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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;

import com.google.common.collect.ImmutableList;
import io.trino.spi.Page;
import io.trino.spi.PageBuilder;
import io.trino.spi.block.BlockBuilder;
import io.trino.spi.type.Type;
import io.trino.sql.planner.plan.PlanNodeId;

import java.util.List;
import java.util.OptionalLong;

import static com.google.common.base.Preconditions.checkState;
import static io.trino.spi.type.BigintType.BIGINT;
import static java.util.Objects.requireNonNull;

public class TableMutationOperator
        implements Operator
{
    public static final List TYPES = ImmutableList.of(BIGINT);

    private final OperatorContext operatorContext;
    private final Operation operation;
    private boolean finished;

    public static class TableMutationOperatorFactory
            implements OperatorFactory
    {
        private final int operatorId;
        private final PlanNodeId planNodeId;
        private final Operation operation;
        private boolean closed;

        public TableMutationOperatorFactory(
                int operatorId,
                PlanNodeId planNodeId,
                Operation operation)
        {
            this.operatorId = operatorId;
            this.planNodeId = requireNonNull(planNodeId, "planNodeId is null");
            this.operation = requireNonNull(operation, "operation is null");
        }

        @Override
        public Operator createOperator(DriverContext driverContext)
        {
            checkState(!closed, "Factory is already closed");
            OperatorContext context = driverContext.addOperatorContext(operatorId, planNodeId, TableMutationOperator.class.getSimpleName());
            return new TableMutationOperator(context, operation);
        }

        @Override
        public void noMoreOperators()
        {
            closed = true;
        }

        @Override
        public OperatorFactory duplicate()
        {
            return new TableMutationOperatorFactory(
                    operatorId,
                    planNodeId,
                    operation);
        }
    }

    public TableMutationOperator(OperatorContext operatorContext, Operation operation)
    {
        this.operatorContext = requireNonNull(operatorContext, "operatorContext is null");
        this.operation = requireNonNull(operation, "operation is null");
    }

    @Override
    public OperatorContext getOperatorContext()
    {
        return operatorContext;
    }

    @Override
    public void finish() {}

    @Override
    public boolean isFinished()
    {
        return finished;
    }

    @Override
    public boolean needsInput()
    {
        return false;
    }

    @Override
    public void addInput(Page page)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    public Page getOutput()
    {
        if (finished) {
            return null;
        }
        finished = true;

        OptionalLong rowsUpdatedCount = operation.execute();

        return buildUpdatedCountPage(rowsUpdatedCount);
    }

    private Page buildUpdatedCountPage(OptionalLong count)
    {
        // output page will only be constructed once,
        // so a new PageBuilder is constructed (instead of using PageBuilder.reset)
        PageBuilder page = new PageBuilder(1, TYPES);
        BlockBuilder rowsBuilder = page.getBlockBuilder(0);
        page.declarePosition();
        if (count.isPresent()) {
            BIGINT.writeLong(rowsBuilder, count.getAsLong());
        }
        else {
            rowsBuilder.appendNull();
        }
        return page.build();
    }

    public interface Operation
    {
        OptionalLong execute();
    }
}