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.direct;
  
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.runners.AppliedPTransform;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.WindowedValue;
  
  /**
   * Enforcement tools that verify that executing code conforms to the model.
   *
   * <p>ModelEnforcement is performed on a per-element and per-bundle basis. The {@link
   * ModelEnforcement} is provided with the input bundle as part of {@link
   * ModelEnforcementFactory#forBundle(CommittedBundle, AppliedPTransform)} each element before and
   * after that element is provided to an underlying {@link TransformEvaluator}, and the output {@link
   * TransformResult} and committed output bundles after the {@link TransformEvaluator} has completed.
   *
   * <p>Typically, {@link ModelEnforcement} will obtain required metadata (such as the {@link Coder}
   * of the input {@link PCollection} on construction, and then enforce per-element behavior (such as
   * the immutability of input elements). When the element is output or the bundle is completed, the
   * required conditions can be enforced across all elements.
   */
  interface ModelEnforcement<T> {
    /**
     * Called before a call to {@link TransformEvaluator#processElement(WindowedValue)} on the
     * provided {@link WindowedValue}.
     */
    void beforeElement(WindowedValue<T> element);
  
    /**
     * Called after a call to {@link TransformEvaluator#processElement(WindowedValue)} on the provided
     * {@link WindowedValue}.
     */
    void afterElement(WindowedValue<T> element);
  
    /**
     * Called after a bundle has been completed and {@link TransformEvaluator#finishBundle()} has been
     * called, producing the provided {@link TransformResult} and {@link CommittedBundle output
     * bundles}.
     */
    void afterFinish(
        CommittedBundle<T> input,
        TransformResult<T> result,
        Iterable<? extends CommittedBundle<?>> outputs);
  }
  