brainfuck

#!/usr/bin/env python
#
# rotsix - (c) wtfpl 2017
# minimal brainfuck interpreter

import sys
import getopt


def usage():
    print("./brainfuck -f|--file <file>")
    print("./brainfuck -e|--exp <expression>")
    print("./brainfuck -h|--help")


def clean(code):
    return filter(lambda x: x in ".,[]<>+-", code)


def bracemap(code):
    stack, map = [], {}
    for pos, cmd in enumerate(code):
        if cmd == "[":
            stack.append(pos)
        if cmd == "]":
            start = stack.pop()
            map[start] = pos
            map[pos] = start
    return map


def trans(code):
    code = list(clean(list(code)))
    braces = bracemap(code)

    cells, head, ptr = [0], 0, 0

    while head < len(code):
        cmd = code[head]
        if cmd == ">":
            ptr += 1
            if ptr == len(cells):
                cells.append(0)
        elif cmd == "<":
            ptr = ptr - 1 if ptr > 0 else 0
        elif cmd == "+":
            cells[ptr] = cells[ptr] + 1 if cells[ptr] < 255 else 0
        elif cmd == "-":
            cells[ptr] = cells[ptr] - 1 if cells[ptr] > 0 else 255
        elif cmd == "[" and cells[ptr] == 0:
            head = braces[head]
        elif cmd == "]" and cells[ptr] != 0:
            head = braces[head]
        elif cmd == ".":
            sys.stdout.write(chr(cells[ptr]))
        elif cmd == ",":
            # TODO
            a = 0

        head += 1


def main(args):
    try:
        opts, args = getopt.getopt(args, "f:e:h", ["file", "exp", "help"])
    except getopt.GetoptError:
        usage()
        sys.exit(1)

    for opt, arg in opts:
        if opt in ("-h", "--help"):
            usage()
            sys.exit(0)
        elif opt in ("-f", "--file"):
            with open(arg, "r") as file:
                trans(file.read())
            sys.exit(0)
        elif opt in ("-e", "--exp"):
            trans(arg)
            sys.exit(0)


if __name__ == "__main__":
    main(sys.argv[1:])