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.rex;
  
  import org.apache.calcite.sql.SqlOperator;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.HashMap;
  import java.util.Map;
  
  /**
   * Implementation of {@link RexSqlConvertletTable}.
   */
  public class RexSqlReflectiveConvertletTable implements RexSqlConvertletTable {
    //~ Instance fields --------------------------------------------------------
  
    private final Map<Object, Object> map = new HashMap<>();
  
    //~ Constructors -----------------------------------------------------------
  
    public RexSqlReflectiveConvertletTable() {
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public @Nullable RexSqlConvertlet get(RexCall call) {
      RexSqlConvertlet convertlet;
      final SqlOperator op = call.getOperator();
  
      // Is there a convertlet for this operator
      // (e.g. SqlStdOperatorTable.plusOperator)?
      convertlet = (RexSqlConvertlet) map.get(op);
      if (convertlet != null) {
        return convertlet;
      }
  
      // Is there a convertlet for this class of operator
      // (e.g. SqlBinaryOperator)?
      @Nullable Class<?> clazz = op.getClass();
      while (clazz != null) {
        convertlet = (RexSqlConvertlet) map.get(clazz);
        if (convertlet != null) {
          return convertlet;
        }
        clazz = clazz.getSuperclass();
      }
  
      // Is there a convertlet for this class of expression
      // (e.g. SqlCall)?
      clazz = call.getClass();
      while (clazz != null) {
        convertlet = (RexSqlConvertlet) map.get(clazz);
        if (convertlet != null) {
          return convertlet;
        }
        clazz = clazz.getSuperclass();
      }
      return null;
    }
  
    /**
     * Registers a convertlet for a given operator instance.
     *
     * @param op         Operator instance, say
     * {@link org.apache.calcite.sql.fun.SqlStdOperatorTable#MINUS}
     * @param convertlet Convertlet
     */
    protected void registerOp(SqlOperator op, RexSqlConvertlet convertlet) {
      map.put(op, convertlet);
    }
  }
  