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.cypher.antlr4.visitor;
  
  import com.alibaba.graphscope.common.ir.meta.schema.CommonOptTable;
  import com.alibaba.graphscope.common.ir.rel.CommonTableScan;
  import com.alibaba.graphscope.common.ir.tools.GraphBuilder;
  import com.alibaba.graphscope.grammar.CypherGSBaseVisitor;
  import com.alibaba.graphscope.grammar.CypherGSParser;
  
  import org.apache.calcite.plan.GraphOptCluster;
  import org.apache.calcite.plan.RelOptTable;
  import org.apache.calcite.rel.RelNode;
  
  public class CallSubQueryVisitor extends CypherGSBaseVisitor<RelNode> {
      private final GraphBuilder parentBuilder;
      private final GraphBuilder nestedBuilder;
  
      public CallSubQueryVisitor(GraphBuilder parentBuilder) {
          this.parentBuilder = parentBuilder;
          this.nestedBuilder =
                  GraphBuilder.create(
                          this.parentBuilder.getContext(),
                          (GraphOptCluster) this.parentBuilder.getCluster(),
                          this.parentBuilder.getRelOptSchema());
      }
  
      @Override
      public RelNode visitOC_CallSubQuery(CypherGSParser.OC_CallSubQueryContext ctx) {
          if (parentBuilder.size() > 0) {
              RelNode commonRel = parentBuilder.peek();
              RelOptTable commonTable = new CommonOptTable(commonRel);
              commonRel =
                      new CommonTableScan(
                              commonRel.getCluster(), commonRel.getTraitSet(), commonTable);
              nestedBuilder.push(commonRel);
          }
          return new GraphBuilderVisitor(nestedBuilder).visit(ctx.oC_SubQuery()).build();
      }
  }
  