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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.operator.aggregation;

import io.airlift.stats.TDigest;
import io.trino.operator.aggregation.state.TDigestAndPercentileState;
import io.trino.spi.block.BlockBuilder;
import io.trino.spi.function.AggregationFunction;
import io.trino.spi.function.AggregationState;
import io.trino.spi.function.CombineFunction;
import io.trino.spi.function.InputFunction;
import io.trino.spi.function.OutputFunction;
import io.trino.spi.function.SqlType;
import io.trino.spi.type.StandardTypes;

import static com.google.common.base.Preconditions.checkState;
import static io.trino.operator.scalar.TDigestFunctions.verifyWeight;
import static io.trino.spi.StandardErrorCode.INVALID_FUNCTION_ARGUMENT;
import static io.trino.spi.type.DoubleType.DOUBLE;
import static io.trino.util.Failures.checkCondition;

@AggregationFunction("approx_percentile")
public final class ApproximateDoublePercentileAggregations
{
    private ApproximateDoublePercentileAggregations() {}

    @InputFunction
    public static void input(@AggregationState TDigestAndPercentileState state, @SqlType(StandardTypes.DOUBLE) double value, @SqlType(StandardTypes.DOUBLE) double percentile)
    {
        TDigest digest = state.getDigest();

        if (digest == null) {
            digest = new TDigest();
            state.setDigest(digest);
            state.addMemoryUsage(digest.estimatedInMemorySizeInBytes());
        }

        state.addMemoryUsage(-digest.estimatedInMemorySizeInBytes());
        digest.add(value);
        state.addMemoryUsage(digest.estimatedInMemorySizeInBytes());

        // use last percentile
        state.setPercentile(percentile);
    }

    @InputFunction
    public static void weightedInput(@AggregationState TDigestAndPercentileState state, @SqlType(StandardTypes.DOUBLE) double value, @SqlType(StandardTypes.DOUBLE) double weight, @SqlType(StandardTypes.DOUBLE) double percentile)
    {
        verifyWeight(weight);

        TDigest digest = state.getDigest();

        if (digest == null) {
            digest = new TDigest();
            state.setDigest(digest);
            state.addMemoryUsage(digest.estimatedInMemorySizeInBytes());
        }

        state.addMemoryUsage(-digest.estimatedInMemorySizeInBytes());
        digest.add(value, weight);
        state.addMemoryUsage(digest.estimatedInMemorySizeInBytes());

        // use last percentile
        state.setPercentile(percentile);
    }

    @CombineFunction
    public static void combine(@AggregationState TDigestAndPercentileState state, TDigestAndPercentileState otherState)
    {
        TDigest input = otherState.getDigest();

        TDigest previous = state.getDigest();
        if (previous == null) {
            state.setDigest(input);
            state.addMemoryUsage(input.estimatedInMemorySizeInBytes());
        }
        else {
            state.addMemoryUsage(-previous.estimatedInMemorySizeInBytes());
            previous.mergeWith(input);
            state.addMemoryUsage(previous.estimatedInMemorySizeInBytes());
        }
        state.setPercentile(otherState.getPercentile());
    }

    @OutputFunction(StandardTypes.DOUBLE)
    public static void output(@AggregationState TDigestAndPercentileState state, BlockBuilder out)
    {
        TDigest digest = state.getDigest();
        double percentile = state.getPercentile();
        if (digest == null || digest.getCount() == 0.0) {
            out.appendNull();
        }
        else {
            checkState(percentile != -1.0, "Percentile is missing");
            checkCondition(0 <= percentile && percentile <= 1, INVALID_FUNCTION_ARGUMENT, "Percentile must be between 0 and 1");
            DOUBLE.writeDouble(out, digest.valueAt(percentile));
        }
    }
}