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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.util;

import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.function.Function;

import org.neo4j.internal.helpers.collection.NumberAwareStringComparator;

import static org.neo4j.util.Preconditions.checkState;

public class Converters
{
    private Converters()
    {
    }

    public static  Function optional()
    {
        return from -> null;
    }

    private static final Comparator BY_FILE_NAME = Comparator.comparing( Path::getFileName );

    private static final Comparator BY_FILE_NAME_WITH_CLEVER_NUMBERS =
            ( o1, o2 ) -> NumberAwareStringComparator.INSTANCE.compare( o1.toAbsolutePath().toString(), o2.toAbsolutePath().toString() );

    public static Function regexFiles( final boolean cleverNumberRegexSort )
    {
        return name ->
        {
            Comparator sorting = cleverNumberRegexSort ? BY_FILE_NAME_WITH_CLEVER_NUMBERS : BY_FILE_NAME;
            List files = Validators.matchingFiles( name.trim() );
            files.sort( sorting );
            return files.toArray( new Path[0] );
        };
    }

    public static Function toFiles( final String delimiter, final Function eachFileConverter )
    {
        return from ->
        {
            if ( from == null )
            {
                return new Path[0];
            }

            String[] names = quotationAwareSplit( from, delimiter );
            List files = new ArrayList<>();
            for ( String name : names )
            {
                files.addAll( Arrays.asList( eachFileConverter.apply( name ) ) );
            }
            return files.toArray( new Path[0] );
        };
    }

    /**
     * Splits a string by the delimiter, but will not split by delimiters inside ' quatation characters. Example:
     *
     *      * The first part,'the second, but longer part',the third part
     * 
     *
     * Will be split into:
     * 
     *     The first part
     *     the second, but longer part
     *     the third part
     * 
     *
     * @param from string to be split into smaller parts.
     * @param delimiter the delimiter to split on.
     * @return an array of parts split from the provided string, where delimiters inside quoted strings will not be split.
     */
    private static String[] quotationAwareSplit( String from, String delimiter )
    {
        String[] parts = from.split( delimiter );
        List mendedParts = new ArrayList<>();
        for ( int i = 0; i < parts.length; i++ )
        {
            String part = parts[i];
            if ( part.startsWith( "'" ) )
            {
                // put back together the parts which were split by a comma, but where inside quotation
                while ( !part.endsWith( "'" ) )
                {
                    checkState( i + 1 < parts.length, "When splitting \"%s\" the inner start quote in part \"%s\" had no matching end quote", from, part );
                    part += delimiter + parts[++i];
                }
                part = part.substring( 1, part.length() - 1 ); // remove the quotation
            }
            mendedParts.add( part );
        }
        return mendedParts.toArray( new String[0] );
    }
}