/*
 * 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.spi.plan.PlanNodeId;
import io.airlift.units.DataSize;
import io.airlift.units.Duration;

import java.util.Map;

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,
            long planNodeInputPositions,
            DataSize planNodeInputDataSize,
            long planNodeRawInputPositions,
            DataSize planNodeRawInputDataSize,
            long planNodeOutputPositions,
            DataSize planNodeOutputDataSize,
            Map<String, OperatorInputStats> operatorInputStats,
            long planNodeNullJoinBuildKeyCount,
            long planNodeJoinBuildKeyCount,
            Map<String, OperatorHashCollisionsStats> operatorHashCollisionsStats)
    {
        super(planNodeId, planNodeScheduledTime, planNodeCpuTime, planNodeInputPositions, planNodeInputDataSize, planNodeRawInputPositions, planNodeRawInputDataSize,
                planNodeOutputPositions, planNodeOutputDataSize, operatorInputStats, planNodeNullJoinBuildKeyCount, planNodeJoinBuildKeyCount);
        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.getPlanNodeInputPositions(),
                merged.getPlanNodeInputDataSize(),
                merged.getPlanNodeRawInputPositions(),
                merged.getPlanNodeRawInputDataSize(),
                merged.getPlanNodeOutputPositions(),
                merged.getPlanNodeOutputDataSize(),
                merged.operatorInputStats,
                merged.getPlanNodeNullJoinBuildKeyCount(),
                merged.getPlanNodeJoinBuildKeyCount(),
                operatorHashCollisionsStats);
    }
}
