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;
  
  
  import org.apache.kafka.streams.kstream.Windowed;
  
  import java.time.Instant;
  
  /**
   * A session store that only supports read operations. Implementations should be thread-safe as
   * concurrent reads and writes are expected.
   *
   * @param <K>   the key type
   * @param <AGG> the aggregated value type
   */
  public interface ReadOnlySessionStore<K, AGG> {
  
      /**
       * Fetch any sessions with the matching key and the sessions end is &ge; earliestSessionEndTime
       * and the sessions start is &le; latestSessionStartTime iterating from earliest to latest.
       * I.e., earliestSessionEndTime is the lower bound of the search interval and latestSessionStartTime
       * is the upper bound of the search interval, and the method returns all sessions that overlap
       * with the search interval.
       * Thus, if a session ends before earliestSessionEndTime, or starts after latestSessionStartTime
       * it won't be contained in the result:
       * <pre>{@code
       * earliestSessionEndTime: ESET
       * latestSessionStartTime: LSST
       *
       *                       [ESET............LSST]
       * [not-included] [included]   [included]   [included] [not-included]
       * }</pre>
       * <p>
       * This iterator must be closed after use.
       *
       * @param key                    the key to return sessions for
       * @param earliestSessionEndTime the end timestamp of the earliest session to search for, where
       *                               iteration starts.
       * @param latestSessionStartTime the end timestamp of the latest session to search for, where
       *                               iteration ends.
       * @return iterator of sessions with the matching key and aggregated values, from earliest to
       * latest session time.
       * @throws NullPointerException If null is used for key.
       */
      default KeyValueIterator<Windowed<K>, AGG> findSessions(final K key,
                                                              final long earliestSessionEndTime,
                                                              final long latestSessionStartTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Fetch any sessions with the matching key and the sessions end is &ge; earliestSessionEndTime
       * and the sessions start is &le; latestSessionStartTime iterating from earliest to latest.
       * I.e., earliestSessionEndTime is the lower bound of the search interval and latestSessionStartTime
       * is the upper bound of the search interval, and the method returns all sessions that overlap
       * with the search interval.
       * Thus, if a session ends before earliestSessionEndTime, or starts after latestSessionStartTime
       * it won't be contained in the result:
       * <pre>{@code
       * earliestSessionEndTime: ESET
       * latestSessionStartTime: LSST
       *
       *                       [ESET............LSST]
       * [not-included] [included]   [included]   [included] [not-included]
       * }</pre>
       * <p>
       * This iterator must be closed after use.
       *
       * @param key                    the key to return sessions for
       * @param earliestSessionEndTime the end timestamp of the earliest session to search for, where
       *                               iteration starts.
       * @param latestSessionStartTime the end timestamp of the latest session to search for, where
       *                               iteration ends.
       * @return iterator of sessions with the matching key and aggregated values, from earliest to
       * latest session time.
       * @throws NullPointerException If null is used for key.
       */
      default KeyValueIterator<Windowed<K>, AGG> findSessions(final K key,
                                                              final Instant earliestSessionEndTime,
                                                              final Instant latestSessionStartTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Fetch any sessions with the matching key and the sessions end is &ge; earliestSessionEndTime
       * and the sessions start is &le; latestSessionStartTime iterating from latest to earliest.
       * I.e., earliestSessionEndTime is the lower bound of the search interval and latestSessionStartTime
       * is the upper bound of the search interval, and the method returns all sessions that overlap
       * with the search interval.
       * Thus, if a session ends before earliestSessionEndTime, or starts after latestSessionStartTime
       * it won't be contained in the result:
       * <pre>{@code
       * earliestSessionEndTime: ESET
       * latestSessionStartTime: LSST
       *
       *                       [ESET............LSST]
       * [not-included] [included]   [included]   [included] [not-included]
       * }</pre>
       * <p>
       * This iterator must be closed after use.
       *
       * @param key                    the key to return sessions for
       * @param earliestSessionEndTime the end timestamp of the earliest session to search for, where
       *                               iteration ends.
       * @param latestSessionStartTime the end timestamp of the latest session to search for, where
       *                               iteration starts.
       * @return backward iterator of sessions with the matching key and aggregated values, from
       * latest to earliest session time.
       * @throws NullPointerException If null is used for key.
       */
      default KeyValueIterator<Windowed<K>, AGG> backwardFindSessions(final K key,
                                                                      final long earliestSessionEndTime,
                                                                      final long latestSessionStartTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Fetch any sessions with the matching key and the sessions end is &ge; earliestSessionEndTime
       * and the sessions start is &le; latestSessionStartTime iterating from latest to earliest.
       * I.e., earliestSessionEndTime is the lower bound of the search interval and latestSessionStartTime
       * is the upper bound of the search interval, and the method returns all sessions that overlap
       * with the search interval.
       * Thus, if a session ends before earliestSessionEndTime, or starts after latestSessionStartTime
       * it won't be contained in the result:
       * <pre>{@code
       * earliestSessionEndTime: ESET
       * latestSessionStartTime: LSST
       *
       *                       [ESET............LSST]
       * [not-included] [included]   [included]   [included] [not-included]
       * }</pre>
       * <p>
       * This iterator must be closed after use.
       *
       * @param key                    the key to return sessions for
       * @param earliestSessionEndTime the end timestamp of the earliest session to search for, where
       *                               iteration ends.
       * @param latestSessionStartTime the end timestamp of the latest session to search for, where
       *                               iteration starts.
       * @return backward iterator of sessions with the matching key and aggregated values, from
       * latest to earliest session time.
       * @throws NullPointerException If null is used for key.
       */
      default KeyValueIterator<Windowed<K>, AGG> backwardFindSessions(final K key,
                                                                      final Instant earliestSessionEndTime,
                                                                      final Instant latestSessionStartTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Fetch any sessions in the given range of keys and the sessions end is &ge;
       * earliestSessionEndTime and the sessions start is &le; latestSessionStartTime iterating from
       * earliest to latest.
       * I.e., earliestSessionEndTime is the lower bound of the search interval and latestSessionStartTime
       * is the upper bound of the search interval, and the method returns all sessions that overlap
       * with the search interval.
       * Thus, if a session ends before earliestSessionEndTime, or starts after latestSessionStartTime
       * it won't be contained in the result:
       * <pre>{@code
       * earliestSessionEndTime: ESET
       * latestSessionStartTime: LSST
       *
       *                       [ESET............LSST]
       * [not-included] [included]   [included]   [included] [not-included]
       * }</pre>
       * <p>
       * This iterator must be closed after use.
       *
       * @param keyFrom                The first key that could be in the range
       * A null value indicates a starting position from the first element in the store.
       * @param keyTo                  The last key that could be in the range
       * A null value indicates that the range ends with the last element in the store.
       * @param earliestSessionEndTime the end timestamp of the earliest session to search for, where
