#!/usr/bin/python3
"Generate mazes."
import random
import sys

# Using the heavy box-drawing characters from Unicode, stored in
# parallel arrays.

chars  = '━┃┏┓┗┛┣┫┳┻╋╸╺╹╻ '
left   = '1001010111110000'     # 1 if line touches left, 0 otherwise
right  = '1010101011101000'     # mutatis mutandis
top    = '0100111101100100'
bottom = '0111001110100010'

def render(h, v):
    for hline, upline, downline in zip(h, v[:-1], v[1:]):
        row = []
        for r, l, u, d in zip(hline[1:], hline[:-1], upline, downline):
            row.append(random.choice([c for i, c in enumerate(chars)
                                      if  l == left[i]
                                      and r == right[i]
                                      and u == top[i]
                                      and d == bottom[i]]))
        yield ''.join(row)


class UnionFind:
    def __init__(self):
        self.parent = {}

    def root(self, cell):
        descendants = []
        while self.parent.get(cell, cell) != cell:
            descendants.append(cell)
            cell = self.parent[cell]

        # We have reached the end of the chain; now snap all the
        # pointers to it.
        for descendant in descendants:
            self.parent[descendant] = cell

        return cell

    def connect(self, start, end):
        start = self.root(start)
        end = self.root(end)
        self.parent[start] = end

    def connected(self, a, b):
        return self.root(a) == self.root(b)


def genmaze(w, h):
    h, v = ([['0'] + ['1'] * w + ['0'] for i in range(h+1)],
            [['0'] * (w+1)] + [['1'] * (w+1) for i in range(h)] + [['0'] * (w+1)])
    h[0][1] = '0'               # entry
    h[-1][-2] = '0'             # exit

    walls = ([('h', r, c) for r in range(1, len(h)-1) for c in range(len(h[0]))]
             + [('v', r, c) for r in range(len(v)) for c in range(1, len(v[0])-1)])

    random.shuffle(walls)

    state = UnionFind()
    for wall in walls:
        t, r, c = wall
        cell_b = (r+1, c) if t == 'h' else (r, c+1)

        if not state.connected((r, c), cell_b):
            state.connect((r, c), cell_b)
            (h if t == 'h' else v)[r][c] = '0'

    return h, v
    

if __name__ == '__main__':
    h, v = genmaze(64, 16) if len(sys.argv) == 1 else genmaze(int(sys.argv[1]), int(sys.argv[2]))
    for line in render(h, v):
        print(line)