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.streams.errors.InvalidStateStoreException;
  import org.apache.kafka.streams.kstream.Windowed;
  import org.apache.kafka.streams.state.KeyValueIterator;
  import org.apache.kafka.streams.state.QueryableStoreType;
  import org.apache.kafka.streams.state.ReadOnlySessionStore;
  
  import java.util.List;
  import java.util.Objects;
  
  /**
   * Wrapper over the underlying {@link ReadOnlySessionStore}s found in a {@link
   * org.apache.kafka.streams.processor.internals.ProcessorTopology}
   */
  public class CompositeReadOnlySessionStore<K, V> implements ReadOnlySessionStore<K, V> {
      private final StateStoreProvider storeProvider;
      private final QueryableStoreType<ReadOnlySessionStore<K, V>> queryableStoreType;
      private final String storeName;
  
      public CompositeReadOnlySessionStore(final StateStoreProvider storeProvider,
                                           final QueryableStoreType<ReadOnlySessionStore<K, V>> queryableStoreType,
                                           final String storeName) {
          this.storeProvider = storeProvider;
          this.queryableStoreType = queryableStoreType;
          this.storeName = storeName;
      }
  
      @Override
      public KeyValueIterator<Windowed<K>, V> findSessions(final K key,
                                                           final long earliestSessionEndTime,
                                                           final long latestSessionStartTime) {
          Objects.requireNonNull(key, "key can't be null");
          final List<ReadOnlySessionStore<K, V>> stores = storeProvider.stores(storeName, queryableStoreType);
          for (final ReadOnlySessionStore<K, V> store : stores) {
              try {
                  final KeyValueIterator<Windowed<K>, V> result =
                      store.findSessions(key, earliestSessionEndTime, latestSessionStartTime);
  
                  if (!result.hasNext()) {
                      result.close();
                  } else {
                      return result;
                  }
              } catch (final InvalidStateStoreException ise) {
                  throw new InvalidStateStoreException(
                      "State store  [" + storeName + "] is not available anymore" +
                          " and may have been migrated to another instance; " +
                          "please re-discover its location from the state metadata.",
                      ise
                  );
              }
          }
          return KeyValueIterators.emptyIterator();
      }
  
      @Override
      public KeyValueIterator<Windowed<K>, V> backwardFindSessions(final K key,
                                                                   final long earliestSessionEndTime,
                                                                   final long latestSessionStartTime) {
          Objects.requireNonNull(key, "key can't be null");
          final List<ReadOnlySessionStore<K, V>> stores = storeProvider.stores(storeName, queryableStoreType);
          for (final ReadOnlySessionStore<K, V> store : stores) {
              try {
                  final KeyValueIterator<Windowed<K>, V> result = store.backwardFindSessions(key, earliestSessionEndTime, latestSessionStartTime);
                  if (!result.hasNext()) {
                      result.close();
                  } else {
                      return result;
                  }
              } catch (final InvalidStateStoreException ise) {
                  throw new InvalidStateStoreException(
                      "State store  [" + storeName + "] is not available anymore" +
                          " and may have been migrated to another instance; " +
                          "please re-discover its location from the state metadata.",
                      ise
                  );
              }
          }
          return KeyValueIterators.emptyIterator();
      }
  
      @Override
      public KeyValueIterator<Windowed<K>, V> findSessions(final K keyFrom,
                                                           final K keyTo,
                                                           final long earliestSessionEndTime,
                                                           final long latestSessionStartTime) {
          final List<ReadOnlySessionStore<K, V>> stores = storeProvider.stores(storeName, queryableStoreType);
          for (final ReadOnlySessionStore<K, V> store : stores) {
              try {
                  final KeyValueIterator<Windowed<K>, V> result =
                      store.findSessions(keyFrom, keyTo, earliestSessionEndTime, latestSessionStartTime);
                  if (!result.hasNext()) {
                      result.close();
                  } else {
                      return result;
                  }
              } catch (final InvalidStateStoreException ise) {
                  throw new InvalidStateStoreException(
                      "State store  [" + storeName + "] is not available anymore" +
                          " and may have been migrated to another instance; " +
                          "please re-discover its location from the state metadata.",
                      ise
                  );
              }
          }
          return KeyValueIterators.emptyIterator();
      }
  
