# Copyright (C) 2001-2006 Python Software Foundation

# Author: Ben Gertzfield, Barry Warsaw

# Contact: email-sig@python.org

__all__ = [

    'Charset',

    'add_alias',

    'add_charset',

    'add_codec',

    ]

import email.base64mime

import email.quoprimime

from email import errors

from email.encoders import encode_7or8bit

# Flags for types of header encodings

QP          = 1 # Quoted-Printable

BASE64      = 2 # Base64

SHORTEST    = 3 # the shorter of QP and base64, but only for headers

# In "=?charset?q?hello_world?=", the =?, ?q?, and ?= add up to 7

MISC_LEN = 7

DEFAULT_CHARSET = 'us-ascii'

# Defaults

CHARSETS = {

    # input        header enc  body enc output conv

    'iso-8859-1':  (QP,        QP,      None),

    'iso-8859-2':  (QP,        QP,      None),

    'iso-8859-3':  (QP,        QP,      None),

    'iso-8859-4':  (QP,        QP,      None),

    # iso-8859-5 is Cyrillic, and not especially used

    # iso-8859-6 is Arabic, also not particularly used

    # iso-8859-7 is Greek, QP will not make it readable

    # iso-8859-8 is Hebrew, QP will not make it readable

    'iso-8859-9':  (QP,        QP,      None),

    'iso-8859-10': (QP,        QP,      None),

    # iso-8859-11 is Thai, QP will not make it readable

    'iso-8859-13': (QP,        QP,      None),

    'iso-8859-14': (QP,        QP,      None),

    'iso-8859-15': (QP,        QP,      None),

    'windows-1252':(QP,        QP,      None),

    'viscii':      (QP,        QP,      None),

    'us-ascii':    (None,      None,    None),

    'big5':        (BASE64,    BASE64,  None),

    'gb2312':      (BASE64,    BASE64,  None),

    'euc-jp':      (BASE64,    None,    'iso-2022-jp'),

    'shift_jis':   (BASE64,    None,    'iso-2022-jp'),

    'iso-2022-jp': (BASE64,    None,    None),

    'koi8-r':      (BASE64,    BASE64,  None),

    'utf-8':       (SHORTEST,  BASE64, 'utf-8'),

    # We're making this one up to represent raw unencoded 8-bit

    '8bit':        (None,      BASE64, 'utf-8'),

    }

# Aliases for other commonly-used names for character sets.  Map

# them to the real ones used in email.

ALIASES = {

    'latin_1': 'iso-8859-1',

    'latin-1': 'iso-8859-1',

    'latin_2': 'iso-8859-2',

    'latin-2': 'iso-8859-2',

    'latin_3': 'iso-8859-3',

    'latin-3': 'iso-8859-3',

    'latin_4': 'iso-8859-4',

    'latin-4': 'iso-8859-4',

    'latin_5': 'iso-8859-9',

    'latin-5': 'iso-8859-9',

    'latin_6': 'iso-8859-10',

    'latin-6': 'iso-8859-10',

    'latin_7': 'iso-8859-13',

    'latin-7': 'iso-8859-13',

    'latin_8': 'iso-8859-14',

    'latin-8': 'iso-8859-14',

    'latin_9': 'iso-8859-15',

    'latin-9': 'iso-8859-15',

    'cp949':   'ks_c_5601-1987',

    'euc_jp':  'euc-jp',

    'euc_kr':  'euc-kr',

    'ascii':   'us-ascii',

    }

# Map charsets to their Unicode codec strings.

CODEC_MAP = {

    'gb2312':      'eucgb2312_cn',

    'big5':        'big5_tw',

    # Hack: We don't want *any* conversion for stuff marked us-ascii, as all

    # sorts of garbage might be sent to us in the guise of 7-bit us-ascii.

    # Let that stuff pass through without conversion to/from Unicode.

    'us-ascii':    None,

    }

# Convenience functions for extending the above mappings

def add_charset(charset, header_enc=None, body_enc=None, output_charset=None):

    """Add character set properties to the global registry.

    charset is the input character set, and must be the canonical name of a

    character set.

    Optional header_enc and body_enc is either Charset.QP for

    quoted-printable, Charset.BASE64 for base64 encoding, Charset.SHORTEST for

    the shortest of qp or base64 encoding, or None for no encoding.  SHORTEST

    is only valid for header_enc.  It describes how message headers and

    message bodies in the input charset are to be encoded.  Default is no

    encoding.

    Optional output_charset is the character set that the output should be

    in.  Conversions will proceed from input charset, to Unicode, to the

    output charset when the method Charset.convert() is called.  The default

    is to output in the same character set as the input.

