comments-api: make edit API resilent to bad version data.

rhodecode/model/comment.py

@@ -1,833 +1,837 b''
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2011-2020 RhodeCode GmbH
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License, version 3
 # (only), as published by the Free Software Foundation.
 #
 # This program 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 General Public License for more details.
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 # This program is dual-licensed. If you wish to learn more about the
 # RhodeCode Enterprise Edition, including its added features, Support services,
 # and proprietary license terms, please see https://rhodecode.com/licenses/
 
 """
 comments model for RhodeCode
 """
 import datetime
 
 import logging
 import traceback
 import collections
 
 from pyramid.threadlocal import get_current_registry, get_current_request
 from sqlalchemy.sql.expression import null
 from sqlalchemy.sql.functions import coalesce
 
 from rhodecode.lib import helpers as h, diffs, channelstream, hooks_utils
 from rhodecode.lib import audit_logger
 from rhodecode.lib.exceptions import CommentVersionMismatch
-from rhodecode.lib.utils2 import extract_mentioned_users, safe_str
+from rhodecode.lib.utils2 import extract_mentioned_users, safe_str, safe_int
 from rhodecode.model import BaseModel
 from rhodecode.model.db import (
     ChangesetComment,
     User,
     Notification,
     PullRequest,
     AttributeDict,
     ChangesetCommentHistory,
 )
 from rhodecode.model.notification import NotificationModel
 from rhodecode.model.meta import Session
 from rhodecode.model.settings import VcsSettingsModel
 from rhodecode.model.notification import EmailNotificationModel
 from rhodecode.model.validation_schema.schemas import comment_schema
 
 
 log = logging.getLogger(__name__)
 
 
 class CommentsModel(BaseModel):
 
     cls = ChangesetComment
 
     DIFF_CONTEXT_BEFORE = 3
     DIFF_CONTEXT_AFTER = 3
 
     def __get_commit_comment(self, changeset_comment):
         return self._get_instance(ChangesetComment, changeset_comment)
 
     def __get_pull_request(self, pull_request):
         return self._get_instance(PullRequest, pull_request)
 
     def _extract_mentions(self, s):
         user_objects = []
         for username in extract_mentioned_users(s):
             user_obj = User.get_by_username(username, case_insensitive=True)
             if user_obj:
                 user_objects.append(user_obj)
         return user_objects
 
     def _get_renderer(self, global_renderer='rst', request=None):
         request = request or get_current_request()
 
         try:
             global_renderer = request.call_context.visual.default_renderer
         except AttributeError:
             log.debug("Renderer not set, falling back "
                       "to default renderer '%s'", global_renderer)
         except Exception:
             log.error(traceback.format_exc())
         return global_renderer
 
     def aggregate_comments(self, comments, versions, show_version, inline=False):
         # group by versions, and count until, and display objects
 
         comment_groups = collections.defaultdict(list)
         [comment_groups[
              _co.pull_request_version_id].append(_co) for _co in comments]
 
         def yield_comments(pos):
             for co in comment_groups[pos]:
                 yield co
 
         comment_versions = collections.defaultdict(
             lambda: collections.defaultdict(list))
         prev_prvid = -1
         # fake last entry with None, to aggregate on "latest" version which
         # doesn't have an pull_request_version_id
         for ver in versions + [AttributeDict({'pull_request_version_id': None})]:
             prvid = ver.pull_request_version_id
             if prev_prvid == -1:
                 prev_prvid = prvid
 
             for co in yield_comments(prvid):
                 comment_versions[prvid]['at'].append(co)
 
             # save until
             current = comment_versions[prvid]['at']
             prev_until = comment_versions[prev_prvid]['until']
             cur_until = prev_until + current
             comment_versions[prvid]['until'].extend(cur_until)
 
