core/src/main/java/org/apache/calcite/sql/fun/SqlOverlayFunction.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.fun;

import org.apache.calcite.sql.SqlCall;
import org.apache.calcite.sql.SqlFunction;
import org.apache.calcite.sql.SqlFunctionCategory;
import org.apache.calcite.sql.SqlKind;
import org.apache.calcite.sql.SqlWriter;
import org.apache.calcite.sql.type.OperandTypes;
import org.apache.calcite.sql.type.ReturnTypes;
import org.apache.calcite.sql.type.SqlOperandTypeChecker;

/**
 * The <code>OVERLAY</code> function.
 */
public class SqlOverlayFunction extends SqlFunction {
  //~ Static fields/initializers ---------------------------------------------

  private static final SqlOperandTypeChecker OTC_CUSTOM =
      OperandTypes.STRING_STRING_INTEGER
          .or(OperandTypes.STRING_STRING_INTEGER_INTEGER);

  //~ Constructors -----------------------------------------------------------

  public SqlOverlayFunction() {
    super(
        "OVERLAY",
        SqlKind.OTHER_FUNCTION,
        ReturnTypes.DYADIC_STRING_SUM_PRECISION_NULLABLE_VARYING,
        null,
        OTC_CUSTOM,
        SqlFunctionCategory.STRING);
  }

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

  @Override public void unparse(
      SqlWriter writer,
      SqlCall call,
      int leftPrec,
      int rightPrec) {
    final SqlWriter.Frame frame = writer.startFunCall(getName());
    call.operand(0).unparse(writer, leftPrec, rightPrec);
    writer.sep("PLACING");
    call.operand(1).unparse(writer, leftPrec, rightPrec);
    writer.sep("FROM");
    call.operand(2).unparse(writer, leftPrec, rightPrec);
    if (4 == call.operandCount()) {
      writer.sep("FOR");
      call.operand(3).unparse(writer, leftPrec, rightPrec);
    }
    writer.endFunCall(frame);
  }

  @Override public String getSignatureTemplate(final int operandsCount) {
    switch (operandsCount) {
    case 3:
      return "{0}({1} PLACING {2} FROM {3})";
    case 4:
      return "{0}({1} PLACING {2} FROM {3} FOR {4})";
    default:
      throw new IllegalArgumentException("operandsCount shuld be 3 or 4, got " + operandsCount);
    }
  }
}