"""Common utilies to format / semd emails.

:organization: Logilab

:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.

:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr

:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses

"""

__docformat__ = "restructuredtext en"

from base64 import b64encode, b64decode

from itertools import repeat

from time import time

from email.MIMEMultipart import MIMEMultipart

from email.MIMEText import MIMEText

from email.MIMEImage import MIMEImage

from email.Header import Header

try:

    from socket import gethostname

except ImportError:

    def gethostname(): # gae

        return 'XXX'

from cubicweb.view import EntityView

from cubicweb.entity import Entity

def header(ustring):

    return Header(ustring.encode('UTF-8'), 'UTF-8')

def addrheader(uaddr, uname=None):

    # even if an email address should be ascii, encode it using utf8 since

    # automatic tests may generate non ascii email address

    addr = uaddr.encode('UTF-8')

    if uname:

        return '%s <%s>' % (header(uname).encode(), addr)

    return addr

def construct_message_id(appid, eid, withtimestamp=True):

    if withtimestamp:

        addrpart = 'eid=%s&timestamp=%.10f' % (eid, time())

    else:

        addrpart = 'eid=%s' % eid

    # we don't want any equal sign nor trailing newlines

    leftpart = b64encode(addrpart, '.-').rstrip().rstrip('=')

    return '<%s@%s.%s>' % (leftpart, appid, gethostname())

def parse_message_id(msgid, appid):

    if msgid[0] == '<':

        msgid = msgid[1:]

    if msgid[-1] == '>':

        msgid = msgid[:-1]

    try:

        values, qualif = msgid.split('@')

        padding = len(values) % 4

        values = b64decode(str(values + '='*padding), '.-')

        values = dict(v.split('=') for v in values.split('&'))

        fromappid, host = qualif.split('.', 1)

    except:

        return None

    if appid != fromappid or host != gethostname():

        return None

    return values

def format_mail(uinfo, to_addrs, content, subject="",

                cc_addrs=(), msgid=None, references=(), config=None):

    """Sends an Email to 'e_addr' with content 'content', and subject 'subject'

    to_addrs and cc_addrs are expected to be a list of email address without

    name

    """

    assert type(content) is unicode, repr(content)

    msg = MIMEText(content.encode('UTF-8'), 'plain', 'UTF-8')

    # safety: keep only the first newline

    subject = subject.splitlines()[0]

    msg['Subject'] = header(subject)

    if uinfo.get('email'):

        email = uinfo['email']

    elif config and config['sender-addr']:

        email = unicode(config['sender-addr'])

    else:

        email = u''

    if uinfo.get('name'):

        name = uinfo['name']

    elif config and config['sender-addr']:

        name = unicode(config['sender-name'])

    else:

        name = u''

    msg['From'] = addrheader(email, name)

    if config and config['sender-addr'] and config['sender-addr'] != email:

        appaddr = addrheader(config['sender-addr'], config['sender-name'])

        msg['Reply-to'] = '%s, %s' % (msg['From'], appaddr)

    elif email:

        msg['Reply-to'] = msg['From']

    if config is not None:

        msg['X-CW'] = config.appid

    unique_addrs = lambda addrs: sorted(set(addr for addr in addrs if addr is not None))

    msg['To'] = ', '.join(addrheader(addr) for addr in unique_addrs(to_addrs))

    if cc_addrs:

        msg['Cc'] = ', '.join(addrheader(addr) for addr in unique_addrs(cc_addrs))

    if msgid:

        msg['Message-id'] = msgid

    if references:

        msg['References'] = ', '.join(references)

    return msg

class HtmlEmail(MIMEMultipart):

    def __init__(self, subject, textcontent, htmlcontent,

                 sendermail=None, sendername=None, recipients=None, ccrecipients=None):

        MIMEMultipart.__init__(self, 'related')

        self['Subject'] = header(subject)

        self.preamble = 'This is a multi-part message in MIME format.'