             # save outdated
             if inline:
                 outdated = [x for x in cur_until
                             if x.outdated_at_version(show_version)]
             else:
                 outdated = [x for x in cur_until
                             if x.older_than_version(show_version)]
             display = [x for x in cur_until if x not in outdated]
 
             comment_versions[prvid]['outdated'] = outdated
             comment_versions[prvid]['display'] = display
 
             prev_prvid = prvid
 
         return comment_versions
 
     def get_repository_comments(self, repo, comment_type=None, user=None, commit_id=None):
         qry = Session().query(ChangesetComment) \
             .filter(ChangesetComment.repo == repo)
 
         if comment_type and comment_type in ChangesetComment.COMMENT_TYPES:
             qry = qry.filter(ChangesetComment.comment_type == comment_type)
 
         if user:
             user = self._get_user(user)
             if user:
                 qry = qry.filter(ChangesetComment.user_id == user.user_id)
 
         if commit_id:
             qry = qry.filter(ChangesetComment.revision == commit_id)
 
         qry = qry.order_by(ChangesetComment.created_on)
         return qry.all()
 
     def get_repository_unresolved_todos(self, repo):
         todos = Session().query(ChangesetComment) \
             .filter(ChangesetComment.repo == repo) \
             .filter(ChangesetComment.resolved_by == None) \
             .filter(ChangesetComment.comment_type
                     == ChangesetComment.COMMENT_TYPE_TODO)
         todos = todos.all()
 
         return todos
 
     def get_pull_request_unresolved_todos(self, pull_request, show_outdated=True):
 
         todos = Session().query(ChangesetComment) \
             .filter(ChangesetComment.pull_request == pull_request) \
             .filter(ChangesetComment.resolved_by == None) \
             .filter(ChangesetComment.comment_type
                     == ChangesetComment.COMMENT_TYPE_TODO)
 
         if not show_outdated:
             todos = todos.filter(
                 coalesce(ChangesetComment.display_state, '') !=
                 ChangesetComment.COMMENT_OUTDATED)
 
         todos = todos.all()
 
         return todos
 
     def get_pull_request_resolved_todos(self, pull_request, show_outdated=True):
 
         todos = Session().query(ChangesetComment) \
             .filter(ChangesetComment.pull_request == pull_request) \
             .filter(ChangesetComment.resolved_by != None) \
             .filter(ChangesetComment.comment_type
                     == ChangesetComment.COMMENT_TYPE_TODO)
 
         if not show_outdated:
             todos = todos.filter(
                 coalesce(ChangesetComment.display_state, '') !=
                 ChangesetComment.COMMENT_OUTDATED)
 
         todos = todos.all()
 
         return todos
 
     def get_commit_unresolved_todos(self, commit_id, show_outdated=True):
 
         todos = Session().query(ChangesetComment) \
             .filter(ChangesetComment.revision == commit_id) \
             .filter(ChangesetComment.resolved_by == None) \
             .filter(ChangesetComment.comment_type
                     == ChangesetComment.COMMENT_TYPE_TODO)
 
         if not show_outdated:
             todos = todos.filter(
                 coalesce(ChangesetComment.display_state, '') !=
                 ChangesetComment.COMMENT_OUTDATED)
 
         todos = todos.all()
 
         return todos
 
     def get_commit_resolved_todos(self, commit_id, show_outdated=True):
 
         todos = Session().query(ChangesetComment) \
             .filter(ChangesetComment.revision == commit_id) \
             .filter(ChangesetComment.resolved_by != None) \
             .filter(ChangesetComment.comment_type
                     == ChangesetComment.COMMENT_TYPE_TODO)
 
         if not show_outdated:
             todos = todos.filter(
                 coalesce(ChangesetComment.display_state, '') !=
                 ChangesetComment.COMMENT_OUTDATED)
 
         todos = todos.all()
 
         return todos
 
     def _log_audit_action(self, action, action_data, auth_user, comment):
         audit_logger.store(
             action=action,
             action_data=action_data,
             user=auth_user,
             repo=comment.repo)
 
     def create(self, text, repo, user, commit_id=None, pull_request=None,
                f_path=None, line_no=None, status_change=None,
                status_change_type=None, comment_type=None,
                resolves_comment_id=None, closing_pr=False, send_email=True,
                renderer=None, auth_user=None, extra_recipients=None):
         """
         Creates new comment for commit or pull request.
         IF status_change is not none this comment is associated with a
         status change of commit or commit associated with pull request
 
