# Τεκμηρίωση του Django - 1.10.7

# Πηγαίος κώδικας για το django.core.mail.message

    from __future__ import unicode_literals

    import mimetypes
    import os
    import random
    import time
    from email import (
        charset as Charset, encoders as Encoders, generator, message_from_string,
    )
    from email.header import Header
    from email.message import Message
    from email.mime.base import MIMEBase
    from email.mime.message import MIMEMessage
    from email.mime.multipart import MIMEMultipart
    from email.mime.text import MIMEText
    from email.utils import formatdate, getaddresses, parseaddr
    from io import BytesIO

    from django.conf import settings
    from django.core.mail.utils import DNS_NAME
    from django.utils import six
    from django.utils.encoding import force_text

    # Don't BASE64-encode UTF-8 messages so that we avoid unwanted attention from
    # some spam filters.
    utf8_charset = Charset.Charset('utf-8')
    utf8_charset.body_encoding = None  # Python defaults to BASE64
    utf8_charset_qp = Charset.Charset('utf-8')
    utf8_charset_qp.body_encoding = Charset.QP

    # Default MIME type to use on attachments (if it is not explicitly given
    # and cannot be guessed).
    DEFAULT_ATTACHMENT_MIME_TYPE = 'application/octet-stream'

    RFC5322_EMAIL_LINE_LENGTH_LIMIT = 998

    class BadHeaderError(ValueError):
        pass

    # Copied from Python 3.2+ standard library, with the following modifications:
    # * Used cached hostname for performance.
    # TODO: replace with email.utils.make_msgid(.., domain=DNS_NAME) when dropping
    # Python 2 (Python 2's version doesn't have domain parameter) (#23905).
    def make_msgid(idstring=None, domain=None):
        """Returns a string suitable for RFC 5322 compliant Message-ID, e.g:

        <20020201195627.33539.96671@nightshade.la.mastaler.com>

        Optional idstring if given is a string used to strengthen the
        uniqueness of the message id.  Optional domain if given provides the
        portion of the message id after the '@'.  It defaults to the locally
        defined hostname.
        """
        timeval = time.time()
        utcdate = time.strftime('%Y%m%d%H%M%S', time.gmtime(timeval))
        pid = os.getpid()
        randint = random.randrange(100000)
        if idstring is None:
            idstring = ''
        else:
            idstring = '.' + idstring
        if domain is None:
            # stdlib uses socket.getfqdn() here instead
            domain = DNS_NAME
        msgid = '<%s.%s.%s%s@%s>' % (utcdate, pid, randint, idstring, domain)
        return msgid

    # Header names that contain structured address data (RFC #5322)
    ADDRESS_HEADERS = {
        'from',
        'sender',
        'reply-to',
        'to',
        'cc',
        'bcc',
        'resent-from',
        'resent-sender',
        'resent-to',
        'resent-cc',
        'resent-bcc',
    }

    def forbid_multi_line_headers(name, val, encoding):
        """Forbids multi-line headers, to prevent header injection."""
        encoding = encoding or settings.DEFAULT_CHARSET
        val = force_text(val)
        if '\n' in val or '\r' in val:
            raise BadHeaderError("Header values can't contain newlines (got %r for header %r)" % (val, name))
        try:
            val.encode('ascii')
        except UnicodeEncodeError:
            if name.lower() in ADDRESS_HEADERS:
                val = ', '.join(sanitize_address(addr, encoding) for addr in getaddresses((val,)))
            else:
                val = Header(val, encoding).encode()
        else:
            if name.lower() == 'subject':
                val = Header(val).encode()
        return str(name), val

    def split_addr(addr, encoding):
        """
        Split the address into local part and domain, properly encoded.

        When non-ascii characters are present in the local part, it must be
        MIME-word encoded. The domain name must be idna-encoded if it contains
        non-ascii characters.
        """
        if '@' in addr:
            localpart, domain = addr.split('@', 1)
            # Try to get the simplest encoding - ascii if possible so that
            # to@example.com doesn't become =?utf-8?q?to?=@example.com. This
            # makes unit testing a bit easier and more readable.
            try:
                localpart.encode('ascii')
            except UnicodeEncodeError:
                localpart = Header(localpart, encoding).encode()
            domain = domain.encode('idna').decode('ascii')
        else:
            localpart = Header(addr, encoding).encode()
            domain = ''
        return (localpart, domain)

    def sanitize_address(addr, encoding):
        """
        Format a pair of (name, address) or an email address string.
        """
        if not isinstance(addr, tuple):
            addr = parseaddr(force_text(addr))
        nm, addr = addr
        localpart, domain = None, None
        nm = Header(nm, encoding).encode()
        try:
            addr.encode('ascii')
        except UnicodeEncodeError:  # IDN or non-ascii in the local part
            localpart, domain = split_addr(addr, encoding)

        if six.PY2:
            # On Python 2, use the stdlib since `email.headerregistry` doesn't exist.
            from email.utils import formataddr
            if localpart and domain:
                addr = '@'.join([localpart, domain])
            return formataddr((nm, addr))

