from base64 import b64encode, b64decode

from itertools import repeat

from time import time

try:

    from socket import gethostname

except ImportError:

    def gethostname(): # gae

        return 'XXX'

from cubicweb.view import EntityView

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

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 user_login(self):

        try:

            # if req is actually a session (we are on the server side), and we

            # have to prevent nested internal session

            return self.req.actual_session().user.login

        except AttributeError:

            return self.req.user.login

    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_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_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 an email message for this view"""

        self._kwargs = kwargs

        recipients = self.recipients()

        if not recipients:

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

            return

        if not isinstance(recipients[0], tuple):

            from warnings import warn

            warn('recipients should now return a list of 2-uple (email, language)',

                 DeprecationWarning, stacklevel=1)

            lang = self.vreg.property_value('ui.language')

            recipients = zip(recipients, repeat(lang))

        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

        userdata = self.req.user_data()

        origlang = self.req.lang

        for emailaddr, lang in recipients:

            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

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

            subject = self.subject()

            msg = format_mail(userdata, [emailaddr], content, subject,

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

            yield [emailaddr], msg

        # restore language

        self.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