         :param text:
         :param repo:
         :param user:
         :param commit_id:
         :param pull_request:
         :param f_path:
         :param line_no:
         :param status_change: Label for status change
         :param comment_type: Type of comment
         :param resolves_comment_id: id of comment which this one will resolve
         :param status_change_type: type of status change
         :param closing_pr:
         :param send_email:
         :param renderer: pick renderer for this comment
         :param auth_user: current authenticated user calling this method
         :param extra_recipients: list of extra users to be added to recipients
         """
 
         if not text:
             log.warning('Missing text for comment, skipping...')
             return
         request = get_current_request()
         _ = request.translate
 
         if not renderer:
             renderer = self._get_renderer(request=request)
 
         repo = self._get_repo(repo)
         user = self._get_user(user)
         auth_user = auth_user or user
 
         schema = comment_schema.CommentSchema()
         validated_kwargs = schema.deserialize(dict(
             comment_body=text,
             comment_type=comment_type,
             comment_file=f_path,
             comment_line=line_no,
             renderer_type=renderer,
             status_change=status_change_type,
             resolves_comment_id=resolves_comment_id,
             repo=repo.repo_id,
             user=user.user_id,
         ))
 
         comment = ChangesetComment()
         comment.renderer = validated_kwargs['renderer_type']
         comment.text = validated_kwargs['comment_body']
         comment.f_path = validated_kwargs['comment_file']
         comment.line_no = validated_kwargs['comment_line']
         comment.comment_type = validated_kwargs['comment_type']
 
         comment.repo = repo
         comment.author = user
         resolved_comment = self.__get_commit_comment(
             validated_kwargs['resolves_comment_id'])
         # check if the comment actually belongs to this PR
         if resolved_comment and resolved_comment.pull_request and \
                 resolved_comment.pull_request != pull_request:
             log.warning('Comment tried to resolved unrelated todo comment: %s',
                         resolved_comment)
             # comment not bound to this pull request, forbid
             resolved_comment = None
 
         elif resolved_comment and resolved_comment.repo and \
                 resolved_comment.repo != repo:
             log.warning('Comment tried to resolved unrelated todo comment: %s',
                         resolved_comment)
             # comment not bound to this repo, forbid
             resolved_comment = None
 
         comment.resolved_comment = resolved_comment
 
         pull_request_id = pull_request
 
         commit_obj = None
         pull_request_obj = None
 
         if commit_id:
             notification_type = EmailNotificationModel.TYPE_COMMIT_COMMENT
             # do a lookup, so we don't pass something bad here
             commit_obj = repo.scm_instance().get_commit(commit_id=commit_id)
             comment.revision = commit_obj.raw_id
 
         elif pull_request_id:
             notification_type = EmailNotificationModel.TYPE_PULL_REQUEST_COMMENT
             pull_request_obj = self.__get_pull_request(pull_request_id)
             comment.pull_request = pull_request_obj
         else:
             raise Exception('Please specify commit or pull_request_id')
 
         Session().add(comment)
         Session().flush()
         kwargs = {
             'user': user,
             'renderer_type': renderer,
             'repo_name': repo.repo_name,
             'status_change': status_change,
             'status_change_type': status_change_type,
             'comment_body': text,
             'comment_file': f_path,
             'comment_line': line_no,
             'comment_type': comment_type or 'note',
             'comment_id': comment.comment_id
         }
 
         if commit_obj:
             recipients = ChangesetComment.get_users(
                 revision=commit_obj.raw_id)
             # add commit author if it's in RhodeCode system
             cs_author = User.get_from_cs_author(commit_obj.author)
             if not cs_author:
                 # use repo owner if we cannot extract the author correctly
                 cs_author = repo.user
             recipients += [cs_author]
 
             commit_comment_url = self.get_url(comment, request=request)
             commit_comment_reply_url = self.get_url(
                 comment, request=request,
                 anchor='comment-{}/?/ReplyToComment'.format(comment.comment_id))
 
             target_repo_url = h.link_to(
                 repo.repo_name,
                 h.route_url('repo_summary', repo_name=repo.repo_name))
 