    Both input_charset and output_charset must have Unicode codec entries in

    the module's charset-to-codec mapping; use add_codec(charset, codecname)

    to add codecs the module does not know about.  See the codecs module's

    documentation for more information.

    """

    if body_enc == SHORTEST:

        raise ValueError('SHORTEST not allowed for body_enc')

    CHARSETS[charset] = (header_enc, body_enc, output_charset)

def add_alias(alias, canonical):

    """Add a character set alias.

    alias is the alias name, e.g. latin-1

    canonical is the character set's canonical name, e.g. iso-8859-1

    """

    ALIASES[alias] = canonical

def add_codec(charset, codecname):

    """Add a codec that map characters in the given charset to/from Unicode.

    charset is the canonical name of a character set.  codecname is the name

    of a Python codec, as appropriate for the second argument to the unicode()

    built-in, or to the encode() method of a Unicode string.

    """

    CODEC_MAP[charset] = codecname

class Charset:

    """Map character sets to their email properties.

    This class provides information about the requirements imposed on email

    for a specific character set.  It also provides convenience routines for

    converting between character sets, given the availability of the

    applicable codecs.  Given a character set, it will do its best to provide

    information on how to use that character set in an email in an

    RFC-compliant way.

    Certain character sets must be encoded with quoted-printable or base64

    when used in email headers or bodies.  Certain character sets must be

    converted outright, and are not allowed in email.  Instances of this

    module expose the following information about a character set:

    input_charset: The initial character set specified.  Common aliases

                   are converted to their `official' email names (e.g. latin_1

                   is converted to iso-8859-1).  Defaults to 7-bit us-ascii.

    header_encoding: If the character set must be encoded before it can be

                     used in an email header, this attribute will be set to

                     Charset.QP (for quoted-printable), Charset.BASE64 (for

                     base64 encoding), or Charset.SHORTEST for the shortest of

                     QP or BASE64 encoding.  Otherwise, it will be None.

    body_encoding: Same as header_encoding, but describes the encoding for the

                   mail message's body, which indeed may be different than the

                   header encoding.  Charset.SHORTEST is not allowed for

                   body_encoding.

    output_charset: Some character sets must be converted before the can be

                    used in email headers or bodies.  If the input_charset is

                    one of them, this attribute will contain the name of the

                    charset output will be converted to.  Otherwise, it will

                    be None.

    input_codec: The name of the Python codec used to convert the

                 input_charset to Unicode.  If no conversion codec is

                 necessary, this attribute will be None.

    output_codec: The name of the Python codec used to convert Unicode

                  to the output_charset.  If no conversion codec is necessary,

                  this attribute will have the same value as the input_codec.

    """

    def __init__(self, input_charset=DEFAULT_CHARSET):

        # RFC 2046, $4.1.2 says charsets are not case sensitive.  We coerce to

        # unicode because its .lower() is locale insensitive.  If the argument

        # is already a unicode, we leave it at that, but ensure that the

        # charset is ASCII, as the standard (RFC XXX) requires.

        try:

            if isinstance(input_charset, unicode):

                input_charset.encode('ascii')

            else:

                input_charset = unicode(input_charset, 'ascii')

        except UnicodeError:

            raise errors.CharsetError(input_charset)

        input_charset = input_charset.lower()

        # Set the input charset after filtering through the aliases

        self.input_charset = ALIASES.get(input_charset, input_charset)

        # We can try to guess which encoding and conversion to use by the

        # charset_map dictionary.  Try that first, but let the user override

        # it.

        henc, benc, conv = CHARSETS.get(self.input_charset,

                                        (SHORTEST, BASE64, None))

        if not conv:

            conv = self.input_charset

        # Set the attributes, allowing the arguments to override the default.

        self.header_encoding = henc

        self.body_encoding = benc

        self.output_charset = ALIASES.get(conv, conv)

        # Now set the codecs.  If one isn't defined for input_charset,

        # guess and try a Unicode codec with the same name as input_codec.

        self.input_codec = CODEC_MAP.get(self.input_charset,

                                         self.input_charset)

        self.output_codec = CODEC_MAP.get(self.output_charset,

                                          self.output_charset)

    def __str__(self):

        return self.input_charset.lower()

    __repr__ = __str__

    def __eq__(self, other):

        return str(self) == str(other).lower()

    def __ne__(self, other):

        return not self.__eq__(other)

    def get_body_encoding(self):

        """Return the content-transfer-encoding used for body encoding.

        This is either the string `quoted-printable' or `base64' depending on

        the encoding used, or it is a function in which case you should call

        the function with a single argument, the Message object being

        encoded.  The function should then set the Content-Transfer-Encoding

        header itself to whatever is appropriate.

