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.schemas.transforms.providers;
  
  import com.google.auto.service.AutoService;
  import com.google.auto.value.AutoValue;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.stream.Collectors;
  import java.util.stream.IntStream;
  import javax.annotation.Nullable;
  import org.apache.beam.sdk.schemas.AutoValueSchema;
  import org.apache.beam.sdk.schemas.Schema;
  import org.apache.beam.sdk.schemas.annotations.DefaultSchema;
  import org.apache.beam.sdk.schemas.transforms.SchemaTransform;
  import org.apache.beam.sdk.schemas.transforms.SchemaTransformProvider;
  import org.apache.beam.sdk.schemas.transforms.TypedSchemaTransformProvider;
  import org.apache.beam.sdk.transforms.DoFn;
  import org.apache.beam.sdk.transforms.ParDo;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollectionRowTuple;
  import org.apache.beam.sdk.values.Row;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableList;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.primitives.Booleans;
  
  /**
   * An implementation of {@link TypedSchemaTransformProvider} for Explode.
   *
   * <p><b>Internal only:</b> This class is actively being worked on, and it will likely change. We
   * provide no backwards compatibility guarantees, and it should not be implemented outside the Beam
   * repository.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  @AutoService(SchemaTransformProvider.class)
  public class JavaExplodeTransformProvider
      extends TypedSchemaTransformProvider<JavaExplodeTransformProvider.Configuration> {
    protected static final String INPUT_ROWS_TAG = "input";
    protected static final String OUTPUT_ROWS_TAG = "output";
  
    @Override
    protected Class<Configuration> configurationClass() {
      return Configuration.class;
    }
  
    @Override
    protected SchemaTransform from(Configuration configuration) {
      return new ExplodeTransform(configuration);
    }
  
    @Override
    public String identifier() {
      return "beam:schematransform:org.apache.beam:yaml:explode:v1";
    }
  
    @Override
    public List<String> inputCollectionNames() {
      return Collections.singletonList(INPUT_ROWS_TAG);
    }
  
    @Override
    public List<String> outputCollectionNames() {
      return Collections.singletonList(OUTPUT_ROWS_TAG);
    }
  
    @DefaultSchema(AutoValueSchema.class)
    @AutoValue
    public abstract static class Configuration {
      @Nullable
      public abstract List<String> getFields();
  
      @Nullable
      public abstract Boolean getCrossProduct();
  
      public static Builder builder() {
        return new AutoValue_JavaExplodeTransformProvider_Configuration.Builder();
      }
  
      @AutoValue.Builder
      public abstract static class Builder {
  
        public abstract Builder setFields(List<String> fields);
  
        public abstract Builder setCrossProduct(@Nullable Boolean append);
  
        public abstract Configuration build();
      }
    }
  
    /** A {@link SchemaTransform} for Explode. */
    protected static class ExplodeTransform extends SchemaTransform {
  
      private final Configuration configuration;
  
      ExplodeTransform(Configuration configuration) {
        this.configuration = configuration;
      }
  
      @Override
      public PCollectionRowTuple expand(PCollectionRowTuple input) {
        Schema inputSchema = input.get(INPUT_ROWS_TAG).getSchema();
        Schema.Builder outputSchemaBuilder = new Schema.Builder();
        for (Schema.Field field : inputSchema.getFields()) {
          if (configuration.getFields().contains(field.getName())) {
            if (field.getType().getCollectionElementType() == null) {
              throw new IllegalArgumentException(
                  String.format(
                      "Exploded field %s must be an iterable type, got %s.",
                      field.getName(), field.getType()));
            } else {
              outputSchemaBuilder =
                  outputSchemaBuilder.addField(
                      field.getName(), field.getType().getCollectionElementType());
            }
          } else {
            outputSchemaBuilder = outputSchemaBuilder.addField(field);
          }
        }
        Schema outputSchema = outputSchemaBuilder.build();
  
        PCollection<Row> result =
            input
                .get(INPUT_ROWS_TAG)
                .apply(
                    "Explode",
                    ParDo.of(
                        createDoFn(
                            configuration.getFields(),
                            configuration.getCrossProduct(),
                            outputSchema)));
        result.setRowSchema(outputSchema);
  
        return PCollectionRowTuple.of(OUTPUT_ROWS_TAG, result);
      }
  
      private static DoFn<Row, Row> createDoFn(
          List<String> fields, Boolean crossProductObj, Schema outputSchema) {
        boolean crossProduct;
        if (crossProductObj == null) {
          if (fields.size() > 1) {
            throw new IllegalArgumentException(
                "boolean cross product parameter required to explode more than one field");
          }
          crossProduct = false;
        } else {
          crossProduct = crossProductObj;
        }
        int numFields = outputSchema.getFields().size();
        boolean[] toExplode =
            Booleans.toArray(
                IntStream.range(0, numFields)
                    .mapToObj(index -> fields.contains(outputSchema.getField(index).getName()))
                    .collect(Collectors.toList()));
        if (crossProduct) {
          return new DoFn<Row, Row>() {
            @ProcessElement
            public void processElement(@Element Row inputRow, OutputReceiver<Row> out) {
              emitCrossProduct(inputRow, 0, new Object[numFields], out);
            }
  
            private void emitCrossProduct(
                Row inputRow, int index, Object[] current, OutputReceiver<Row> out) {
              if (index == numFields) {
                out.output(Row.withSchema(outputSchema).attachValues(ImmutableList.copyOf(current)));
              } else if (toExplode[index]) {
                for (Object value : inputRow.getIterable(index)) {
                  current[index] = value;
                  emitCrossProduct(inputRow, index + 1, current, out);
                }
              } else {
                current[index] = inputRow.getValue(index);
                emitCrossProduct(inputRow, index + 1, current, out);
              }
            }
          };
        } else {
          return new DoFn<Row, Row>() {
            @ProcessElement
            public void processElement(@Element Row inputRow, OutputReceiver<Row> out) {
              @SuppressWarnings("rawtypes")
              Iterator[] iterators = new Iterator[numFields];
              for (int i = 0; i < numFields; i++) {
                if (toExplode[i]) {
                  iterators[i] = inputRow.getIterable(i).iterator();
                }
              }
              while (IntStream.range(0, numFields)
                  .anyMatch(index -> toExplode[index] && iterators[index].hasNext())) {
                Row.Builder builder = Row.withSchema(outputSchema);
                for (int i = 0; i < numFields; i++) {
                  if (toExplode[i]) {
                    if (iterators[i].hasNext()) {
                      builder.addValue(iterators[i].next());
                    } else {
                      builder.addValue(null);
                    }
                  } else {
                    builder.addValue(inputRow.getValue(i));
                  }
                }
                out.output(builder.build());
              }
            }
          };
        }
      }
    }
  }
  