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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.trino.plugin.pinot.query.aggregation;

import io.trino.matching.Capture;
import io.trino.matching.Captures;
import io.trino.matching.Pattern;
import io.trino.plugin.base.aggregation.AggregateFunctionRule;
import io.trino.plugin.pinot.PinotColumnHandle;
import io.trino.plugin.pinot.query.AggregateExpression;
import io.trino.spi.connector.AggregateFunction;
import io.trino.spi.expression.Variable;

import java.util.Optional;
import java.util.function.Function;

import static com.google.common.base.Verify.verify;
import static io.trino.matching.Capture.newCapture;
import static io.trino.plugin.base.aggregation.AggregateFunctionPatterns.basicAggregation;
import static io.trino.plugin.base.aggregation.AggregateFunctionPatterns.functionName;
import static io.trino.plugin.base.aggregation.AggregateFunctionPatterns.outputType;
import static io.trino.plugin.base.aggregation.AggregateFunctionPatterns.singleArgument;
import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.variable;
import static io.trino.plugin.pinot.PinotSessionProperties.isCountDistinctPushdownEnabled;
import static io.trino.spi.type.BigintType.BIGINT;
import static java.util.Objects.requireNonNull;

public class ImplementCountDistinct
        implements AggregateFunctionRule
{
    private static final Capture ARGUMENT = newCapture();

    private final Function identifierQuote;

    public ImplementCountDistinct(Function identifierQuote)
    {
        this.identifierQuote = requireNonNull(identifierQuote, "identifierQuote is null");
    }

    @Override
    public Pattern getPattern()
    {
        return basicAggregation()
                .with(functionName().equalTo("count"))
                .with(outputType().equalTo(BIGINT))
                .with(singleArgument().matching(variable().capturedAs(ARGUMENT)));
    }

    @Override
    public Optional rewrite(AggregateFunction aggregateFunction, Captures captures, RewriteContext context)
    {
        if (!isCountDistinctPushdownEnabled(context.getSession())) {
            return Optional.empty();
        }
        Variable argument = captures.get(ARGUMENT);
        verify(aggregateFunction.getOutputType() == BIGINT);
        PinotColumnHandle column = (PinotColumnHandle) context.getAssignment(argument.getName());
        return Optional.of(new AggregateExpression("distinctcount", identifierQuote.apply(column.getColumnName()), false));
    }
}