"""Sending Roundup-specific mail over SMTP.
"""
__docformat__ = 'restructuredtext'

import time, quopri, os, socket, smtplib, re, sys, traceback, email

from cStringIO import StringIO

from roundup import __version__
from roundup.date import get_timezone, Date

from email.Utils import formatdate, formataddr, specialsre, escapesre
from email.Message import Message
from email.Header import Header
from email.MIMEBase import MIMEBase
from email.MIMEText import MIMEText
from email.MIMEMultipart import MIMEMultipart

try:
    import pyme, pyme.core
except ImportError:
    pyme = None


class MessageSendError(RuntimeError):
    pass

def encode_quopri(msg):
    orig = msg.get_payload()
    encdata = quopri.encodestring(orig)
    msg.set_payload(encdata)
    del msg['Content-Transfer-Encoding']
    msg['Content-Transfer-Encoding'] = 'quoted-printable'

def nice_sender_header(name, address, charset):
    # construct an address header so it's as human-readable as possible
    # even in the presence of a non-ASCII name part
    if not name:
        return address
    try:
        encname = name.encode('ASCII')
    except UnicodeEncodeError:
        # use Header to encode correctly.
        encname = Header(name, charset=charset).encode()

    # the important bits of formataddr()
    if specialsre.search(encname):
        encname = '"%s"'%escapesre.sub(r'\\\g<0>', encname)

    # now format the header as a string - don't return a Header as anonymous
    # headers play poorly with Messages (eg. won't get wrapped properly)
    return '%s <%s>'%(encname, address)

class Mailer:
    """Roundup-specific mail sending."""
    def __init__(self, config):
        self.config = config

        # set to indicate to roundup not to actually _send_ email
        # this var must contain a file to write the mail to
        self.debug = os.environ.get('SENDMAILDEBUG', '') \
            or config["MAIL_DEBUG"]

        # set timezone so that things like formatdate(localtime=True)
        # use the configured timezone
        # apparently tzset doesn't exist in python under Windows, my bad.
        # my pathetic attempts at googling a Windows-solution failed
        # so if you're on Windows your mail won't use your configured
        # timezone.
        if hasattr(time, 'tzset'):
            os.environ['TZ'] = get_timezone(self.config.TIMEZONE).tzname(None)
            time.tzset()

    def set_message_attributes(self, message, to, subject, author=None):
        ''' Add attributes to a standard output message
        "to"      - recipients list
        "subject" - Subject
        "author"  - (name, address) tuple or None for admin email

        Subject and author are encoded using the EMAIL_CHARSET from the
        config (default UTF-8).
        '''
        # encode header values if they need to be
        charset = getattr(self.config, 'EMAIL_CHARSET', 'utf-8')
        tracker_name = unicode(self.config.TRACKER_NAME, 'utf-8')
        if not author:
            author = (tracker_name, self.config.ADMIN_EMAIL)
            name = author[0]
        else:
            name = unicode(author[0], 'utf-8')
        author = nice_sender_header(name, author[1], charset)
        try:
            message['Subject'] = subject.encode('ascii')
        except UnicodeError:
            message['Subject'] = Header(subject, charset)
        message['To'] = ', '.join(to)
        message['From'] = author
        message['Date'] = formatdate(localtime=True)

        # add a Precedence header so autoresponders ignore us
        message['Precedence'] = 'bulk'

        # Add a unique Roundup header to help filtering
        try:
            message['X-Roundup-Name'] = tracker_name.encode('ascii')
        except UnicodeError:
            message['X-Roundup-Name'] = Header(tracker_name, charset)

        # and another one to avoid loops
        message['X-Roundup-Loop'] = 'hello'
        # finally, an aid to debugging problems
        message['X-Roundup-Version'] = __version__

    def get_standard_message(self, multipart=False):
        '''Form a standard email message from Roundup.
        Returns a Message object.
        '''
        charset = getattr(self.config, 'EMAIL_CHARSET', 'utf-8')
        if multipart:
            message = MIMEMultipart()
        else:
            message = MIMEText("")
            message.set_charset(charset)

        return message

    def standard_message(self, to, subject, content, author=None):
        """Send a standard message.

        Arguments:
        - to: a list of addresses usable by rfc822.parseaddr().
        - subject: the subject as a string.
        - content: the body of the message as a string.
        - author: the sender as a (name, address) tuple

        All strings are assumed to be UTF-8 encoded.
        """
        message = self.get_standard_message()
        self.set_message_attributes(message, to, subject, author)
        message.set_payload(content)
        encode_quopri(message)
        self.smtp_send(to, message.as_string())

    def bounce_message(self, bounced_message, to, error,
                       subject='Failed issue tracker submission', crypt=False):
        """Bounce a message, attaching the failed submission.

        Arguments:
        - bounced_message: an RFC822 Message object.
        - to: a list of addresses usable by rfc822.parseaddr(). Might be
          extended or overridden according to the config
          ERROR_MESSAGES_TO setting.
        - error: the reason of failure as a string.
        - subject: the subject as a string.
        - crypt: require encryption with pgp for user -- applies only to
          mail sent back to the user, not the dispatcher oder admin.

