# 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",
]


from base64 import encodebytes as _bencode
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(b" ", b"=20")


def encode_base64(msg):
    """Encode the message's payload in Base64.

    Also, add an appropriate Content-Transfer-Encoding header.
    """
    orig = msg.get_payload(decode=True)
    encdata = str(_bencode(orig), "ascii")
    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(decode=True)
    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(decode=True)
    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/decode to ASCII
    # succeeds, we know the data must be 7bit, otherwise treat it as 8bit.
    try:
        if isinstance(orig, str):
            orig.encode("ascii")
        else:
            orig.decode("ascii")
    except UnicodeError:
        charset = msg.get_charset()
        output_cset = charset and charset.output_charset
        # iso-2022-* is non-ASCII but encodes to a 7-bit representation
        if output_cset and output_cset.lower().startswith("iso-2022-"):
            msg["Content-Transfer-Encoding"] = "7bit"
        else:
            msg["Content-Transfer-Encoding"] = "8bit"
    else:
        msg["Content-Transfer-Encoding"] = "7bit"


def encode_noop(msg):
    """Do nothing."""