# -*- coding: utf-8 -*-
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# 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 General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""
kallithea.controllers.pullrequests
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

pull requests controller for Kallithea for initializing pull requests

This file was forked by the Kallithea project in July 2014.
Original author and date, and relevant copyright and licensing information is below:
:created_on: May 7, 2012
:author: marcink
:copyright: (c) 2013 RhodeCode GmbH, and others.
:license: GPLv3, see LICENSE.md for more details.
"""

import logging
import traceback
import formencode
import re

from pylons import request, tmpl_context as c
from pylons.i18n.translation import _
from webob.exc import HTTPFound, HTTPNotFound, HTTPForbidden, HTTPBadRequest

from kallithea.config.routing import url
from kallithea.lib import helpers as h
from kallithea.lib import diffs
from kallithea.lib.auth import LoginRequired, HasRepoPermissionAnyDecorator, \
    NotAnonymous
from kallithea.lib.base import BaseRepoController, render
from kallithea.lib.compat import json, OrderedDict
from kallithea.lib.diffs import LimitedDiffContainer
from kallithea.lib.exceptions import UserInvalidException
from kallithea.lib.page import Page
from kallithea.lib.utils import action_logger, jsonify
from kallithea.lib.vcs.exceptions import EmptyRepositoryError, ChangesetDoesNotExistError
from kallithea.lib.vcs.utils import safe_str
from kallithea.lib.vcs.utils.hgcompat import unionrepo
from kallithea.model.db import PullRequest, ChangesetStatus, ChangesetComment, \
    PullRequestReviewers, User
from kallithea.model.pull_request import PullRequestModel
from kallithea.model.meta import Session
from kallithea.model.repo import RepoModel
from kallithea.model.comment import ChangesetCommentsModel
from kallithea.model.changeset_status import ChangesetStatusModel
from kallithea.model.forms import PullRequestForm, PullRequestPostForm
from kallithea.lib.utils2 import safe_int
from kallithea.controllers.changeset import _ignorews_url, _context_url, \
    create_comment
from kallithea.controllers.compare import CompareController
from kallithea.lib.graphmod import graph_data

log = logging.getLogger(__name__)


class PullrequestsController(BaseRepoController):

    def _get_repo_refs(self, repo, rev=None, branch=None, branch_rev=None):
        """return a structure with repo's interesting changesets, suitable for
        the selectors in pullrequest.html

        rev: a revision that must be in the list somehow and selected by default
        branch: a branch that must be in the list and selected by default - even if closed
        branch_rev: a revision of which peers should be preferred and available."""
        # list named branches that has been merged to this named branch - it should probably merge back
        peers = []

        if rev:
            rev = safe_str(rev)

        if branch:
            branch = safe_str(branch)

        if branch_rev:
            branch_rev = safe_str(branch_rev)
            # a revset not restricting to merge() would be better
            # (especially because it would get the branch point)
            # ... but is currently too expensive
            # including branches of children could be nice too
            peerbranches = set()
            for i in repo._repo.revs(
                "sort(parents(branch(id(%s)) and merge()) - branch(id(%s)), -rev)",
                branch_rev, branch_rev):
                abranch = repo.get_changeset(i).branch
                if abranch not in peerbranches:
                    n = 'branch:%s:%s' % (abranch, repo.get_changeset(abranch).raw_id)
                    peers.append((n, abranch))
                    peerbranches.add(abranch)

        selected = None
        tiprev = repo.tags.get('tip')
        tipbranch = None

        branches = []
        for abranch, branchrev in repo.branches.iteritems():
            n = 'branch:%s:%s' % (abranch, branchrev)
            desc = abranch
            if branchrev == tiprev:
                tipbranch = abranch
                desc = '%s (current tip)' % desc
            branches.append((n, desc))
            if rev == branchrev:
                selected = n
            if branch == abranch:
                if not rev:
                    selected = n
                branch = None
        if branch:  # branch not in list - it is probably closed
            branchrev = repo.closed_branches.get(branch)
            if branchrev:
                n = 'branch:%s:%s' % (branch, branchrev)
                branches.append((n, _('%s (closed)') % branch))
                selected = n
                branch = None
            if branch:
                log.debug('branch %r not found in %s', branch, repo)

        bookmarks = []
        for bookmark, bookmarkrev in repo.bookmarks.iteritems():
            n = 'book:%s:%s' % (bookmark, bookmarkrev)
            bookmarks.append((n, bookmark))
            if rev == bookmarkrev:
                selected = n

        tags = []
        for tag, tagrev in repo.tags.iteritems():
            if tag == 'tip':
                continue
            n = 'tag:%s:%s' % (tag, tagrev)
            tags.append((n, tag))
            # note: even if rev == tagrev, don't select the static tag - it must be chosen explicitly

