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.beam.runners.core;
  
  import java.io.IOException;
  import java.io.Serializable;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.state.BagState;
  import org.apache.beam.sdk.state.CombiningState;
  import org.apache.beam.sdk.state.MapState;
  import org.apache.beam.sdk.state.MultimapState;
  import org.apache.beam.sdk.state.OrderedListState;
  import org.apache.beam.sdk.state.SetState;
  import org.apache.beam.sdk.state.State;
  import org.apache.beam.sdk.state.StateSpec;
  import org.apache.beam.sdk.state.ValueState;
  import org.apache.beam.sdk.state.WatermarkHoldState;
  import org.apache.beam.sdk.transforms.Combine.CombineFn;
  import org.apache.beam.sdk.transforms.CombineWithContext.CombineFnWithContext;
  import org.apache.beam.sdk.transforms.GroupByKey;
  import org.apache.beam.sdk.transforms.windowing.TimestampCombiner;
  
  /**
   * An address and specification for a persistent state cell. This includes a unique identifier for
   * the location, the information necessary to encode the value, and details about the intended
   * access pattern.
   *
   * <p>State can be thought of as a sparse table, with each {@code StateTag} defining a column that
   * has cells of type {@code StateT}.
   *
   * <p>Currently, this can only be used in a step immediately following a {@link GroupByKey}.
   *
   * @param <StateT> The type of state being tagged.
   */
  public interface StateTag<StateT extends State> extends Serializable {
  
    /** Append the UTF-8 encoding of this tag to the given {@link Appendable}. */
    void appendTo(Appendable sb) throws IOException;
  
    /** An identifier for the state cell that this tag references. */
    String getId();
  
    /** The specification for the state stored in the referenced cell. */
    StateSpec<StateT> getSpec();
  
    /**
     * Bind this state tag. See {@link StateSpec#bind}.
     *
     * @deprecated Use the {@link StateSpec#bind} method via {@link #getSpec} for now.
     */
    @Deprecated
    StateT bind(StateBinder binder);
  
    /**
     * Visitor for binding a {@link StateSpec} and to the associated {@link State}.
     *
     * @deprecated for migration only; runners should reference the top level {@link
     *     org.apache.beam.sdk.state.StateBinder} and move towards {@link StateSpec} rather than
     *     {@link StateTag}.
     */
    @Deprecated
    public interface StateBinder {
      <T> ValueState<T> bindValue(StateTag<ValueState<T>> spec, Coder<T> coder);
  
      <T> BagState<T> bindBag(StateTag<BagState<T>> spec, Coder<T> elemCoder);
  
      <T> SetState<T> bindSet(StateTag<SetState<T>> spec, Coder<T> elemCoder);
  
      <KeyT, ValueT> MapState<KeyT, ValueT> bindMap(
          StateTag<MapState<KeyT, ValueT>> spec,
          Coder<KeyT> mapKeyCoder,
          Coder<ValueT> mapValueCoder);
  
      <KeyT, ValueT> MultimapState<KeyT, ValueT> bindMultimap(
          StateTag<MultimapState<KeyT, ValueT>> spec, Coder<KeyT> keyCoder, Coder<ValueT> valueCoder);
  
      <T> OrderedListState<T> bindOrderedList(StateTag<OrderedListState<T>> spec, Coder<T> elemCoder);
  
      <InputT, AccumT, OutputT> CombiningState<InputT, AccumT, OutputT> bindCombiningValue(
          StateTag<CombiningState<InputT, AccumT, OutputT>> spec,
          Coder<AccumT> accumCoder,
          CombineFn<InputT, AccumT, OutputT> combineFn);
  
      <InputT, AccumT, OutputT> CombiningState<InputT, AccumT, OutputT> bindCombiningValueWithContext(
          StateTag<CombiningState<InputT, AccumT, OutputT>> spec,
          Coder<AccumT> accumCoder,
          CombineFnWithContext<InputT, AccumT, OutputT> combineFn);
  
      /**
       * Bind to a watermark {@link StateSpec}.
       *
       * <p>This accepts the {@link TimestampCombiner} that dictates how watermark hold timestamps
       * added to the returned {@link WatermarkHoldState} are to be combined.
       */
      WatermarkHoldState bindWatermark(
          StateTag<WatermarkHoldState> spec, TimestampCombiner timestampCombiner);
    }
  }
  