content: /*
   * Copyright 2020 Alibaba Group Holding Limited.
   *
   * Licensed 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 com.alibaba.graphscope.gremlin.antlr4;
  
  import com.alibaba.graphscope.grammar.GremlinGSBaseVisitor;
  import com.alibaba.graphscope.grammar.GremlinGSParser;
  
  import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
  import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversal;
  
  /**
   * This class implements Gremlin grammar's nested-traversal-list methods that returns a {@link Traversal} {@code []}
   * to the callers.
   */
  public class NestedTraversalSourceListVisitor extends GremlinGSBaseVisitor<Traversal[]> {
  
      protected final GremlinGSBaseVisitor<GraphTraversal> tvisitor;
  
      public NestedTraversalSourceListVisitor(final GremlinGSBaseVisitor<GraphTraversal> tvisitor) {
          this.tvisitor = tvisitor;
      }
  
      @Override
      public Traversal[] visitNestedTraversalExpr(
              final GremlinGSParser.NestedTraversalExprContext ctx) {
          final int childCount = ctx.getChildCount();
  
          // handle arbitrary number of traversals that are separated by comma
          final Traversal[] results = new Traversal[(childCount + 1) / 2];
          int childIndex = 0;
          while (childIndex < ctx.getChildCount()) {
              results[childIndex / 2] =
                      tvisitor.visitNestedTraversal(
                              (GremlinGSParser.NestedTraversalContext) ctx.getChild(childIndex));
              // skip comma child
              childIndex += 2;
          }
  
          return results;
      }
  }
  