        # On Python 3, an `email.headerregistry.Address` object is used since
        # email.utils.formataddr() naively encodes the name as ascii (see #25986).
        from email.headerregistry import Address
        from email.errors import InvalidHeaderDefect, NonASCIILocalPartDefect

        if localpart and domain:
            address = Address(nm, username=localpart, domain=domain)
            return str(address)

        try:
            address = Address(nm, addr_spec=addr)
        except (InvalidHeaderDefect, NonASCIILocalPartDefect):
            localpart, domain = split_addr(addr, encoding)
            address = Address(nm, username=localpart, domain=domain)
        return str(address)

    class MIMEMixin():
        def as_string(self, unixfrom=False, linesep='\n'):
            """Return the entire formatted message as a string.
            Optional `unixfrom' when True, means include the Unix From_ envelope
            header.

            This overrides the default as_string() implementation to not mangle
            lines that begin with 'From '. See bug #13433 for details.
            """
            fp = six.StringIO()
            g = generator.Generator(fp, mangle_from_=False)
            if six.PY2:
                g.flatten(self, unixfrom=unixfrom)
            else:
                g.flatten(self, unixfrom=unixfrom, linesep=linesep)
            return fp.getvalue()

        if six.PY2:
            as_bytes = as_string
        else:
            def as_bytes(self, unixfrom=False, linesep='\n'):
                """Return the entire formatted message as bytes.
                Optional `unixfrom' when True, means include the Unix From_ envelope
                header.

                This overrides the default as_bytes() implementation to not mangle
                lines that begin with 'From '. See bug #13433 for details.
                """
                fp = BytesIO()
                g = generator.BytesGenerator(fp, mangle_from_=False)
                g.flatten(self, unixfrom=unixfrom, linesep=linesep)
                return fp.getvalue()

    class SafeMIMEMessage(MIMEMixin, MIMEMessage):

        def __setitem__(self, name, val):
            # message/rfc822 attachments must be ASCII
            name, val = forbid_multi_line_headers(name, val, 'ascii')
            MIMEMessage.__setitem__(self, name, val)

    class SafeMIMEText(MIMEMixin, MIMEText):

        def __init__(self, _text, _subtype='plain', _charset=None):
            self.encoding = _charset
            if _charset == 'utf-8':
                # Unfortunately, Python < 3.5 doesn't support setting a Charset instance
                # as MIMEText init parameter (http://bugs.python.org/issue16324).
                # We do it manually and trigger re-encoding of the payload.
                MIMEText.__init__(self, _text, _subtype, None)
                del self['Content-Transfer-Encoding']
                has_long_lines = any(len(l) > RFC5322_EMAIL_LINE_LENGTH_LIMIT for l in _text.splitlines())
                # Quoted-Printable encoding has the side effect of shortening long
                # lines, if any (#22561).
                self.set_payload(_text, utf8_charset_qp if has_long_lines else utf8_charset)
                self.replace_header('Content-Type', 'text/%s; charset="%s"' % (_subtype, _charset))
            elif _charset is None:
                # the default value of '_charset' is 'us-ascii' on Python 2
                MIMEText.__init__(self, _text, _subtype)
            else:
                MIMEText.__init__(self, _text, _subtype, _charset)

        def __setitem__(self, name, val):
            name, val = forbid_multi_line_headers(name, val, self.encoding)
            MIMEText.__setitem__(self, name, val)

    class SafeMIMEMultipart(MIMEMixin, MIMEMultipart):

        def __init__(self, _subtype='mixed', boundary=None, _subparts=None, encoding=None, **_params):
            self.encoding = encoding
            MIMEMultipart.__init__(self, _subtype, boundary, _subparts, **_params)

        def __setitem__(self, name, val):
            name, val = forbid_multi_line_headers(name, val, self.encoding)
            MIMEMultipart.__setitem__(self, name, val)

    class EmailMessage(object):
        """
        A container for email information.
        """
        content_subtype = 'plain'
        mixed_subtype = 'mixed'
        encoding = None     # None => use settings default

        def __init__(self, subject='', body='', from_email=None, to=None, bcc=None,
                     connection=None, attachments=None, headers=None, cc=None,
                     reply_to=None):
            """
            Initialize a single email message (which can be sent to multiple
            recipients).

