import java.awt.geom.Point2D;

/**
 * Provides CS 160, Lab 4 functionality for the Triangle class.
 * 
 * @author John Paxton 
 * @version October 1, 2008
 */

public class Triangle
{
    /**
     * Create a triangle from 3 points.
     * @param p1 the first point
     * @param p2 the second point
     * @param p3 the third point
     */
    
    Triangle (Point2D.Double p1, Point2D.Double p2, Point2D.Double p3)
    {
        point1 = p1;
        point2 = p2;
        point3 = p3;
    }
    
    /**
     * Calculate and return the perimeter of a triangle
     * @return the perimeter of a triangle
     */
    
    public double getPerimeter()
    {   
        return getLineLength(point1, point2) + getLineLength(point2, point3) +
               getLineLength(point3, point1);
    }
    
    /**
     * Calculate the area of a triangle using Heron's rule.
     * @return the area of a triangle
     */
    
    public double getArea()
    {
        double s = getPerimeter() / 2;
        
        return Math.sqrt(s * (s - getLineLength(point1, point2)) *
            (s - getLineLength(point2, point3)) * (s - getLineLength(point3, point1)));
    }
    
    /**
     * Calculate and return the length of a line between two points
     * @param point1 the first point
     * @param point2 the second point
     * @return the distance between the two points
     */
    
    private double getLineLength(Point2D.Double point1, Point2D.Double point2)
    {
        double x1 = point1.getX();
        double y1 = point1.getY();
        double x2 = point2.getX();
        double y2 = point2.getY();
        
        return Math.sqrt( (x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1) );
    }
    
    private Point2D.Double point1;      // first point of triangle
    private Point2D.Double point2;      // second point of triangle
    private Point2D.Double point3;      // third point of triangle
}