        # prio 1: rev was selected as existing entry above

        # prio 2: create special entry for rev; rev _must_ be used
        specials = []
        if rev and selected is None:
            selected = 'rev:%s:%s' % (rev, rev)
            specials = [(selected, '%s: %s' % (_("Changeset"), rev[:12]))]

        # prio 3: most recent peer branch
        if peers and not selected:
            selected = peers[0][0]

        # prio 4: tip revision
        if not selected:
            if h.is_hg(repo):
                if tipbranch:
                    selected = 'branch:%s:%s' % (tipbranch, tiprev)
                else:
                    selected = 'tag:null:' + repo.EMPTY_CHANGESET
                    tags.append((selected, 'null'))
            else:
                if 'master' in repo.branches:
                    selected = 'branch:master:%s' % repo.branches['master']
                else:
                    k, v = repo.branches.items()[0]
                    selected = 'branch:%s:%s' % (k, v)

        groups = [(specials, _("Special")),
                  (peers, _("Peer branches")),
                  (bookmarks, _("Bookmarks")),
                  (branches, _("Branches")),
                  (tags, _("Tags")),
                  ]
        return [g for g in groups if g[0]], selected

    def _get_is_allowed_change_status(self, pull_request):
        if pull_request.is_closed():
            return False

        owner = self.authuser.user_id == pull_request.owner_id
        reviewer = PullRequestReviewers.query() \
            .filter(PullRequestReviewers.pull_request == pull_request) \
            .filter(PullRequestReviewers.user_id == self.authuser.user_id) \
            .count() != 0

        return self.authuser.admin or owner or reviewer

    @LoginRequired()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    def show_all(self, repo_name):
        c.from_ = request.GET.get('from_') or ''
        c.closed = request.GET.get('closed') or ''
        p = safe_int(request.GET.get('page'), 1)

        q = PullRequest.query(include_closed=c.closed, sorted=True)
        if c.from_:
            q = q.filter_by(org_repo=c.db_repo)
        else:
            q = q.filter_by(other_repo=c.db_repo)
        c.pull_requests = q.all()

        c.pullrequests_pager = Page(c.pull_requests, page=p, items_per_page=100)

        return render('/pullrequests/pullrequest_show_all.html')

    @LoginRequired()
    @NotAnonymous()
    def show_my(self):
        c.closed = request.GET.get('closed') or ''

        c.my_pull_requests = PullRequest.query(
            include_closed=c.closed,
            sorted=True,
        ).filter_by(owner_id=self.authuser.user_id).all()

        c.participate_in_pull_requests = []
        c.participate_in_pull_requests_todo = []
        done_status = set([ChangesetStatus.STATUS_APPROVED, ChangesetStatus.STATUS_REJECTED])
        for pr in PullRequest.query(
            include_closed=c.closed,
            reviewer_id=self.authuser.user_id,
            sorted=True,
        ):
            status = pr.user_review_status(c.authuser.user_id) # very inefficient!!!
            if status in done_status:
                c.participate_in_pull_requests.append(pr)
            else:
                c.participate_in_pull_requests_todo.append(pr)

        return render('/pullrequests/pullrequest_show_my.html')

    @LoginRequired()
    @NotAnonymous()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    def index(self):
        org_repo = c.db_repo
        org_scm_instance = org_repo.scm_instance
        try:
            org_scm_instance.get_changeset()
        except EmptyRepositoryError as e:
            h.flash(h.literal(_('There are no changesets yet')),
                    category='warning')
            raise HTTPFound(location=url('summary_home', repo_name=org_repo.repo_name))

        org_rev = request.GET.get('rev_end')
        # rev_start is not directly useful - its parent could however be used
        # as default for other and thus give a simple compare view
        rev_start = request.GET.get('rev_start')
        other_rev = None
        if rev_start:
            starters = org_repo.get_changeset(rev_start).parents
            if starters:
                other_rev = starters[0].raw_id
            else:
                other_rev = org_repo.scm_instance.EMPTY_CHANGESET
        branch = request.GET.get('branch')

