# -*- coding: utf-8 -*-


from email import policy
from email import _header_value_parser as parser


subjects = [
    '我只是一个有那么一点点长的主题而已',           # not crash
    'Re: 我只是一个有那么一点点长的主题而已',       # crash
    '回复: 回复:【北京大学-2017年招生信息公告】',   # crash
]


for sub in subjects:
    print('-'* 50)
    print('subject:', sub)
    parse_tree = parser.get_unstructured(sub)
    print('parse tree:', repr(parse_tree))

    header = parser.Header([
        parser.HeaderLabel([
            parser.ValueTerminal('Subject', 'header-name'),
            parser.ValueTerminal(':', 'header-sep')]),
        parser.CFWSList([parser.WhiteSpaceTerminal(' ', 'fws')]),
                         parse_tree])

    try:
        folded = header.fold(policy=policy.default)
    except Exception as e:
        print('crashed: ', e)
    else:
        print('folded:', folded)