Parses the given username or channel access hash, given
    a string, username or URL. Returns a tuple consisting of
    both the stripped, lowercase username and whether it is
    a joinchat/ hash (in which case is not lowercase'd).

    Returns ``(None, False)`` if the ``username`` or link is not valid.

def parse_username(username):
    """
    Parses the given username or channel access hash, given
    a string, username or URL. Returns a tuple consisting of
    both the stripped, lowercase username and whether it is
    a joinchat/ hash (in which case is not lowercase'd).

    Returns ``(None, False)`` if the ``username`` or link is not valid.
    """
    username = username.strip()
    m = USERNAME_RE.match(username) or TG_JOIN_RE.match(username)
    if m:
        username = username[m.end():]
        is_invite = bool(m.group(1))
        if is_invite:
            return username, True
        else:
            username = username.rstrip('/')

    if VALID_USERNAME_RE.match(username):
        return username.lower(), False
    else:
        return None, False