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Access to the Neo4j graph database through Java
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/*
 * Copyright (c) 2002-2017 "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.util;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.neo4j.driver.v1.util.Function;

public class Iterables
{
    public static int count( Iterable it )
    {
        if ( it instanceof Collection ) { return ((Collection) it).size(); }
        int size = 0;
        for ( Object o : it )
        {
            size++;
        }
        return size;
    }

    public static  List asList( Iterable it )
    {
        if ( it instanceof List ) { return (List) it; }
        List list = new ArrayList<>();
        for ( T t : it )
        {
            list.add( t );
        }
        return list;
    }

    public static  T single( Iterable it )
    {
        Iterator iterator = it.iterator();
        if ( !iterator.hasNext() )
        {
            throw new IllegalArgumentException( "Given iterable is empty" );
        }
        T result = iterator.next();
        if ( iterator.hasNext() )
        {
            throw new IllegalArgumentException( "Given iterable contains more than one element: " + it );
        }
        return result;
    }

    public static Map map( String ... alternatingKeyValue )
    {
        Map out = new HashMap<>();
        for ( int i = 0; i < alternatingKeyValue.length; i+=2 )
        {
            out.put( alternatingKeyValue[i], alternatingKeyValue[i+1] );
        }
        return out;
    }

    public static  Iterable map(final Iterable it, final Function f)
    {
        return new Iterable()
        {
            @Override
            public Iterator iterator()
            {
                final Iterator aIterator = it.iterator();
                return new Iterator()
                {
                    @Override
                    public boolean hasNext()
                    {
                        return aIterator.hasNext();
                    }

                    @Override
                    public B next()
                    {
                        return f.apply( aIterator.next() );
                    }

                    @Override
                    public void remove()
                    {
                        aIterator.remove();
                    }
                };
            }
        };
    }

    public static  Map mapValues( Map map, Function f )
    {
        HashMap transformed = new HashMap<>( map.size() );
        for ( Entry entry : map.entrySet() )
        {
            transformed.put( entry.getKey(), f.apply( entry.getValue() ) );
        }
        return transformed;
    }
}