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

:organization: Logilab

: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 cubicweb import UnknownEid

from cubicweb.selectors import none_rset

from cubicweb.schema import display_name

from cubicweb.view import Component

from cubicweb.common.mail import format_mail

from cubicweb.server.hooksmanager import Hook

from cubicweb.server.hookhelper import SendMailOp

class SomethingChangedHook(Hook):

    events = ('before_add_relation', 'before_delete_relation',

              'after_add_entity', 'before_update_entity')

    accepts = ('Any',)

    def call(self, session, *args):

        if session.is_super_session or session.repo.config.repairing:

            return # ignore changes triggered by hooks or maintainance shell

        dest = self.config['supervising-addrs']

        if not dest: # no supervisors, don't do this for nothing...

            return

        self.session = session

        if self._call(*args):

            SupervisionMailOp(session)

    def _call(self, *args):

        if self._event() == 'update_entity':

            if args[0].eid in self.session.transaction_data.get('neweids', ()):

                return False

            if args[0].e_schema == 'CWUser':

                updated = set(args[0].iterkeys())

                if not (updated - frozenset(('eid', 'modification_date',

                                             'last_login_time'))):

                    # don't record last_login_time update which are done

                    # automatically at login time

                    return False

        self.session.transaction_data.setdefault('pendingchanges', []).append(

            (self._event(), args))

        return True

    def _event(self):

        return self.event.split('_', 1)[1]

class EntityDeleteHook(SomethingChangedHook):

    events = ('before_delete_entity',)

    def _call(self, eid):

        entity = self.session.entity_from_eid(eid)

        try:

            title = entity.dc_title()

        except:

            # may raise an error during deletion process, for instance due to

            # missing required relation

            title = '#%s' % eid

        self.session.transaction_data.setdefault('pendingchanges', []).append(

            ('delete_entity', (eid, str(entity.e_schema), title)))

        return True

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[0]

            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][1] == '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[1] in ('created_by', 'owned_by', 'is', 'is_instance_of',

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

                                      'wf_info_for') \

                       and changedescr[0] == eid:

                    index['add_relation'].remove(change)

        except KeyError:

            break

    for eid in deleted:

        try:

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

                fromeid, rtype, toeid = change[1]

                if fromeid == eid:

                    index['delete_relation'].remove(change)

                elif toeid == eid:

                    index['delete_relation'].remove(change)

                    if rtype == 'wf_info_for':

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

                            if change[1][0] == fromeid:

                                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

    """

    __select__ = none_rset()

    id = 'supervision_notif'

    def recipients(self):

        return self.config['supervising-addrs']

    def subject(self):

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

    def call(self, changes):

        user = self.req.actual_session().user

        self.w(self.req._('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, entity):

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

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

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

    def update_entity(self, entity):

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

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

        # XXX print changes

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

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

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

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

        self.w(msg % locals())

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

        msg = self.req._('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, fromeid, rtype, toeid):

        _ = self.req._

        session = self.req.actual_session()

        def describe(eid):

            try:

                return _(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 _('unknown external entity')

        return {'rtype': _(rtype),

                'fromeid': fromeid,

                'frometype': describe(fromeid),

                'toeid': toeid,

                'toetype': describe(toeid)}

    def add_relation(self, fromeid, rtype, toeid):

        msg = self.req._('added relation %(rtype)s from %(frometype)s #%(fromeid)s to %(toetype)s #%(toeid)s')

        self.w(msg % self._relation_context(fromeid, rtype, toeid))

    def delete_relation(self, fromeid, rtype, toeid):

        msg = self.req._('deleted relation %(rtype)s from %(frometype)s #%(fromeid)s to %(toetype)s #%(toeid)s')

        self.w(msg % self._relation_context(fromeid, rtype, toeid))

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)