return forward ? treeMap.navigableKeySet().tailSet(from, true).iterator() : treeMap.navigableKeySet().tailSet(from, true).descendingIterator();
          } else {
              return forward ? treeMap.navigableKeySet().subSet(from, true, to, true).iterator() : treeMap.navigableKeySet().subSet(from, true, to, true).descendingIterator();
          }
      }
  
      @Override
      public <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);
  
          final TreeMap<Bytes, byte[]> treeMap = toTreeMap();
  
          return new DelegatingPeekingKeyValueIterator<>(
              name(),
              new MemoryNavigableLRUCache.CacheIterator(treeMap.subMap(from, true, to, false).keySet().iterator(), treeMap)
          );
      }
  
      @Override
      public  KeyValueIterator<Bytes, byte[]> all() {
          return range(null, null);
      }
  
      @Override
      public  KeyValueIterator<Bytes, byte[]> reverseAll() {
          return reverseRange(null, null);
      }
  
      private synchronized TreeMap<Bytes, byte[]> toTreeMap() {
          return new TreeMap<>(this.map);
      }
  
      @Override
      @SuppressWarnings("unchecked")
      public <R> QueryResult<R> query(
          final Query<R> query,
          final PositionBound positionBound,
          final QueryConfig config) {
  
          return StoreQueryUtils.handleBasicQueries(
              query,
              positionBound,
              config,
              this,
              getPosition(),
              context
          );
      }
  
  
      private static class CacheIterator implements KeyValueIterator<Bytes, byte[]> {
          private final Iterator<Bytes> keys;
          private final Map<Bytes, byte[]> entries;
  
          private CacheIterator(final Iterator<Bytes> keys, final Map<Bytes, byte[]> entries) {
              this.keys = keys;
              this.entries = entries;
          }
  
          @Override
          public boolean hasNext() {
              return keys.hasNext();
          }
  
          @Override
          public KeyValue<Bytes, byte[]> next() {
              final Bytes lastKey = keys.next();
              return new KeyValue<>(lastKey, entries.get(lastKey));
          }
  
          @Override
          public void close() {
              // do nothing
          }
  
          @Override
          public Bytes peekNextKey() {
              throw new UnsupportedOperationException("peekNextKey not supported");
          }
      }
  }
  