box-o-sand/onetimepad.py

import random

PAD_MODULO = 3
DEFAULT_PAD_WIDTH = 72
CIPHER_FLOOR = 1
CIPHER_CEIL = 25


def encode(msg, pad):
    return msg


def decode(msg, pad):
    return msg


def create_pad(length, width=DEFAULT_PAD_WIDTH):
    return '\n'.join(create_pad_lines(length, width=width))


def create_pad_lines(length, width=DEFAULT_PAD_WIDTH):
    chars = _create_chars_for_pad(length)
    lines = _chunk_chars_into_lines(chars, width=width)
    for line in lines:
        yield line
        yield ''
        yield ''


def _create_chars_for_pad(length):
    chars = []
    for char in range(length):
        chars.append(_AS_ALPHA[random.randint(CIPHER_FLOOR, CIPHER_CEIL)])
    return ''.join(chars)


def _chunk_chars_into_lines(chars, width=DEFAULT_PAD_WIDTH):
    lines = []
    for chunk in _as_line_chunks(chars, width=width):
        lines.append(chunk)
    return lines


def _as_line_chunks(chars, width=DEFAULT_PAD_WIDTH):
    chunk = []
    for char in chars:
        chunk.append(char)
        if len(chunk) == width:
            yield ''.join(chunk)
            chunk = []
    if len(chunk) < width:
        chunk += (['.'] * (width - len(chunk)))
    yield ''.join(chunk)


def _padfill(text, pad):
    padlines = pad.splitlines()
    textlines = _chunk_chars_into_lines(text, _get_textwidth(pad))
    for lineno, padline in enumerate(padlines[:]):
        if _is_padline(lineno) or _is_cipherline(lineno):
            continue
        else:
            padlines[lineno] = textlines.pop(0) if textlines[1:] else ''
    return padlines


def _get_textwidth(text):
    return max([len(line) for line in text.splitlines()])


def _is_padline(lineno):
    return not lineno % PAD_MODULO


def _is_txtline(lineno):
    return (lineno % 2 and not lineno % PAD_MODULO)


def _is_cipherline(lineno):
    return lineno % PAD_MODULO


def _mk_as_alpha():
    as_alpha = dict()
    a_chr = ord('A')
    past_j = False

    for char in range(CIPHER_CEIL + 1):
        letter = chr(a_chr + char)
        if letter != 'J':
            key = char + (1 if not past_j else 0)
            as_alpha[key] = letter
        else:
            past_j = True
    return as_alpha


_AS_ALPHA = _mk_as_alpha()