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.operator;
  
  import org.apache.beam.sdk.extensions.euphoria.core.annotation.audience.Audience;
  import org.apache.beam.sdk.extensions.euphoria.core.annotation.operator.Derived;
  import org.apache.beam.sdk.extensions.euphoria.core.annotation.operator.StateComplexity;
  import org.apache.beam.sdk.extensions.euphoria.core.client.functional.UnaryFunction;
  import org.apache.beam.sdk.extensions.euphoria.core.client.functional.UnaryFunctionEnv;
  import org.apache.beam.sdk.extensions.euphoria.core.client.io.Collector;
  import org.apache.beam.sdk.extensions.euphoria.core.client.operator.base.Builders;
  import org.apache.beam.sdk.extensions.euphoria.core.client.operator.base.Operator;
  import org.apache.beam.sdk.extensions.euphoria.core.client.type.TypeAware;
  import org.apache.beam.sdk.extensions.euphoria.core.client.util.PCollectionLists;
  import org.apache.beam.sdk.extensions.euphoria.core.translate.OperatorTransform;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollectionList;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Simple one-to-one transformation of input elements. It is a special case of {@link FlatMap} with
   * exactly one output element for every one input element. No context is provided inside the map
   * function.
   *
   * <h3>Builders:</h3>
   *
   * <ol>
   *   <li>{@code [named] ..................} give name to the operator [optional]
   *   <li>{@code of .......................} input dataset
   *   <li>{@code using ....................} apply {@link UnaryFunction} or {@link UnaryFunctionEnv}
   *       to input elements
   *   <li>{@code output ...................} build output dataset
   * </ol>
   *
   * @deprecated Use Java SDK directly, Euphoria is scheduled for removal in a future release.
   */
  @Audience(Audience.Type.CLIENT)
  @Derived(state = StateComplexity.ZERO, repartitions = 0)
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  @Deprecated
  public class MapElements<InputT, OutputT> extends Operator<OutputT>
      implements CompositeOperator<InputT, OutputT>, TypeAware.Output<OutputT> {
  
    /**
     * Starts building a nameless {@link MapElements} operator to process the given input dataset.
     *
     * @param <InputT> the type of elements of the input dataset
     * @param input the input data set to be processed
     * @return a builder to complete the setup of the new operator
     * @see #named(String)
     * @see OfBuilder#of(PCollection)
     */
    public static <InputT> UsingBuilder<InputT> of(PCollection<InputT> input) {
      return named(null).of(input);
    }
  
    /**
     * Starts building a named {@link MapElements} operator.
     *
     * @param name a user provided name of the new operator to build
     * @return a builder to complete the setup of the new operator
     */
    public static OfBuilder named(@Nullable String name) {
      return new Builder<>(name);
    }
  
    /** Builder for the 'of' step. */
    public interface OfBuilder extends Builders.Of {
  
      @Override
      <InputT> UsingBuilder<InputT> of(PCollection<InputT> input);
    }
  
    /** MapElements builder which adds mapper to operator under build. */
    public interface UsingBuilder<InputT> {
  
      /**
       * The mapping function that takes input element and outputs the OutputT type element. If you
       * want use aggregators use rather {@link #using(UnaryFunctionEnv)}.
       *
       * @param <OutputT> type of output elements
       * @param mapper the mapping function
       * @return the next builder to complete the setup of the {@link MapElements} operator
       */
      default <OutputT> Builders.Output<OutputT> using(UnaryFunction<InputT, OutputT> mapper) {
        return using(mapper, null);
      }
  
      default <OutputT> Builders.Output<OutputT> using(
          UnaryFunction<InputT, OutputT> mapper, @Nullable TypeDescriptor<OutputT> outputType) {
        return using((el, ctx) -> mapper.apply(el), outputType);
      }
  
      /**
       * The mapping function that takes input element and outputs the OutputT type element.
       *
       * @param <OutputT> type of output elements
       * @param mapper the mapping function
       * @return the next builder to complete the setup of the {@link MapElements} operator
       */
      default <OutputT> Builders.Output<OutputT> using(UnaryFunctionEnv<InputT, OutputT> mapper) {
        return using(mapper, null);
      }
  
      <OutputT> Builders.Output<OutputT> using(
          UnaryFunctionEnv<InputT, OutputT> mapper, @Nullable TypeDescriptor<OutputT> outputType);
    }
  
    private static class Builder<InputT, OutputT>
        implements OfBuilder, UsingBuilder<InputT>, Builders.Output<OutputT> {
  
      private final @Nullable String name;
      private PCollection<InputT> input;
      private UnaryFunctionEnv<InputT, OutputT> mapper;
      private @Nullable TypeDescriptor<OutputT> outputType;
  
      Builder(@Nullable String name) {
        this.name = name;
      }
  
      @Override
      public <T> UsingBuilder<T> of(PCollection<T> input) {
        @SuppressWarnings("unchecked")
        final Builder<T, ?> cast = (Builder) this;
        cast.input = input;
        return cast;
      }
  
      @Override
      public <T> Builders.Output<T> using(
          UnaryFunctionEnv<InputT, T> mapper, @Nullable TypeDescriptor<T> outputType) {
        @SuppressWarnings("unchecked")
        final Builder<InputT, T> cast = (Builder) this;
        cast.mapper = mapper;
        cast.outputType = outputType;
        return cast;
      }
  
      @Override
      public PCollection<OutputT> output() {
        final MapElements<InputT, OutputT> operator = new MapElements<>(name, mapper, outputType);
        return OperatorTransform.apply(operator, PCollectionList.of(input));
      }
    }
  
    private final UnaryFunctionEnv<InputT, OutputT> mapper;
  
    private MapElements(
        @Nullable String name,
        UnaryFunctionEnv<InputT, OutputT> mapper,
        @Nullable TypeDescriptor<OutputT> outputType) {
      super(name, outputType);
      this.mapper = mapper;
    }
  
    @Override
    public PCollection<OutputT> expand(PCollectionList<InputT> inputs) {
      return FlatMap.named(getName().orElse(null))
          .of(PCollectionLists.getOnlyElement(inputs))
          .using(
              (InputT elem, Collector<OutputT> coll) ->
                  coll.collect(getMapper().apply(elem, coll.asContext())),
              getOutputType().orElse(null))
          .output();
    }
  
    public UnaryFunctionEnv<InputT, OutputT> getMapper() {
      return mapper;
    }
  }
  