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.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.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableMap;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * {@link PTransform} for parsing JSON {@link String Strings}. Parse {@link PCollection} of {@link
   * String Strings} in JSON format into a {@link PCollection} of objects represented by those JSON
   * {@link String Strings} using Jackson.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class ParseJsons<OutputT> extends PTransform<PCollection<String>, PCollection<OutputT>> {
    private static final ObjectMapper DEFAULT_MAPPER = new ObjectMapper();
  
    private final Class<? extends OutputT> outputClass;
    private ObjectMapper customMapper;
  
    /**
     * Creates a {@link ParseJsons} {@link PTransform} that will parse JSON {@link String Strings}
     * into a {@code PCollection<OutputT>} using a Jackson {@link ObjectMapper}.
     */
    public static <OutputT> ParseJsons<OutputT> of(Class<? extends OutputT> outputClass) {
      return new ParseJsons<>(outputClass);
    }
  
    private ParseJsons(Class<? extends OutputT> outputClass) {
      this.outputClass = outputClass;
    }
  
    /** Use custom Jackson {@link ObjectMapper} instead of the default one. */
    public ParseJsons<OutputT> withMapper(ObjectMapper mapper) {
      ParseJsons<OutputT> newTransform = new ParseJsons<>(outputClass);
      newTransform.customMapper = mapper;
      return newTransform;
    }
  
    /**
     * Returns a new {@link ParseJsonsWithFailures} transform that catches exceptions raised while
     * parsing elements, with the given type descriptor used for the failure collection but the
     * exception handler yet to be specified using {@link
     * ParseJsonsWithFailures#exceptionsVia(ProcessFunction)}.
     *
     * <p>See {@link WithFailures} documentation for usage patterns of the returned {@link
     * WithFailures.Result}.
     */
    public <NewFailureT> ParseJsonsWithFailures<NewFailureT> exceptionsInto(
        TypeDescriptor<NewFailureT> failureTypeDescriptor) {
      return new ParseJsonsWithFailures<>(null, failureTypeDescriptor);
    }
  
    /**
     * Returns a new {@link ParseJsonsWithFailures} transform that catches exceptions raised while
     * parsing 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<MyPojo>, KV<String, Map<String, String>>> result =
     *     json.apply(
     *         ParseJsons.of(MyPojo.class)
     *             .exceptionsVia(new WithFailures.ExceptionAsMapHandler<String>() {}));
     *
     * PCollection<MyPojo> output = result.output(); // valid POJOs
     * PCollection<KV<String, Map<String, String>>> failures = result.failures();
     * }</pre>
     */
    public <FailureT> ParseJsonsWithFailures<FailureT> exceptionsVia(
        InferableFunction<WithFailures.ExceptionElement<String>, FailureT> exceptionHandler) {
      return new ParseJsonsWithFailures<>(
          exceptionHandler, exceptionHandler.getOutputTypeDescriptor());
    }
  
    /**
     * Returns a new {@link ParseJsonsWithFailures} transform that catches exceptions raised while
     * parsing 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<MyPojo>, KV<String, Map<String, String>>> result =
     *     json.apply(
     *         ParseJsons.of(MyPojo.class)
     *             .exceptionsVia());
     *
     * PCollection<MyPojo> output = result.output(); // valid POJOs
     * PCollection<KV<String, Map<String, String>>> failures = result.failures();
     * }</pre>
     */
    public ParseJsonsWithFailures<KV<String, Map<String, String>>> exceptionsVia() {
      DefaultExceptionAsMapHandler<String> exceptionHandler =
          new DefaultExceptionAsMapHandler<String>() {};
      return new ParseJsonsWithFailures<>(
          exceptionHandler, exceptionHandler.getOutputTypeDescriptor());
    }
  
    private OutputT readValue(String input) throws IOException {
      ObjectMapper mapper = Optional.ofNullable(customMapper).orElse(DEFAULT_MAPPER);
      return mapper.readValue(input, outputClass);
    }
  
    @Override
    public PCollection<OutputT> expand(PCollection<String> input) {
      return input.apply(
          MapElements.via(
              new SimpleFunction<String, OutputT>() {
                @Override
                public OutputT apply(String input) {
                  try {
                    return readValue(input);
                  } catch (IOException e) {
                    throw new RuntimeException(
                        "Failed to parse a " + outputClass.getName() + " from JSON value: " + input,
                        e);
                  }
                }
              }));
    }
  
    /** A {@code PTransform} that adds exception handling to {@link ParseJsons}. */
    public class ParseJsonsWithFailures<FailureT>
        extends PTransform<PCollection<String>, WithFailures.Result<PCollection<OutputT>, FailureT>> {
  
      private @Nullable InferableFunction<WithFailures.ExceptionElement<String>, FailureT>
          exceptionHandler;
  
      private final transient @Nullable TypeDescriptor<FailureT> failureType;
  
      ParseJsonsWithFailures(
          InferableFunction<WithFailures.ExceptionElement<String>, FailureT> exceptionHandler,
          TypeDescriptor<FailureT> failureType) {
        this.exceptionHandler = exceptionHandler;
        this.failureType = failureType;
      }
  
      /**
       * Returns a new {@link ParseJsonsWithFailures} transform that catches exceptions raised while
       * parsing 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 ParseJsons#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<MyPojo>, KV<String, Map<String, String>>> result =
       *     json.apply(
       *         ParseJsons.of(MyPojo.class)
       *             .exceptionsInto(
       *                 TypeDescriptors.kvs(TypeDescriptors.strings(), TypeDescriptors.strings()))
       *             .exceptionsVia(
       *                 f -> KV.of(f.element(), f.exception().getClass().getCanonicalName())));
       *
       * PCollection<MyPojo> output = result.output(); // valid POJOs
       * PCollection<KV<String, Map<String, String>>> failures = result.failures();
       * }</pre>
       */
      public ParseJsonsWithFailures<FailureT> exceptionsVia(
          ProcessFunction<WithFailures.ExceptionElement<String>, FailureT> exceptionHandler) {
        return new ParseJsonsWithFailures<>(
            new InferableFunction<WithFailures.ExceptionElement<String>, FailureT>(
                exceptionHandler) {},
            failureType);
      }
  
      @Override
      public WithFailures.Result<PCollection<OutputT>, FailureT> expand(PCollection<String> input) {
        return input.apply(
            MapElements.into(new TypeDescriptor<OutputT>() {})
                .via(
                    Contextful.fn(
                        (Contextful.Fn<String, OutputT>) (input1, c) -> readValue(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 IOException}, 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<OutputT>
        extends SimpleFunction<
            WithFailures.ExceptionElement<OutputT>, KV<OutputT, Map<String, String>>> {
      @Override
      public KV<OutputT, Map<String, String>> apply(WithFailures.ExceptionElement<OutputT> f)
          throws RuntimeException {
        if (!(f.exception() instanceof IOException)) {
          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())));
      }
    }
  }
  