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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.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.AbstractQueue;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Queue;

import java.util.function.Function;

public class Iterables
{
    @SuppressWarnings( "rawtypes" )
    private static final Queue EMPTY_QUEUE = new EmptyQueue();
    private static final float DEFAULT_HASH_MAP_LOAD_FACTOR = 0.75F;

    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 = newHashMapWithSize( alternatingKeyValue.length / 2 );
        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();
                    }
                };
            }
        };
    }

    @SuppressWarnings( "unchecked" )
    public static  Queue emptyQueue()
    {
        return (Queue) EMPTY_QUEUE;
    }

    public static  HashMap newHashMapWithSize( int expectedSize )
    {
        return new HashMap<>( hashMapCapacity( expectedSize ) );
    }

    public static  LinkedHashMap newLinkedHashMapWithSize( int expectedSize )
    {
        return new LinkedHashMap<>( hashMapCapacity( expectedSize ) );
    }

    private static int hashMapCapacity( int expectedSize )
    {
        if ( expectedSize < 3 )
        {
            if ( expectedSize < 0 )
            {
                throw new IllegalArgumentException( "Illegal map size: " + expectedSize );
            }
            return expectedSize + 1;
        }
        return (int) ((float) expectedSize / DEFAULT_HASH_MAP_LOAD_FACTOR + 1.0F);
    }

    private static class EmptyQueue extends AbstractQueue
    {
        @Override
        public Iterator iterator()
        {
            return Collections.emptyIterator();
        }

        @Override
        public int size()
        {
            return 0;
        }

        @Override
        public boolean offer( T t )
        {
            throw new UnsupportedOperationException();
        }

        @Override
        public T poll()
        {
            return null;
        }

        @Override
        public T peek()
        {
            return null;
        }
    }
}