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.transforms;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkNotNull;
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkState;
  
  import org.apache.beam.sdk.transforms.Contextful.Fn;
  import org.apache.beam.sdk.transforms.WithFailures.ExceptionElement;
  import org.apache.beam.sdk.transforms.display.DisplayData;
  import org.apache.beam.sdk.transforms.display.HasDisplayData;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollectionTuple;
  import org.apache.beam.sdk.values.TupleTag;
  import org.apache.beam.sdk.values.TupleTagList;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.apache.beam.sdk.values.TypeDescriptors;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /** {@code PTransform}s for mapping a simple function over the elements of a {@link PCollection}. */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class MapElements<InputT, OutputT>
      extends PTransform<PCollection<? extends InputT>, PCollection<OutputT>> {
  
    private final transient @Nullable TypeDescriptor<InputT> inputType;
    private final transient TypeDescriptor<OutputT> outputType;
  
    private final @Nullable Object fn;
  
    private MapElements(
        @Nullable Object fn,
        @Nullable TypeDescriptor<InputT> inputType,
        TypeDescriptor<OutputT> outputType) {
      this.fn = fn;
      this.inputType = inputType;
      this.outputType = outputType;
    }
  
    /**
     * For {@code InferableFunction<InputT, OutputT>} {@code fn}, returns a {@code PTransform} that
     * takes an input {@code PCollection<InputT>} and returns a {@code PCollection<OutputT>}
     * containing {@code fn.apply(v)} for every element {@code v} in the input.
     *
     * <p>{@link InferableFunction} has the advantage of providing type descriptor information, but it
     * is generally more convenient to specify output type via {@link #into(TypeDescriptor)}, and
     * provide the mapping as a lambda expression to {@link #via(ProcessFunction)}.
     *
     * <p>Example usage:
     *
     * <pre>{@code
     * PCollection<String> words = ...;
     * PCollection<Integer> wordsPerLine = words.apply(MapElements.via(
     *     new InferableFunction<String, Integer>() {
     *       public Integer apply(String word) throws Exception {
     *         return word.length();
     *       }
     *     }));
     * }</pre>
     */
    public static <InputT, OutputT> MapElements<InputT, OutputT> via(
        final InferableFunction<InputT, OutputT> fn) {
      return new MapElements<>(fn, fn.getInputTypeDescriptor(), fn.getOutputTypeDescriptor());
    }
  
    /** Binary compatibility adapter for {@link #via(InferableFunction)}. */
    public static <InputT, OutputT> MapElements<InputT, OutputT> via(
        final SimpleFunction<InputT, OutputT> fn) {
      return via((InferableFunction<InputT, OutputT>) fn);
    }
  
    /**
     * Returns a new {@link MapElements} transform with the given type descriptor for the output type,
     * but the mapping function yet to be specified using {@link #via(ProcessFunction)}.
     */
    public static <OutputT> MapElements<?, OutputT> into(final TypeDescriptor<OutputT> outputType) {
      return new MapElements<>(null, null, outputType);
    }
  
    /**
     * For a {@code ProcessFunction<InputT, OutputT>} {@code fn} and output type descriptor, returns a
     * {@code PTransform} that takes an input {@code PCollection<InputT>} and returns a {@code
     * PCollection<OutputT>} containing {@code fn.apply(v)} for every element {@code v} in the input.
     *
     * <p>Example usage:
     *
     * <pre>{@code
     * PCollection<Integer> wordLengths = words.apply(
     *     MapElements.into(TypeDescriptors.integers())
     *                .via((String word) -> word.length()));
     * }</pre>
     */
    public <NewInputT> MapElements<NewInputT, OutputT> via(ProcessFunction<NewInputT, OutputT> fn) {
      return new MapElements<>(fn, TypeDescriptors.inputOf(fn), outputType);
    }
  
    /** Binary compatibility adapter for {@link #via(ProcessFunction)}. */
    public <NewInputT> MapElements<NewInputT, OutputT> via(
        SerializableFunction<NewInputT, OutputT> fn) {
      return via((ProcessFunction<NewInputT, OutputT>) fn);
    }
  