        # Attach alternative text message

        alternative = MIMEMultipart('alternative')

        self.attach(alternative)

        msgtext = MIMEText(textcontent.encode('UTF-8'), 'plain', 'UTF-8')

        alternative.attach(msgtext)

        # Attach html message

        msghtml = MIMEText(htmlcontent.encode('UTF-8'), 'html', 'UTF-8')

        alternative.attach(msghtml)

        if sendermail or sendername:

            self['From'] = addrheader(sendermail, sendername)

        if recipients:

            self['To'] = ', '.join(addrheader(addr) for addr in recipients if addr is not None)

        if ccrecipients:

            self['Cc'] = ', '.join(addrheader(addr) for addr in ccrecipients if addr is not None)

    def attach_image(self, data, htmlId):

        image = MIMEImage(data)

        image.add_header('Content-ID', '<%s>' % htmlId)

        self.attach(image)

class NotificationView(EntityView):

    """abstract view implementing the "email" API (eg to simplify sending

    notification)

    """

    # XXX refactor this class to work with len(rset) > 1

    msgid_timestamp = True

    def recipients(self):

        finder = self.vreg['components'].select('recipients_finder', self.req,

                                                rset=self.rset,

                                                row=self.row or 0,

                                                col=self.col or 0)

        return finder.recipients()

    def subject(self):

        entity = self.entity(self.row or 0, self.col or 0)

        subject = self.req._(self.message)

        etype = entity.dc_type()

        eid = entity.eid

        login = self.user_data['login']

        return self.req._('%(subject)s %(etype)s #%(eid)s (%(login)s)') % locals()

    def context(self, **kwargs):

        entity = self.entity(self.row or 0, self.col or 0)

        for key, val in kwargs.iteritems():

            if val and isinstance(val, unicode) and val.strip():

               kwargs[key] = self.req._(val)

        kwargs.update({'user': self.user_data['login'],

                       'eid': entity.eid,

                       'etype': entity.dc_type(),

                       'url': entity.absolute_url(),

                       'title': entity.dc_long_title(),})

        return kwargs

    def cell_call(self, row, col=0, **kwargs):

        self.w(self.req._(self.content) % self.context(**kwargs))

    def construct_message_id(self, eid):

        return construct_message_id(self.config.appid, eid, self.msgid_timestamp)

    def render_emails(self, **kwargs):

        """generate and send emails for this view (one per recipient)"""

        self._kwargs = kwargs

        recipients = self.recipients()

        if not recipients:

            self.info('skipping %s notification, no recipients', self.id)

            return

        if self.rset is not None:

            entity = self.entity(self.row or 0, self.col or 0)

            # if the view is using timestamp in message ids, no way to reference

            # previous email

            if not self.msgid_timestamp:

                refs = [self.construct_message_id(eid)

                        for eid in entity.notification_references(self)]

            else:

                refs = ()

            msgid = self.construct_message_id(entity.eid)

        else:

            refs = ()

            msgid = None

        req = self.req

        self.user_data = req.user_data()

        origlang = req.lang

        for something in recipients:

            if isinstance(something, Entity):

                # hi-jack self.req to get a session for the returned user

                self.req = self.req.hijack_user(something)

                emailaddr = something.get_email()

            else:

                emailaddr, lang = something

                self.req.set_language(lang)

            # since the same view (eg self) may be called multiple time and we

            # need a fresh stream at each iteration, reset it explicitly

            self.w = None

            # XXX call render before subject to set .row/.col attributes on the

            #     view

            try:

                content = self.render(row=0, col=0, **kwargs)

                subject = self.subject()

            except SkipEmail:

                continue

            msg = format_mail(self.user_data, [emailaddr], content, subject,

                              config=self.config, msgid=msgid, references=refs)

            yield [emailaddr], msg

        # restore language

        req.set_language(origlang)

    def render_and_send(self, **kwargs):

        """generate and send an email message for this view"""

        delayed = kwargs.pop('delay_to_commit', None)

        for recipients, msg in self.render_emails(**kwargs):

            if delayed is None:

                self.send(recipients, msg)

            elif delayed:

                self.send_on_commit(recipients, msg)

            else:

                self.send_now(recipients, msg)

    def send_now(self, recipients, msg):

        self.config.sendmails([(msg, recipients)])

    def send_on_commit(self, recipients, msg):

        raise NotImplementedError

    send = send_now

class SkipEmail(Exception):

    """raise this if you decide to skip an email during its generation"""