core/src/main/java/org/apache/calcite/sql/SqlSpecialOperator.java

/*
 * 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.sql;

import org.apache.calcite.sql.parser.SqlParserPos;
import org.apache.calcite.sql.type.SqlOperandTypeChecker;
import org.apache.calcite.sql.type.SqlOperandTypeInference;
import org.apache.calcite.sql.type.SqlReturnTypeInference;
import org.apache.calcite.util.PrecedenceClimbingParser;
import org.apache.calcite.util.Util;

import org.checkerframework.checker.nullness.qual.Nullable;

import java.util.function.Predicate;

/**
 * Generic operator for nodes with special syntax.
 */
public class SqlSpecialOperator extends SqlOperator {
  //~ Constructors -----------------------------------------------------------

  public SqlSpecialOperator(
      String name,
      SqlKind kind) {
    this(name, kind, 2);
  }

  public SqlSpecialOperator(
      String name,
      SqlKind kind,
      int prec) {
    this(name, kind, prec, true, null, null, null);
  }

  public SqlSpecialOperator(
      String name,
      SqlKind kind,
      int prec,
      boolean leftAssoc,
      @Nullable SqlReturnTypeInference returnTypeInference,
      @Nullable SqlOperandTypeInference operandTypeInference,
      @Nullable SqlOperandTypeChecker operandTypeChecker) {
    super(
        name,
        kind,
        prec,
        leftAssoc,
        returnTypeInference,
        operandTypeInference,
        operandTypeChecker);
  }

  //~ Methods ----------------------------------------------------------------

  @Override public SqlSyntax getSyntax() {
    return SqlSyntax.SPECIAL;
  }

  /**
   * Reduces a list of operators and arguments according to the rules of
   * precedence and associativity. Returns the ordinal of the node which
   * replaced the expression.
   *
   * <p>The default implementation throws
   * {@link UnsupportedOperationException}.
   *
   * @param ordinal indicating the ordinal of the current operator in the list
   *                on which a possible reduction can be made
   * @param list    List of alternating
   *     {@link org.apache.calcite.sql.parser.SqlParserUtil.ToTreeListItem} and
   *     {@link SqlNode}
   * @return ordinal of the node which replaced the expression
   */
  public ReduceResult reduceExpr(
      int ordinal,
      TokenSequence list) {
    throw Util.needToImplement(this);
  }

  /** List of tokens: the input to a parser. Every token is either an operator
   * ({@link SqlOperator}) or an expression ({@link SqlNode}), and every token
   * has a position. */
  public interface TokenSequence {
    int size();
    SqlOperator op(int i);
    SqlParserPos pos(int i);
    boolean isOp(int i);
    SqlNode node(int i);
    void replaceSublist(int start, int end, SqlNode e);

    /** Creates a parser whose token sequence is a copy of a subset of this
     * token sequence. */
    PrecedenceClimbingParser parser(int start,
        Predicate<PrecedenceClimbingParser.Token> predicate);
  }

  /** Result of applying
   * {@link org.apache.calcite.util.PrecedenceClimbingParser.Special#apply}.
   * Tells the caller which range of tokens to replace, and with what. */
  public static class ReduceResult {
    public final int startOrdinal;
    public final int endOrdinal;
    public final SqlNode node;

    public ReduceResult(int startOrdinal, int endOrdinal, SqlNode node) {
      this.startOrdinal = startOrdinal;
      this.endOrdinal = endOrdinal;
      this.node = node;
    }
  }
}