    /** Like {@link #via(ProcessFunction)}, but supports access to context, such as side inputs. */
    public <NewInputT> MapElements<NewInputT, OutputT> via(Contextful<Fn<NewInputT, OutputT>> fn) {
      return new MapElements<>(fn, TypeDescriptors.inputOf(fn.getClosure()), outputType);
    }
  
    @Override
    public PCollection<OutputT> expand(PCollection<? extends InputT> input) {
      checkNotNull(fn, "Must specify a function on MapElements using .via()");
      if (fn instanceof Contextful) {
        return input.apply(
            "Map",
            ParDo.of(
                    new MapDoFn() {
                      @ProcessElement
                      public void processElement(ProcessContext c) throws Exception {
                        c.output(
                            ((Contextful<Fn<InputT, OutputT>>) fn)
                                .getClosure()
                                .apply(c.element(), Fn.Context.wrapProcessContext(c)));
                      }
                    })
                .withSideInputs(
                    ((Contextful<Fn<InputT, OutputT>>) fn).getRequirements().getSideInputs()));
      } else if (fn instanceof ProcessFunction) {
        return input.apply(
            "Map",
            ParDo.of(
                new MapDoFn() {
                  @ProcessElement
                  public void processElement(
                      @Element InputT element, OutputReceiver<OutputT> receiver) throws Exception {
                    receiver.output(((ProcessFunction<InputT, OutputT>) fn).apply(element));
                  }
                }));
      } else {
        throw new IllegalArgumentException(
            String.format("Unknown type of fn class %s", fn.getClass()));
      }
    }
  
    /** A DoFn implementation that handles a trivial map call. */
    @SuppressWarnings("unused") // for outer
    private abstract class MapDoFn extends DoFn<InputT, OutputT> {
  
      /** Holds {@link MapDoFn#outer instance} of enclosing class, used by runner implementations. */
      final MapElements<InputT, OutputT> outer = MapElements.this;
  
      @Override
      public void populateDisplayData(DisplayData.Builder builder) {
        builder.delegate(MapElements.this);
      }
  
      @Override
      public TypeDescriptor<InputT> getInputTypeDescriptor() {
        return inputType;
      }
  
      @Override
      public TypeDescriptor<OutputT> getOutputTypeDescriptor() {
        checkState(
            outputType != null,
            "%s output type descriptor was null; "
                + "this probably means that getOutputTypeDescriptor() was called after "
                + "serialization/deserialization, but it is only available prior to "
                + "serialization, for constructing a pipeline and inferring coders",
            MapElements.class.getSimpleName());
        return outputType;
      }
    }
  
    @Override
    public void populateDisplayData(DisplayData.Builder builder) {
      super.populateDisplayData(builder);
      Object fnForDisplayData;
      if (fn instanceof Contextful) {
        fnForDisplayData = ((Contextful<?>) fn).getClosure();
      } else {
        fnForDisplayData = fn;
      }
      builder.add(DisplayData.item("class", fnForDisplayData.getClass()));
      if (fnForDisplayData instanceof HasDisplayData) {
        builder.include("fn", (HasDisplayData) fnForDisplayData);
      }
    }
  
    /**
     * Returns a new {@link MapWithFailures} transform that catches exceptions raised while mapping
     * elements, with the given type descriptor used for the failure collection but the exception
     * handler yet to be specified using {@link MapWithFailures#exceptionsVia(ProcessFunction)}.
     *
     * <p>See {@link WithFailures} documentation for usage patterns of the returned {@link
     * WithFailures.Result}.
     */
    public <NewFailureT> MapWithFailures<InputT, OutputT, NewFailureT> exceptionsInto(
        TypeDescriptor<NewFailureT> failureTypeDescriptor) {
      return new MapWithFailures<>(fn, inputType, outputType, null, failureTypeDescriptor);
    }
  
