fps = 30
width = 640
height = 480

import random


class Alien:
    """
       Effectivly a very simple sprite class, with it's properties
       defined in it's init code.
    """
    
    def __init__(self):
        self.alienImage = pygame.image.load('eyealien.png')
        self.alienImage.convert_alpha()
        
        self.pos = [50,50]
        self.direction = [1,1]
        
        self.velocity = [2.5, 2.5]


    def draw(self, display):
        display.blit(self.alienImage, self.pos)
        
        
    def update(self):
        """
            Update is called every frame.
            Adjust the alien't position based on it's
            velocity.
        """

        if self.pos[0] > ( width - self.alienImage.get_width() ) \
                or self.pos[0] < 0:
            self.direction[0] *= -1

        if self.pos[1] > ( height - self.alienImage.get_width() ) \
                or self.pos[1] < 0:
            self.direction[1] *= -1
        

        self.pos[0] += self.velocity[0] * self.direction[0]
        self.pos[1] += self.velocity[1] * self.direction[1]  



# Ugh, has to be global because it is initialized in a function
# and used in a different scope.
global alien

def initState():
    """
        Called by the controller, used to initialize variables
        and objects that maintain state.
    """
    global alien
    
    alien = Alien()

    

# check to see if the pygame module is in the namespace
try:
    pygame
except NameError:
    # pygame doesn't exsist, so import it.
    # this only happens once.
    import pygame
    from pygame.locals import *

    # initialize the pygame display
    pygame.init()
    pygame.display.set_mode((width,height),0,32)
    display = pygame.display.get_surface()

    # initialize the pygame clock
    clk = pygame.time.Clock()
    
    initState()

def play():
    """ Main game logic, called once per frame."""
    global alien

    # fill the display with black.  Clears the screen.
    pygame.draw.rect(display, (0,0,0,255),(0,0,width,height))


    # draw a shape.
    pygame.draw.ellipse(display, (180,40,200,255),(200,160,100,50))

    # move the alien
    alien.update()
    
    # draw the alien
    alien.draw(display)
    
    # update the display.
    pygame.display.flip()

    # check for events, and return true if we get an exit signal.
    events = pygame.event.get()
    for event in events:
        if event.type == KEYDOWN and event.key == K_r:
            # reinitialize the program state.
            initState()
        if event.type == QUIT or (event.type == KEYDOWN 
                                    and event.key == K_ESCAPE):
            return True
    
    # try to maintain a set frame rate.
    clk.tick(fps)
    
    # No exit signal was recived, so return false.
    return False