if co.pull_request and co.pull_request.is_closed():

        # don't allow deleting comments on closed pull request

        raise HTTPForbidden()

    owner = co.author_id == request.authuser.user_id

    repo_admin = h.HasRepoPermissionLevel('admin')(repo_name)

    if h.HasPermissionAny('hg.admin')() or repo_admin or owner:

        ChangesetCommentsModel().delete(comment=co)

        meta.Session().commit()

        return True

    else:

        raise HTTPForbidden()

class ChangesetController(BaseRepoController):

    def _before(self, *args, **kwargs):

        super(ChangesetController, self)._before(*args, **kwargs)

        c.affected_files_cut_off = 60

    def _index(self, revision, method):

        c.pull_request = None

        c.fulldiff = request.GET.get('fulldiff') # for reporting number of changed files

        # get ranges of revisions if preset

        rev_range = revision.split('...')[:2]

        c.cs_repo = c.db_repo

        try:

            if len(rev_range) == 2:

                rev_start = rev_range[0]

                rev_end = rev_range[1]

                rev_ranges = c.db_repo_scm_instance.get_changesets(start=rev_start,

                                                             end=rev_end)

            else:

                rev_ranges = [c.db_repo_scm_instance.get_changeset(revision)]

            c.cs_ranges = list(rev_ranges)

            if not c.cs_ranges:

                raise RepositoryError('Changeset range returned empty result')

        except (ChangesetDoesNotExistError, EmptyRepositoryError):

            log.debug(traceback.format_exc())

            msg = _('Such revision does not exist for this repository')

            h.flash(msg, category='error')

            raise HTTPNotFound()

        c.changes = OrderedDict()

        c.lines_added = 0  # count of lines added

        c.lines_deleted = 0  # count of lines removes

        c.changeset_statuses = db.ChangesetStatus.STATUSES

        comments = dict()

                            .get_inline_comments(c.db_repo.repo_id,

                                                 revision=changeset.raw_id)

                c.inline_comments.extend(inlines)

            cs2 = changeset.raw_id

            cs1 = changeset.parents[0].raw_id if changeset.parents else EmptyChangeset().raw_id

            ignore_whitespace_diff = h.get_ignore_whitespace_diff(request.GET)

            diff_context_size = h.get_diff_context_size(request.GET)

            raw_diff = diffs.get_diff(c.db_repo_scm_instance, cs1, cs2,

                ignore_whitespace=ignore_whitespace_diff, context=diff_context_size)

            diff_limit = None if c.fulldiff else self.cut_off_limit

            file_diff_data = []

            if method == 'show':

                diff_processor = diffs.DiffProcessor(raw_diff,

                                                     vcs=c.db_repo_scm_instance.alias,

                                                     diff_limit=diff_limit)

                c.limited_diff = diff_processor.limited_diff

                for f in diff_processor.parsed:

                    st = f['stats']

                    c.lines_added += st['added']

                    c.lines_deleted += st['deleted']

                    filename = f['filename']

                    fid = h.FID(changeset.raw_id, filename)

                    url_fid = h.FID('', filename)

                    file_diff_data.append((fid, url_fid, f['operation'], f['old_filename'], filename, html_diff, st))

            else:

                # downloads/raw we only need RAW diff nothing else

                file_diff_data.append(('', None, None, None, raw_diff, None))

            c.changes[changeset.raw_id] = (cs1, cs2, file_diff_data)

        # sort comments in creation order

        c.comments = [com for com_id, com in sorted(comments.items())]

        # count inline comments

        for __, lines in c.inline_comments:

            for comments in lines.values():

                c.inline_cnt += len(comments)

        if len(c.cs_ranges) == 1:

            c.changeset = c.cs_ranges[0]

            c.parent_tmpl = ''.join(['# Parent  %s\n' % x.raw_id

                                     for x in c.changeset.parents])

            c.changeset_graft_source_hash = ascii_str(c.changeset.extra.get(b'source', b''))

            c.changeset_transplant_source_hash = ascii_str(binascii.hexlify(c.changeset.extra.get(b'transplant_source', b'')))

        if method == 'download':

            response.content_type = 'text/plain'

            response.content_disposition = 'attachment; filename=%s.diff' \

                                            % revision[:12]

                log.error('cannot compare across repos %s and %s', org_repo, other_repo)

                h.flash(_('Cannot compare repositories without using common ancestor'), category='error')

                raise HTTPBadRequest

            rev1 = c.a_rev

        diff_limit = None if fulldiff else self.cut_off_limit

        log.debug('running diff between %s and %s in %s',

                  rev1, c.cs_rev, org_repo.scm_instance.path)