    /**
     * Returns a new {@link MapWithFailures} transform that catches exceptions raised while mapping
     * elements, passing the raised exception instance and the input element being processed through
     * the given {@code exceptionHandler} and emitting the result to a failure collection.
     *
     * <p>This method takes advantage of the type information provided by {@link InferableFunction},
     * meaning that a call to {@link #exceptionsInto(TypeDescriptor)} may not be necessary.
     *
     * <p>See {@link WithFailures} documentation for usage patterns of the returned {@link
     * WithFailures.Result}.
     *
     * <p>Example usage:
     *
     * <pre>{@code
     * Result<PCollection<String>, String>> result = words.apply(
     *     MapElements
     *         .into(TypeDescriptors.integers())
     *         .via((String word) -> 1 / word.length)  // Could throw ArithmeticException
     *         .exceptionsVia(new WithFailures.ExceptionAsMapHandler<String>() {}));
     * PCollection<Integer> output = result.output();
     * PCollection<String> failures = result.failures();
     * }</pre>
     */
    public <FailureT> MapWithFailures<InputT, OutputT, FailureT> exceptionsVia(
        InferableFunction<ExceptionElement<InputT>, FailureT> exceptionHandler) {
      return new MapWithFailures<>(
          fn, inputType, outputType, exceptionHandler, exceptionHandler.getOutputTypeDescriptor());
    }
  
    /** A {@code PTransform} that adds exception handling to {@link MapElements}. */
    public static class MapWithFailures<InputT, OutputT, FailureT>
        extends PTransform<PCollection<InputT>, WithFailures.Result<PCollection<OutputT>, FailureT>> {
  
      private final transient TypeDescriptor<InputT> inputType;
      private final transient TypeDescriptor<OutputT> outputType;
      private final transient @Nullable TypeDescriptor<FailureT> failureType;
      private final Object fn;
      private final @Nullable ProcessFunction<ExceptionElement<InputT>, FailureT> exceptionHandler;
  
      MapWithFailures(
          Object fn,
          TypeDescriptor<InputT> inputType,
          TypeDescriptor<OutputT> outputType,
          @Nullable ProcessFunction<ExceptionElement<InputT>, FailureT> exceptionHandler,
          @Nullable TypeDescriptor<FailureT> failureType) {
        this.fn = fn;
        this.inputType = inputType;
        this.outputType = outputType;
        this.exceptionHandler = exceptionHandler;
        this.failureType = failureType;
      }
  
      /**
       * Returns a {@code PTransform} that catches exceptions raised while mapping elements, passing
       * the raised exception instance and the input element being processed through the given {@code
       * exceptionHandler} and emitting the result to a failure collection.
       *
       * <p>Example usage:
       *
       * <pre>{@code
       * Result<PCollection<Integer>, String> result = words.apply(
       *     MapElements
       *         .into(TypeDescriptors.integers())
       *         .via((String word) -> 1 / word.length())  // Could throw ArithmeticException
       *         .exceptionsInto(TypeDescriptors.strings())
       *         .exceptionsVia((ExceptionElement<String> ee) -> ee.exception().getMessage()));
       * PCollection<Integer> output = result.output();
       * PCollection<String> failures = result.failures();
       * }</pre>
       */
      public MapWithFailures<InputT, OutputT, FailureT> exceptionsVia(
          ProcessFunction<ExceptionElement<InputT>, FailureT> exceptionHandler) {
        return new MapWithFailures<>(fn, inputType, outputType, exceptionHandler, failureType);
      }
  
      @Override
      public WithFailures.Result<PCollection<OutputT>, FailureT> expand(PCollection<InputT> input) {
        checkArgument(exceptionHandler != null, ".exceptionsVia() is required");
        MapWithFailuresDoFn doFn;
        PCollectionTuple tuple;
        if (fn instanceof Contextful) {
          doFn =
              new MapWithFailuresDoFn() {
                @ProcessElement
                public void processElement(@Element InputT element, ProcessContext c)
                    throws Exception {
                  boolean exceptionWasThrown = false;
                  OutputT result = null;
                  try {
                    result =
                        ((Contextful<Fn<InputT, OutputT>>) fn)
                            .getClosure()
                            .apply(element, Fn.Context.wrapProcessContext(c));
                  } catch (Exception e) {
                    exceptionWasThrown = true;
                    ExceptionElement<InputT> exceptionElement = ExceptionElement.of(element, e);
                    c.output(failureTag, exceptionHandler.apply(exceptionElement));
                  }
                  // We make sure our output occurs outside the try block, since runners may implement
                  // fusion by having output() directly call the body of another DoFn, potentially
                  // catching
                  // exceptions unrelated to this transform.
                  if (!exceptionWasThrown) {
                    c.output(result);
                  }
                }
              };
          tuple =
              input.apply(
                  MapWithFailures.class.getSimpleName(),
                  ParDo.of(doFn)
                      .withOutputTags(doFn.outputTag, TupleTagList.of(doFn.failureTag))
                      .withSideInputs(
                          ((Contextful<Fn<InputT, OutputT>>) fn).getRequirements().getSideInputs()));
  
