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.runners.dataflow.worker;
  
  import com.google.api.services.dataflow.model.Source;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.ServiceLoader;
  import java.util.Set;
  import org.apache.beam.runners.dataflow.util.CloudObject;
  import org.apache.beam.runners.dataflow.util.CloudObjects;
  import org.apache.beam.runners.dataflow.worker.util.CloudSourceUtils;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.NativeReader;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.util.common.ReflectHelpers;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableMap;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Lists;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Maps;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Sets;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * An immutable registry from {@link String} identifiers (provided to the worker by the Dataflow
   * service) to appropriate {@link ReaderFactory} instances.
   */
  @SuppressWarnings({
    "rawtypes", // TODO(https://github.com/apache/beam/issues/20447)
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class ReaderRegistry implements ReaderFactory {
  
    /**
     * A {@link ReaderRegistry} with each {@link ReaderFactory} known to the Dataflow worker already
     * registered.
     *
     * <p>Uses {@link ServiceLoader} to dynamically bind well known types to reader factories via a
     * {@link ReaderFactory.Registrar}.
     */
    public static ReaderRegistry defaultRegistry() {
      Set<ReaderFactory.Registrar> readerFactoryRegistrars =
          Sets.newTreeSet(ReflectHelpers.ObjectsClassComparator.INSTANCE);
      readerFactoryRegistrars.addAll(
          Lists.newArrayList(
              ServiceLoader.load(ReaderFactory.Registrar.class, ReflectHelpers.findClassLoader())));
  
      ImmutableMap.Builder<String, ReaderFactory> factories = ImmutableMap.builder();
      for (ReaderFactory.Registrar registrar : readerFactoryRegistrars) {
        factories.putAll(registrar.factories());
      }
      return new ReaderRegistry(factories.build());
    }
  
    /** Builds a new {@link ReaderRegistry} with the provided mappings. */
    private ReaderRegistry(Map<String, ReaderFactory> factories) {
      // ConcatReader requires special treatment: Recursive access to the registry since it calls
      // back to create its sub-readers lazily.
      this.factories = new HashMap<>(factories);
      this.factories.put(ConcatReader.SOURCE_NAME, ConcatReaderFactory.withRegistry(this));
    }
  
    /** A map from the short names of predefined sources to the associated {@link ReaderFactory}. */
    private final Map<String, ReaderFactory> factories;
  
    /**
     * Returns a new {@link ReaderRegistry} with the provided identifier associated with the provided
     * {@link ReaderFactory}, overriding any existing binding for that identifier.
     */
    public ReaderRegistry register(String readerSpecType, ReaderFactory factory) {
      Map<String, ReaderFactory> newFactories = Maps.newHashMap();
      newFactories.putAll(factories);
      newFactories.put(readerSpecType, factory);
      return new ReaderRegistry(newFactories);
    }
  
    /**
     * Creates a {@link NativeReader} according to the provided {@code sourceSpec}, by dispatching on
     * the type of {@link CloudObject} to instantiate.
     */
    @Override
    public NativeReader<?> create(
        CloudObject sourceSpec,
        @Nullable Coder<?> coder,
        @Nullable PipelineOptions options,
        @Nullable DataflowExecutionContext executionContext,
        DataflowOperationContext operationContext)
        throws Exception {
  
      ReaderFactory readerFactory = factories.get(sourceSpec.getClassName());
      if (readerFactory == null) {
        throw new IllegalArgumentException(
            String.format(
                "Unable to create a Reader: Unknown Reader type in Source specification: %s",
                sourceSpec.getClassName()));
      }
      return readerFactory.create(sourceSpec, coder, options, executionContext, operationContext);
    }
  
    /**
     * Creates a {@link NativeReader} from a Dataflow API {@link Source} specification, using the
     * {@link Coder} contained in the {@link Source} specification.
     */
    public NativeReader<?> create(
        Source cloudSource,
        @Nullable PipelineOptions options,
        @Nullable DataflowExecutionContext executionContext,
        DataflowOperationContext operationContext)
        throws Exception {
  
      cloudSource = CloudSourceUtils.flattenBaseSpecs(cloudSource);
      CloudObject sourceSpec = CloudObject.fromSpec(cloudSource.getSpec());
      Coder<?> coder = null;
      if (cloudSource.getCodec() != null) {
        coder = CloudObjects.coderFromCloudObject(CloudObject.fromSpec(cloudSource.getCodec()));
      }
      return create(sourceSpec, coder, options, executionContext, operationContext);
    }
  }
  