        c.cs_repos = [(org_repo.repo_name, org_repo.repo_name)]
        c.default_cs_repo = org_repo.repo_name
        c.cs_refs, c.default_cs_ref = self._get_repo_refs(org_scm_instance, rev=org_rev, branch=branch)

        default_cs_ref_type, default_cs_branch, default_cs_rev = c.default_cs_ref.split(':')
        if default_cs_ref_type != 'branch':
            default_cs_branch = org_repo.get_changeset(default_cs_rev).branch

        # add org repo to other so we can open pull request against peer branches on itself
        c.a_repos = [(org_repo.repo_name, '%s (self)' % org_repo.repo_name)]

        if org_repo.parent:
            # add parent of this fork also and select it.
            # use the same branch on destination as on source, if available.
            c.a_repos.append((org_repo.parent.repo_name, '%s (parent)' % org_repo.parent.repo_name))
            c.a_repo = org_repo.parent
            c.a_refs, c.default_a_ref = self._get_repo_refs(
                    org_repo.parent.scm_instance, branch=default_cs_branch, rev=other_rev)

        else:
            c.a_repo = org_repo
            c.a_refs, c.default_a_ref = self._get_repo_refs(org_scm_instance, rev=other_rev)

        # gather forks and add to this list ... even though it is rare to
        # request forks to pull from their parent
        for fork in org_repo.forks:
            c.a_repos.append((fork.repo_name, fork.repo_name))

        return render('/pullrequests/pullrequest.html')

    @LoginRequired()
    @NotAnonymous()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    @jsonify
    def repo_info(self, repo_name):
        repo = c.db_repo
        refs, selected_ref = self._get_repo_refs(repo.scm_instance)
        return {
            'description': repo.description.split('\n', 1)[0],
            'selected_ref': selected_ref,
            'refs': refs,
            }

    @LoginRequired()
    @NotAnonymous()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    def create(self, repo_name):
        repo = c.db_repo
        try:
            _form = PullRequestForm(repo.repo_id)().to_python(request.POST)
        except formencode.Invalid as errors:
            log.error(traceback.format_exc())
            log.error(str(errors))
            msg = _('Error creating pull request: %s') % errors.msg
            h.flash(msg, 'error')
            raise HTTPBadRequest

        # heads up: org and other might seem backward here ...
        org_repo_name = _form['org_repo']
        org_ref = _form['org_ref'] # will have merge_rev as rev but symbolic name
        org_repo = RepoModel()._get_repo(org_repo_name)
        (org_ref_type,
         org_ref_name,
         org_rev) = org_ref.split(':')
        if org_ref_type == 'rev':
            org_ref_type = 'branch'
            cs = org_repo.scm_instance.get_changeset(org_rev)
            org_ref = '%s:%s:%s' % (org_ref_type, cs.branch, cs.raw_id)

        other_repo_name = _form['other_repo']
        other_ref = _form['other_ref'] # will have symbolic name and head revision
        other_repo = RepoModel()._get_repo(other_repo_name)
        (other_ref_type,
         other_ref_name,
         other_rev) = other_ref.split(':')
        if other_ref_type == 'rev':
            cs = other_repo.scm_instance.get_changeset(other_rev)
            other_ref_name = cs.raw_id[:12]
            other_ref = '%s:%s:%s' % (other_ref_type, other_ref_name, cs.raw_id)

        cs_ranges, _cs_ranges_not, ancestor_rev = \
            CompareController._get_changesets(org_repo.scm_instance.alias,
                                              other_repo.scm_instance, other_rev, # org and other "swapped"
                                              org_repo.scm_instance, org_rev,
                                              )
        if ancestor_rev is None:
            ancestor_rev = org_repo.scm_instance.EMPTY_CHANGESET
        revisions = [cs_.raw_id for cs_ in cs_ranges]