             # commit specifics
             kwargs.update({
                 'commit': commit_obj,
                 'commit_message': commit_obj.message,
                 'commit_target_repo_url': target_repo_url,
                 'commit_comment_url': commit_comment_url,
                 'commit_comment_reply_url': commit_comment_reply_url
             })
 
         elif pull_request_obj:
             # get the current participants of this pull request
             recipients = ChangesetComment.get_users(
                 pull_request_id=pull_request_obj.pull_request_id)
             # add pull request author
             recipients += [pull_request_obj.author]
 
             # add the reviewers to notification
             recipients += [x.user for x in pull_request_obj.reviewers]
 
             pr_target_repo = pull_request_obj.target_repo
             pr_source_repo = pull_request_obj.source_repo
 
             pr_comment_url = self.get_url(comment, request=request)
             pr_comment_reply_url = self.get_url(
                 comment, request=request,
                 anchor='comment-{}/?/ReplyToComment'.format(comment.comment_id))
 
             pr_url = h.route_url(
                 'pullrequest_show',
                 repo_name=pr_target_repo.repo_name,
                 pull_request_id=pull_request_obj.pull_request_id, )
 
             # set some variables for email notification
             pr_target_repo_url = h.route_url(
                 'repo_summary', repo_name=pr_target_repo.repo_name)
 
             pr_source_repo_url = h.route_url(
                 'repo_summary', repo_name=pr_source_repo.repo_name)
 
             # pull request specifics
             kwargs.update({
                 'pull_request': pull_request_obj,
                 'pr_id': pull_request_obj.pull_request_id,
                 'pull_request_url': pr_url,
                 'pull_request_target_repo': pr_target_repo,
                 'pull_request_target_repo_url': pr_target_repo_url,
                 'pull_request_source_repo': pr_source_repo,
                 'pull_request_source_repo_url': pr_source_repo_url,
                 'pr_comment_url': pr_comment_url,
                 'pr_comment_reply_url': pr_comment_reply_url,
                 'pr_closing': closing_pr,
             })
 
         recipients += [self._get_user(u) for u in (extra_recipients or [])]
 
         if send_email:
             # pre-generate the subject for notification itself
             (subject,
              _h, _e,  # we don't care about those
              body_plaintext) = EmailNotificationModel().render_email(
                 notification_type, **kwargs)
 
             mention_recipients = set(
                 self._extract_mentions(text)).difference(recipients)
 
             # create notification objects, and emails
             NotificationModel().create(
                 created_by=user,
                 notification_subject=subject,
                 notification_body=body_plaintext,
                 notification_type=notification_type,
                 recipients=recipients,
                 mention_recipients=mention_recipients,
                 email_kwargs=kwargs,
             )
 
         Session().flush()
         if comment.pull_request:
             action = 'repo.pull_request.comment.create'
         else:
             action = 'repo.commit.comment.create'
 
         comment_data = comment.get_api_data()
         self._log_audit_action(
             action, {'data': comment_data}, auth_user, comment)
 
         msg_url = ''
         channel = None
         if commit_obj:
             msg_url = commit_comment_url
             repo_name = repo.repo_name
             channel = u'/repo${}$/commit/{}'.format(
                 repo_name,
                 commit_obj.raw_id
             )
         elif pull_request_obj:
             msg_url = pr_comment_url
             repo_name = pr_target_repo.repo_name
             channel = u'/repo${}$/pr/{}'.format(
                 repo_name,
                 pull_request_id
             )
 
         message = '<strong>{}</strong> {} - ' \
                   '<a onclick="window.location=\'{}\';' \
                   'window.location.reload()">' \
                   '<strong>{}</strong></a>'
         message = message.format(
             user.username, _('made a comment'), msg_url,
             _('Show it now'))
 
         channelstream.post_message(
             channel, message, user.username,
             registry=get_current_registry())
 
         return comment
 
     def edit(self, comment_id, text, auth_user, version):
         """
         Change existing comment for commit or pull request.
 