       *                               iteration starts.
       * @param latestSessionStartTime the end timestamp of the latest session to search for, where
       *                               iteration ends.
       * @return iterator of sessions with the matching keys and aggregated values, from earliest to
       * latest session time.
       */
      default KeyValueIterator<Windowed<K>, AGG> findSessions(final K keyFrom,
                                                              final K keyTo,
                                                              final long earliestSessionEndTime,
                                                              final long latestSessionStartTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Fetch any sessions in the given range of keys and the sessions end is &ge;
       * earliestSessionEndTime and the sessions start is &le; latestSessionStartTime iterating from
       * earliest to latest.
       * I.e., earliestSessionEndTime is the lower bound of the search interval and latestSessionStartTime
       * is the upper bound of the search interval, and the method returns all sessions that overlap
       * with the search interval.
       * Thus, if a session ends before earliestSessionEndTime, or starts after latestSessionStartTime
       * it won't be contained in the result:
       * <pre>{@code
       * earliestSessionEndTime: ESET
       * latestSessionStartTime: LSST
       *
       *                       [ESET............LSST]
       * [not-included] [included]   [included]   [included] [not-included]
       * }</pre>
       * <p>
       * This iterator must be closed after use.
       *
       * @param keyFrom                The first key that could be in the range
       * A null value indicates a starting position from the first element in the store.
       * @param keyTo                  The last key that could be in the range
       * A null value indicates that the range ends with the last element in the store.
       * @param earliestSessionEndTime the end timestamp of the earliest session to search for, where
       *                               iteration starts.
       * @param latestSessionStartTime the end timestamp of the latest session to search for, where
       *                               iteration ends.
       * @return iterator of sessions with the matching keys and aggregated values, from earliest to
       * latest session time.
       */
      default KeyValueIterator<Windowed<K>, AGG> findSessions(final K keyFrom,
                                                              final K keyTo,
                                                              final Instant earliestSessionEndTime,
                                                              final Instant latestSessionStartTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Fetch any sessions in the given range of keys and the sessions end is &ge;
       * earliestSessionEndTime and the sessions start is &le; latestSessionStartTime iterating from
       * latest to earliest.
       * I.e., earliestSessionEndTime is the lower bound of the search interval and latestSessionStartTime
       * is the upper bound of the search interval, and the method returns all sessions that overlap
       * with the search interval.
       * Thus, if a session ends before earliestSessionEndTime, or starts after latestSessionStartTime
       * it won't be contained in the result:
       * <pre>{@code
       * earliestSessionEndTime: ESET
       * latestSessionStartTime: LSST
       *
       *                       [ESET............LSST]
       * [not-included] [included]   [included]   [included] [not-included]
       * }</pre>
       * <p>
       * This iterator must be closed after use.
       *
       * @param keyFrom                The first key that could be in the range
       * A null value indicates a starting position from the first element in the store.
       * @param keyTo                  The last key that could be in the range
       * A null value indicates that the range ends with the last element in the store.
       * @param earliestSessionEndTime the end timestamp of the earliest session to search for, where
       *                               iteration ends.
       * @param latestSessionStartTime the end timestamp of the latest session to search for, where
       *                               iteration starts.
       * @return backward iterator of sessions with the matching keys and aggregated values, from
       * latest to earliest session time.
       */
      default KeyValueIterator<Windowed<K>, AGG> backwardFindSessions(final K keyFrom,
                                                                      final K keyTo,
                                                                      final long earliestSessionEndTime,
                                                                      final long latestSessionStartTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Fetch any sessions in the given range of keys and the sessions end is &ge;
       * earliestSessionEndTime and the sessions start is &le; latestSessionStartTime iterating from
       * latest to earliest.
       * I.e., earliestSessionEndTime is the lower bound of the search interval and latestSessionStartTime
       * is the upper bound of the search interval, and the method returns all sessions that overlap
       * with the search interval.
       * Thus, if a session ends before earliestSessionEndTime, or starts after latestSessionStartTime
       * it won't be contained in the result:
       * <pre>{@code
       * earliestSessionEndTime: ESET
       * latestSessionStartTime: LSST
       *
       *                       [ESET............LSST]
       * [not-included] [included]   [included]   [included] [not-included]
       * }</pre>
       * <p>
       * This iterator must be closed after use.
       *
       * @param keyFrom                The first key that could be in the range
       * A null value indicates a starting position from the first element in the store.
       * @param keyTo                  The last key that could be in the range
       * A null value indicates that the range ends with the last element in the store.
       * @param earliestSessionEndTime the end timestamp of the earliest session to search for, where
       *                               iteration ends.
       * @param latestSessionStartTime the end timestamp of the latest session to search for, where
       *                               iteration starts.
       * @return backward iterator of sessions with the matching keys and aggregated values, from
       * latest to earliest session time.
       */
      default KeyValueIterator<Windowed<K>, AGG> backwardFindSessions(final K keyFrom,
                                                                      final K keyTo,
                                                                      final Instant earliestSessionEndTime,
                                                                      final Instant latestSessionStartTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Get the value of key from a single session.
       *
       * @param key              the key to fetch
       * @param sessionStartTime start timestamp of the session
       * @param sessionEndTime   end timestamp of the session
       * @return The value or {@code null} if no session with the exact start and end timestamp exists
       *         for the given key
       * @throws NullPointerException If {@code null} is used for any key.
       */
      default AGG fetchSession(final K key,
                               final long sessionStartTime,
                               final long sessionEndTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Get the value of key from a single session.
       *
       * @param key              the key to fetch
       * @param sessionStartTime start timestamp of the session
       * @param sessionEndTime   end timestamp of the session
       * @return The value or {@code null} if no session with the exact start and end timestamp exists
       *         for the given key
       * @throws NullPointerException If {@code null} is used for any key.
       */
      default AGG fetchSession(final K key,
                               final Instant sessionStartTime,
                               final Instant sessionEndTime) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Retrieve all aggregated sessions for the provided key. This iterator must be closed after
       * use.
       * <p>
       * For each key, the iterator guarantees ordering of sessions, starting from the oldest/earliest
       * available session to the newest/latest session.
       *
       * @param key record key to find aggregated session values for
       * @return KeyValueIterator containing all sessions for the provided key, from oldest to newest
       * session.
       * @throws NullPointerException If null is used for key.
       */
      KeyValueIterator<Windowed<K>, AGG> fetch(final K key);
  