        # hack: ancestor_rev is not an other_rev but we want to show the
        # requested destination and have the exact ancestor
        other_ref = '%s:%s:%s' % (other_ref_type, other_ref_name, ancestor_rev)

        reviewer_ids = []

        title = _form['pullrequest_title']
        if not title:
            if org_repo_name == other_repo_name:
                title = '%s to %s' % (h.short_ref(org_ref_type, org_ref_name),
                                      h.short_ref(other_ref_type, other_ref_name))
            else:
                title = '%s#%s to %s#%s' % (org_repo_name, h.short_ref(org_ref_type, org_ref_name),
                                            other_repo_name, h.short_ref(other_ref_type, other_ref_name))
        description = _form['pullrequest_desc'].strip() or _('No description')
        try:
            pull_request = PullRequestModel().create(
                self.authuser.user_id, org_repo_name, org_ref, other_repo_name,
                other_ref, revisions, reviewer_ids, title, description
            )
            Session().commit()
            h.flash(_('Successfully opened new pull request'),
                    category='success')
        except UserInvalidException as u:
            h.flash(_('Invalid reviewer "%s" specified') % u, category='error')
            raise HTTPBadRequest()
        except Exception:
            h.flash(_('Error occurred while creating pull request'),
                    category='error')
            log.error(traceback.format_exc())
            raise HTTPFound(location=url('pullrequest_home', repo_name=repo_name))

        raise HTTPFound(location=pull_request.url())

    def create_new_iteration(self, old_pull_request, new_rev, title, description, reviewer_ids):
        org_repo = RepoModel()._get_repo(old_pull_request.org_repo.repo_name)
        org_ref_type, org_ref_name, org_rev = old_pull_request.org_ref.split(':')
        new_org_rev = self._get_ref_rev(org_repo, 'rev', new_rev)

        other_repo = RepoModel()._get_repo(old_pull_request.other_repo.repo_name)
        other_ref_type, other_ref_name, other_rev = old_pull_request.other_ref.split(':') # other_rev is ancestor
        #assert other_ref_type == 'branch', other_ref_type # TODO: what if not?
        new_other_rev = self._get_ref_rev(other_repo, other_ref_type, other_ref_name)

        cs_ranges, _cs_ranges_not, ancestor_rev = CompareController._get_changesets(org_repo.scm_instance.alias,
            other_repo.scm_instance, new_other_rev, # org and other "swapped"
            org_repo.scm_instance, new_org_rev)

        old_revisions = set(old_pull_request.revisions)
        revisions = [cs.raw_id for cs in cs_ranges]
        new_revisions = [r for r in revisions if r not in old_revisions]
        lost = old_revisions.difference(revisions)

        infos = ['This is a new iteration of %s "%s".' %
                 (h.canonical_url('pullrequest_show', repo_name=old_pull_request.other_repo.repo_name,
                      pull_request_id=old_pull_request.pull_request_id),
                  old_pull_request.title)]

        if lost:
            infos.append(_('Missing changesets since the previous iteration:'))
            for r in old_pull_request.revisions:
                if r in lost:
                    rev_desc = org_repo.get_changeset(r).message.split('\n')[0]
                    infos.append('  %s %s' % (h.short_id(r), rev_desc))

        if new_revisions:
            infos.append(_('New changesets on %s %s since the previous iteration:') % (org_ref_type, org_ref_name))
            for r in reversed(revisions):
                if r in new_revisions:
                    rev_desc = org_repo.get_changeset(r).message.split('\n')[0]
                    infos.append('  %s %s' % (h.short_id(r), h.shorter(rev_desc, 80)))

            if ancestor_rev == other_rev:
                infos.append(_("Ancestor didn't change - diff since previous iteration:"))
                infos.append(h.canonical_url('compare_url',
                                 repo_name=org_repo.repo_name, # other_repo is always same as repo_name
                                 org_ref_type='rev', org_ref_name=h.short_id(org_rev), # use old org_rev as base
                                 other_ref_type='rev', other_ref_name=h.short_id(new_org_rev),
                                 )) # note: linear diff, merge or not doesn't matter
            else:
                infos.append(_('This iteration is based on another %s revision and there is no simple diff.') % other_ref_name)
        else:
           infos.append(_('No changes found on %s %s since previous iteration.') % (org_ref_type, org_ref_name))
           # TODO: fail?

