if not text:

            return

        repo = self._get_repo(repo)

        user = self._get_user(user)

        comment = ChangesetComment()

        comment.repo = repo

        comment.author = user

        comment.text = text

        comment.f_path = f_path

        comment.line_no = line_no

        if revision:

            cs = repo.scm_instance.get_changeset(revision)

            desc = "%s - %s" % (cs.short_id, h.shorter(cs.message, 256))

            author_email = cs.author_email

            comment.revision = revision

        elif pull_request:

            pull_request = self.__get_pull_request(pull_request)

            comment.pull_request = pull_request

            desc = pull_request.pull_request_id

        else:

            raise Exception('Please specify revision or pull_request_id')

        self.sa.add(comment)

        self.sa.flush()

        # make notification

        line = ''

        body = text

        #changeset

        if revision:

            if line_no:

                line = _('on line %s') % line_no

            subj = safe_unicode(

                h.link_to('Re commit: %(desc)s %(line)s' % \

                          {'desc': desc, 'line': line},

                          h.url('changeset_home', repo_name=repo.repo_name,

                                revision=revision,

                                anchor='comment-%s' % comment.comment_id,

                                qualified=True,

                          )

                )

            )

            notification_type = Notification.TYPE_CHANGESET_COMMENT

            # get the current participants of this changeset

            recipients = ChangesetComment.get_users(revision=revision)

            # add changeset author if it's in rhodecode system

            recipients += [User.get_by_email(author_email)]

            email_kwargs = {

                'status_change': status_change,

            }

        #pull request

        elif pull_request:

            _url = h.url('pullrequest_show',

                repo_name=pull_request.other_repo.repo_name,

                pull_request_id=pull_request.pull_request_id,

                anchor='comment-%s' % comment.comment_id,

                qualified=True,

            )

            subj = safe_unicode(

                h.link_to('Re pull request: %(desc)s %(line)s' % \

                          {'desc': desc, 'line': line}, _url)

            )

            notification_type = Notification.TYPE_PULL_REQUEST_COMMENT

            # get the current participants of this pull request

            recipients = ChangesetComment.get_users(pull_request_id=

                                                pull_request.pull_request_id)

            # add pull request author

            recipients += [pull_request.author]

            # add the reviewers to notification

            recipients += [x.user for x in pull_request.reviewers]

            #set some variables for email notification

            email_kwargs = {

                'pr_id': pull_request.pull_request_id,

                'status_change': status_change,

                'pr_comment_url': _url,

                'pr_comment_user': h.person(user.email),

                'pr_target_repo': h.url('summary_home',

                                   repo_name=pull_request.other_repo.repo_name,

                                   qualified=True)

            }

        # create notification objects, and emails

        NotificationModel().create(

            created_by=user, subject=subj, body=body,

            recipients=recipients, type_=notification_type,

            email_kwargs=email_kwargs

        )

        mention_recipients = set(self._extract_mentions(body))\

                                .difference(recipients)

        if mention_recipients:

            subj = _('[Mention]') + ' ' + subj

            NotificationModel().create(

                created_by=user, subject=subj, body=body,

                recipients=mention_recipients,

                type_=notification_type,

            )

        return comment

    def delete(self, comment):

        """

        Deletes given comment

        :param comment_id:

        """

        comment = self.__get_changeset_comment(comment)

        self.sa.delete(comment)

        return comment

    def get_comments(self, repo_id, revision=None, pull_request=None):

        """

        Get's main comments based on revision or pull_request_id

        :param repo_id:

        :type repo_id:

        :param revision:

        :type revision:

        :param pull_request:

        :type pull_request:

        """

        q = ChangesetComment.query()\

                .filter(ChangesetComment.repo_id == repo_id)\

                .filter(ChangesetComment.line_no == None)\

                .filter(ChangesetComment.f_path == None)

        if revision:

            q = q.filter(ChangesetComment.revision == revision)

        elif pull_request:

            pull_request = self.__get_pull_request(pull_request)

            q = q.filter(ChangesetComment.pull_request == pull_request)

        else:

            raise Exception('Please specify revision or pull_request')

        q = q.order_by(ChangesetComment.created_on)

        return q.all()

    def get_inline_comments(self, repo_id, revision=None, pull_request=None):

        q = self.sa.query(ChangesetComment)\

            .filter(ChangesetComment.repo_id == repo_id)\

            .filter(ChangesetComment.line_no != None)\

            .filter(ChangesetComment.f_path != None)\

            .order_by(ChangesetComment.comment_id.asc())\

        if revision:

            q = q.filter(ChangesetComment.revision == revision)

        elif pull_request:

            pull_request = self.__get_pull_request(pull_request)

            q = q.filter(ChangesetComment.pull_request == pull_request)

        else:

            raise Exception('Please specify revision or pull_request_id')

        comments = q.all()

        paths = defaultdict(lambda: defaultdict(list))

        for co in comments:

            paths[co.f_path][co.line_no].append(co)

        return paths.items()