         :param comment_id:
         :param text:
         :param auth_user: current authenticated user calling this method
         :param version: last comment version
         """
         if not text:
             log.warning('Missing text for comment, skipping...')
             return
 
         comment = ChangesetComment.get(comment_id)
         old_comment_text = comment.text
         comment.text = text
         comment.modified_at = datetime.datetime.now()
+        version = safe_int(version)
 
+        # NOTE(marcink): this returns initial comment + edits, so v2 from ui
+        # would return 3 here
         comment_version = ChangesetCommentHistory.get_version(comment_id)
-        if (comment_version - version) != 1:
+
+        if isinstance(version, (int, long)) and (comment_version - version) != 1:
             log.warning(
                 'Version mismatch comment_version {} submitted {}, skipping'.format(
-                    comment_version,
+                    comment_version-1,  # -1 since note above
                     version
                 )
             )
             raise CommentVersionMismatch()
 
         comment_history = ChangesetCommentHistory()
         comment_history.comment_id = comment_id
         comment_history.version = comment_version
         comment_history.created_by_user_id = auth_user.user_id
         comment_history.text = old_comment_text
         # TODO add email notification
         Session().add(comment_history)
         Session().add(comment)
         Session().flush()
 
         if comment.pull_request:
             action = 'repo.pull_request.comment.edit'
         else:
             action = 'repo.commit.comment.edit'
 
         comment_data = comment.get_api_data()
         comment_data['old_comment_text'] = old_comment_text
         self._log_audit_action(
             action, {'data': comment_data}, auth_user, comment)
 
         return comment_history
 
     def delete(self, comment, auth_user):
         """
         Deletes given comment
         """
         comment = self.__get_commit_comment(comment)
         old_data = comment.get_api_data()
         Session().delete(comment)
 
         if comment.pull_request:
             action = 'repo.pull_request.comment.delete'
         else:
             action = 'repo.commit.comment.delete'
 
         self._log_audit_action(
             action, {'old_data': old_data}, auth_user, comment)
 
         return comment
 
     def get_all_comments(self, repo_id, revision=None, pull_request=None):
         q = ChangesetComment.query()\
                 .filter(ChangesetComment.repo_id == repo_id)
         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 commit or pull_request')
         q = q.order_by(ChangesetComment.created_on)
         return q.all()
 
     def get_url(self, comment, request=None, permalink=False, anchor=None):
         if not request:
             request = get_current_request()
 
         comment = self.__get_commit_comment(comment)
         if anchor is None:
             anchor = 'comment-{}'.format(comment.comment_id)
 
         if comment.pull_request:
             pull_request = comment.pull_request
             if permalink:
                 return request.route_url(
                     'pull_requests_global',
                     pull_request_id=pull_request.pull_request_id,
                     _anchor=anchor)
             else:
                 return request.route_url(
                     'pullrequest_show',
                     repo_name=safe_str(pull_request.target_repo.repo_name),
                     pull_request_id=pull_request.pull_request_id,
                     _anchor=anchor)
 
         else:
             repo = comment.repo
             commit_id = comment.revision
 
             if permalink:
                 return request.route_url(
                     'repo_commit', repo_name=safe_str(repo.repo_id),
                     commit_id=commit_id,
                     _anchor=anchor)
 
             else:
                 return request.route_url(
                     'repo_commit', repo_name=safe_str(repo.repo_name),
                     commit_id=commit_id,
                     _anchor=anchor)
 
     def get_comments(self, repo_id, revision=None, pull_request=None):
         """
         Gets main comments based on revision or pull_request_id
 
