from email import policy
from email.parser import BytesParser

original_msg = b'Date: Fri, 09 Apr 2021 00:00:00 -0000\nFrom: First Last <first.last@example.tld>\nTo: "John Doe (Company)" <jdoe@example.tld>\nSubject: Multi-Part Message\nMessage-ID: <abc123@hostname>\nReply-To: First Last <first.last@example.tld>\nMIME-Version: 1.0\nContent-Type: multipart/mixed; boundary===--12345--12345--12345--==\n\n\n--==--12345--12345--12345--==\nContent-type: text/plain; name="attachment-1"\n\nContents of attachment #1 with just plain ascii text\n--==--12345--12345--12345--==\nContent-type: text/plain; name="attachment-2"\n\nContents of attachment #2 which contains utf-8 encoded text such as \xc3\xa9\n--==--12345--12345--12345--==--\n'

my_8bit_policy = policy.default.clone(cte_type='8bit', utf8=True, refold_source='none')
my_7bit_policy = policy.default.clone(cte_type='7bit', utf8=False, refold_source='none')
policies = [my_8bit_policy, my_7bit_policy]
my_parser = BytesParser(policy=my_8bit_policy)

def print_sep(label=None):
    if label is not None:
        print(' {} '.format(label).center(70, '-'))
    else:
        print('{}'.format('-'*70))

def run_test(msg, policies):
    for p in policies:
        print("Convert message using as_bytes() with policy: ", p)
        try: 
            _ = msg.as_bytes(policy=p)
            print("Success")
        except Exception as err:
            print("Failed - Exception:", err)

msg = my_parser.parsebytes(original_msg)

print_sep("Original Message")
print(original_msg.decode('utf-8'))
print_sep("Original 'as_string()'")
print(msg.as_string())
print_sep("Additional observations")
print("List of defects in original message: ", msg.defects)
print("Any 'preamble': ", msg.preamble)
print_sep("Test #1: Running as_bytes() test on original message")
print("Boundary: ", msg.get_boundary())
run_test(msg, policies)
print_sep("Test #2: Correcting boundary and re-running test")
msg.set_boundary('==--12345--12345--12345--==')
print("Boundary: ", msg.get_boundary())
run_test(msg, policies)

print_sep("Test #3: Re-parsing corrected boundary and re-running test")
new_msg = original_msg.replace(b'boundary===--12345--12345--12345--==', b'boundary="==--12345--12345--12345--=="')
msg = my_parser.parsebytes(new_msg)
print("Boundary: ", msg.get_boundary())
run_test(msg, policies)

print_sep("Test #4: What would happen if original was not multipart?")
simple_msg = new_msg.replace(b'Content-Type: multipart/mixed; boundary="==--12345--12345--12345--=="', b'Content-Type: text/plain;')
msg = my_parser.parsebytes(simple_msg)
run_test(msg, policies)

print_sep("Test #5: Fully correcting original messsage")
corrected_msg = new_msg.replace(b'Content-type: text/plain; name="attachment-2"', b'Content-type: text/plain; charset=utf-8; name="attachment-2"\nContent-Transfer-Encoding: 8bit')
msg = my_parser.parsebytes(corrected_msg)
run_test(msg, policies)