        # hack: ancestor_rev is not an other_ref but we want to show the
        # requested destination and have the exact ancestor
        new_other_ref = '%s:%s:%s' % (other_ref_type, other_ref_name, ancestor_rev)
        new_org_ref = '%s:%s:%s' % (org_ref_type, org_ref_name, new_org_rev)

        try:
            title, old_v = re.match(r'(.*)\(v(\d+)\)\s*$', title).groups()
            v = int(old_v) + 1
        except (AttributeError, ValueError):
            v = 2
        title = '%s (v%s)' % (title.strip(), v)

        # using a mail-like separator, insert new iteration info in description with latest first
        descriptions = description.replace('\r\n', '\n').split('\n-- \n', 1)
        description = descriptions[0].strip() + '\n\n-- \n' + '\n'.join(infos)
        if len(descriptions) > 1:
            description += '\n\n' + descriptions[1].strip()

        try:
            pull_request = PullRequestModel().create(
                self.authuser.user_id,
                old_pull_request.org_repo.repo_name, new_org_ref,
                old_pull_request.other_repo.repo_name, new_other_ref,
                revisions, reviewer_ids, title, description
            )
        except UserInvalidException as u:
            h.flash(_('Invalid reviewer "%s" specified') % u, category='error')
            raise HTTPBadRequest()
        except Exception:
            h.flash(_('Error occurred while creating pull request'),
                    category='error')
            log.error(traceback.format_exc())
            raise HTTPFound(location=old_pull_request.url())

        ChangesetCommentsModel().create(
            text=_('Closed, next iteration: %s .') % pull_request.url(canonical=True),
            repo=old_pull_request.other_repo_id,
            author=c.authuser.user_id,
            pull_request=old_pull_request.pull_request_id,
            closing_pr=True)
        PullRequestModel().close_pull_request(old_pull_request.pull_request_id)

        Session().commit()
        h.flash(_('New pull request iteration created'),
                category='success')

        raise HTTPFound(location=pull_request.url())

    # pullrequest_post for PR editing
    @LoginRequired()
    @NotAnonymous()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    def post(self, repo_name, pull_request_id):
        pull_request = PullRequest.get_or_404(pull_request_id)
        if pull_request.is_closed():
            raise HTTPForbidden()
        assert pull_request.other_repo.repo_name == repo_name
        #only owner or admin can update it
        owner = pull_request.owner_id == c.authuser.user_id
        repo_admin = h.HasRepoPermissionAny('repository.admin')(c.repo_name)
        if not (h.HasPermissionAny('hg.admin')() or repo_admin or owner):
            raise HTTPForbidden()

        _form = PullRequestPostForm()().to_python(request.POST)
        reviewer_ids = set(int(s) for s in _form['review_members'])

        org_reviewer_ids = set(int(s) for s in _form['org_review_members'])
        current_reviewer_ids = set(prr.user_id for prr in pull_request.reviewers)
        other_added = [User.get(u) for u in current_reviewer_ids - org_reviewer_ids]
        other_removed = [User.get(u) for u in org_reviewer_ids - current_reviewer_ids]
        if other_added:
            h.flash(_('Meanwhile, the following reviewers have been added: %s') %
                    (', '.join(u.username for u in other_added)),
                    category='warning')
        if other_removed:
            h.flash(_('Meanwhile, the following reviewers have been removed: %s') %
                    (', '.join(u.username for u in other_removed)),
                    category='warning')

        if _form['updaterev']:
            return self.create_new_iteration(pull_request,
                                      _form['updaterev'],
                                      _form['pullrequest_title'],
                                      _form['pullrequest_desc'],
                                      reviewer_ids)

        old_description = pull_request.description
        pull_request.title = _form['pullrequest_title']
        pull_request.description = _form['pullrequest_desc'].strip() or _('No description')
        pull_request.owner = User.get_by_username(_form['owner'])
        user = User.get(c.authuser.user_id)
        add_reviewer_ids = reviewer_ids - org_reviewer_ids - current_reviewer_ids
        remove_reviewer_ids = (org_reviewer_ids - reviewer_ids) & current_reviewer_ids
        try:
            PullRequestModel().mention_from_description(user, pull_request, old_description)
            PullRequestModel().add_reviewers(user, pull_request, add_reviewer_ids)
            PullRequestModel().remove_reviewers(user, pull_request, remove_reviewer_ids)
        except UserInvalidException as u:
            h.flash(_('Invalid reviewer "%s" specified') % u, category='error')
            raise HTTPBadRequest()

        Session().commit()
        h.flash(_('Pull request updated'), category='success')

        raise HTTPFound(location=pull_request.url())

