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.plan.visualizer;
  
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.RelWriter;
  import org.apache.calcite.sql.SqlExplainLevel;
  import org.apache.calcite.util.Pair;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  
  /**
   * An implement of RelWriter for explaining a single RelNode.
   * The result only contains the properties of the RelNode,
   * but does not explain the children.
   *
   * <pre>{@code
   * InputExcludedRelWriter relWriter = new InputExcludedRelWriter();
   * rel.explain(relWriter);
   * String digest = relWriter.toString();
   * }</pre>
   *
   */
  class InputExcludedRelWriter implements RelWriter {
  
    private final Map<String, @Nullable Object> values = new LinkedHashMap<>();
  
    InputExcludedRelWriter() {
    }
  
  
    @Override public void explain(RelNode rel, List<Pair<String, @Nullable Object>> valueList) {
      valueList.forEach(pair -> values.put(pair.left, pair.right));
    }
  
    @Override public SqlExplainLevel getDetailLevel() {
      return SqlExplainLevel.EXPPLAN_ATTRIBUTES;
    }
  
    @Override public RelWriter input(String term, RelNode input) {
      // do nothing, ignore input
      return this;
    }
  
    @Override public RelWriter item(String term, @Nullable Object value) {
      this.values.put(term, value);
      return this;
    }
  
    @Override public RelWriter itemIf(String term, @Nullable Object value, boolean condition) {
      if (condition) {
        this.values.put(term, value);
      }
      return this;
    }
  
    @Override public RelWriter done(RelNode node) {
      return this;
    }
  
    @Override public boolean nest() {
      return false;
    }
  
    @Override public String toString() {
      return values.toString();
    }
  }
  