        """
        crypt_to = None
        if crypt:
            crypt_to = to
            to = None
        # see whether we should send to the dispatcher or not
        dispatcher_email = getattr(self.config, "DISPATCHER_EMAIL",
            getattr(self.config, "ADMIN_EMAIL"))
        error_messages_to = getattr(self.config, "ERROR_MESSAGES_TO", "user")
        if error_messages_to == "dispatcher":
            to = [dispatcher_email]
            crypt = False
            crypt_to = None
        elif error_messages_to == "both":
            if crypt:
                to = [dispatcher_email]
            else:
                to.append(dispatcher_email)

        message = self.get_standard_message(multipart=True)

        # add the error text
        part = MIMEText('\n'.join(error))
        message.attach(part)

        # attach the original message to the returned message
        body = []
        for header in bounced_message.headers:
            body.append(header)
        try:
            bounced_message.rewindbody()
        except IOError, errmessage:
            body.append("*** couldn't include message body: %s ***" %
                errmessage)
        else:
            body.append('\n')
            body.append(bounced_message.fp.read())
        part = MIMEText(''.join(body))
        message.attach(part)

        if to:
            # send
            self.set_message_attributes(message, to, subject)
            try:
                self.smtp_send(to, message.as_string())
            except MessageSendError:
                # squash mail sending errors when bouncing mail
                # TODO this *could* be better, as we could notify admin of the
                # problem (even though the vast majority of bounce errors are
                # because of spam)
                pass
        if crypt_to:
            plain = pyme.core.Data(message.as_string())
            cipher = pyme.core.Data()
            ctx = pyme.core.Context()
            ctx.set_armor(1)
            keys = []
            adrs = []
            for adr in crypt_to:
                ctx.op_keylist_start(adr, 0)
                # only first key per email
                k = ctx.op_keylist_next()
                if k is not None:
                    adrs.append(adr)
                    keys.append(k)
                ctx.op_keylist_end()
            crypt_to = adrs
        if crypt_to:
            try:
                ctx.op_encrypt(keys, 1, plain, cipher)
                cipher.seek(0,0)
                message=MIMEMultipart('encrypted', boundary=None,
                    _subparts=None, protocol="application/pgp-encrypted")
                part=MIMEBase('application', 'pgp-encrypted')
                part.set_payload("Version: 1\r\n")
                message.attach(part)
                part=MIMEBase('application', 'octet-stream')
                part.set_payload(cipher.read())
                message.attach(part)
            except pyme.GPGMEError:
                crypt_to = None
        if crypt_to:
            self.set_message_attributes(message, crypt_to, subject)
            try:
                self.smtp_send(crypt_to, message.as_string())
            except MessageSendError:
                # ignore on error, see above.
                pass

    def exception_message(self):
        '''Send a message to the admins with information about the latest
        traceback.
        '''
        subject = '%s: %s'%(self.config.TRACKER_NAME, sys.exc_info()[1])
        to = [self.config.ADMIN_EMAIL]
        content = '\n'.join(traceback.format_exception(*sys.exc_info()))
        self.standard_message(to, subject, content)

    def smtp_send(self, to, message, sender=None):
        """Send a message over SMTP, using roundup's config.

        Arguments:
        - to: a list of addresses usable by rfc822.parseaddr().
        - message: a StringIO instance with a full message.
        - sender: if not 'None', the email address to use as the
        envelope sender.  If 'None', the admin email is used.
        """

        if not sender:
            sender = self.config.ADMIN_EMAIL
        if self.debug:
            # don't send - just write to a file, use unix from line so
            # that resulting file can be openened in a mailer
            fmt = '%a %b %m %H:%M:%S %Y'
            unixfrm = 'From %s %s' % (sender, Date ('.').pretty (fmt))
            open(self.debug, 'a').write('%s\nFROM: %s\nTO: %s\n%s\n\n' %
                                        (unixfrm, sender,
                                         ', '.join(to), message))
        else:
            # now try to send the message
            try:
                # send the message as admin so bounces are sent there
                # instead of to roundup
                smtp = SMTPConnection(self.config)
                smtp.sendmail(sender, to, message)
            except socket.error, value:
                raise MessageSendError("Error: couldn't send email: "
                                       "mailhost %s"%value)
            except smtplib.SMTPException, msg:
                raise MessageSendError("Error: couldn't send email: %s"%msg)

class SMTPConnection(smtplib.SMTP):
    ''' Open an SMTP connection to the mailhost specified in the config
    '''
    def __init__(self, config):
        smtplib.SMTP.__init__(self, config.MAILHOST, port=config['MAIL_PORT'],
                              local_hostname=config['MAIL_LOCAL_HOSTNAME'])

        # start the TLS if requested
        if config["MAIL_TLS"]:
            self.ehlo()
            self.starttls(config["MAIL_TLS_KEYFILE"],
                config["MAIL_TLS_CERTFILE"])

        # ok, now do we also need to log in?
        mailuser = config["MAIL_USERNAME"]
        if mailuser:
            self.login(mailuser, config["MAIL_PASSWORD"])

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