/*
 * 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.beam.runners.flink.translation.wrappers.streaming.stableinput;

import java.util.stream.Stream;

/**
 * A handler for buffering elements which cannot be processed yet because {@link
 * org.apache.beam.sdk.transforms.DoFn.RequiresStableInput} is used and a checkpoint is currently
 * pending.
 *
 * <p>When a DoFn is annotated with @RequiresStableInput we are only allowed to process elements
 * after a checkpoint has completed. This ensures that the input is stable and we produce idempotent
 * results on failures.
 */
interface BufferingElementsHandler {

  /** Returns all buffered elements. */
  Stream<BufferedElement> getElements();

  /** Adds the given element to the buffered elements. */
  void buffer(BufferedElement element);

  /** Clears buffered elements. */
  void clear();
}
