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Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.
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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.kernel.impl.api;

import org.eclipse.collections.api.map.primitive.ImmutableLongObjectMap;
import org.eclipse.collections.api.set.primitive.MutableLongSet;
import org.eclipse.collections.impl.factory.primitive.LongObjectMaps;
import org.eclipse.collections.impl.factory.primitive.LongSets;

import org.neo4j.kernel.api.InnerTransactionHandler;
import org.neo4j.kernel.api.KernelTransactionHandle;
import org.neo4j.kernel.api.exceptions.Status;

/**
 * The public methods of this class are synchronized as we expect it to be accessed from both the executing thread and possibly from a different thread which
 * marks the transaction to be terminated.
 */
class InnerTransactionHandlerImpl implements InnerTransactionHandler
{
    /**
     * The transaction for this handler has been closed/terminated.
     */
    private boolean closed;
    /**
     * The reason for terminating this handler's transaction. Is not null once marked for termination.
     */
    private Status terminationReason;
    private MutableLongSet innerTransactionIds;
    private final KernelTransactions kernelTransactions;

    InnerTransactionHandlerImpl( KernelTransactions kernelTransactions )
    {
        this.kernelTransactions = kernelTransactions;
    }

    /**
     * {@inheritDoc}
     * 
     * We assume this method to only be called from the executing thread.
     */
    @Override
    public synchronized void registerInnerTransaction( long innerTransactionId )
    {
        if ( closed )
        {
            throw new IllegalStateException( "The inner transaction handler is already closed." );
        }
        else if ( terminationReason != null )
        {
            terminateInnerTransaction( terminationReason, getTransactionHandlesById(), innerTransactionId );
        }
        else
        {
            if ( innerTransactionIds == null )
            {
                innerTransactionIds = LongSets.mutable.empty();
            }
            innerTransactionIds.add( innerTransactionId );
        }
    }

    /**
     * {@inheritDoc}
     * 

     * We assume this method to only be called from the executing thread.
     */
    @Override
    public synchronized void removeInnerTransaction( long innerTransactionId )
    {
        if ( innerTransactionIds != null )
        {
            innerTransactionIds.remove( innerTransactionId );
        }
    }

    /**
     * @return {@code true} if any open inner transaction is currently connected to this transaction.
     */
    synchronized boolean hasInnerTransaction()
    {
        return innerTransactionIds != null && !innerTransactionIds.isEmpty();
    }

    /**
     * Terminates all the inner transactions contained in this handler and all handlers subsequently registered with this handler.
     * 

     * This method may be called from a thread different from the executing thread.
     */
    synchronized void terminateInnerTransactions( Status reason )
    {
        terminationReason = reason;
        var handlesById = getTransactionHandlesById();
        if ( innerTransactionIds != null )
        {
            innerTransactionIds.forEach( innerTransactionId -> terminateInnerTransaction( reason, handlesById, innerTransactionId ) );
            innerTransactionIds.clear();
            innerTransactionIds = null;
        }
    }

    private ImmutableLongObjectMap getTransactionHandlesById()
    {
        return LongObjectMaps.immutable.from(
                kernelTransactions.executingTransactions(),
                KernelTransactionHandle::getUserTransactionId,
                a -> a
        );
    }

    private void terminateInnerTransaction( Status reason, ImmutableLongObjectMap handlesById, long innerTransactionId )
    {
        KernelTransactionHandle kernelTransactionHandle = handlesById.get( innerTransactionId );
        if ( kernelTransactionHandle != null )
        {
            kernelTransactionHandle.markForTermination( reason );
        }
    }

    /**
     * Marks this handler as closed, once the transaction that this handler belongs to is closed.
     * 
     * We assume this method to only be called from the executing thread and to have no further interaction with this handler from that thread.
     */
    synchronized void close()
    {
        this.closed = true;
        if ( this.innerTransactionIds != null )
        {
            this.innerTransactionIds.clear();
        }
        this.innerTransactionIds = null;
    }
}