            All strings used to create the message can be unicode strings
            (or UTF-8 bytestrings). The SafeMIMEText class will handle any
            necessary encoding conversions.
            """
            if to:
                if isinstance(to, six.string_types):
                    raise TypeError('"to" argument must be a list or tuple')
                self.to = list(to)
            else:
                self.to = []
            if cc:
                if isinstance(cc, six.string_types):
                    raise TypeError('"cc" argument must be a list or tuple')
                self.cc = list(cc)
            else:
                self.cc = []
            if bcc:
                if isinstance(bcc, six.string_types):
                    raise TypeError('"bcc" argument must be a list or tuple')
                self.bcc = list(bcc)
            else:
                self.bcc = []
            if reply_to:
                if isinstance(reply_to, six.string_types):
                    raise TypeError('"reply_to" argument must be a list or tuple')
                self.reply_to = list(reply_to)
            else:
                self.reply_to = []
            self.from_email = from_email or settings.DEFAULT_FROM_EMAIL
            self.subject = subject
            self.body = body
            self.attachments = attachments or []
            self.extra_headers = headers or {}
            self.connection = connection

        def get_connection(self, fail_silently=False):
            from django.core.mail import get_connection
            if not self.connection:
                self.connection = get_connection(fail_silently=fail_silently)
            return self.connection

        def message(self):
            encoding = self.encoding or settings.DEFAULT_CHARSET
            msg = SafeMIMEText(self.body, self.content_subtype, encoding)
            msg = self._create_message(msg)
            msg['Subject'] = self.subject
            msg['From'] = self.extra_headers.get('From', self.from_email)
            msg['To'] = self.extra_headers.get('To', ', '.join(map(force_text, self.to)))
            if self.cc:
                msg['Cc'] = ', '.join(map(force_text, self.cc))
            if self.reply_to:
                msg['Reply-To'] = self.extra_headers.get('Reply-To', ', '.join(map(force_text, self.reply_to)))

            # Email header names are case-insensitive (RFC 2045), so we have to
            # accommodate that when doing comparisons.
            header_names = [key.lower() for key in self.extra_headers]
            if 'date' not in header_names:
                msg['Date'] = formatdate()
            if 'message-id' not in header_names:
                # Use cached DNS_NAME for performance
                msg['Message-ID'] = make_msgid(domain=DNS_NAME)
            for name, value in self.extra_headers.items():
                if name.lower() in ('from', 'to'):  # From and To are already handled
                    continue
                msg[name] = value
            return msg

        def recipients(self):
            """
            Returns a list of all recipients of the email (includes direct
            addressees as well as Cc and Bcc entries).
            """
            return self.to + self.cc + self.bcc

        def send(self, fail_silently=False):
            """Sends the email message."""
            if not self.recipients():
                # Don't bother creating the network connection if there's nobody to
                # send to.
                return 0
            return self.get_connection(fail_silently).send_messages([self])

        def attach(self, filename=None, content=None, mimetype=None):
            """
            Attaches a file with the given filename and content. The filename can
            be omitted and the mimetype is guessed, if not provided.

            If the first parameter is a MIMEBase subclass it is inserted directly
            into the resulting message attachments.
            """
            if isinstance(filename, MIMEBase):
                assert content is None
                assert mimetype is None
                self.attachments.append(filename)
            else:
                assert content is not None
                self.attachments.append((filename, content, mimetype))

        def attach_file(self, path, mimetype=None):
            """
            Attaches a file from the filesystem.

