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/*
 * Licensed 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 io.prestosql.plugin.jdbc.expression;

import io.prestosql.matching.Captures;
import io.prestosql.matching.Pattern;
import io.prestosql.plugin.jdbc.JdbcClient;
import io.prestosql.plugin.jdbc.JdbcExpression;
import io.prestosql.plugin.jdbc.JdbcTypeHandle;
import io.prestosql.spi.connector.AggregateFunction;
import io.prestosql.spi.type.BigintType;

import java.util.List;
import java.util.Optional;

import static com.google.common.base.Verify.verify;
import static io.prestosql.plugin.jdbc.expression.AggregateFunctionPatterns.basicAggregation;
import static io.prestosql.plugin.jdbc.expression.AggregateFunctionPatterns.functionName;
import static io.prestosql.plugin.jdbc.expression.AggregateFunctionPatterns.inputs;
import static io.prestosql.spi.type.BigintType.BIGINT;
import static java.util.Objects.requireNonNull;

/**
 * Implements {@code count(*)}.
 */
public class ImplementCountAll
        implements AggregateFunctionRule
{
    private final JdbcTypeHandle bigintTypeHandle;

    /**
     * @param bigintTypeHandle A {@link JdbcTypeHandle} that will be mapped to {@link BigintType} by {@link JdbcClient#toPrestoType}.
     */
    public ImplementCountAll(JdbcTypeHandle bigintTypeHandle)
    {
        this.bigintTypeHandle = requireNonNull(bigintTypeHandle, "bigintTypeHandle is null");
    }

    @Override
    public Pattern getPattern()
    {
        return basicAggregation()
                .with(functionName().equalTo("count"))
                .with(inputs().equalTo(List.of()));
    }

    @Override
    public Optional rewrite(AggregateFunction aggregateFunction, Captures captures, RewriteContext context)
    {
        verify(aggregateFunction.getOutputType() == BIGINT);
        return Optional.of(new JdbcExpression("count(*)", bigintTypeHandle));
    }
}