    @LoginRequired()
    @NotAnonymous()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    @jsonify
    def delete(self, repo_name, pull_request_id):
        pull_request = PullRequest.get_or_404(pull_request_id)
        #only owner can delete it !
        if pull_request.owner_id == c.authuser.user_id:
            PullRequestModel().delete(pull_request)
            Session().commit()
            h.flash(_('Successfully deleted pull request'),
                    category='success')
            raise HTTPFound(location=url('my_pullrequests'))
        raise HTTPForbidden()

    @LoginRequired()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    def show(self, repo_name, pull_request_id, extra=None):
        repo_model = RepoModel()
        c.users_array = repo_model.get_users_js()
        c.user_groups_array = repo_model.get_user_groups_js()
        c.pull_request = PullRequest.get_or_404(pull_request_id)
        c.allowed_to_change_status = self._get_is_allowed_change_status(c.pull_request)
        cc_model = ChangesetCommentsModel()
        cs_model = ChangesetStatusModel()

        # pull_requests repo_name we opened it against
        # ie. other_repo must match
        if repo_name != c.pull_request.other_repo.repo_name:
            raise HTTPNotFound

        # load compare data into template context
        c.cs_repo = c.pull_request.org_repo
        (c.cs_ref_type,
         c.cs_ref_name,
         c.cs_rev) = c.pull_request.org_ref.split(':')

        c.a_repo = c.pull_request.other_repo
        (c.a_ref_type,
         c.a_ref_name,
         c.a_rev) = c.pull_request.other_ref.split(':') # other_rev is ancestor

        org_scm_instance = c.cs_repo.scm_instance # property with expensive cache invalidation check!!!
        c.cs_repo = c.cs_repo
        try:
            c.cs_ranges = [org_scm_instance.get_changeset(x)
                           for x in c.pull_request.revisions]
        except ChangesetDoesNotExistError:
            c.cs_ranges = []
            h.flash(_('Revision %s not found in %s') % (x, c.cs_repo.repo_name),
                'error')
        c.cs_ranges_org = None # not stored and not important and moving target - could be calculated ...
        revs = [ctx.revision for ctx in reversed(c.cs_ranges)]
        c.jsdata = json.dumps(graph_data(org_scm_instance, revs))

        c.is_range = False
        try:
            if c.a_ref_type == 'rev': # this looks like a free range where target is ancestor
                cs_a = org_scm_instance.get_changeset(c.a_rev)
                root_parents = c.cs_ranges[0].parents
                c.is_range = cs_a in root_parents
                #c.merge_root = len(root_parents) > 1 # a range starting with a merge might deserve a warning
        except ChangesetDoesNotExistError: # probably because c.a_rev not found
            pass
        except IndexError: # probably because c.cs_ranges is empty, probably because revisions are missing
            pass

        avail_revs = set()
        avail_show = []
        c.cs_branch_name = c.cs_ref_name
        c.a_branch_name = None
        other_scm_instance = c.a_repo.scm_instance
        c.update_msg = ""
        c.update_msg_other = ""
        try:
            if not c.cs_ranges:
                c.update_msg = _('Error: changesets not found when displaying pull request from %s.') % c.cs_rev
            elif org_scm_instance.alias == 'hg' and c.a_ref_name != 'ancestor':
                if c.cs_ref_type != 'branch':
                    c.cs_branch_name = org_scm_instance.get_changeset(c.cs_ref_name).branch # use ref_type ?
                c.a_branch_name = c.a_ref_name
                if c.a_ref_type != 'branch':
                    try:
                        c.a_branch_name = other_scm_instance.get_changeset(c.a_ref_name).branch # use ref_type ?
                    except EmptyRepositoryError:
                        c.a_branch_name = 'null' # not a branch name ... but close enough
                # candidates: descendants of old head that are on the right branch
                #             and not are the old head itself ...
                #             and nothing at all if old head is a descendant of target ref name
                if not c.is_range and other_scm_instance._repo.revs('present(%s)::&%s', c.cs_ranges[-1].raw_id, c.a_branch_name):
                    c.update_msg = _('This pull request has already been merged to %s.') % c.a_branch_name
                elif c.pull_request.is_closed():
                    c.update_msg = _('This pull request has been closed and can not be updated.')
                else: # look for descendants of PR head on source branch in org repo
                    avail_revs = org_scm_instance._repo.revs('%s:: & branch(%s)',
                                                             revs[0], c.cs_branch_name)
                    if len(avail_revs) > 1: # more than just revs[0]
                        # also show changesets that not are descendants but would be merged in
                        targethead = other_scm_instance.get_changeset(c.a_branch_name).raw_id
                        if org_scm_instance.path != other_scm_instance.path:
                            # Note: org_scm_instance.path must come first so all
                            # valid revision numbers are 100% org_scm compatible
                            # - both for avail_revs and for revset results
                            hgrepo = unionrepo.unionrepository(org_scm_instance.baseui,
                                                               org_scm_instance.path,
                                                               other_scm_instance.path)
                        else:
                            hgrepo = org_scm_instance._repo
                        show = set(hgrepo.revs('::%ld & !::parents(%s) & !::%s',
                                               avail_revs, revs[0], targethead))
                        c.update_msg = _('The following additional changes are available on %s:') % c.cs_branch_name
                    else:
                        show = set()
                        avail_revs = set() # drop revs[0]
                        c.update_msg = _('No additional changesets found for iterating on this pull request.')