            The mimetype will be set to the DEFAULT_ATTACHMENT_MIME_TYPE if it is
            not specified and cannot be guessed or (PY3 only) if it suggests
            text/* for a binary file.
            """
            filename = os.path.basename(path)
            if not mimetype:
                mimetype, _ = mimetypes.guess_type(filename)
                if not mimetype:
                    mimetype = DEFAULT_ATTACHMENT_MIME_TYPE
            basetype, subtype = mimetype.split('/', 1)
            read_mode = 'r' if basetype == 'text' else 'rb'
            content = None

            with open(path, read_mode) as f:
                try:
                    content = f.read()
                except UnicodeDecodeError:
                    # If mimetype suggests the file is text but it's actually
                    # binary, read() will raise a UnicodeDecodeError on Python 3.
                    pass

            # If the previous read in text mode failed, try binary mode.
            if content is None:
                with open(path, 'rb') as f:
                    content = f.read()
                    mimetype = DEFAULT_ATTACHMENT_MIME_TYPE

            self.attach(filename, content, mimetype)

        def _create_message(self, msg):
            return self._create_attachments(msg)

        def _create_attachments(self, msg):
            if self.attachments:
                encoding = self.encoding or settings.DEFAULT_CHARSET
                body_msg = msg
                msg = SafeMIMEMultipart(_subtype=self.mixed_subtype, encoding=encoding)
                if self.body:
                    msg.attach(body_msg)
                for attachment in self.attachments:
                    if isinstance(attachment, MIMEBase):
                        msg.attach(attachment)
                    else:
                        msg.attach(self._create_attachment(*attachment))
            return msg

        def _create_mime_attachment(self, content, mimetype):
            """
            Converts the content, mimetype pair into a MIME attachment object.

            If the mimetype is message/rfc822, content may be an
            email.Message or EmailMessage object, as well as a str.
            """
            basetype, subtype = mimetype.split('/', 1)
            if basetype == 'text':
                encoding = self.encoding or settings.DEFAULT_CHARSET
                attachment = SafeMIMEText(content, subtype, encoding)
            elif basetype == 'message' and subtype == 'rfc822':
                # Bug #18967: per RFC2046 s5.2.1, message/rfc822 attachments
                # must not be base64 encoded.
                if isinstance(content, EmailMessage):
                    # convert content into an email.Message first
                    content = content.message()
                elif not isinstance(content, Message):
                    # For compatibility with existing code, parse the message
                    # into an email.Message object if it is not one already.
                    content = message_from_string(content)

                attachment = SafeMIMEMessage(content, subtype)
            else:
                # Encode non-text attachments with base64.
                attachment = MIMEBase(basetype, subtype)
                attachment.set_payload(content)
                Encoders.encode_base64(attachment)
            return attachment

        def _create_attachment(self, filename, content, mimetype=None):
            """
            Converts the filename, content, mimetype triple into a MIME attachment
            object.
            """
            if mimetype is None:
                mimetype, _ = mimetypes.guess_type(filename)
                if mimetype is None:
                    mimetype = DEFAULT_ATTACHMENT_MIME_TYPE
            attachment = self._create_mime_attachment(content, mimetype)
            if filename:
                try:
                    filename.encode('ascii')
                except UnicodeEncodeError:
                    if six.PY2:
                        filename = filename.encode('utf-8')
                    filename = ('utf-8', '', filename)
                attachment.add_header('Content-Disposition', 'attachment',
                                      filename=filename)
            return attachment

    class EmailMultiAlternatives(EmailMessage):
        """
        A version of EmailMessage that makes it easy to send multipart/alternative
        messages. For example, including text and HTML versions of the text is
        made easier.
        """
        alternative_subtype = 'alternative'

        def __init__(self, subject='', body='', from_email=None, to=None, bcc=None,
                     connection=None, attachments=None, headers=None, alternatives=None,
                     cc=None, reply_to=None):
            """
            Initialize a single email message (which can be sent to multiple
            recipients).

            All strings used to create the message can be unicode strings (or UTF-8
            bytestrings). The SafeMIMEText class will handle any necessary encoding
            conversions.
            """
            super(EmailMultiAlternatives, self).__init__(
                subject, body, from_email, to, bcc, connection, attachments,
                headers, cc, reply_to,
            )
            self.alternatives = alternatives or []

        def attach_alternative(self, content, mimetype):
            """Attach an alternative content representation."""
            assert content is not None
            assert mimetype is not None
            self.alternatives.append((content, mimetype))

        def _create_message(self, msg):
            return self._create_attachments(self._create_alternatives(msg))

        def _create_alternatives(self, msg):
            encoding = self.encoding or settings.DEFAULT_CHARSET
            if self.alternatives:
                body_msg = msg
                msg = SafeMIMEMultipart(_subtype=self.alternative_subtype, encoding=encoding)
                if self.body:
                    msg.attach(body_msg)
                for alternative in self.alternatives:
                    msg.attach(self._create_mime_attachment(*alternative))
            return msg