package calculator;

import java.util.Iterator;

public class VList implements Iterable{
	
	Node head;
	
	public class Node {
		int value;
		char variable;
		Node next;
		
		public Node()
		{
			value = -1;
			variable = ' ';
			next = null;
		}
		public Node( char variable, int value ) {
			this.value = value;
			this.variable = variable;
			next = null;
		}
	}
	
	public VList(){
		head = new Node();
	}
	
	public int size()
	{
		int sz = 0;
		Node currentNode = head.next;
		while( currentNode != null )
		{
			currentNode = currentNode.next;
			sz++;
		}
		return sz;
	}
	
	public void addIntNode( int value )
	{
		Node newNode = new Node(' ', value);
		newNode.next = head.next;
		head.next = newNode;
	}
	
	public Node removeNode( )
	{
		Node remove = head.next;
		if( remove != null )
			head.next = head.next.next;
		
		return remove;
	}
	
	public Node getVariableNode( char variable )
	{
		Node currentNode = head.next;
		
		while(currentNode != null && currentNode.variable != variable)
			currentNode = currentNode.next;
		
		return currentNode; 
	}
	
	public int getVariableValue( char variable ) throws undefinedVariableException 
	{
		Node varNode = getVariableNode( variable ); 
		if( varNode != null )
			return varNode.value;
		else
			throw new undefinedVariableException("Variable " + variable + " not defined.");
	}
	
	public void addVariableNode( char variable, int value )
	{
		Node varNode = getVariableNode( variable ); 
		if( varNode != null )
		{
			varNode.value = value;
		}
		else
		{
			Node newNode = new Node(variable, value);
			newNode.next = head.next;
			head.next = newNode;
		}
	}
	
	public VlistIterator iterator( )
	{
		return new VlistIterator();
	}
	
	public class VlistIterator implements Iterator{
		Node current;
		
		VlistIterator()
		{
			current = head.next;
		}

		public boolean hasNext() {
			return (current != null);
		}

		public Node next() {
			Node ret = current;
			current = current.next;
			return ret;
		}

		public void remove() {
			// Not implemented
		}
	}
}