import iso6937
import codecs

codecs.register(lambda encoding_name: iso6937.getregentry() if
                encoding_name == 'iso6937' else
                None)


def parse_bytes(bytes_as_string):
    """Parses /x11/xab to bytearray(b'\x11\xab')
    """
    return bytearray([int(b, 16) for b in
                      bytes_as_string.split('/x') if
                      b != ''])


def read_charmap(charmap_file):
    charmap = []
    with open(charmap_file) as lines:
        in_charmap = False
        for line in lines:
            if not in_charmap and line == 'CHARMAP\n':
                in_charmap = True
                continue
            if in_charmap and line == 'END CHARMAP\n':
                in_charmap = False
                continue
            if in_charmap:
                codepoint, char, description = line[:-1].split(maxsplit=2)
                charmap.append((chr(int(codepoint[2:-1], 16)),
                                parse_bytes(char),
                                description))
    return charmap

charmap = read_charmap('ISO_6937')
for decoded, encoded, description in charmap:
    if 'NON-SPACING' in description:
        continue
    got = encoded.decode(encoding='iso6937')
    if got != decoded:
        print("Decoding {encoded} ({description}) should give {decoded}, got {got}".format(
            encoded=encoded,
            decoded=decoded,
            got=got,
            description=description))
    got = bytearray(decoded.encode(encoding='iso6937'))
    if got != encoded:
        print("Encoding {decoded} ({description}) should give {encoded}, got {got}".format(
            encoded=encoded,
            decoded=decoded,
            got=got,
            description=description))