import java.awt.Color;
import java.awt.Graphics;
import java.awt.Dimension;
import java.awt.Polygon;

public class Graph
{
    private double xMin;
    private double xMax;
    private double yMin;
    private double yMax;

    private Color      theColor;
    private Dimension  theSize;
    private Polygon    thePoints;

    public Graph(String fName,   Parser parser, 
                 double x1,  double x2, double y1, double y2, 
                 Color c,   Dimension d)
    {
        initGraph(x1, x2, y1, y2, c, d);

	parser.define(fName);
        parser.parse();

        int ixMax  = theSize.width;
        int iyMax  = theSize.height;
        int iSteps = theSize.width;

        double deltaX = (xMax - xMin) / iSteps;
        double x;
        double y;
        int iy;

        thePoints = new Polygon();

        for (int i=0; i <= iSteps; i++)
        {
            x = xMin + i * deltaX;
            parser.setVariable("x",x);
            y = parser.evaluate();
            if (y > yMax) 
               iy = -1;
            else if (y < yMin)
               iy = theSize.height + 1;
            else
               iy = toScreen(y,iyMax,yMax, yMin);
            thePoints.addPoint(i,iy);
        }
    }

    public Graph(String fName,   Parser parser, 
                 double x1,  double x2, double y1, double y2, 
                 int    sumStart, int sumEnd,
                 Color c,   Dimension d)
    {
        initGraph(x1, x2, y1, y2, c, d);

	parser.define(fName);
        parser.parse();

        int ixMax  = theSize.width;
        int iyMax  = theSize.height;
        int iSteps = theSize.width;

        double deltaX = (xMax - xMin) / iSteps;
        double x, y;
        int iy;

        thePoints = new Polygon();

        for (int i=0; i <= iSteps; i++)
        {
            x = xMin + i * deltaX;
            parser.setVariable("x",x);
            y = 0;
            for (int isum=sumStart; isum <= sumEnd; isum++)
            {
               parser.setVariable(2,isum);
               y += parser.evaluate();
            }
            if (y > yMax) 
               iy = -1;
            else if (y < yMin)
               iy = theSize.height + 1;
            else
               iy = toScreen(y,iyMax,yMax, yMin);
            thePoints.addPoint(i,iy);
        }
    }

    private void initGraph(double x1, double x2, double y1, double y2, 
                           Color c, Dimension d)
    {
        xMin = x1;
        xMax = x2;
        yMin = y1;
        yMax = y2;
        theColor    = c;
        theSize     = d;
    }

    public void drawAxis(Graphics g, Color c)
    {
        int ix0 = toScreen(0.0, theSize.width, xMin, xMax);
        int iy0 = toScreen(0.0, theSize.height, yMax, yMin);

        g.setColor(c);
        g.drawLine(ix0, 0, ix0, theSize.height);
        g.drawLine(0, iy0, theSize.width, iy0);
    }

    public void drawGraph(Graphics g)
    {
        g.setColor(theColor);
        g.drawPolygon(thePoints);
    }

   private int toScreen(double x, int iMax, double min, double max)
   {
      return (int)Math.round( iMax / (max - min) * (x - max) + iMax);
   }

}