#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""Simple implementation of the Game of Life.

The very clever idea of using a Python set of 2-tuples for this is not
original to me.  It gives us reasonably efficient membership tests,
iteration over members, and full-board-state comparisons.

"""
import sys
import time


def show(b):
    "ANSI-art render of a board that is a set of (x, y) tuples on stdout."
    if not b:
        return

    x0 = min(x for x, y in b)
    xn = max(x for x, y in b)
    y0 = min(y for x, y in b)
    yn = max(y for x, y in b)

    sys.stdout.write('\033[H')
    for y in range(y0 - y0%8, yn+2):
        print(''.join('\033[44;34m##\033[0m' if (x, y) in b else '  '
                      for x in range(x0 - x0%8, xn+2))
              + '\033[K')  # erase-to-end-of-line ANSI escape sequence


def succ(board):
    "Calculate the successor of a Life board."
    return {pos
            for pos in {n for cell in board for n in neighborhood(*cell)}
            for t in [sum(n in board for n in neighborhood(*pos))]
            if pos in board and t in (3, 4)  # not 2,3 because center included
            or pos not in board and t == 3
    }


def neighborhood(x, y):
    "Return the coordinates of the 3×3 Moore neighborhood, including center."
    return [(x+dx, y+dy) for dx in [-1, 0, 1] for dy in [-1, 0, 1]]


def main(me, *args):
    if not args:
        sys.stderr.write("Usage: {} 1,0 2,0 0,1 1,1 1,2 # e.g.\n".format(me))
        return -1
    
    old = board = {(int(x), int(y)) for a in args for x, y in [a.split(',')]}
    t = 0
    while True:
        show(board)
        board = succ(board)
        time.sleep(.0167)

        if t % 2:  # detect infinite loops, though not gliders
            old = succ(old)
            if old == board:
                print("(and so on)")
                break
        t += 1        


if __name__ == '__main__':
    try:
        sys.exit(main(*sys.argv))
    finally:
        sys.stdout.write("\033[0m")