package jp.ac.u_ryukyu.ie.cr.shoshi.jungle.store.impl;

import java.util.Iterator;

import fj.P2;
import fj.data.Either;
import fj.data.List;

import jp.ac.u_ryukyu.ie.cr.shoshi.jungle.core.Children;
import jp.ac.u_ryukyu.ie.cr.shoshi.jungle.core.Node;
import jp.ac.u_ryukyu.ie.cr.shoshi.jungle.util.IterableWrapper;

public class DefaultChildren implements Children
{
	private final List<DefaultNode> children;
	private static final List<DefaultNode> EMPTY = List.nil();
	
	public enum Error{
		INVALID_POSITION;
	}
	
	public DefaultChildren()
	{
		this(EMPTY);
	}
	
	public DefaultChildren(List<DefaultNode> _children)
	{
		children = _children;
	}
	
	@Override
	public int size()
	{
		return children.length();
	}
	
	public DefaultChildren add(DefaultNode _newNode)
	{
		return new DefaultChildren(children.snoc(_newNode));
	}
	
	public Either<Error,DefaultChildren> insert(DefaultNode _newNode,int _pos)
	{
		if(!check(_pos)){
			return Either.left(Error.INVALID_POSITION);
		}
		
		P2<List<DefaultNode>,List<DefaultNode>> split = children.splitAt(_pos);
		List<DefaultNode> newChildren = split._1().snoc(_newNode).append(split._2());
		
		return Either.right(new DefaultChildren(newChildren));
	}
	
	public Either<Error,DefaultChildren> delete(int _pos)
	{
		if(!check(_pos)){
			return Either.left(Error.INVALID_POSITION);
		}
		
		P2<List<DefaultNode>,List<DefaultNode>> split = children.splitAt(_pos);
		List<DefaultNode> newChildren = split._1().init().append(split._2());
		
		return Either.right(new DefaultChildren(newChildren));
	}
	
	public boolean check(int _pos)
	{
		if(children.length() < _pos){
			return false;
		}
		
		return true;
	}

	@Override
	public Iterator<Node> iterator()
	{
		return (new IterableWrapper<Node>(children)).iterator();
	}
}