         :param repo_id:
         :param revision:
         :param 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 commit 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._get_inline_comments_query(repo_id, revision, pull_request)
         return self._group_comments_by_path_and_line_number(q)
 
     def get_inline_comments_count(self, inline_comments, skip_outdated=True,
                                   version=None):
         inline_cnt = 0
         for fname, per_line_comments in inline_comments.iteritems():
             for lno, comments in per_line_comments.iteritems():
                 for comm in comments:
                     if not comm.outdated_at_version(version) and skip_outdated:
                         inline_cnt += 1
 
         return inline_cnt
 
     def get_outdated_comments(self, repo_id, pull_request):
         # TODO: johbo: Remove `repo_id`, it is not needed to find the comments
         # of a pull request.
         q = self._all_inline_comments_of_pull_request(pull_request)
         q = q.filter(
             ChangesetComment.display_state ==
             ChangesetComment.COMMENT_OUTDATED
         ).order_by(ChangesetComment.comment_id.asc())
 
         return self._group_comments_by_path_and_line_number(q)
 
     def _get_inline_comments_query(self, repo_id, revision, pull_request):
         # TODO: johbo: Split this into two methods: One for PR and one for
         # commit.
         if revision:
             q = Session().query(ChangesetComment).filter(
                 ChangesetComment.repo_id == repo_id,
                 ChangesetComment.line_no != null(),
                 ChangesetComment.f_path != null(),
                 ChangesetComment.revision == revision)
 
         elif pull_request:
             pull_request = self.__get_pull_request(pull_request)
             if not CommentsModel.use_outdated_comments(pull_request):
                 q = self._visible_inline_comments_of_pull_request(pull_request)
             else:
                 q = self._all_inline_comments_of_pull_request(pull_request)
 
         else:
             raise Exception('Please specify commit or pull_request_id')
         q = q.order_by(ChangesetComment.comment_id.asc())
         return q
 
     def _group_comments_by_path_and_line_number(self, q):
         comments = q.all()
         paths = collections.defaultdict(lambda: collections.defaultdict(list))
         for co in comments:
             paths[co.f_path][co.line_no].append(co)
         return paths
 
     @classmethod
     def needed_extra_diff_context(cls):
         return max(cls.DIFF_CONTEXT_BEFORE, cls.DIFF_CONTEXT_AFTER)
 
     def outdate_comments(self, pull_request, old_diff_data, new_diff_data):
         if not CommentsModel.use_outdated_comments(pull_request):
             return
 
         comments = self._visible_inline_comments_of_pull_request(pull_request)
         comments_to_outdate = comments.all()
 
         for comment in comments_to_outdate:
             self._outdate_one_comment(comment, old_diff_data, new_diff_data)
 
     def _outdate_one_comment(self, comment, old_diff_proc, new_diff_proc):
         diff_line = _parse_comment_line_number(comment.line_no)
 
         try:
             old_context = old_diff_proc.get_context_of_line(
                 path=comment.f_path, diff_line=diff_line)
             new_context = new_diff_proc.get_context_of_line(
                 path=comment.f_path, diff_line=diff_line)
         except (diffs.LineNotInDiffException,
                 diffs.FileNotInDiffException):
             comment.display_state = ChangesetComment.COMMENT_OUTDATED
             return
 
         if old_context == new_context:
             return
 
         if self._should_relocate_diff_line(diff_line):
             new_diff_lines = new_diff_proc.find_context(
                 path=comment.f_path, context=old_context,
                 offset=self.DIFF_CONTEXT_BEFORE)
             if not new_diff_lines:
                 comment.display_state = ChangesetComment.COMMENT_OUTDATED
             else:
                 new_diff_line = self._choose_closest_diff_line(
                     diff_line, new_diff_lines)
                 comment.line_no = _diff_to_comment_line_number(new_diff_line)
         else:
             comment.display_state = ChangesetComment.COMMENT_OUTDATED
 
     def _should_relocate_diff_line(self, diff_line):
         """
         Checks if relocation shall be tried for the given `diff_line`.
 
