"""some hooks and views to handle supervising of any data changes

"""

__docformat__ = "restructuredtext en"

from cubicweb import UnknownEid

from cubicweb.selectors import none_rset

from cubicweb.schema import display_name

from cubicweb.view import Component

from cubicweb.mail import format_mail

from cubicweb.server.hook import SendMailOp

def filter_changes(changes):

    """

    * when an entity has been deleted:

      * don't show deletion of its relations

      * don't show related TrInfo deletion if any

    * when an entity has been added don't show owned_by relation addition

    * don't show new TrInfo entities if any

    """

    # first build an index of changes

    index = {}

    added, deleted = set(), set()

    for change in changes[:]:

        event, changedescr = change

        if event == 'add_entity':

            entity = changedescr.entity

            added.add(entity.eid)

            if entity.e_schema == 'TrInfo':

                changes.remove(change)

                event = 'change_state'

                change = (event,

                          (entity.wf_info_for[0],

                           entity.from_state[0], entity.to_state[0]))

                changes.append(change)

        elif event == 'delete_entity':

            deleted.add(changedescr[0])

        index.setdefault(event, set()).add(change)

    for key in ('delete_relation', 'add_relation'):

        for change in index.get(key, {}).copy():

            if change[1].rtype == 'in_state':

                index[key].remove(change)

    # filter changes

    for eid in added:

        try:

            for change in index['add_relation'].copy():

                changedescr = change[1]

                # skip meta-relations which are set automatically

                # XXX generate list below using rtags (category = 'generated')

                if changedescr.rtype in ('created_by', 'owned_by', 'is', 'is_instance_of',

                                      'from_state', 'to_state', 'by_transition',

                                      'wf_info_for') \

                       and changedescr.eidfrom == eid:

                    index['add_relation'].remove(change)

        except KeyError:

            break

    for eid in deleted:

        try:

            for change in index['delete_relation'].copy():

                if change[1].eidfrom == eid:

                    index['delete_relation'].remove(change)

                elif change[1].eidto == eid:

                    index['delete_relation'].remove(change)

                    if change[1].rtype == 'wf_info_for':

                        for change_ in index['delete_entity'].copy():

                            if change_[1].eidfrom == change[1].eidfrom:

                                index['delete_entity'].remove(change_)

        except KeyError:

            break

    for change in changes:

        event, changedescr = change

        if change in index[event]:

            yield change

class SupervisionEmailView(Component):

    """view implementing the email API for data changes supervision notification

    """

    __regid__ = 'supervision_notif'

    __select__ = none_rset()

    def recipients(self):

        return self._cw.vreg.config['supervising-addrs']

    def subject(self):

        return self._cw._('[%s supervision] changes summary') % self._cw.vreg.config.appid

    def call(self, changes):

        user = self._cw.user

        self.w(self._cw._('user %s has made the following change(s):\n\n')

               % user.login)

        for event, changedescr in filter_changes(changes):

            self.w(u'* ')

            getattr(self, event)(changedescr)

            self.w(u'\n\n')

    def _entity_context(self, entity):

        return {'eid': entity.eid,

                'etype': entity.dc_type().lower(),

                'title': entity.dc_title()}

    def add_entity(self, changedescr):

        msg = self._cw._('added %(etype)s #%(eid)s (%(title)s)')

        self.w(u'%s\n' % (msg % self._entity_context(changedescr.entity)))

        self.w(u'  %s' % changedescr.entity.absolute_url())

    def update_entity(self, changedescr):

        msg = self._cw._('updated %(etype)s #%(eid)s (%(title)s)')

        self.w(u'%s\n' % (msg % self._entity_context(changedescr.entity)))

        # XXX print changes

        self.w(u'  %s' % changedescr.entity.absolute_url())

    def delete_entity(self, (eid, etype, title)):

        msg = self._cw._('deleted %(etype)s #%(eid)s (%(title)s)')

        etype = display_name(self._cw, etype).lower()

        self.w(msg % locals())

    def change_state(self, (entity, fromstate, tostate)):

        msg = self._cw._('changed state of %(etype)s #%(eid)s (%(title)s)')

        self.w(u'%s\n' % (msg % self._entity_context(entity)))

        self.w(_('  from state %(fromstate)s to state %(tostate)s\n' %

                 {'fromstate': _(fromstate.name), 'tostate': _(tostate.name)}))

        self.w(u'  %s' % entity.absolute_url())

    def _relation_context(self, changedescr):

        session = self._cw

        def describe(eid):

            try:

                return session._(session.describe(eid)[0]).lower()

            except UnknownEid:

                # may occurs when an entity has been deleted from an external

                # source and we're cleaning its relation

                return session._('unknown external entity')

        eidfrom, rtype, eidto = changedescr.eidfrom, changedescr.rtype, changedescr.eidto

        return {'rtype': session._(rtype),

                'eidfrom': eidfrom,

                'frometype': describe(eidfrom),

                'eidto': eidto,

                'toetype': describe(eidto)}

    def add_relation(self, changedescr):

        msg = self._cw._('added relation %(rtype)s from %(frometype)s #%(eidfrom)s to %(toetype)s #%(eidto)s')

        self.w(msg % self._relation_context(changedescr))

    def delete_relation(self, changedescr):

        msg = self._cw._('deleted relation %(rtype)s from %(frometype)s #%(eidfrom)s to %(toetype)s #%(eidto)s')

        self.w(msg % self._relation_context(changedescr))

class SupervisionMailOp(SendMailOp):

    """special send email operation which should be done only once for a bunch

    of changes

    """

    def _get_view(self):

        return self.session.vreg['components'].select('supervision_notif',

                                                      self.session)

    def _prepare_email(self):

        session = self.session

        config = session.vreg.config

        uinfo = {'email': config['sender-addr'],

                 'name': config['sender-name']}

        view = self._get_view()

        content = view.render(changes=session.transaction_data.get('pendingchanges'))

        recipients = view.recipients()

        msg = format_mail(uinfo, recipients, content, view.subject(), config=config)

        self.to_send = [(msg, recipients)]

    def commit_event(self):

        self._prepare_email()

        SendMailOp.commit_event(self)