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.sdk.extensions.euphoria.core.client.util;
  
  import java.io.Serializable;
  import java.util.stream.Stream;
  import org.apache.beam.sdk.extensions.euphoria.core.client.functional.BinaryFunction;
  import org.apache.beam.sdk.extensions.euphoria.core.client.functional.BinaryFunctor;
  import org.apache.beam.sdk.extensions.euphoria.core.client.functional.CombinableReduceFunction;
  import org.apache.beam.sdk.extensions.euphoria.core.client.functional.ReduceFunctor;
  import org.apache.beam.sdk.extensions.euphoria.core.client.io.Collector;
  import org.apache.beam.sdk.extensions.euphoria.core.translate.SingleValueContext;
  
  /** Apply a folding function. */
  /** @deprecated Use Java SDK directly, Euphoria is scheduled for removal in a future release. */
  @Deprecated
  public class Fold implements Serializable {
  
    /**
     * Return a {@link CombinableReduceFunction} that performs a fold operation and emits result after
     * fold of all input data.
     *
     * @param <T> element type
     * @param fold the associative fold function
     * @return the {@link CombinableReduceFunction}
     */
    public static <T> CombinableReduceFunction<T> of(BinaryFunction<T, T, T> fold) {
      return s ->
          s.reduce(fold::apply)
              .orElseThrow(() -> new IllegalStateException("Received empty stream on input!"));
    }
  
    /**
     * Return a {@link CombinableReduceFunction} that performs a fold operation and emits result after
     * fold of all input data.
     *
     * @param <T> element type
     * @param identity the zero element
     * @param fold the associative fold function
     * @return the {@link CombinableReduceFunction}
     */
    public static <T> CombinableReduceFunction<T> of(T identity, BinaryFunction<T, T, T> fold) {
      return s -> s.reduce(identity, fold::apply);
    }
  
    /**
     * Return a {@link ReduceFunctor} that performs a fold operation and emits result after fold of
     * all input data.
     *
     * @param <T> element type
     * @param identity the zero element
     * @param fold the associative fold function
     * @return the {@link CombinableReduceFunction}
     */
    public static <T> ReduceFunctor<T, T> of(T identity, BinaryFunctor<T, T, T> fold) {
      return (Stream<T> s, Collector<T> ctx) -> {
        final SingleValueContext<T> wrap = new SingleValueContext<>(ctx.asContext());
        final T ret =
            s.reduce(
                identity,
                (a, b) -> {
                  fold.apply(a, b, wrap);
                  return wrap.getAndResetValue();
                });
        ctx.collect(ret);
      };
    }
  }
  