# Copyright (C) 2001-2006 Python Software Foundation

# Author: Barry Warsaw

# Contact: email-sig@python.org

"""Encodings and related functions."""

__all__ = [

    'encode_7or8bit',

    'encode_base64',

    'encode_noop',

    'encode_quopri',

    ]

import base64

from quopri import encodestring as _encodestring

def _qencode(s):

    enc = _encodestring(s, quotetabs=True)

    # Must encode spaces, which quopri.encodestring() doesn't do

    return enc.replace(' ', '=20')

def _bencode(s):

    # We can't quite use base64.encodestring() since it tacks on a "courtesy

    # newline".  Blech!

    if not s:

        return s

    hasnewline = (s[-1] == '\n')

    value = base64.encodestring(s)

    if not hasnewline and value[-1] == '\n':

        return value[:-1]

    return value

def encode_base64(msg):

    """Encode the message's payload in Base64.

    Also, add an appropriate Content-Transfer-Encoding header.

    """

    orig = msg.get_payload()

    encdata = _bencode(orig)

    msg.set_payload(encdata)

    msg['Content-Transfer-Encoding'] = 'base64'

def encode_quopri(msg):

    """Encode the message's payload in quoted-printable.

    Also, add an appropriate Content-Transfer-Encoding header.

    """

    orig = msg.get_payload()

    encdata = _qencode(orig)

    msg.set_payload(encdata)

    msg['Content-Transfer-Encoding'] = 'quoted-printable'

def encode_7or8bit(msg):

    """Set the Content-Transfer-Encoding header to 7bit or 8bit."""

    orig = msg.get_payload()

    if orig is None:

        # There's no payload.  For backwards compatibility we use 7bit

        msg['Content-Transfer-Encoding'] = '7bit'

        return

    # We play a trick to make this go fast.  If encoding to ASCII succeeds, we

    # know the data must be 7bit, otherwise treat it as 8bit.

    try:

        orig.encode('ascii')

    except UnicodeError:

        # iso-2022-* is non-ASCII but still 7-bit

        charset = msg.get_charset()

        output_cset = charset and charset.output_charset

        if output_cset and output_cset.lower().startswith('iso-2202-'):

            msg['Content-Transfer-Encoding'] = '7bit'

        else:

            msg['Content-Transfer-Encoding'] = '8bit'

    else:

        msg['Content-Transfer-Encoding'] = '7bit'

def encode_noop(msg):

    """Do nothing."""