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.sql.fun;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexCallBinding;
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlCallBinding;
  import org.apache.calcite.sql.SqlFunctionCategory;
  import org.apache.calcite.sql.SqlIdentifier;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlOperandCountRange;
  import org.apache.calcite.sql.SqlOperatorBinding;
  import org.apache.calcite.sql.SqlUtil;
  import org.apache.calcite.sql.type.ReturnTypes;
  import org.apache.calcite.sql.type.SqlOperandCountRanges;
  import org.apache.calcite.sql.type.SqlTypeUtil;
  import org.apache.calcite.sql.validate.SqlValidator;
  import org.apache.calcite.sql.validate.SqlValidatorScope;
  
  import java.nio.charset.Charset;
  import java.util.List;
  
  import static org.apache.calcite.sql.type.NonNullableAccessors.getCollation;
  
  import static java.util.Objects.requireNonNull;
  
  /** Oracle's "CONVERT(charValue, destCharsetName[, srcCharsetName])" function.
   *
   * <p>It has a slight different semantics to standard SQL's
   * {@link SqlStdOperatorTable#CONVERT} function on operands' order, and default
   * charset will be used if the {@code srcCharsetName} is not specified.
   *
   * <p>Returns null if {@code charValue} is null or empty. */
  public class SqlOracleConvertFunction extends SqlConvertFunction {
      //~ Constructors -----------------------------------------------------------
  
    public SqlOracleConvertFunction(String name) {
      super(name, SqlKind.CONVERT_ORACLE, ReturnTypes.ARG0, null, null,
          SqlFunctionCategory.STRING);
    }
  
      //~ Methods ----------------------------------------------------------------
  
    @Override public void validateCall(SqlCall call, SqlValidator validator,
        SqlValidatorScope scope, SqlValidatorScope operandScope) {
      final List<SqlNode> operands = call.getOperandList();
      operands.get(0).validateExpr(validator, scope);
      // validate if the Charsets are legal.
      assert operands.get(1) instanceof SqlIdentifier;
      final String src_charset = operands.get(1).toString();
      SqlUtil.getCharset(src_charset);
      if (operands.size() == 3) {
        assert operands.get(2) instanceof SqlIdentifier;
        final String dest_charset = operands.get(2).toString();
        SqlUtil.getCharset(dest_charset);
      }
      super.validateQuantifier(validator, call);
    }
  
    @Override public RelDataType inferReturnType(
        SqlOperatorBinding opBinding) {
      final RelDataType ret = opBinding.getOperandType(0);
      if (SqlTypeUtil.isNull(ret)) {
        return ret;
      }
      final String descCharsetName;
      if (opBinding instanceof SqlCallBinding) {
        descCharsetName = ((SqlCallBinding) opBinding).getCall().operand(1).toString();
      } else {
        descCharsetName = ((RexCallBinding) opBinding).getStringLiteralOperand(1);
      }
      assert descCharsetName != null;
      Charset descCharset = SqlUtil.getCharset(descCharsetName);
      return opBinding
          .getTypeFactory().createTypeWithCharsetAndCollation(ret, descCharset, getCollation(ret));
    }
  
    @Override public RelDataType deriveType(SqlValidator validator,
        SqlValidatorScope scope, SqlCall call) {
      RelDataType nodeType =
          validator.deriveType(scope, call.operand(0));
      requireNonNull(nodeType, "nodeType");
      RelDataType ret = validateOperands(validator, scope, call);
      if (SqlTypeUtil.isNull(ret)) {
        return ret;
      }
      Charset descCharset = SqlUtil.getCharset(call.operand(1).toString());
      return validator.getTypeFactory()
          .createTypeWithCharsetAndCollation(ret, descCharset, getCollation(ret));
    }
  
    @Override public String getSignatureTemplate(final int operandsCount) {
      switch (operandsCount) {
      case 2:
        return "{0}({1}, {2})";
      case 3:
        return "{0}({1}, {2}, {3})";
      default:
        throw new IllegalStateException("operandsCount should be 2 or 3, got "
            + operandsCount);
      }
    }
  
    @Override public SqlOperandCountRange getOperandCountRange() {
      return SqlOperandCountRanges.between(2, 3);
    }
  }
  