From 156f70912213b6520e9056050a8827de66e80176 Mon Sep 17 00:00:00 2001
From: Simon McVittie <smcv@debian.org>
Date: Fri, 4 Nov 2011 19:32:41 +0000
Subject: [PATCH] trail: new plugin (3rd attempt)

---
 IkiWiki/Plugin/trail.pm     | 486 ++++++++++++++++++++++++++++++++++++
 doc/style.css               |  35 +++
 doc/templates.mdwn          |   2 +
 t/trail.t                   | 159 ++++++++++++
 templates/page.tmpl         |  11 +
 templates/trails.tmpl       |  23 ++
 themes/actiontabs/style.css |   5 +
 themes/blueview/style.css   |   9 +-
 8 files changed, 728 insertions(+), 2 deletions(-)
 create mode 100644 IkiWiki/Plugin/trail.pm
 create mode 100755 t/trail.t
 create mode 100644 templates/trails.tmpl

diff --git a/IkiWiki/Plugin/trail.pm b/IkiWiki/Plugin/trail.pm
new file mode 100644
index 000000000..e9b4d9cd4
--- /dev/null
+++ b/IkiWiki/Plugin/trail.pm
@@ -0,0 +1,486 @@
+#!/usr/bin/perl
+# Copyright © 2008-2011 Joey Hess
+# Copyright © 2009-2011 Simon McVittie <http://smcv.pseudorandom.co.uk/>
+# Licensed under the GNU GPL, version 2, or any later version published by the
+# Free Software Foundation
+package IkiWiki::Plugin::trail;
+
+use warnings;
+use strict;
+use IkiWiki 3.00;
+
+sub import {
+	hook(type => "getsetup", id => "trail", call => \&getsetup);
+	hook(type => "needsbuild", id => "trail", call => \&needsbuild);
+	hook(type => "preprocess", id => "trail", call => \&preprocess_trail, scan => 1);
+	hook(type => "preprocess", id => "trailinline", call => \&preprocess_trailinline, scan => 1);
+	hook(type => "preprocess", id => "trailitem", call => \&preprocess_trailitem, scan => 1);
+	hook(type => "preprocess", id => "traillink", call => \&preprocess_traillink, scan => 1);
+	hook(type => "pagetemplate", id => "trail", call => \&pagetemplate);
+}
+
+=head1 Page state
+
+If a page C<$T> is a trail, then it can have
+
+=over
+
+=item * C<$pagestate{$T}{trail}{contents}>
+
+Reference to an array of pagespecs or links in the trail.
+
+=item * C<$pagestate{$T}{trail}{sort}>
+
+A [[ikiwiki/pagespec/sorting]] order; if absent or undef, the trail is in
+the order given by the links that form it
+
+=item * C<$pagestate{$T}{trail}{circular}>
+
+True if this trail is circular (i.e. going "next" from the last item is
+allowed, and takes you back to the first)
+
+=item * C<$pagestate{$T}{trail}{reverse}>
+
+True if C<sort> is to be reversed.
+
+=back
+
+If a page C<$M> is a member of a trail C<$T>, then it has
+
+=over
+
+=item * C<$pagestate{$M}{trail}{item}{$T}[0]>
+
+The page before this one in C<$T> at the last rebuild, or undef.
+
+=item * C<$pagestate{$M}{trail}{item}{$T}[1]>
+
+The page after this one in C<$T> at the last refresh, or undef.
+
+=back
+
+=cut
+
+sub getsetup () {
+	return
+		plugin => {
+			safe => 1,
+			rebuild => undef,
+		},
+}
+
+sub needsbuild (@) {
+	my $needsbuild=shift;
+	foreach my $page (keys %pagestate) {
+		if (exists $pagestate{$page}{trail}) {
+			if (exists $pagesources{$page} &&
+			    grep { $_ eq $pagesources{$page} } @$needsbuild) {
+				# Remove state, it will be re-added
+				# if the preprocessor directive is still
+				# there during the rebuild. {item} is the
+				# only thing that's added for items, not
+				# trails, and it's harmless to delete that -
+				# the item is being rebuilt anyway.