         If a comment points into the first lines, then we can have a situation
         that after an update another line has been added on top. In this case
         we would find the context still and move the comment around. This
         would be wrong.
         """
         should_relocate = (
             (diff_line.new and diff_line.new > self.DIFF_CONTEXT_BEFORE) or
             (diff_line.old and diff_line.old > self.DIFF_CONTEXT_BEFORE))
         return should_relocate
 
     def _choose_closest_diff_line(self, diff_line, new_diff_lines):
         candidate = new_diff_lines[0]
         best_delta = _diff_line_delta(diff_line, candidate)
         for new_diff_line in new_diff_lines[1:]:
             delta = _diff_line_delta(diff_line, new_diff_line)
             if delta < best_delta:
                 candidate = new_diff_line
                 best_delta = delta
         return candidate
 
     def _visible_inline_comments_of_pull_request(self, pull_request):
         comments = self._all_inline_comments_of_pull_request(pull_request)
         comments = comments.filter(
             coalesce(ChangesetComment.display_state, '') !=
             ChangesetComment.COMMENT_OUTDATED)
         return comments
 
     def _all_inline_comments_of_pull_request(self, pull_request):
         comments = Session().query(ChangesetComment)\
             .filter(ChangesetComment.line_no != None)\
             .filter(ChangesetComment.f_path != None)\
             .filter(ChangesetComment.pull_request == pull_request)
         return comments
 
     def _all_general_comments_of_pull_request(self, pull_request):
         comments = Session().query(ChangesetComment)\
             .filter(ChangesetComment.line_no == None)\
             .filter(ChangesetComment.f_path == None)\
             .filter(ChangesetComment.pull_request == pull_request)
 
         return comments
 
     @staticmethod
     def use_outdated_comments(pull_request):
         settings_model = VcsSettingsModel(repo=pull_request.target_repo)
         settings = settings_model.get_general_settings()
         return settings.get('rhodecode_use_outdated_comments', False)
 
     def trigger_commit_comment_hook(self, repo, user, action, data=None):
         repo = self._get_repo(repo)
         target_scm = repo.scm_instance()
         if action == 'create':
             trigger_hook = hooks_utils.trigger_comment_commit_hooks
         elif action == 'edit':
             # TODO(dan): when this is supported we trigger edit hook too
             return
         else:
             return
 
         log.debug('Handling repo %s trigger_commit_comment_hook with action %s: %s',
                   repo, action, trigger_hook)
         trigger_hook(
             username=user.username,
             repo_name=repo.repo_name,
             repo_type=target_scm.alias,
             repo=repo,
             data=data)
 
 
 def _parse_comment_line_number(line_no):
     """
     Parses line numbers of the form "(o|n)\d+" and returns them in a tuple.
     """
     old_line = None
     new_line = None
     if line_no.startswith('o'):
         old_line = int(line_no[1:])
     elif line_no.startswith('n'):
         new_line = int(line_no[1:])
     else:
         raise ValueError("Comment lines have to start with either 'o' or 'n'.")
     return diffs.DiffLineNumber(old_line, new_line)
 
 
 def _diff_to_comment_line_number(diff_line):
     if diff_line.new is not None:
         return u'n{}'.format(diff_line.new)
     elif diff_line.old is not None:
         return u'o{}'.format(diff_line.old)
     return u''
 
 
 def _diff_line_delta(a, b):
     if None not in (a.new, b.new):
         return abs(a.new - b.new)
     elif None not in (a.old, b.old):
         return abs(a.old - b.old)
     else:
         raise ValueError(
             "Cannot compute delta between {} and {}".format(a, b))