//******************************************************************************
// AddEm.java:	Applet
//
//******************************************************************************
import java.applet.*;
import java.awt.*;

//=============================================================================
// Main Class for applet AddEm
//
//=============================================================================
public class AddEm extends Applet
{

	private int m_BitWidth = 8;
	// dimention used to compute following
	private Dimension m_MySize = new Dimension(0,0);
	// size of each square
	private int m_SqSize = 0 ;
	// border around each square
	private int m_SqBord = 0 ;
	// width of square plus border
	private int m_SqOfft = 0 ;
	// offset for first bit position
	private int m_SqOff0 = 0 ;
	// numbers to add
	private boolean m_In1[] ;
	private boolean	m_In2[] ;
	// the carries
	private boolean m_Carry[] ;
	// the result
	private boolean m_Sum[] ;


	private final String PARAM_BitWidth = "BitWidth";

	// AddEm Class Constructor
	//--------------------------------------------------------------------
	public AddEm()
	{

	}

	// APPLET INFO SUPPORT:
	//		The getAppletInfo() method returns a string describing the applet's
	// author, copyright date, or miscellaneous information.

	public String getAppletInfo()
	{
		return "Name: AddEm\r\n" +
		       "Author: Dean Brock\r\n" +
		       "Created with Microsoft Visual J++ Version 1.0";
	}


	public String[][] getParameterInfo()
	{
		String[][] info =
		{
			{ PARAM_BitWidth, "int", "Width of the adder" },
		};
		return info;		
	}

	public void init()
	{

		String param;
		int i;

		// BitWidth: Width of the adder
		param = getParameter(PARAM_BitWidth);
		if (param != null)
			m_BitWidth = Integer.parseInt(param);

		m_In1 = new boolean [m_BitWidth] ;
		m_In2 = new boolean [m_BitWidth] ;
		m_Sum = new boolean [m_BitWidth] ;
		m_Carry = new boolean [m_BitWidth+1] ;
		// I bet there's a better way to do this
		for (i=0; i<m_BitWidth; ++i)
		{
			m_In1[i]   = false ;
			m_In2[i]   = false ;
			m_Sum[i]   = false ;
			m_Carry[i] = false ;
		}
		m_Carry[m_BitWidth] = false ;

		resize(750, 240);

	}

	private void setBitColor(boolean b, Graphics g)
	{
		if (b)
			g.setColor(Color.red) ;
		else
			g.setColor(Color.black)	;
	}

	// AddEm Paint Handler

	public void paint(Graphics g)
	{
		int i, carpos, colpos;
		Dimension presDim = size() ;
		if (presDim != m_MySize)
		{
			m_MySize = presDim ;
			int offset = Math.min(m_MySize.width/(m_BitWidth+1),
					      m_MySize.height/4) ;
			m_SqSize = (offset*8)/9 ;
			m_SqBord = m_SqSize/8 ;
			m_SqOfft = m_SqSize+m_SqBord ;
			m_SqOff0 = m_SqOfft/2 ;
		}

		for (i=0, carpos = m_BitWidth*m_SqOfft ;
			 i<m_BitWidth ;
			 ++i, carpos -= m_SqOfft)
		{
			setBitColor(m_Carry[i], g);
			g.fillOval(carpos,          0, m_SqSize, m_SqSize) ;
			colpos = carpos - m_SqOff0 ;
			setBitColor(m_In1[i], g);
			g.fillRect(colpos,   m_SqOfft, m_SqSize, m_SqSize) ;
			setBitColor(m_In2[i], g);
			g.fillRect(colpos, 2*m_SqOfft, m_SqSize, m_SqSize) ;
			setBitColor(m_Sum[i], g);
			g.fillOval(colpos, 3*m_SqOfft, m_SqSize, m_SqSize) ;
		}
		setBitColor(m_Carry[m_BitWidth], g);
		g.fillOval(carpos, 0, m_SqSize, m_SqSize) ;
	}	

	private void recomputeOutputs()
	{
		int i;
		for (i=0; i<m_BitWidth; ++i)
		{
			m_Sum[i] = m_In1[i] != m_In2[i] != m_Carry[i] ;
			m_Carry[i+1] = (m_In1[i] && m_In2[i])
						   || (m_In1[i] && m_Carry[i])
						   || (m_In2[i] && m_Carry[i]);
		}
	}


	public boolean mouseDown(Event evt, int x, int y)
	{
		int xbitPos = (x-m_SqOff0)/m_SqOfft ;
		int xbitRem = (x-m_SqOff0)%m_SqOfft ;
		int ybitPos = y/m_SqOfft ;
		int ybitRem = y%m_SqOfft ;
		// Replace (-1 < xbitPos) with (0 <= xbitPos)
		// and the microsoft compiler does the wrong thing
		if ((-1 < xbitPos) && (xbitPos < m_BitWidth) && 
			(0 <= xbitRem) && (xbitRem < m_SqSize) &&
			(1 <= ybitPos) && (ybitPos <= 2) &&
			(0 <= ybitRem) && (ybitRem < m_SqSize) )
		{
			if (ybitPos == 1 )
				m_In1[m_BitWidth-1-xbitPos] =
				  !m_In1[m_BitWidth-1-xbitPos] ;
			else
				m_In2[m_BitWidth-1-xbitPos] =
				  !m_In2[m_BitWidth-1-xbitPos] ;
			recomputeOutputs() ;
			repaint() ;
		}
		return true;
	}


}