+				delete $pagestate{$page}{trail};
+			}
+		}
+	}
+	return $needsbuild;
+}
+
+=for wiki
+
+The `trail` directive is supplied by the [[plugins/contrib/trail]]
+plugin. It sets options for the trail represented by this page. Example usage:
+
+    \[[!trail sort="meta(date)" circular="no" pages="blog/posts/*"]]
+
+The available options are:
+
+* `sort`: sets a [[ikiwiki/pagespec/sorting]] order; if not specified, the
+  items of the trail are ordered according to the first link to each item
+  found on the trail page
+
+* `circular`: if set to `yes` or `1`, the trail is made into a loop by
+  making the last page's "next" link point to the first page, and the first
+  page's "previous" link point to the last page
+
+* `pages`: add the given pages to the trail
+
+=cut
+
+sub preprocess_trail (@) {
+	my %params = @_;
+
+	if (exists $params{circular}) {
+		$pagestate{$params{page}}{trail}{circular} =
+			IkiWiki::yesno($params{circular});
+	}
+
+	if (exists $params{sort}) {
+		$pagestate{$params{page}}{trail}{sort} = $params{sort};
+	}
+
+	if (exists $params{reverse}) {
+		$pagestate{$params{page}}{trail}{reverse} = $params{reverse};
+	}
+
+	if (exists $params{pages}) {
+		push @{$pagestate{$params{page}}{trail}{contents}}, "pagespec $params{pages}";
+	}
+
+	if (exists $params{pagenames}) {
+		my @list = map { "link $_" } split ' ', $params{pagenames};
+		push @{$pagestate{$params{page}}{trail}{contents}}, @list;
+	}
+
+	return "";
+}
+
+=for wiki
+
+The `trailinline` directive is supplied by the [[plugins/contrib/trail]]
+plugin. It behaves like the [[trail]] and [[inline]] directives combined.
+Like [[inline]], it includes the selected pages into the page with the
+directive and/or an RSS or Atom feed; like [[trail]], it turns the
+included pages into a "trail" in which each page has a link to the
+previous and next pages.
+
+    \[[!inline sort="meta(date)" circular="no" pages="blog/posts/*"]]
+
+All the options for the [[inline]] and [[trail]] directives are valid.
+
+The `show`, `skip` and `feedshow` options from [[inline]] do not apply
+to the trail.
+
+* `sort`: sets a [[ikiwiki/pagespec/sorting]] order; if not specified, the
+  items of the trail are ordered according to the first link to each item
+  found on the trail page
+
+* `circular`: if set to `yes` or `1`, the trail is made into a loop by
+  making the last page's "next" link point to the first page, and the first
+  page's "previous" link point to the last page
+
+* `pages`: add the given pages to the trail
+
+=cut
+
+sub preprocess_trailinline (@) {
+	preprocess_trail(@_);
+	return unless defined wantarray;
+
+	if (IkiWiki->can("preprocess_inline")) {
+		return IkiWiki::preprocess_inline(@_);
+	}
+	else {
+		error("trailinline directive requires the inline plugin");
+	}
+}
+
+=for wiki
+
+The `trailitem` directive is supplied by the [[plugins/contrib/trail]] plugin.
+It is used like this:
+
+    \[[!trailitem some_other_page]]
+
+to add `some_other_page` to the trail represented by this page, without
+generating a visible hyperlink.
+
+=cut
+
+sub preprocess_trailitem (@) {
+	my $link = shift;
+	shift;
+
+	my %params = @_;
+	my $trail = $params{page};
+
+	$link = linkpage($link);
+
+	add_link($params{page}, $link, 'trail');
+	push @{$pagestate{$params{page}}{trail}{contents}}, "link $link";
+
+	return "";
+}
+
+=for wiki
+
+The `traillink` directive is supplied by the [[plugins/contrib/trail]] plugin.
