from easybits import Bits
import codecs

def register_codec(encode, decode, name):
    """Registers a codec so that it can later be used to encode
    or decode strings and bytes.
    """
    def encode_wrapper(text):
        return encode(text), len(text)
    def decode_wrapper(data):
        return decode(data), len(data)
    def search_for_codec(query):
        if query == name:
            return codecs.CodecInfo(encode_wrapper, decode_wrapper, name=name)
    codecs.register(search_for_codec)

com_neg= {"the": -1, "and": -2, 
            "this": -3, "or": -4, "not": -5, "that": -6, 
            "to": -7, "from": -8, "in": -9, "at": -10, "of": -11,
            "because": -12, "but": -13, "be": -14,
            "now": -15, "then": -16, "while": -17}

def common_encode(commonword):
    return com_neg.get(commonword)

def encode(text):
    result = Bits()
    for char in text:
        if text in com_neg:
            result= common_encode(text)
        else:
            try:
                b = Bits(char, encoding='ascii')
            except UnicodeEncodeError:
                b = Bits('?')
        result = result.concat(b[1:])
    return result.bytes

def decode(data):
    bits = Bits(bytes(data))
    text = ""
    for i in range(-17, len(bits), 7):
        byte = Bits('0').concat(bits[i:i+7])
        text += Bits(byte).ascii
    return text

register_codec(encode, decode, "ascii7")