                    # TODO: handle branch heads that not are tip-most
                    brevs = org_scm_instance._repo.revs('%s - %ld - %s', c.cs_branch_name, avail_revs, revs[0])
                    if brevs:
                        # also show changesets that are on branch but neither ancestors nor descendants
                        show.update(org_scm_instance._repo.revs('::%ld - ::%ld - ::%s', brevs, avail_revs, c.a_branch_name))
                        show.add(revs[0]) # make sure graph shows this so we can see how they relate
                        c.update_msg_other = _('Note: Branch %s has another head: %s.') % (c.cs_branch_name,
                            h.short_id(org_scm_instance.get_changeset((max(brevs))).raw_id))

                    avail_show = sorted(show, reverse=True)

            elif org_scm_instance.alias == 'git':
                c.cs_repo.scm_instance.get_changeset(c.cs_rev) # check it exists - raise ChangesetDoesNotExistError if not
                c.update_msg = _("Git pull requests don't support iterating yet.")
        except ChangesetDoesNotExistError:
            c.update_msg = _('Error: some changesets not found when displaying pull request from %s.') % c.cs_rev

        c.avail_revs = avail_revs
        c.avail_cs = [org_scm_instance.get_changeset(r) for r in avail_show]
        c.avail_jsdata = json.dumps(graph_data(org_scm_instance, avail_show))

        raw_ids = [x.raw_id for x in c.cs_ranges]
        c.cs_comments = c.cs_repo.get_comments(raw_ids)
        c.statuses = c.cs_repo.statuses(raw_ids)

        ignore_whitespace = request.GET.get('ignorews') == '1'
        line_context = safe_int(request.GET.get('context'), 3)
        c.ignorews_url = _ignorews_url
        c.context_url = _context_url
        c.fulldiff = request.GET.get('fulldiff')
        diff_limit = self.cut_off_limit if not c.fulldiff else None

        # we swap org/other ref since we run a simple diff on one repo
        log.debug('running diff between %s and %s in %s',
                  c.a_rev, c.cs_rev, org_scm_instance.path)
        try:
            txtdiff = org_scm_instance.get_diff(rev1=safe_str(c.a_rev), rev2=safe_str(c.cs_rev),
                                                ignore_whitespace=ignore_whitespace,
                                                context=line_context)
        except ChangesetDoesNotExistError:
            txtdiff =  _("The diff can't be shown - the PR revisions could not be found.")
        diff_processor = diffs.DiffProcessor(txtdiff or '', format='gitdiff',
                                             diff_limit=diff_limit)
        _parsed = diff_processor.prepare()

        c.limited_diff = False
        if isinstance(_parsed, LimitedDiffContainer):
            c.limited_diff = True

        c.file_diff_data = OrderedDict()
        c.lines_added = 0
        c.lines_deleted = 0

        for f in _parsed:
            st = f['stats']
            c.lines_added += st['added']
            c.lines_deleted += st['deleted']
            filename = f['filename']
            fid = h.FID('', filename)
            diff = diff_processor.as_html(enable_comments=True,
                                          parsed_lines=[f])
            c.file_diff_data[fid] = (None, f['operation'], f['old_filename'], filename, diff, st)

