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.flink;
  
  import org.apache.beam.sdk.Pipeline;
  
  /**
   * The role of this class is to translate the Beam operators to their Flink counterparts. If we have
   * a streaming job, this is instantiated as a {@link FlinkStreamingPipelineTranslator}. In other
   * case, i.e. for a batch job, a {@link FlinkBatchPipelineTranslator} is created. Correspondingly,
   * the {@link org.apache.beam.sdk.values.PCollection}-based user-provided job is translated into a
   * {@link org.apache.flink.streaming.api.datastream.DataStream} (for streaming) or a {@link
   * org.apache.flink.api.java.DataSet} (for batch) one.
   */
  abstract class FlinkPipelineTranslator extends Pipeline.PipelineVisitor.Defaults {
  
    /**
     * Translates the pipeline by passing this class as a visitor.
     *
     * @param pipeline The pipeline to be translated
     */
    public void translate(Pipeline pipeline) {
      pipeline.traverseTopologically(this);
    }
  
    /**
     * Utility formatting method.
     *
     * @param n number of spaces to generate
     * @return String with "|" followed by n spaces
     */
    protected static String genSpaces(int n) {
      StringBuilder builder = new StringBuilder();
      for (int i = 0; i < n; i++) {
        builder.append("|   ");
      }
      return builder.toString();
    }
  }
  