# copyright 2003-2012 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb is free software: you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option)
# any later version.
#
# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
"""Common utilies to format / send emails."""

__docformat__ = "restructuredtext en"

from base64 import b64encode, b64decode
from time import time
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.mime.image import MIMEImage
from email.header import Header
from socket import gethostname

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 Exception:
        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
    try:
        subject = subject.splitlines()[0]
        msg['Subject'] = header(subject)
    except IndexError:
        pass # no 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

    # to be defined on concrete sub-classes
    content = None # body of the mail
    message = None # action verb of the subject

    # this is usually the method to call
    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 cell_call(self, row, col=0, **kwargs):
        self.w(self._cw._(self.content) % self.context(**kwargs))

    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.__regid__)
            return
        if self.cw_rset is not None:
            entity = self.cw_rset.get_entity(self.cw_row or 0, self.cw_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.cw_adapt_to('INotifiable').notification_references(self)]
            else:
                refs = ()
            msgid = self.construct_message_id(entity.eid)
        else:
            refs = ()
            msgid = None
        req = self._cw
        self.user_data = req.user_data()
        origlang = req.lang
        for something in recipients:
            if isinstance(something, Entity):
                # hi-jack self._cw to get a session for the returned user
                self._cw = self._cw.hijack_user(something)
                emailaddr = something.cw_adapt_to('IEmailable').get_email()
            else:
                emailaddr, lang = something
                self._cw.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
            except Exception as ex:
                # shouldn't make the whole transaction fail because of rendering
                # error (unauthorized or such) XXX check it doesn't actually
                # occurs due to rollback on such error
                self.exception(str(ex))
                continue
            msg = format_mail(self.user_data, [emailaddr], content, subject,
                              config=self._cw.vreg.config, msgid=msgid, references=refs)
            yield [emailaddr], msg
        # restore language
        req.set_language(origlang)

    # recipients / email sending ###############################################

    def recipients(self):
        """return a list of either 2-uple (email, language) or user entity to
        who this email should be sent
        """
        finder = self._cw.vreg['components'].select(
            'recipients_finder', self._cw, rset=self.cw_rset,
            row=self.cw_row or 0, col=self.cw_col or 0)
        return finder.recipients()

    def send_now(self, recipients, msg):
        self._cw.vreg.config.sendmails([(msg, recipients)])

    def send_on_commit(self, recipients, msg):
        raise NotImplementedError

    send = send_now

    # email generation helpers #################################################

    def construct_message_id(self, eid):
        return construct_message_id(self._cw.vreg.config.appid, eid,
                                    self.msgid_timestamp)

    def format_field(self, attr, value):
        return ':%(attr)s: %(value)s' % {'attr': attr, 'value': value}

    def format_section(self, attr, value):
        return '%(attr)s\n%(ul)s\n%(value)s\n' % {
            'attr': attr, 'ul': '-'*len(attr), 'value': value}

    def subject(self):
        entity = self.cw_rset.get_entity(self.cw_row or 0, self.cw_col or 0)
        subject = self._cw._(self.message)
        etype = entity.dc_type()
        eid = entity.eid
        login = self.user_data['login']
        return self._cw._('%(subject)s %(etype)s #%(eid)s (%(login)s)') % locals()

    def context(self, **kwargs):
        entity = self.cw_rset.get_entity(self.cw_row or 0, self.cw_col or 0)
        for key, val in kwargs.iteritems():
            if val and isinstance(val, unicode) and val.strip():
               kwargs[key] = self._cw._(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


class SkipEmail(Exception):
    """raise this if you decide to skip an email during its generation"""