+It generates a visible [[ikiwiki/WikiLink]], and also adds the linked page to
+the trail represented by the page containing the directive.
+
+In its simplest form, the first parameter is like the content of a WikiLink:
+
+    \[[!traillink some_other_page]]
+
+The displayed text can also be overridden, either with a `|` symbol or with
+a `text` parameter:
+
+    \[[!traillink Click_here_to_start_the_trail|some_other_page]]
+    \[[!traillink some_other_page text="Click here to start the trail"]]
+
+=cut
+
+sub preprocess_traillink (@) {
+	my $link = shift;
+	shift;
+
+	my %params = @_;
+	my $trail = $params{page};
+
+	$link =~ qr{
+			(?:
+				([^\|]+)	# 1: link text
+				\|		# followed by |
+			)?			# optional
+
+			(.+)			# 2: page to link to
+		}x;
+
+	my $linktext = $1;
+	$link = linkpage($2);
+
+	add_link($params{page}, $link, 'trail');
+	push @{$pagestate{$params{page}}{trail}{contents}}, "link $link";
+
+	if (defined $linktext) {
+		$linktext = pagetitle($linktext);
+	}
+
+	if (exists $params{text}) {
+		$linktext = $params{text};
+	}
+
+	if (defined $linktext) {
+		return htmllink($trail, $params{destpage},
+			$link, linktext => $linktext);
+	}
+
+	return htmllink($trail, $params{destpage}, $link);
+}
+
+# trail => [member1, member2]
+my %trail_to_members;
+# member => { trail => [prev, next] }
+# e.g. if %trail_to_members = (
+#	trail1 => ["member1", "member2"],
+#	trail2 => ["member0", "member1"],
+# )
+#
+# then $member_to_trails{member1} = {
+#	trail1 => [undef, "member2"],
+#	trail2 => ["member0", undef],
+# }
+my %member_to_trails;
+
+# member => 1
+my %rebuild_trail_members;
+
+sub trails_differ {
+	my ($old, $new) = @_;
+
+	foreach my $trail (keys %$old) {
+		if (! exists $new->{$trail}) {
+			return 1;
+		}
+		my ($old_p, $old_n) = @{$old->{$trail}};
+		my ($new_p, $new_n) = @{$new->{$trail}};
+		$old_p = "" unless defined $old_p;
+		$old_n = "" unless defined $old_n;
+		$new_p = "" unless defined $new_p;
+		$new_n = "" unless defined $new_n;
+		if ($old_p ne $new_p) {
+			return 1;
+		}
+		if ($old_n ne $new_n) {
+			return 1;
+		}
+	}
+
+	foreach my $trail (keys %$new) {
+		if (! exists $old->{$trail}) {
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+my $done_prerender = 0;
+
+my %origsubs;
+
+sub prerender {
+	return if $done_prerender;
+
+	$origsubs{render_backlinks} = \&IkiWiki::render_backlinks;
+	inject(name => "IkiWiki::render_backlinks", call => \&render_backlinks);
+
+	%trail_to_members = ();
+	%member_to_trails = ();
+
+	foreach my $trail (keys %pagestate) {
+		next unless exists $pagestate{$trail}{trail}{contents};
+
+		my $members = [];
+		my @contents = @{$pagestate{$trail}{trail}{contents}};
+
+
+		foreach my $c (@contents) {
+			if ($c =~ m/^pagespec (.*)$/) {
+				push @$members, pagespec_match_list($trail, $1);
+			}
+			elsif ($c =~ m/^link (.*)$/) {
+				my $best = bestlink($trail, $1);
+				push @$members, $best if length $best;
