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Access to the Neo4j graph database through Java
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/**
 * Copyright (c) 2002-2016 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * 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 org.neo4j.driver.internal;

import java.util.Map;

import org.neo4j.driver.internal.spi.Connection;
import org.neo4j.driver.internal.spi.Logger;
import org.neo4j.driver.internal.types.InternalTypeSystem;
import org.neo4j.driver.v1.Record;
import org.neo4j.driver.v1.Session;
import org.neo4j.driver.v1.Statement;
import org.neo4j.driver.v1.StatementResult;
import org.neo4j.driver.v1.Transaction;
import org.neo4j.driver.v1.Value;
import org.neo4j.driver.v1.Values;
import org.neo4j.driver.v1.exceptions.ClientException;
import org.neo4j.driver.v1.types.TypeSystem;

import static org.neo4j.driver.v1.Values.value;

public class InternalSession implements Session
{
    private final Connection connection;

    private final Logger logger;

    /** Called when a transaction object is closed */
    private final Runnable txCleanup = new Runnable()
    {
        @Override
        public void run()
        {
            currentTransaction = null;
        }
    };

    private InternalTransaction currentTransaction;
    private boolean isOpen = true;

    public InternalSession( Connection connection, Logger logger )
    {
        this.connection = connection;
        this.logger = logger;
    }

    @Override
    public StatementResult run( String statementText )
    {
        return run( statementText, Values.EmptyMap );
    }

    @Override
    public StatementResult run( String statementText, Map statementParameters )
    {
        Value params = statementParameters == null ? Values.EmptyMap : value(statementParameters);
        return run( statementText, params );
    }

    @Override
    public StatementResult run( String statementTemplate, Record statementParameters )
    {
        Value params = statementParameters == null ? Values.EmptyMap : value( statementParameters.asMap() );
        return run( statementTemplate, params );
    }

    @Override
    public StatementResult run( String statementText, Value statementParameters )
    {
        return run( new Statement( statementText, statementParameters ) );
    }

    @Override
    public StatementResult run( Statement statement )
    {
        ensureConnectionIsValidBeforeRunningSession();
        InternalStatementResult cursor = new InternalStatementResult( connection, statement );
        connection.run( statement.text(), statement.parameters().asMap( Values.ofValue() ), cursor.runResponseCollector() );
        connection.pullAll( cursor.pullAllResponseCollector() );
        connection.flush();
        return cursor;
    }

    @Override
    public boolean isOpen()
    {
        return isOpen;
    }

    @Override
    public void close()
    {
        if( !isOpen )
        {
            throw new ClientException( "This session has already been closed." );
        }
        else
        {
            isOpen = false;
            if ( currentTransaction != null )
            {
                try
                {
                    currentTransaction.close();
                }
                catch ( Throwable e )
                {
                    // Best-effort
                }
            }
            connection.sync();
            connection.close();
        }
    }

    @Override
    public Transaction beginTransaction()
    {
        ensureConnectionIsValidBeforeOpeningTransaction();
        currentTransaction = new InternalTransaction( connection, txCleanup );
        connection.onError( new Runnable() {
            @Override
            public void run()
            {
                //must check if transaction has been closed
                if (currentTransaction != null)
                {
                    currentTransaction.markAsRolledBack();
                    currentTransaction = null;
                    connection.onError( null );
                }
            }
        });
        return currentTransaction;
    }

    @Override
    public TypeSystem typeSystem()
    {
        return InternalTypeSystem.TYPE_SYSTEM;
    }

    private void ensureConnectionIsValidBeforeRunningSession()
    {
        ensureNoOpenTransactionBeforeRunningSession();
        ensureConnectionIsOpen();
    }

    private void ensureConnectionIsValidBeforeOpeningTransaction()
    {
        ensureNoOpenTransactionBeforeOpeningTransaction();
        ensureConnectionIsOpen();
    }

    @Override
    protected void finalize() throws Throwable
    {
        if( isOpen )
        {
            logger.error( "Neo4j Session object leaked, please ensure that your application calls the `close` " +
                          "method on Sessions before disposing of the objects.", null );
            connection.close();
        }
        super.finalize();
    }

    private void ensureNoOpenTransactionBeforeRunningSession()
    {
        if ( currentTransaction != null )
        {
            throw new ClientException( "Statements cannot be run directly on a session with an open transaction;" +
                                       " either run from within the transaction or use a different session." );
        }
    }

    private void ensureNoOpenTransactionBeforeOpeningTransaction()
    {
        if ( currentTransaction != null )
        {
            throw new ClientException( "You cannot begin a transaction on a session with an open transaction;" +
                                       " either run from within the transaction or use a different session." );
        }
    }

    private void ensureConnectionIsOpen()
    {
        if ( !connection.isOpen() )
        {
            throw new ClientException( "The current session cannot be reused as the underlying connection with the " +
                                       "server has been closed due to unrecoverable errors. " +
                                       "Please close this session and retry your statement in another new session." );
        }
    }
}