/*
 * 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 com.facebook.presto.sql.planner.planPrinter;

import com.facebook.presto.operator.DynamicFilterStats;
import com.facebook.presto.spi.plan.PlanNodeId;
import io.airlift.units.DataSize;
import io.airlift.units.Duration;

import java.util.Map;
import java.util.Optional;

import static com.google.common.base.Preconditions.checkArgument;
import static java.lang.Math.max;
import static java.lang.Math.sqrt;
import static java.util.Objects.requireNonNull;
import static java.util.stream.Collectors.toMap;

public class HashCollisionPlanNodeStats
        extends PlanNodeStats
{
    private final Map<String, OperatorHashCollisionsStats> operatorHashCollisionsStats;

    public HashCollisionPlanNodeStats(
            PlanNodeId planNodeId,
            Duration planNodeScheduledTime,
            Duration planNodeCpuTime,
            Duration planNodeBlockedWallTime,
            Duration planNodeAddInputWallTime,
            Duration planNodeGetOutputWallTime,
            Duration planNodeFinishWallTime,
            long planNodeInputPositions,
            DataSize planNodeInputDataSize,
            long planNodeRawInputPositions,
            DataSize planNodeRawInputDataSize,
            long planNodeOutputPositions,
            DataSize planNodeOutputDataSize,
            DataSize planNodePeakMemorySize,
            Map<String, OperatorInputStats> operatorInputStats,
            long planNodeNullJoinBuildKeyCount,
            long planNodeJoinBuildKeyCount,
            long planNodeNullJoinProbeKeyCount,
            long planNodeJoinProbeKeyCount,
            Optional<DynamicFilterStats> dynamicFilterStats,
            Map<String, OperatorHashCollisionsStats> operatorHashCollisionsStats)
    {
        super(planNodeId, planNodeScheduledTime, planNodeCpuTime, planNodeBlockedWallTime, planNodeAddInputWallTime, planNodeGetOutputWallTime, planNodeFinishWallTime,
                planNodeInputPositions, planNodeInputDataSize, planNodeRawInputPositions, planNodeRawInputDataSize, planNodeOutputPositions, planNodeOutputDataSize,
                planNodePeakMemorySize, operatorInputStats, planNodeNullJoinBuildKeyCount, planNodeJoinBuildKeyCount, planNodeNullJoinProbeKeyCount, planNodeJoinProbeKeyCount, dynamicFilterStats);
        this.operatorHashCollisionsStats = requireNonNull(operatorHashCollisionsStats, "operatorHashCollisionsStats is null");
    }

    public Map<String, Double> getOperatorHashCollisionsAverages()
    {
        return operatorHashCollisionsStats.entrySet().stream()
                .collect(toMap(
                        Map.Entry::getKey,
                        entry -> entry.getValue().getWeightedHashCollisions() / operatorInputStats.get(entry.getKey()).getInputPositions()));
    }

    public Map<String, Double> getOperatorHashCollisionsStdDevs()
    {
        return operatorHashCollisionsStats.entrySet().stream()
                .collect(toMap(
                        Map.Entry::getKey,
                        entry -> computedWeightedStdDev(
                                entry.getValue().getWeightedSumSquaredHashCollisions(),
                                entry.getValue().getWeightedHashCollisions(),
                                operatorInputStats.get(entry.getKey()).getInputPositions())));
    }

    private static double computedWeightedStdDev(double sumSquared, double sum, double totalWeight)
    {
        double average = sum / totalWeight;
        double variance = (sumSquared - 2 * sum * average) / totalWeight + average * average;
        // variance might be negative because of numeric inaccuracy, therefore we need to use max
        return sqrt(max(variance, 0d));
    }

    public Map<String, Double> getOperatorExpectedCollisionsAverages()
    {
        return operatorHashCollisionsStats.entrySet().stream()
                .collect(toMap(
                        Map.Entry::getKey,
                        entry -> entry.getValue().getWeightedExpectedHashCollisions() / operatorInputStats.get(entry.getKey()).getInputPositions()));
    }

    @Override
    public PlanNodeStats mergeWith(PlanNodeStats other)
    {
        checkArgument(other instanceof HashCollisionPlanNodeStats, "other is not an instanceof HashCollisionPlanNodeStats");
        PlanNodeStats merged = super.mergeWith(other);

        return new HashCollisionPlanNodeStats(
                merged.getPlanNodeId(),
                merged.getPlanNodeScheduledTime(),
                merged.getPlanNodeCpuTime(),
                merged.getPlanNodeBlockedWallTime(),
                merged.getPlanNodeAddInputWallTime(),
                merged.getPlanNodeGetOutputWallTime(),
                merged.getPlanNodeFinishWallTime(),
                merged.getPlanNodeInputPositions(),
                merged.getPlanNodeInputDataSize(),
                merged.getPlanNodeRawInputPositions(),
                merged.getPlanNodeRawInputDataSize(),
                merged.getPlanNodeOutputPositions(),
                merged.getPlanNodeOutputDataSize(),
                merged.getPlanNodePeakMemorySize(),
                merged.operatorInputStats,
                merged.getPlanNodeNullJoinBuildKeyCount(),
                merged.getPlanNodeJoinBuildKeyCount(),
                merged.getPlanNodeNullJoinProbeKeyCount(),
                merged.getPlanNodeJoinProbeKeyCount(),
                merged.getDynamicFilterStats(),
                operatorHashCollisionsStats);
    }
}