        raw_diff = diffs.get_diff(org_repo.scm_instance, rev1=rev1, rev2=c.cs_rev,

                                      ignore_whitespace=ignore_whitespace_diff,

                                      context=diff_context_size)

        diff_processor = diffs.DiffProcessor(raw_diff, diff_limit=diff_limit)

        c.limited_diff = diff_processor.limited_diff

        c.file_diff_data = []

        c.lines_added = 0

        c.lines_deleted = 0

        for f in diff_processor.parsed:

            st = f['stats']

            c.lines_added += st['added']

            c.lines_deleted += st['deleted']

            filename = f['filename']

            fid = h.FID('', filename)

            c.file_diff_data.append((fid, None, f['operation'], f['old_filename'], filename, html_diff, st))

        return render('compare/compare_diff.html')

            raw_diff = diffs.get_gitdiff(node1, node2,

                                      ignore_whitespace=ignore_whitespace_diff,

                                      context=diff_context_size)

            diff_name = '%s_vs_%s.diff' % (diff1, diff2)

            response.content_type = 'text/plain'

            response.content_disposition = (

                'attachment; filename=%s' % diff_name

            )

            return raw_diff

        elif c.action == 'raw':

            raw_diff = diffs.get_gitdiff(node1, node2,

                                      ignore_whitespace=ignore_whitespace_diff,

                                      context=diff_context_size)

            response.content_type = 'text/plain'

            return raw_diff

        else:

            fid = h.FID(diff2, node2.path)

            diff_limit = None if fulldiff else self.cut_off_limit

            c.a_rev, c.cs_rev, a_path, diff, st, op = diffs.wrapped_diff(filenode_old=node1,

                                         filenode_new=node2,

                                         diff_limit=diff_limit,

                                         ignore_whitespace=ignore_whitespace_diff,

            c.file_diff_data = [(fid, fid, op, a_path, node2.path, diff, st)]

            return render('files/file_diff.html')

    @LoginRequired(allow_default_user=True)

    @HasRepoPermissionLevelDecorator('read')

    def diff_2way(self, repo_name, f_path):

        diff1 = request.GET.get('diff1', '')

        diff2 = request.GET.get('diff2', '')

        try:

            if diff1 not in ['', None, 'None', '0' * 12, '0' * 40]:

                c.changeset_1 = c.db_repo_scm_instance.get_changeset(diff1)

                try:

                    node1 = c.changeset_1.get_node(f_path)

                    if node1.is_dir():

                        raise NodeError('%s path is a %s not a file'

                                        % (node1, type(node1)))

                except NodeDoesNotExistError:

                    c.changeset_1 = EmptyChangeset(cs=diff1,

                                                   revision=c.changeset_1.revision,

                                                   repo=c.db_repo_scm_instance)

                    node1 = FileNode(f_path, '', changeset=c.changeset_1)

            else:

                c.changeset_1 = EmptyChangeset(repo=c.db_repo_scm_instance)

                node1 = FileNode(f_path, '', changeset=c.changeset_1)

        diff_context_size = h.get_diff_context_size(request.GET)

        fulldiff = request.GET.get('fulldiff')

        diff_limit = None if fulldiff else self.cut_off_limit

        # 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:

            raw_diff = diffs.get_diff(org_scm_instance, rev1=c.a_rev, rev2=c.cs_rev,

                                      ignore_whitespace=ignore_whitespace_diff, context=diff_context_size)

        except ChangesetDoesNotExistError:

            raw_diff = safe_bytes(_("The diff can't be shown - the PR revisions could not be found."))

        diff_processor = diffs.DiffProcessor(raw_diff, diff_limit=diff_limit)

        c.limited_diff = diff_processor.limited_diff

        c.file_diff_data = []

        c.lines_added = 0

        c.lines_deleted = 0

        for f in diff_processor.parsed:

            st = f['stats']

            c.lines_added += st['added']

            c.lines_deleted += st['deleted']

            filename = f['filename']

            fid = h.FID('', filename)

            c.file_diff_data.append((fid, None, f['operation'], f['old_filename'], filename, html_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 = db.ChangesetStatus.STATUSES

        c.is_ajax_preview = False

        c.ancestors = None # [c.a_rev] ... but that is shown in an other way

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

    r"""Make a string safe for including in an id attribute.

    The HTML spec says that id attributes 'must begin with

    a letter ([A-Za-z]) and may be followed by any number

    of letters, digits ([0-9]), hyphens ("-"), underscores

    ("_"), colons (":"), and periods (".")'. These regexps

    are slightly over-zealous, in that they remove colons

    and periods unnecessarily.

    Whitespace is transformed into underscores, and then

    anything which is not a hyphen or a character that

    matches \w (alphanumerics and underscore) is removed.