      @Override
      public KeyValueIterator<Windowed<K>, V> backwardFindSessions(final K keyFrom,
                                                                   final K keyTo,
                                                                   final long earliestSessionEndTime,
                                                                   final long latestSessionStartTime) {
          final List<ReadOnlySessionStore<K, V>> stores = storeProvider.stores(storeName, queryableStoreType);
          for (final ReadOnlySessionStore<K, V> store : stores) {
              try {
                  final KeyValueIterator<Windowed<K>, V> result =
                      store.backwardFindSessions(keyFrom, keyTo, earliestSessionEndTime, latestSessionStartTime);
                  if (!result.hasNext()) {
                      result.close();
                  } else {
                      return result;
                  }
              } catch (final InvalidStateStoreException ise) {
                  throw new InvalidStateStoreException(
                      "State store  [" + storeName + "] is not available anymore" +
                          " and may have been migrated to another instance; " +
                          "please re-discover its location from the state metadata.",
                      ise
                  );
              }
          }
          return KeyValueIterators.emptyIterator();
      }
  
      @Override
      public V fetchSession(final K key, final long earliestSessionEndTime, final long latestSessionStartTime) {
          Objects.requireNonNull(key, "key can't be null");
          final List<ReadOnlySessionStore<K, V>> stores = storeProvider.stores(storeName, queryableStoreType);
          for (final ReadOnlySessionStore<K, V> store : stores) {
              try {
                  return store.fetchSession(key, earliestSessionEndTime, latestSessionStartTime);
              } catch (final InvalidStateStoreException ise) {
                  throw new InvalidStateStoreException(
                      "State store  [" + storeName + "] is not available anymore" +
                          " and may have been migrated to another instance; " +
                          "please re-discover its location from the state metadata.",
                      ise
                  );
              }
          }
          return null;
      }
  
      @Override
      public KeyValueIterator<Windowed<K>, V> fetch(final K key) {
          Objects.requireNonNull(key, "key can't be null");
          final List<ReadOnlySessionStore<K, V>> stores = storeProvider.stores(storeName, queryableStoreType);
          for (final ReadOnlySessionStore<K, V> store : stores) {
              try {
                  final KeyValueIterator<Windowed<K>, V> result = store.fetch(key);
                  if (!result.hasNext()) {
                      result.close();
                  } else {
                      return result;
                  }
              } catch (final InvalidStateStoreException ise) {
                  throw new InvalidStateStoreException("State store  [" + storeName + "] is not available anymore" +
                                                               " and may have been migrated to another instance; " +
                                                               "please re-discover its location from the state metadata. " +
                                                               "Original error message: " + ise);
              }
          }
          return KeyValueIterators.emptyIterator();
      }
  
      @Override
      public KeyValueIterator<Windowed<K>, V> backwardFetch(final K key) {
          Objects.requireNonNull(key, "key can't be null");
          final List<ReadOnlySessionStore<K, V>> stores = storeProvider.stores(storeName, queryableStoreType);
          for (final ReadOnlySessionStore<K, V> store : stores) {
              try {
                  final KeyValueIterator<Windowed<K>, V> result = store.backwardFetch(key);
                  if (!result.hasNext()) {
                      result.close();
                  } else {
                      return result;
                  }
              } catch (final InvalidStateStoreException ise) {
                  throw new InvalidStateStoreException(
                      "State store  [" + storeName + "] is not available anymore" +
                          " and may have been migrated to another instance; " +
                          "please re-discover its location from the state metadata.",
                      ise
                  );
              }
          }
          return KeyValueIterators.emptyIterator();
      }
  
      @Override
      public KeyValueIterator<Windowed<K>, V> fetch(final K keyFrom, final K keyTo) {
          final NextIteratorFunction<Windowed<K>, V, ReadOnlySessionStore<K, V>> nextIteratorFunction =
              store -> store.fetch(keyFrom, keyTo);
          return new DelegatingPeekingKeyValueIterator<>(storeName,
                                                         new CompositeKeyValueIterator<>(
                                                                 storeProvider.stores(storeName, queryableStoreType).iterator(),
                                                                 nextIteratorFunction));
      }
  
      @Override
      public KeyValueIterator<Windowed<K>, V> backwardFetch(final K keyFrom, final K keyTo) {
          final NextIteratorFunction<Windowed<K>, V, ReadOnlySessionStore<K, V>> nextIteratorFunction =
              store -> store.backwardFetch(keyFrom, keyTo);
          return new DelegatingPeekingKeyValueIterator<>(
              storeName,
              new CompositeKeyValueIterator<>(
                  storeProvider.stores(storeName, queryableStoreType).iterator(),
                  nextIteratorFunction
              )
          );
      }
  }
  