+			}
+		}
+
+		if (defined $pagestate{$trail}{trail}{sort}) {
+			# re-sort
+			@$members = pagespec_match_list($trail, 'internal(*)',
+				list => $members,
+				sort => $pagestate{$trail}{trail}{sort});
+		}
+
+		if (IkiWiki::yesno $pagestate{$trail}{trail}{reverse}) {
+			@$members = reverse @$members;
+		}
+
+		# uniquify
+		my %seen;
+		my @tmp;
+		foreach my $member (@$members) {
+			push @tmp, $member unless $seen{$member};
+			$seen{$member} = 1;
+		}
+		$members = [@tmp];
+
+		for (my $i = 0; $i <= $#$members; $i++) {
+			my $member = $members->[$i];
+			my $prev;
+			$prev = $members->[$i - 1] if $i > 0;
+			my $next = $members->[$i + 1];
+
+			add_depends($member, $trail);
+
+			$member_to_trails{$member}{$trail} = [$prev, $next];
+		}
+
+		if ((scalar @$members) > 1 && $pagestate{$trail}{trail}{circular}) {
+			$member_to_trails{$members->[0]}{$trail}[0] = $members->[$#$members];
+			$member_to_trails{$members->[$#$members]}{$trail}[1] = $members->[0];
+		}
+
+		$trail_to_members{$trail} = $members;
+	}
+
+	foreach my $member (keys %pagestate) {
+		if (exists $pagestate{$member}{trail}{item} &&
+			! exists $member_to_trails{$member}) {
+			$rebuild_trail_members{$member} = 1;
+			delete $pagestate{$member}{trailitem};
+		}
+	}
+
+	foreach my $member (keys %member_to_trails) {
+		if (! exists $pagestate{$member}{trail}{item}) {
+			$rebuild_trail_members{$member} = 1;
+		}
+		else {
+			if (trails_differ($pagestate{$member}{trail}{item},
+					$member_to_trails{$member})) {
+				$rebuild_trail_members{$member} = 1;
+			}
+		}
+
+		$pagestate{$member}{trail}{item} = $member_to_trails{$member};
+	}
+
+	$done_prerender = 1;
+}
+
+# This is called at about the right time that we can hijack it to render
+# extra pages.
+sub render_backlinks ($) {
+	my $blc = shift;
+
+	foreach my $member (keys %rebuild_trail_members) {
+		next unless exists $pagesources{$member};
+
+		IkiWiki::render($pagesources{$member}, sprintf(gettext("building %s, its previous or next page has changed"), $member));
+	}
+
+	$origsubs{render_backlinks}($blc);
+}
+
+sub title_of ($) {
+	my $page = shift;
+	if (defined ($pagestate{$page}{meta}{title})) {
+		return $pagestate{$page}{meta}{title};
+	}
+	return pagetitle(IkiWiki::basename($page));
+}
+
+my $recursive = 0;
+
+sub pagetemplate (@) {
+	my %params = @_;
+	my $page = $params{page};
+	my $template = $params{template};
+
+	if ($template->query(name => 'trails') && ! $recursive) {
+		prerender();
+
+		$recursive = 1;
+		my $inner = template("trails.tmpl", blind_cache => 1);
+		IkiWiki::run_hooks(pagetemplate => sub {
+				shift->(%params, template => $inner)
+			});
+		$template->param(trails => $inner->output);
+		$recursive = 0;
+	}
+
+	if ($template->query(name => 'trailloop')) {
+		prerender();
+
+		my @trails;
+
+		# sort backlinks by page name to have a consistent order
+		foreach my $trail (sort keys %{$member_to_trails{$page}}) {
+
