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.streams.errors.InvalidStateStoreException;
  import org.apache.kafka.streams.state.KeyValueIterator;
  import org.apache.kafka.streams.state.QueryableStoreType;
  import org.apache.kafka.streams.state.ReadOnlyKeyValueStore;
  
  import java.util.List;
  import java.util.Objects;
  
  /**
   * A wrapper over the underlying {@link ReadOnlyKeyValueStore}s found in a {@link
   * org.apache.kafka.streams.processor.internals.ProcessorTopology}
   *
   * @param <K> key type
   * @param <V> value type
   */
  public class CompositeReadOnlyKeyValueStore<K, V> implements ReadOnlyKeyValueStore<K, V> {
  
      private final StateStoreProvider storeProvider;
      private final QueryableStoreType<ReadOnlyKeyValueStore<K, V>> storeType;
      private final String storeName;
  
      public CompositeReadOnlyKeyValueStore(final StateStoreProvider storeProvider,
                                            final QueryableStoreType<ReadOnlyKeyValueStore<K, V>> storeType,
                                            final String storeName) {
          this.storeProvider = storeProvider;
          this.storeType = storeType;
          this.storeName = storeName;
      }
  
  
      @Override
      public V get(final K key) {
          Objects.requireNonNull(key);
          final List<ReadOnlyKeyValueStore<K, V>> stores = storeProvider.stores(storeName, storeType);
          for (final ReadOnlyKeyValueStore<K, V> store : stores) {
              try {
                  final V result = store.get(key);
                  if (result != null) {
                      return result;
                  }
              } catch (final InvalidStateStoreException e) {
                  throw new InvalidStateStoreException("State store is not available anymore and may have been migrated to another instance; please re-discover its location from the state metadata.");
              }
  
          }
          return null;
      }
  
      @Override
      public KeyValueIterator<K, V> range(final K from, final K to) {
          final NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>> nextIteratorFunction = new NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>>() {
              @Override
              public KeyValueIterator<K, V> apply(final ReadOnlyKeyValueStore<K, V> store) {
                  try {
                      return store.range(from, to);
                  } catch (final InvalidStateStoreException e) {
                      throw new InvalidStateStoreException("State store is not available anymore and may have been migrated to another instance; please re-discover its location from the state metadata.");
                  }
              }
          };
          final List<ReadOnlyKeyValueStore<K, V>> stores = storeProvider.stores(storeName, storeType);
          return new DelegatingPeekingKeyValueIterator<>(
              storeName,
              new CompositeKeyValueIterator<>(stores.iterator(), nextIteratorFunction));
      }
  
      @Override
      public KeyValueIterator<K, V> reverseRange(final K from, final K to) {
          final NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>> nextIteratorFunction = new NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>>() {
              @Override
              public KeyValueIterator<K, V> apply(final ReadOnlyKeyValueStore<K, V> store) {
                  try {
                      return store.reverseRange(from, to);
                  } catch (final InvalidStateStoreException e) {
                      throw new InvalidStateStoreException("State store is not available anymore and may have been migrated to another instance; please re-discover its location from the state metadata.");
                  }
              }
          };
          final List<ReadOnlyKeyValueStore<K, V>> stores = storeProvider.stores(storeName, storeType);
          return new DelegatingPeekingKeyValueIterator<>(
              storeName,
              new CompositeKeyValueIterator<>(stores.iterator(), nextIteratorFunction));
      }
  
      @Override
      public <PS extends Serializer<P>, P> KeyValueIterator<K, V> prefixScan(final P prefix, final PS prefixKeySerializer) {
          Objects.requireNonNull(prefix);
          Objects.requireNonNull(prefixKeySerializer);
          final NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>> nextIteratorFunction = new NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>>() {
              @Override
              public KeyValueIterator<K, V> apply(final ReadOnlyKeyValueStore<K, V> store) {
                  try {
                      return store.prefixScan(prefix, prefixKeySerializer);
                  } catch (final InvalidStateStoreException e) {
                      throw new InvalidStateStoreException("State store is not available anymore and may have been migrated to another instance; please re-discover its location from the state metadata.");
                  }
              }
          };
          final List<ReadOnlyKeyValueStore<K, V>> stores = storeProvider.stores(storeName, storeType);
          return new DelegatingPeekingKeyValueIterator<>(
              storeName,
              new CompositeKeyValueIterator<>(stores.iterator(), nextIteratorFunction));
      }
  
      @Override
      public KeyValueIterator<K, V> all() {
          final NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>> nextIteratorFunction = new NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>>() {
              @Override
              public KeyValueIterator<K, V> apply(final ReadOnlyKeyValueStore<K, V> store) {
                  try {
                      return store.all();
                  } catch (final InvalidStateStoreException e) {
                      throw new InvalidStateStoreException("State store is not available anymore and may have been migrated to another instance; please re-discover its location from the state metadata.");
                  }
              }
          };
          final List<ReadOnlyKeyValueStore<K, V>> stores = storeProvider.stores(storeName, storeType);
          return new DelegatingPeekingKeyValueIterator<>(
              storeName,
              new CompositeKeyValueIterator<>(stores.iterator(), nextIteratorFunction));
      }
  
      @Override
      public KeyValueIterator<K, V> reverseAll() {
          final NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>> nextIteratorFunction = new NextIteratorFunction<K, V, ReadOnlyKeyValueStore<K, V>>() {
              @Override
              public KeyValueIterator<K, V> apply(final ReadOnlyKeyValueStore<K, V> store) {
                  try {
                      return store.reverseAll();
                  } catch (final InvalidStateStoreException e) {
                      throw new InvalidStateStoreException("State store is not available anymore and may have been migrated to another instance; please re-discover its location from the state metadata.");
                  }
              }
          };
          final List<ReadOnlyKeyValueStore<K, V>> stores = storeProvider.stores(storeName, storeType);
          return new DelegatingPeekingKeyValueIterator<>(
              storeName,
              new CompositeKeyValueIterator<>(stores.iterator(), nextIteratorFunction));
      }
  
      @Override
      public long approximateNumEntries() {
          final List<ReadOnlyKeyValueStore<K, V>> stores = storeProvider.stores(storeName, storeType);
          long total = 0;
          for (final ReadOnlyKeyValueStore<K, V> store : stores) {
              total += store.approximateNumEntries();
              if (total < 0) {
                  return Long.MAX_VALUE;
              }
          }
          return total;
      }
  
  }
  