#!/usr/bin/env python
# coding: utf-8

# # Conway's Game of Life
# 
# This is a (slightly) modified version of [Glowing Python](# http://glowingpython.blogspot.co.il/2015/10/game-of-life-with-python.html
# )'s code. I make it available here because it features a few nice things:
# 
# * how to make a movie using matplotlib.animation
# * how to write a generator (function with yield)
# * how to plot a sparce array (```spy```)
# 
# See the result on my website, [yairmau.com](yairmau.com), specifically the page [/tutorials/python](yairmau.com/tutorials/python).

# In[1]:


import numpy as np
from matplotlib import pyplot as plt
import matplotlib.animation as manimation


def life(X, steps):
    """
     Conway's Game of Life.
     - X, matrix with the initial state of the game.
     - steps, number of generations.
    """
    def roll_it(x, y):
        # rolls the matrix X in a given direction
        # x=1, y=0 left;  x=-1, y=0 right;
        return np.roll(np.roll(X, y, axis=0), x, axis=1)

    for _ in range(steps):
        # count the number of neighbours
        # the universe is considered toroidal
        Y = roll_it(1, 0) + roll_it(0, 1) + \
            roll_it(-1, 0) + roll_it(0, -1) + \
            roll_it(1, 1) + roll_it(-1, -1) + \
            roll_it(1, -1) + roll_it(-1, 1)
        # game of life rules
        X = np.logical_or(np.logical_and(X, Y == 2), Y == 3)
        X = X.astype(int)
        yield X


# In[2]:


dimensions = (90, 160)  # height, width
X = np.zeros(dimensions)  # Y by X dead cells
middle_y = dimensions[0] / 2
middle_x = dimensions[1] / 2

N_iterations = 600

# acorn initial condition
# http://www.conwaylife.com/w/index.php?title=Acorn
X[middle_y, middle_x:middle_x+2] = 1
X[middle_y, middle_x+4:middle_x+7] = 1
X[middle_y+1, middle_x+3] = 1
X[middle_y+2, middle_x+1] = 1


# In[3]:


FFMpegWriter = manimation.writers['ffmpeg']
metadata = dict(title='Game of life', artist='Acorn initial condition')
writer = FFMpegWriter(fps=10, metadata=metadata)

fig = plt.figure()
fig.patch.set_facecolor('black')
with writer.saving(fig, "game_of_life.mp4", 300):  # last argument: dpi
    plt.spy(X, origin='lower')
    plt.axis('off')
    writer.grab_frame()
    plt.clf()
    for i, x in enumerate(life(X, N_iterations)):
        plt.title("iteration: {:03d}".format(i + 1))
        plt.spy(x, origin='lower')
        plt.axis('off')
        writer.grab_frame()
        plt.clf()