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.util.construction;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
  
  import java.util.Map;
  import java.util.Set;
  import org.apache.beam.sdk.runners.AppliedPTransform;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.TupleTag;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  
  /** */
  @SuppressWarnings({"nullness", "keyfor"}) // TODO(https://github.com/apache/beam/issues/20497)
  public class PTransformReplacements {
    /**
     * Gets the singleton input of an {@link AppliedPTransform}, ignoring any additional inputs
     * returned by {@link PTransform#getAdditionalInputs()}.
     */
    public static <T> PCollection<T> getSingletonMainInput(
        AppliedPTransform<? extends PCollection<? extends T>, ?, ?> application) {
      return getSingletonMainInput(
          application.getInputs(), application.getTransform().getAdditionalInputs().keySet());
    }
  
    private static <T> PCollection<T> getSingletonMainInput(
        Map<TupleTag<?>, PCollection<?>> inputs, Set<TupleTag<?>> ignoredTags) {
      PCollection<T> mainInput = null;
      for (Map.Entry<TupleTag<?>, PCollection<?>> input : inputs.entrySet()) {
        if (!ignoredTags.contains(input.getKey())) {
          checkArgument(
              mainInput == null,
              "Got multiple inputs that are not additional inputs for a "
                  + "singleton main input: %s and %s",
              mainInput,
              input.getValue());
          checkArgument(
              input.getValue() instanceof PCollection,
              "Unexpected input type %s",
              input.getValue().getClass());
          mainInput = (PCollection<T>) input.getValue();
        }
      }
      checkArgument(
          mainInput != null,
          "No main input found in inputs: Inputs %s, Side Input tags %s",
          inputs,
          ignoredTags);
      return mainInput;
    }
  
    public static <T> PCollection<T> getSingletonMainOutput(
        AppliedPTransform<?, PCollection<T>, ? extends PTransform<?, PCollection<T>>> transform) {
      return (PCollection<T>) Iterables.getOnlyElement(transform.getOutputs().values());
    }
  }
  