        Returns "quoted-printable" if self.body_encoding is QP.

        Returns "base64" if self.body_encoding is BASE64.

        Returns "7bit" otherwise.

        """

        assert self.body_encoding <> SHORTEST

        if self.body_encoding == QP:

            return 'quoted-printable'

        elif self.body_encoding == BASE64:

            return 'base64'

        else:

            return encode_7or8bit

    def convert(self, s):

        """Convert a string from the input_codec to the output_codec."""

        if self.input_codec <> self.output_codec:

            return unicode(s, self.input_codec).encode(self.output_codec)

        else:

            return s

    def to_splittable(self, s):

        """Convert a possibly multibyte string to a safely splittable format.

        Uses the input_codec to try and convert the string to Unicode, so it

        can be safely split on character boundaries (even for multibyte

        characters).

        Returns the string as-is if it isn't known how to convert it to

        Unicode with the input_charset.

        Characters that could not be converted to Unicode will be replaced

        with the Unicode replacement character U+FFFD.

        """

        if isinstance(s, unicode) or self.input_codec is None:

            return s

        try:

            return unicode(s, self.input_codec, 'replace')

        except LookupError:

            # Input codec not installed on system, so return the original

            # string unchanged.

            return s

    def from_splittable(self, ustr, to_output=True):

        """Convert a splittable string back into an encoded string.

        Uses the proper codec to try and convert the string from Unicode back

        into an encoded format.  Return the string as-is if it is not Unicode,

        or if it could not be converted from Unicode.

        Characters that could not be converted from Unicode will be replaced

        with an appropriate character (usually '?').

        If to_output is True (the default), uses output_codec to convert to an

        encoded format.  If to_output is False, uses input_codec.

        """

        if to_output:

            codec = self.output_codec

        else:

            codec = self.input_codec

        if not isinstance(ustr, unicode) or codec is None:

            return ustr

        try:

            return ustr.encode(codec, 'replace')

        except LookupError:

            # Output codec not installed

            return ustr

    def get_output_charset(self):

        """Return the output character set.

        This is self.output_charset if that is not None, otherwise it is

        self.input_charset.

        """

        return self.output_charset or self.input_charset

    def encoded_header_len(self, s):

        """Return the length of the encoded header string."""

        cset = self.get_output_charset()

        # The len(s) of a 7bit encoding is len(s)

        if self.header_encoding == BASE64:

            return email.base64mime.base64_len(s) + len(cset) + MISC_LEN

        elif self.header_encoding == QP:

            return email.quoprimime.header_quopri_len(s) + len(cset) + MISC_LEN

        elif self.header_encoding == SHORTEST:

            lenb64 = email.base64mime.base64_len(s)

            lenqp = email.quoprimime.header_quopri_len(s)

            return min(lenb64, lenqp) + len(cset) + MISC_LEN

        else:

            return len(s)

    def header_encode(self, s, convert=False):

        """Header-encode a string, optionally converting it to output_charset.

        If convert is True, the string will be converted from the input

        charset to the output charset automatically.  This is not useful for

        multibyte character sets, which have line length issues (multibyte

        characters must be split on a character, not a byte boundary); use the

        high-level Header class to deal with these issues.  convert defaults

        to False.

        The type of encoding (base64 or quoted-printable) will be based on

        self.header_encoding.

        """

        cset = self.get_output_charset()

        if convert:

            s = self.convert(s)

        # 7bit/8bit encodings return the string unchanged (modulo conversions)

        if self.header_encoding == BASE64:

            return email.base64mime.header_encode(s, cset)

        elif self.header_encoding == QP:

            return email.quoprimime.header_encode(s, cset, maxlinelen=None)

        elif self.header_encoding == SHORTEST:

            lenb64 = email.base64mime.base64_len(s)

            lenqp = email.quoprimime.header_quopri_len(s)

            if lenb64 < lenqp:

                return email.base64mime.header_encode(s, cset)

            else:

                return email.quoprimime.header_encode(s, cset, maxlinelen=None)

        else:

            return s

    def body_encode(self, s, convert=True):

        """Body-encode a string and convert it to output_charset.

        If convert is True (the default), the string will be converted from

        the input charset to output charset automatically.  Unlike

        header_encode(), there are no issues with byte boundaries and

        multibyte charsets in email bodies, so this is usually pretty safe.

        The type of encoding (base64 or quoted-printable) will be based on

        self.body_encoding.

        """

        if convert:

            s = self.convert(s)

        # 7bit/8bit encodings return the string unchanged (module conversions)

        if self.body_encoding is BASE64:

            return email.base64mime.body_encode(s)

        elif self.body_encoding is QP:

            return email.quoprimime.body_encode(s)

        else:

            return s