        } else if (fn instanceof ProcessFunction) {
          ProcessFunction<InputT, OutputT> closure = (ProcessFunction<InputT, OutputT>) fn;
          doFn =
              new MapWithFailuresDoFn() {
                @ProcessElement
                public void processElement(@Element InputT element, ProcessContext c)
                    throws Exception {
                  boolean exceptionWasThrown = false;
                  OutputT result;
                  try {
                    result = closure.apply(element);
                  } catch (Exception e) {
                    result = null;
                    exceptionWasThrown = true;
                    ExceptionElement<InputT> exceptionElement = ExceptionElement.of(element, e);
                    c.output(failureTag, exceptionHandler.apply(exceptionElement));
                  }
                  // We make sure our output occurs outside the try block, since runners may implement
                  // fusion by having output() directly call the body of another DoFn, potentially
                  // catching
                  // exceptions unrelated to this transform.
                  if (!exceptionWasThrown) {
                    c.output(result);
                  }
                }
              };
          tuple =
              input.apply(
                  MapWithFailures.class.getSimpleName(),
                  ParDo.of(doFn).withOutputTags(doFn.outputTag, TupleTagList.of(doFn.failureTag)));
        } else {
          throw new IllegalArgumentException(
              String.format("Unknown type of fn class %s", fn.getClass()));
        }
        return WithFailures.Result.of(tuple, doFn.outputTag, doFn.failureTag);
      }
  
      @Override
      public void populateDisplayData(DisplayData.Builder builder) {
        super.populateDisplayData(builder);
        Object fnForDisplayData;
        if (fn instanceof Contextful) {
          fnForDisplayData = ((Contextful<?>) fn).getClosure();
        } else {
          fnForDisplayData = fn;
        }
        builder.add(DisplayData.item("class", fnForDisplayData.getClass()));
        if (fnForDisplayData instanceof HasDisplayData) {
          builder.include("fn", (HasDisplayData) fnForDisplayData);
        }
        builder.add(DisplayData.item("exceptionHandler.class", exceptionHandler.getClass()));
        if (exceptionHandler instanceof HasDisplayData) {
          builder.include("exceptionHandler", (HasDisplayData) exceptionHandler);
        }
      }
  
      /** A concrete TupleTag that allows coder inference based on failureType. */
      private class FailureTag extends TupleTag<FailureT> {
        @Override
        public TypeDescriptor<FailureT> getTypeDescriptor() {
          return failureType;
        }
      }
  
      /** A DoFn implementation that handles exceptions and outputs a secondary failure collection. */
      private abstract class MapWithFailuresDoFn extends DoFn<InputT, OutputT> {
        final TupleTag<OutputT> outputTag = new TupleTag<OutputT>() {};
        final TupleTag<FailureT> failureTag = new FailureTag();
  
        @Override
        public void populateDisplayData(DisplayData.Builder builder) {
          builder.delegate(MapWithFailures.this);
        }
  
        @Override
        public TypeDescriptor<InputT> getInputTypeDescriptor() {
          return inputType;
        }
  
        @Override
        public TypeDescriptor<OutputT> getOutputTypeDescriptor() {
          checkState(
              outputType != null,
              "%s output type descriptor was null; "
                  + "this probably means that getOutputTypeDescriptor() was called after "
                  + "serialization/deserialization, but it is only available prior to "
                  + "serialization, for constructing a pipeline and inferring coders",
              MapWithFailures.class.getSimpleName());
          return outputType;
        }
      }
    }
  }
  