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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.cost;

import io.prestosql.Session;
import io.prestosql.execution.scheduler.NodeSchedulerConfig;
import io.prestosql.metadata.InternalNode;
import io.prestosql.metadata.InternalNodeManager;

import javax.inject.Inject;

import java.util.Set;
import java.util.function.IntSupplier;

import static io.prestosql.SystemSessionProperties.getCostEstimationWorkerCount;
import static io.prestosql.SystemSessionProperties.getHashPartitionCount;
import static java.lang.Math.min;
import static java.lang.Math.toIntExact;
import static java.util.Objects.requireNonNull;

public class TaskCountEstimator
{
    private final IntSupplier numberOfNodes;

    @Inject
    public TaskCountEstimator(NodeSchedulerConfig nodeSchedulerConfig, InternalNodeManager nodeManager)
    {
        requireNonNull(nodeSchedulerConfig, "nodeSchedulerConfig is null");
        requireNonNull(nodeManager, "nodeManager is null");
        this.numberOfNodes = () -> {
            Set activeNodes = nodeManager.getAllNodes().getActiveNodes();
            if (nodeSchedulerConfig.isIncludeCoordinator()) {
                return activeNodes.size();
            }
            return toIntExact(activeNodes.stream()
                    .filter(node -> !node.isCoordinator())
                    .count());
        };
    }

    public TaskCountEstimator(IntSupplier numberOfNodes)
    {
        this.numberOfNodes = requireNonNull(numberOfNodes, "numberOfNodes is null");
    }

    public int estimateSourceDistributedTaskCount(Session session)
    {
        Integer costEstimationWorkerCount = getCostEstimationWorkerCount(session);
        if (costEstimationWorkerCount != null) {
            return costEstimationWorkerCount;
        }
        return numberOfNodes.getAsInt();
    }

    public int estimateHashedTaskCount(Session session)
    {
        return min(estimateSourceDistributedTaskCount(session), getHashPartitionCount(session));
    }
}