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.Collection;
  import java.util.Collections;
  import java.util.List;
  import org.apache.beam.sdk.schemas.AutoValueSchema;
  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.Flatten;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollectionList;
  import org.apache.beam.sdk.values.PCollectionRowTuple;
  import org.apache.beam.sdk.values.Row;
  
  /**
   * An implementation of {@link TypedSchemaTransformProvider} for Flatten.
   *
   * <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 FlattenTransformProvider
      extends TypedSchemaTransformProvider<FlattenTransformProvider.Configuration> {
    protected static final String OUTPUT_ROWS_TAG = "output";
  
    @Override
    protected Class<Configuration> configurationClass() {
      return Configuration.class;
    }
  
    @Override
    protected SchemaTransform from(Configuration configuration) {
      return new SchemaTransform() {
        @Override
        public PCollectionRowTuple expand(PCollectionRowTuple input) {
          return PCollectionRowTuple.of(
              OUTPUT_ROWS_TAG,
              PCollectionList.of((Iterable<PCollection<Row>>) (Collection) input.expand().values())
                  .apply(Flatten.pCollections())
                  .setRowSchema(
                      ((PCollection<Row>) input.expand().values().iterator().next()).getSchema()));
        }
      };
    }
  
    @Override
    public String identifier() {
      return "beam:schematransform:org.apache.beam:yaml:flatten:v1";
    }
  
    @Override
    public List<String> inputCollectionNames() {
      return Collections.emptyList();
    }
  
    @Override
    public List<String> outputCollectionNames() {
      return Collections.singletonList(OUTPUT_ROWS_TAG);
    }
  
    @DefaultSchema(AutoValueSchema.class)
    @AutoValue
    public abstract static class Configuration {
  
      public static Builder builder() {
        return new AutoValue_FlattenTransformProvider_Configuration.Builder();
      }
  
      @AutoValue.Builder
      public abstract static class Builder {
  
        public abstract Configuration build();
      }
    }
  }
  