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.SqlIdentifier;
  import org.apache.calcite.sql.SqlLiteral;
  import org.apache.calcite.sql.SqlNode;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Converts expressions from {@link RexNode} to {@link SqlNode}.
   *
   * <p>For most purposes, {@link org.apache.calcite.rel.rel2sql.SqlImplementor}
   * is superior. See in particular
   * {@link org.apache.calcite.rel.rel2sql.SqlImplementor.Context#toSql(RexProgram, RexNode)}.
   */
  public interface RexToSqlNodeConverter {
    //~ Methods ----------------------------------------------------------------
  
    /**
     * Converts a {@link RexNode} to a {@link SqlNode} expression,
     * typically by dispatching to one of the other interface methods.
     *
     * @param node RexNode to translate
     * @return SqlNode, or null if no translation was available
     */
    @Nullable SqlNode convertNode(RexNode node);
  
    /**
     * Converts a {@link RexCall} to a {@link SqlNode} expression.
     *
     * @param call RexCall to translate
     * @return SqlNode, or null if no translation was available
     */
    @Nullable SqlNode convertCall(RexCall call);
  
    /**
     * Converts a {@link RexLiteral} to a {@link SqlLiteral}.
     *
     * @param literal RexLiteral to translate
     * @return SqlNode, or null if no translation was available
     */
    @Nullable SqlNode convertLiteral(RexLiteral literal);
  
    /**
     * Converts a {@link RexInputRef} to a {@link SqlIdentifier}.
     *
     * @param ref RexInputRef to translate
     * @return SqlNode, or null if no translation was available
     */
    @Nullable SqlNode convertInputRef(RexInputRef ref);
  }
  