package com.planet_ink.coffee_mud.core.collections;
import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.Vector;
/*
   Copyright 2012-2020 Bo Zimmerman

   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.
*/
public class FilteredListIterator<K> implements ListIterator<K>
{
	private final ListIterator<K>  iter;
	private Filterer<K> 	filterer;
	private K 				nextElement = null;
	private K 				prevElement = null;
	private boolean 		initialized = false;

	public FilteredListIterator(final ListIterator<K> eset, final Filterer<K> fil)
	{
		iter=eset;
		filterer=fil;
	}

	public void setFilterer(final Filterer<K> fil)
	{
		filterer=fil;
	}

	private void stageNextElement()
	{
		prevElement=nextElement;
		nextElement = null;
		while((nextElement==null) && (iter.hasNext()))
		{
			nextElement = iter.next();
			if(filterer.passesFilter(nextElement))
				return;
			nextElement = null;
		}
	}

	private void stagePrevElement()
	{
		nextElement=prevElement;
		prevElement = null;
		while((prevElement==null) && (iter.hasPrevious()))
		{
			prevElement = iter.previous();
			if(filterer.passesFilter(prevElement))
				return;
			prevElement = null;
		}
	}

	private void initialize()
	{
		if(!initialized)
		{
			stageNextElement();
			stagePrevElement();
			initialized=true;
		}
	}

	@Override
	public boolean hasNext()
	{
		if(!initialized)
			initialize();
		return nextElement!=null;
	}

	@Override
	public K next()
	{
		if(!hasNext())
			throw new NoSuchElementException();
		final K element = nextElement;
		stageNextElement();
		return element;
	}

	@Override
	public void remove()
	{
		throw new java.lang.IllegalArgumentException();
	}

	@Override
	public void add(final K e)
	{
		throw new java.lang.IllegalArgumentException();
	}

	@Override
	public boolean hasPrevious()
	{
		if(!initialized)
			initialize();
		return prevElement!=null;
	}

	@Override
	public int nextIndex()
	{
		throw new java.lang.IllegalArgumentException();
	}

	@Override
	public K previous()
	{
		if(!hasPrevious())
			throw new NoSuchElementException();
		final K element = prevElement;
		stagePrevElement();
		return element;
	}

	@Override
	public int previousIndex()
	{
		throw new java.lang.IllegalArgumentException();
	}

	@Override
	public void set(final K e)
	{
		throw new java.lang.IllegalArgumentException();
	}
}
