#
#   file: triangle.py
#
#   The program draws a triangle based on three user's mouse clicks. 
#   Then it finds the perimeter of the rectangle and displays it
#   in the same graphics window, where rectangle is drawn.
#   Program uses function for finding the distance between two points.
#

from graphics import *

def main():
    win=GraphWin("Drawing a triangle",640,480)
    win.setBackground('white')

    message=Text(Point(320,20),"This program draws a triangle from three mouse clicks.")
    msg=Text(Point(320,40),"Please click a mouse in three different places inside this window.")
    message.draw(win)
    msg.draw(win)

    p1=win.getMouse() # getting first point
    p2=win.getMouse() # getting second point
    p3=win.getMouse() # getting fourth point

    tr=Polygon(p1,p2,p3) 
    tr.setOutline('blue')
    tr.setFill('yellow')
    tr.draw(win)

    P=distance(p1,p2)+distance(p2,p3)+distance(p1,p3) # finds the perimeter

    message.setText("The perimeter of the triangle is %0.2f pixels" % P)
    msg.setText("Click a mouse anywhere in this window to finish the program")
    x=win.getMouse()
    
    win.close()


# This function finds the distance between two points
def distance(p1,p2):
    import math # importing math library for the square root operation

    dx=p2.getX()-p1.getY() # dx = x2-x1
    dy=p2.getY()-p1.getY() # dy = y2-y1
    dist=math.sqrt(dx*dx+dy*dy)

    return dist

main()