+			my $members = $trail_to_members{$trail};
+			my ($prev, $next) = @{$member_to_trails{$page}{$trail}};
+			my ($prevurl, $nexturl, $prevtitle, $nexttitle);
+
+			if (defined $prev) {
+				add_depends($params{destpage}, $prev);
+				$prevurl = urlto($prev, $page);
+				$prevtitle = title_of($prev);
+			}
+
+			if (defined $next) {
+				add_depends($params{destpage}, $next);
+				$nexturl = urlto($next, $page);
+				$nexttitle = title_of($next);
+			}
+
+			push @trails, {
+				prevpage => $prev,
+				prevtitle => $prevtitle,
+				prevurl => $prevurl,
+				nextpage => $next,
+				nexttitle => $nexttitle,
+				nexturl => $nexturl,
+				trailpage => $trail,
+				trailtitle => title_of($trail),
+				trailurl => urlto($trail, $page),
+			};
+		}
+
+		$template->param(trailloop => \@trails);
+	}
+}
+
+1;
diff --git a/doc/style.css b/doc/style.css
index 7bbfe5d2a..35a133198 100644
--- a/doc/style.css
+++ b/doc/style.css
@@ -501,3 +501,38 @@ a.openid_large_btn:focus {
 .fileupload-content .ui-progressbar-value {
 	background: url(ikiwiki/images/pbar-ani.gif);
 }
+
+.trail {
+	display: block;
+	clear: both;
+	position: relative;
+}
+
+.trailprev {
+	display: block;
+	text-align: left;
+	position: absolute;
+	top: 0%;
+	left: 3%;
+	width: 30%;
+}
+
+.trailup {
+	display: block;
+	text-align: center;
+	margin-left: 35%;
+	margin-right: 35%;
+}
+
+.trailnext {
+	display: block;
+	text-align: right;
+	position: absolute;
+	top: 0%;
+	width: 30%;
+	right: 3%;
+}
+
+.trailsep {
+	display: none;
+}
diff --git a/doc/templates.mdwn b/doc/templates.mdwn
index d189fa073..43bf9ee51 100644
--- a/doc/templates.mdwn
+++ b/doc/templates.mdwn
@@ -80,6 +80,8 @@ Here is a full list of the template files used:
 * `autotag.tmpl` - Filled in by the tag plugin to make tag pages.
 * `calendarmonth.tmpl`, `calendaryear.tmpl` - Used by ikiwiki-calendar to
   make calendar archive pages.
+* `trails.tmpl` - Used by the trail plugin to generate links on each page
+  that is a member of a trail.
 * `editpage.tmpl`, `editconflict.tmpl`, `editcreationconflict.tmpl`,
   `editfailedsave.tmpl`, `editpagegone.tmpl`, `pocreatepage.tmpl`,
   `editcomment.tmpl` `commentmoderation.tmpl`, `renamesummary.tmpl`,
diff --git a/t/trail.t b/t/trail.t
new file mode 100755
index 000000000..ce7d92048
--- /dev/null
+++ b/t/trail.t
@@ -0,0 +1,159 @@
+#!/usr/bin/perl
+use warnings;
+use strict;
+use Test::More 'no_plan';
+use IkiWiki;
+
+my $blob;
+
+ok(! system("rm -rf t/tmp"));
+ok(! system("mkdir t/tmp"));
+
+# Use a rather stylized template to override the default rendering, to make
+# it easy to search for the desired results
+writefile("templates/trails.tmpl", "t/tmp/in", <<EOF
+<TMPL_LOOP TRAILLOOP>
+<TMPL_IF __FIRST__><nav></TMPL_IF>
+<div>
+trail=<TMPL_VAR TRAILPAGE> n=<TMPL_VAR NEXTPAGE> p=<TMPL_VAR PREVPAGE>
+</div>
+<div>
+<TMPL_IF PREVURL>
+<a href="<TMPL_VAR PREVURL>">&lt; <TMPL_VAR PREVTITLE></a>
+</TMPL_IF> |
