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.jackson;
  
  import com.fasterxml.jackson.core.JsonProcessingException;
  import com.fasterxml.jackson.databind.ObjectMapper;
  import java.io.IOException;
  import java.util.Arrays;
  import java.util.Map;
  import java.util.Optional;
  import org.apache.beam.sdk.transforms.Contextful;
  import org.apache.beam.sdk.transforms.InferableFunction;
  import org.apache.beam.sdk.transforms.MapElements;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.transforms.ProcessFunction;
  import org.apache.beam.sdk.transforms.Requirements;
  import org.apache.beam.sdk.transforms.SimpleFunction;
  import org.apache.beam.sdk.transforms.WithFailures;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.apache.beam.sdk.values.TypeDescriptors;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableMap;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * {@link PTransform} for serializing objects to JSON {@link String Strings}. Transforms a {@code
   * PCollection<InputT>} into a {@link PCollection} of JSON {@link String Strings} representing
   * objects in the original {@link PCollection} using Jackson.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class AsJsons<InputT> extends PTransform<PCollection<InputT>, PCollection<String>> {
    private static final ObjectMapper DEFAULT_MAPPER = new ObjectMapper();
  
    private final Class<? extends InputT> inputClass;
    private ObjectMapper customMapper;
  
    /**
     * Creates a {@link AsJsons} {@link PTransform} that will transform a {@code PCollection<InputT>}
     * into a {@link PCollection} of JSON {@link String Strings} representing those objects using a
     * Jackson {@link ObjectMapper}.
     */
    public static <InputT> AsJsons<InputT> of(Class<? extends InputT> inputClass) {
      return new AsJsons<>(inputClass);
    }
  
    private AsJsons(Class<? extends InputT> inputClass) {
      this.inputClass = inputClass;
    }
  
    /** Use custom Jackson {@link ObjectMapper} instead of the default one. */
    public AsJsons<InputT> withMapper(ObjectMapper mapper) {
      AsJsons<InputT> newTransform = new AsJsons<>(inputClass);
      newTransform.customMapper = mapper;
      return newTransform;
    }
  
    /**
     * Returns a new {@link AsJsonsWithFailures} transform that catches exceptions raised while
     * writing JSON elements, with the given type descriptor used for the failure collection but the
     * exception handler yet to be specified using {@link
     * AsJsonsWithFailures#exceptionsVia(ProcessFunction)}.
     *
     * <p>See {@link WithFailures} documentation for usage patterns of the returned {@link
     * WithFailures.Result}.
     */
    public <NewFailureT> AsJsonsWithFailures<NewFailureT> exceptionsInto(
        TypeDescriptor<NewFailureT> failureTypeDescriptor) {
      return new AsJsonsWithFailures<>(null, failureTypeDescriptor);
    }
  
    /**
     * Returns a new {@link AsJsonsWithFailures} transform that catches exceptions raised while
     * writing JSON 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>See {@link WithFailures} documentation for usage patterns of the returned {@link
     * WithFailures.Result}.
     *
     * <p>Example usage:
     *
     * <pre>{@code
     * WithFailures.Result<PCollection<String>, KV<MyPojo, Map<String, String>>> result =
     *     pojos.apply(
     *         AsJsons.of(MyPojo.class)
     *             .exceptionsVia(new WithFailures.ExceptionAsMapHandler<MyPojo>() {}));
     *
     * PCollection<String> output = result.output(); // valid json elements
     * PCollection<KV<MyPojo, Map<String, String>>> failures = result.failures();
     * }</pre>
     */
    public <FailureT> AsJsonsWithFailures<FailureT> exceptionsVia(
        InferableFunction<WithFailures.ExceptionElement<InputT>, FailureT> exceptionHandler) {
      return new AsJsonsWithFailures<>(exceptionHandler, exceptionHandler.getOutputTypeDescriptor());
    }
  
    /**
     * Returns a new {@link AsJsonsWithFailures} transform that catches exceptions raised while
     * writing JSON elements, passing the raised exception instance and the input element being
     * processed through the default exception handler {@link DefaultExceptionAsMapHandler} and
     * emitting the result to a failure collection.
     *
     * <p>See {@link DefaultExceptionAsMapHandler} for more details about default handler behavior.
     *
     * <p>See {@link WithFailures} documentation for usage patterns of the returned {@link
     * WithFailures.Result}.
     *
     * <p>Example usage:
     *
     * <pre>{@code
     * WithFailures.Result<PCollection<String>, KV<MyPojo, Map<String, String>>> result =
     *     pojos.apply(
     *         AsJsons.of(MyPojo.class)
     *             .exceptionsVia());
     *
     * PCollection<String> output = result.output(); // valid json elements
     * PCollection<KV<MyPojo, Map<String, String>>> failures = result.failures();
     * }</pre>
     */
    public AsJsonsWithFailures<KV<InputT, Map<String, String>>> exceptionsVia() {
      DefaultExceptionAsMapHandler<InputT> exceptionHandler =
          new DefaultExceptionAsMapHandler<InputT>() {};
      return new AsJsonsWithFailures<>(exceptionHandler, exceptionHandler.getOutputTypeDescriptor());
    }
  
    private String writeValue(InputT input) throws JsonProcessingException {
      ObjectMapper mapper = Optional.ofNullable(customMapper).orElse(DEFAULT_MAPPER);
      return mapper.writeValueAsString(input);
    }
  
