# https://gist.github.com/bennuttall/6952575
# modified a lot

import random, simplegui

# cells
width = 15
height = 15
scale = 9  # pixels per cell

neighbour_cells = [(-1, -1), (-1, 0), (-1, 1), (0, -1),
                   (0, 1), (1, -1), (1, 0), (1, 1)]

def evolve_cell(alive, neighbours):
    return neighbours == 3 or (alive and neighbours == 2)

def count_neighbours(grid, position):
    x,y = position
    count = 0
    for ox,oy in neighbour_cells:
      dx = x + ox
      dy = y + oy
      if True:
        # wrap
        if dx < 0: dx = dx + width
        if dx >= width: dx = dx - width
        if dy < 0: dy = dy + height
        if dy >= width: dy = dy - height
        count += grid[dx][dy]
      else:
        # no wrap
        if dx >= 0 and dx < width and dy >= 0 and dy < height:
          count += grid[dx][dy]
    return count

def make_empty_grid(x, y):
    grid = []
    for r in range(x):
        row = []
        for c in range(y):
            row.append(0)
        grid.append(row)
    return grid

def make_random_grid(x, y):
        grid = []
        for r in range(x):
            row = []
            for c in range(y):
                row.append(random.randint(0,1))
            grid.append(row)
        return grid

# use the old grid as the new one
def evolve(grid, new_grid):
    x = len(grid)
    y = len(grid[0])
    for r in range(x):
        for c in range(y):
            cell = grid[r][c]
            neighbours = count_neighbours(grid, (r, c))
            new_grid[r][c] = 1 if evolve_cell(cell, neighbours) else 0
    # store the outgoing world for next time
    return (new_grid, grid)

slowdown = 0

# Handler to draw on canvas
def draw(canvas):
  global world, oldworld
  global slowdown
  for x in range(width):
    for y in range(height):
      alive = world[x][y]
      col = 'black' if alive else 'white'
      try:
        # canvas.draw_circle(center_point, radius, line_width, line_color, fill_color)
        canvas.draw_circle([x * scale + scale//2, y * scale + scale//2], scale//2, 1, '#ccc', col)
      except Exception as e:
        # I don't get this!
        col = 'red'
        canvas.draw_circle([x * scale + scale//2, y * scale + scale//2], scale//2, 1, col, col)
  # only change the world every N steps
  slowdown += 1
  if slowdown >= 3 and enable:
    slowdown = 0
    # store the outgoing world for next time
    world, oldworld = evolve(world, oldworld)

def button_handler_stop():
  global enable
  enable = False
  label.set_text('Stopped')

def button_handler_go():
  global enable
  enable = True
  label.set_text('Running')

def mouse_handler_click(position):
  global mouse_click_new_val
  x, y = position
  x = x // scale
  y = y // scale
  # 0 <--> 1
  world[x][y] = 1 - world[x][y]
  mouse_click_new_val = world[x][y]

def mouse_handler_drag(position):
  x, y = position
  x = x // scale
  y = y // scale
  world[x][y] = mouse_click_new_val

def init():
  global world, oldworld
  global enable
  # make two arrays which we use alternately
  world = make_random_grid(width, height)
  oldworld = make_empty_grid(width, height)
  enable = False

def main():
  # Create a frame and assign callbacks to event handlers
  frame = simplegui.create_frame("Conway Life", width * scale, height * scale)
  frame.set_canvas_background('white')
  frame.set_draw_handler(draw)
  frame.set_mouseclick_handler(mouse_handler_click)
  frame.set_mousedrag_handler(mouse_handler_drag)
  frame.add_button('Stop', button_handler_stop)
  frame.add_button('Go',   button_handler_go)
  global label
  label = frame.add_label('Stopped')

  init()

  # Start the frame animation
  frame.start()

if __name__ == '__main__':
    main()