hazelcast-master/hazelcast-sql/src/main/java/com/hazelcast/sql/impl/expression/CastExpression.java
/*
 * Copyright 2023 Hazelcast Inc.
 *
 * Licensed under the Hazelcast Community License (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://hazelcast.com/hazelcast-community-license
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.hazelcast.sql.impl.expression;

import com.hazelcast.jet.sql.impl.JetSqlSerializerHook;
import com.hazelcast.sql.impl.row.Row;
import com.hazelcast.sql.impl.type.QueryDataType;
import com.hazelcast.sql.impl.type.converter.Converter;

/**
 * Implements evaluation of SQL CAST operator.
 */
public final class CastExpression<T> extends UniExpressionWithType<T> {

    public CastExpression() {
        // No-op.
    }

    private CastExpression(Expression<?> operand, QueryDataType resultType) {
        super(operand, resultType);
    }

    public static CastExpression<?> create(Expression<?> operand, QueryDataType resultType) {
        return new CastExpression<>(operand, resultType);
    }

    @Override
    public int getClassId() {
        return JetSqlSerializerHook.EXPRESSION_CAST;
    }

    @SuppressWarnings("unchecked")
    @Override
    public T eval(Row row, ExpressionEvalContext context) {
        Object value = operand.eval(row, context);

        if (value == null) {
            return null;
        }

        Converter fromConverter = operand.getType().getConverter();
        Converter toConverter = resultType.getConverter();
        return (T) toConverter.convertToSelf(fromConverter, value);
    }

}