    @Override
    public PCollection<String> expand(PCollection<InputT> input) {
      return input.apply(
          MapElements.via(
              new SimpleFunction<InputT, String>() {
                @Override
                public String apply(InputT input) {
                  try {
                    return writeValue(input);
                  } catch (IOException e) {
                    throw new RuntimeException(
                        "Failed to serialize " + inputClass.getName() + " value: " + input, e);
                  }
                }
              }));
    }
  
    /** A {@code PTransform} that adds exception handling to {@link AsJsons}. */
    public class AsJsonsWithFailures<FailureT>
        extends PTransform<PCollection<InputT>, WithFailures.Result<PCollection<String>, FailureT>> {
  
      private @Nullable InferableFunction<WithFailures.ExceptionElement<InputT>, FailureT>
          exceptionHandler;
  
      private final transient @Nullable TypeDescriptor<FailureT> failureType;
  
      AsJsonsWithFailures(
          InferableFunction<WithFailures.ExceptionElement<InputT>, FailureT> exceptionHandler,
          TypeDescriptor<FailureT> failureType) {
        this.exceptionHandler = exceptionHandler;
        this.failureType = failureType;
      }
  
      /**
       * Returns a new {@link AsJsonsWithFailures} transform that catches exceptions raised while
       * writing JSON 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. It is supposed to be used along with {@link
       * AsJsons#exceptionsInto(TypeDescriptor)} and get lambda function as exception handler.
       *
       * <p>See {@link WithFailures} documentation for usage patterns of the returned {@link
       * WithFailures.Result}.
       *
       * <p>Example usage:
       *
       * <pre>{@code
       * WithFailures.Result<PCollection<String>, KV<MyPojo, Map<String, String>>> result =
       *     pojos.apply(
       *         AsJsons.of(MyPojo.class)
       *             .exceptionsInto(
       *                 TypeDescriptors.kvs(
       *                     TypeDescriptor.of(MyPojo.class), TypeDescriptors.strings()))
       *             .exceptionsVia(
       *                 f -> KV.of(f.element(), f.exception().getClass().getCanonicalName())));
       *
       * PCollection<String> output = result.output(); // valid json elements
       * PCollection<KV<MyPojo, Map<String, String>>> failures = result.failures();
       * }</pre>
       */
      public AsJsonsWithFailures<FailureT> exceptionsVia(
          ProcessFunction<WithFailures.ExceptionElement<InputT>, FailureT> exceptionHandler) {
        return new AsJsonsWithFailures<>(
            new InferableFunction<WithFailures.ExceptionElement<InputT>, FailureT>(
                exceptionHandler) {},
            failureType);
      }
  
      @Override
      public WithFailures.Result<PCollection<String>, FailureT> expand(PCollection<InputT> input) {
        return input.apply(
            MapElements.into(TypeDescriptors.strings())
                .via(
                    Contextful.fn(
                        (Contextful.Fn<InputT, String>) (input1, c) -> writeValue(input1),
                        Requirements.empty()))
                .exceptionsInto(failureType)
                .exceptionsVia(exceptionHandler));
      }
    }
  
    /**
     * A default handler that extracts information from an exception to a {@code Map<String, String>}
     * and returns a {@link KV} where the key is the input element that failed processing, and the
     * value is the map of exception attributes. It handles only {@code JsonProcessingException},
     * other type of exceptions will be rethrown as {@code RuntimeException}.
     *
     * <p>The keys populated in the map are "className", "message", and "stackTrace" of the exception.
     */
    private static class DefaultExceptionAsMapHandler<InputT>
        extends SimpleFunction<
            WithFailures.ExceptionElement<InputT>, KV<InputT, Map<String, String>>> {
      @Override
      public KV<InputT, Map<String, String>> apply(WithFailures.ExceptionElement<InputT> f)
          throws RuntimeException {
        if (!(f.exception() instanceof JsonProcessingException)) {
          throw new RuntimeException(f.exception());
        }
        return KV.of(
            f.element(),
            ImmutableMap.of(
                "className", f.exception().getClass().getName(),
                "message", f.exception().getMessage(),
                "stackTrace", Arrays.toString(f.exception().getStackTrace())));
      }
    }
  }
  