    """

    # Transform all whitespace to underscore

    idstring = re.sub(r'\s', "_", idstring)

    # Remove everything that is not a hyphen or a member of \w

    idstring = re.sub(r'(?!-)\W', "", idstring).lower()

    return idstring

def as_html(table_class='code-difftable', line_class='line',

            old_lineno_class='lineno old', new_lineno_class='lineno new',

            no_lineno_class='lineno',

    """

    Return given diff as html table with customized css classes

    """

    _html_empty = True

    _html = []

    _html.append('''<table class="%(table_class)s">\n''' % {

        'table_class': table_class

    })

    for file_info in parsed_lines:

        count_no_lineno = 0  # counter to allow comments on lines without new/old line numbers

        for chunk in file_info['chunks']:

            _html_empty = False

            for change in chunk:

                _html.append('''<tr class="%(lc)s %(action)s">\n''' % {

                    'lc': line_class,

                    'action': change['action']

                })

                if change['old_lineno'] or change['new_lineno']:

                    ###########################################################

                    # OLD LINE NUMBER

                    ###########################################################

                    anchor_old = "%(filename)s_o%(oldline_no)s" % {

                        'filename': _safe_id(file_info['filename']),

                        'nlc': new_lineno_class

                    })

                    _html.append('''<a href="%(url)s" data-pseudo-content="%(label)s"></a>''' % {

                        'label': change['new_lineno'],

                        'url': '#%s' % anchor_new,

                    })

                    _html.append('''</td>\n''')

                else:

                    ###########################################################

                    # NO LINE NUMBER

                    ###########################################################

                    anchor = "%(filename)s_%(count_no_lineno)s" % {

                        'filename': _safe_id(file_info['filename']),

                        'count_no_lineno': count_no_lineno,

                    }

                    count_no_lineno += 1

                    _html.append('''\t<td id="%(anchor)s" class="%(olc)s" colspan="2">''' % {

                        'anchor': anchor,

                        'olc': no_lineno_class,

                    })

                    _html.append('''</td>\n''')

                ###########################################################

                # CODE

                ###########################################################

                    'cc': code_class,

                })

                _html.append('''\n\t\t<div class="add-bubble"><div>&nbsp;</div></div><pre>%(code)s</pre>\n''' % {

                    'code': change['line']

                })

                _html.append('''\t</td>''')

                _html.append('''\n</tr>\n''')

    _html.append('''</table>''')

    if _html_empty:

        return None

    return ''.join(_html)

def wrap_to_table(html):

    """Given a string with html, return it wrapped in a table, similar to what

    DiffProcessor returns."""

    return '''\

              <table class="code-difftable">

                <td class="lineno new"></td>

                </tr>

              </table>''' % html

def wrapped_diff(filenode_old, filenode_new, diff_limit=None,

    """

    Returns a file diff wrapped into a table.

    Checks for diff_limit and presents a message if the diff is too big.

    """

    if filenode_old is None:

        filenode_old = FileNode(filenode_new.path, '', EmptyChangeset())

    op = None

    a_path = filenode_old.path # default, might be overriden by actual rename in diff

    if filenode_old.is_binary or filenode_new.is_binary:

        html_diff = wrap_to_table(_('Binary file'))

        stats = (0, 0)

    elif diff_limit != -1 and (

            diff_limit is None or

            (filenode_old.size < diff_limit and filenode_new.size < diff_limit)):

        raw_diff = get_gitdiff(filenode_old, filenode_new,

                                ignore_whitespace=ignore_whitespace,

                                context=line_context)

        diff_processor = DiffProcessor(raw_diff)

        if diff_processor.parsed: # there should be exactly one element, for the specified file

            f = diff_processor.parsed[0]

            op = f['operation']

            a_path = f['old_filename']

        stats = diff_processor.stat()

    else:

        html_diff = wrap_to_table(_('Changeset was too big and was cut off, use '

                               'diff menu to display this diff'))

        stats = (0, 0)

    if not html_diff:

        submodules = [o for o in [filenode_new, filenode_old] if isinstance(o, SubModuleNode)]

        if submodules:

            html_diff = wrap_to_table(h.escape('Submodule %r' % submodules[0]))

        else:

            html_diff = wrap_to_table(_('No changes detected'))

    cs1 = filenode_old.changeset.raw_id

    cs2 = filenode_new.changeset.raw_id

    return cs1, cs2, a_path, html_diff, stats, op

def get_gitdiff(filenode_old, filenode_new, ignore_whitespace=True, context=3):

    """

    Returns git style diff between given ``filenode_old`` and ``filenode_new``.

    """