"""Maze Gen, a scrolling terminal animation by Al Sweigart."""
import random, shutil, sys, time

DELAY = 0.04  # Pause between rows in seconds.
WIDTH = None  # None uses the terminal width.
JOIN_CHANCE = 0.5  # Chance that neighboring cells are joined.
WALL, PATH = '█', ' '

def get_width(width=None):
    result = shutil.get_terminal_size()[0] if width is None else width
    return result - 1 if sys.platform == 'win32' else result

def maze_gen(delay=DELAY, width=WIDTH):
    maze_width = max(3, (get_width(width) - 1) // 2)
    sets, next_set, first_row = list(range(maze_width)), maze_width, True
    while True:
        current_width = get_width(width); maze_width = max(3, (current_width - 1) // 2)
        while len(sets) < maze_width: sets.append(next_set); next_set += 1
        sets = sets[:maze_width]; right_walls = [True] * maze_width
        for i in range(maze_width - 1):
            if sets[i] != sets[i + 1] and random.random() < JOIN_CHANCE:
                right_walls[i] = False; old_set, new_set = sets[i + 1], sets[i]
                sets = [new_set if item == old_set else item for item in sets]
        if first_row:
            print((WALL * (maze_width * 2 + 1))[:current_width]); time.sleep(delay); first_row = False
        print((WALL + ''.join(PATH + (WALL if i == maze_width - 1 or right_walls[i] else PATH) for i in range(maze_width)))[:current_width]); time.sleep(delay)
        bottom_walls, groups = [True] * maze_width, {}
        for i, set_id in enumerate(sets): groups.setdefault(set_id, []).append(i)
        for cells in groups.values():
            opened = [cell for cell in cells if random.random() < JOIN_CHANCE]
            if not opened: opened = [random.choice(cells)]
            for cell in opened: bottom_walls[cell] = False
        print((WALL + ''.join((WALL if bottom_walls[i] else PATH) + WALL for i in range(maze_width)))[:current_width]); time.sleep(delay)
        for i in range(maze_width):
            if bottom_walls[i]: sets[i] = next_set; next_set += 1

try: maze_gen()
except KeyboardInterrupt: print('Maze Gen, by Al Sweigart al@inventwithpython.com')