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.calcite.adapter.pig;
  
  import org.apache.calcite.plan.Convention;
  import org.apache.calcite.rel.RelNode;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Relational expression that uses the Pig calling convention.
   */
  public interface PigRel extends RelNode {
  
    /**
     * Converts this node to a Pig Latin statement.
     */
    void implement(Implementor implementor);
  
    // String getPigRelationAlias();
    //
    // String getFieldName(int index);
  
    /** Calling convention for relational operations that occur in Pig. */
    Convention CONVENTION = new Convention.Impl("PIG", PigRel.class);
  
    /**
     * Callback for the implementation process that converts a tree of
     * {@link PigRel} nodes into complete Pig Latin script.
     */
    class Implementor {
  
      /**
       * An ordered list of Pig Latin statements.
       *
       * <p>See
       * <a href="https://pig.apache.org/docs/r0.13.0/start.html#pl-statements">
       * Pig Latin reference</a>.
       */
      private final List<String> statements = new ArrayList<>();
  
      public String getTableName(RelNode input) {
        final List<String> qualifiedName = input.getTable().getQualifiedName();
        return qualifiedName.get(qualifiedName.size() - 1);
      }
  
      public String getPigRelationAlias(RelNode input) {
        return getTableName(input);
      }
  
      public String getFieldName(RelNode input, int index) {
        return input.getRowType().getFieldList().get(index).getName();
      }
  
      public void addStatement(String statement) {
        statements.add(statement);
      }
  
      public void visitChild(int ordinal, RelNode input) {
        assert ordinal == 0;
        ((PigRel) input).implement(this);
      }
  
      public List<String> getStatements() {
        return statements;
      }
  
      public String getScript() {
        return String.join("\n", statements);
      }
    }
  }
  