        # inline comments
        c.inline_cnt = 0
        c.inline_comments = cc_model.get_inline_comments(
                                c.db_repo.repo_id,
                                pull_request=pull_request_id)
        # count inline comments
        for __, lines in c.inline_comments:
            for comments in lines.values():
                c.inline_cnt += len(comments)
        # comments
        c.comments = cc_model.get_comments(c.db_repo.repo_id,
                                           pull_request=pull_request_id)

        # (badly named) pull-request status calculation based on reviewer votes
        (c.pull_request_reviewers,
         c.pull_request_pending_reviewers,
         c.current_voting_result,
         ) = cs_model.calculate_pull_request_result(c.pull_request)
        c.changeset_statuses = ChangesetStatus.STATUSES

        c.as_form = False
        c.ancestor = None # there is one - but right here we don't know which
        return render('/pullrequests/pullrequest_show.html')

    @LoginRequired()
    @NotAnonymous()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    @jsonify
    def comment(self, repo_name, pull_request_id):
        pull_request = PullRequest.get_or_404(pull_request_id)

        status = request.POST.get('changeset_status')
        close_pr = request.POST.get('save_close')
        delete = request.POST.get('save_delete')
        f_path = request.POST.get('f_path')
        line_no = request.POST.get('line')

        if (status or close_pr or delete) and (f_path or line_no):
            # status votes and closing is only possible in general comments
            raise HTTPBadRequest()

        allowed_to_change_status = self._get_is_allowed_change_status(pull_request)
        if not allowed_to_change_status:
            if status or close_pr:
                h.flash(_('No permission to change pull request status'), 'error')
                raise HTTPForbidden()

        if delete == "delete":
            if (pull_request.owner_id == c.authuser.user_id or
                h.HasPermissionAny('hg.admin')() or
                h.HasRepoPermissionAny('repository.admin')(pull_request.org_repo.repo_name) or
                h.HasRepoPermissionAny('repository.admin')(pull_request.other_repo.repo_name)
                ) and not pull_request.is_closed():
                PullRequestModel().delete(pull_request)
                Session().commit()
                h.flash(_('Successfully deleted pull request %s') % pull_request_id,
                        category='success')
                return {
                   'location': url('my_pullrequests'), # or repo pr list?
                }
                raise HTTPFound(location=url('my_pullrequests')) # or repo pr list?
            raise HTTPForbidden()

        text = request.POST.get('text', '').strip()

        comment = create_comment(
            text,
            status,
            pull_request_id=pull_request_id,
            f_path=f_path,
            line_no=line_no,
            closing_pr=close_pr,
        )

        action_logger(self.authuser,
                      'user_commented_pull_request:%s' % pull_request_id,
                      c.db_repo, self.ip_addr, self.sa)

        if status:
            ChangesetStatusModel().set_status(
                c.db_repo.repo_id,
                status,
                c.authuser.user_id,
                comment,
                pull_request=pull_request_id
            )

        if close_pr:
            PullRequestModel().close_pull_request(pull_request_id)
            action_logger(self.authuser,
                          'user_closed_pull_request:%s' % pull_request_id,
                          c.db_repo, self.ip_addr, self.sa)

        Session().commit()

        if not request.environ.get('HTTP_X_PARTIAL_XHR'):
            raise HTTPFound(location=pull_request.url())

        data = {
           'target_id': h.safeid(h.safe_unicode(request.POST.get('f_path'))),
        }
        if comment is not None:
            c.comment = comment
            data.update(comment.get_dict())
            data.update({'rendered_text':
                         render('changeset/changeset_comment_block.html')})

        return data

    @LoginRequired()
    @NotAnonymous()
    @HasRepoPermissionAnyDecorator('repository.read', 'repository.write',
                                   'repository.admin')
    @jsonify
    def delete_comment(self, repo_name, comment_id):
        co = ChangesetComment.get(comment_id)
        if co.pull_request.is_closed():
            #don't allow deleting comments on closed pull request
            raise HTTPForbidden()

        owner = co.author_id == c.authuser.user_id
        repo_admin = h.HasRepoPermissionAny('repository.admin')(c.repo_name)
        if h.HasPermissionAny('hg.admin')() or repo_admin or owner:
            ChangesetCommentsModel().delete(comment=co)
            Session().commit()
            return True
        else:
            raise HTTPForbidden()