// classes defining graph arc or link structure
// author: p gray
// date: 26 june 98

import java.awt.*;

class Link {
	static int maxLinkId = 0;
	int id;
	Node nodes[] = new Node[2];
	boolean selected = false;
	
	
	Link(Node startNode, Node endNode)	{
		
		id = maxLinkId++;
		nodes[0] = startNode;
		nodes[1] = endNode;
	}
	
	// accessing
	
	public String id()	{
		return Integer.toString(id);
	}
	
	public boolean hasNode(Node node)	{
		if ((nodes[0] == node) | (nodes[1] == node))
			return(true);
		else return(false);
	}
	
	public int getID()	{
		return(id);
	}
	
	// selection methods
	public boolean isSelected()	{
		return selected;
	}
	
	public void select()	{
		selected = true;
	}
	
	public void unselect()	{
		selected = false;
	}
	
	// displaying
	public void display(Graphics g)	{
		if (selected)
			g.setColor(Color.red);
		else
			g.setColor(Color.black);
		g.drawLine(nodes[0].origX()+(nodes[0].width/2), nodes[0].origY()+(nodes[0].height/2),nodes[1].origX()+(nodes[0].width/2), nodes[1].origY()+(nodes[0].height/2));
	}
	
}