      /**
       * Retrieve all aggregated sessions for the provided key. This iterator must be closed after
       * use.
       * <p>
       * For each key, the iterator guarantees ordering of sessions, starting from the newest/latest
       * available session to the oldest/earliest session.
       *
       * @param key record key to find aggregated session values for
       * @return backward KeyValueIterator containing all sessions for the provided key, from newest
       * to oldest session.
       * @throws NullPointerException If null is used for key.
       */
      default KeyValueIterator<Windowed<K>, AGG> backwardFetch(final K key) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  
      /**
       * Retrieve all aggregated sessions for the given range of keys. This iterator must be closed
       * after use.
       * <p>
       * For each key, the iterator guarantees ordering of sessions, starting from the oldest/earliest
       * available session to the newest/latest session.
       *
       * @param keyFrom first key in the range to find aggregated session values for
       * A null value indicates a starting position from the first element in the store.
       * @param keyTo   last key in the range to find aggregated session values for
       * A null value indicates that the range ends with the last element in the store.
       * @return KeyValueIterator containing all sessions for the provided key, from oldest to newest
       * session.
       */
      KeyValueIterator<Windowed<K>, AGG> fetch(final K keyFrom, final K keyTo);
  
      /**
       * Retrieve all aggregated sessions for the given range of keys. This iterator must be closed
       * after use.
       * <p>
       * For each key, the iterator guarantees ordering of sessions, starting from the newest/latest
       * available session to the oldest/earliest session.
       *
       * @param keyFrom first key in the range to find aggregated session values for
       * A null value indicates a starting position from the first element in the store.
       * @param keyTo   last key in the range to find aggregated session values for
       * A null value indicates that the range ends with the last element in the store.
       * @return backward KeyValueIterator containing all sessions for the provided key, from newest
       * to oldest session.
       */
      default KeyValueIterator<Windowed<K>, AGG> backwardFetch(final K keyFrom, final K keyTo) {
          throw new UnsupportedOperationException(
              "This API is not supported by this implementation of ReadOnlySessionStore.");
      }
  }
  