+<a href="<TMPL_VAR TRAILURL>">^ <TMPL_VAR TRAILTITLE> ^</a>
+| <TMPL_IF NEXTURL>
+<a href="<TMPL_VAR NEXTURL>"><TMPL_VAR NEXTTITLE> &gt;</a>
+</TMPL_IF>
+</div>
+<TMPL_IF __LAST__></nav></TMPL_IF>
+</TMPL_LOOP>
+EOF
+);
+writefile("badger.mdwn", "t/tmp/in", "[[!meta title=\"The Breezy Badger\"]]\ncontent of badger");
+writefile("mushroom.mdwn", "t/tmp/in", "content of mushroom");
+writefile("snake.mdwn", "t/tmp/in", "content of snake");
+writefile("ratty.mdwn", "t/tmp/in", "content of ratty");
+writefile("mr_toad.mdwn", "t/tmp/in", "content of mr toad");
+writefile("add.mdwn", "t/tmp/in", '[[!trail pagenames="add/a add/b add/c add/d add/e"]]');
+writefile("add/b.mdwn", "t/tmp/in", "b");
+writefile("add/d.mdwn", "t/tmp/in", "d");
+writefile("del.mdwn", "t/tmp/in", '[[!trail pages="del/*" sort=title]]');
+writefile("del/a.mdwn", "t/tmp/in", "a");
+writefile("del/b.mdwn", "t/tmp/in", "b");
+writefile("del/c.mdwn", "t/tmp/in", "c");
+writefile("del/d.mdwn", "t/tmp/in", "d");
+writefile("del/e.mdwn", "t/tmp/in", "e");
+writefile("self_referential.mdwn", "t/tmp/in", '[[!trail pagenames="self_referential" circular=yes]]');
+
+writefile("meme.mdwn", "t/tmp/in", <<EOF
+[[!trail]]
+* [[!traillink badger]]
+* [[!traillink badger text="This is a link to badger, with a title"]]
+* [[!traillink That_is_the_badger|badger]]
+* [[!traillink badger]]
+* [[!traillink mushroom]]
+* [[!traillink mushroom]]
+* [[!traillink snake]]
+* [[!traillink snake]]
+EOF
+);
+
+writefile("wind_in_the_willows.mdwn", "t/tmp/in", <<EOF
+[[!trail circular=yes sort=title pages="ratty or badger or mr_toad"]]
+[[!trailitem moley]]
+EOF
+);
+
+ok(! system("make -s ikiwiki.out"));
+
+my $command = "perl -I. ./ikiwiki.out -set usedirs=0 -plugin trail -plugin inline -url=http://example.com -cgiurl=http://example.com/ikiwiki.cgi -rss -atom -underlaydir=underlays/basewiki -set underlaydirbase=underlays -templatedir=templates t/tmp/in t/tmp/out -verbose";
+
+ok(! system($command));
+
+ok(! system("$command -refresh"));
+
+$blob = readfile("t/tmp/out/meme.html");
+ok($blob =~ /<a href="(\.\/)?badger.html">badger<\/a>/m);
+ok($blob =~ /<a href="(\.\/)?badger.html">This is a link to badger, with a title<\/a>/m);
+ok($blob =~ /<a href="(\.\/)?badger.html">That is the badger<\/a>/m);
+
+$blob = readfile("t/tmp/out/badger.html");
+ok($blob =~ /^trail=meme n=mushroom p=$/m);
+ok($blob =~ /^trail=wind_in_the_willows n=mr_toad p=ratty$/m);
+
+ok(! -f "t/tmp/out/moley.html");
+
+$blob = readfile("t/tmp/out/mr_toad.html");
+ok($blob !~ /^trail=meme/m);
+ok($blob =~ /^trail=wind_in_the_willows n=ratty p=badger$/m);
+# meta title is respected for pages that have one
+ok($blob =~ /">&lt; The Breezy Badger<\/a>/m);
+# pagetitle for pages that don't
+ok($blob =~ /">ratty &gt;<\/a>/m);
+
+$blob = readfile("t/tmp/out/ratty.html");
+ok($blob !~ /^trail=meme/m);
+ok($blob =~ /^trail=wind_in_the_willows n=badger p=mr_toad$/m);
+
+$blob = readfile("t/tmp/out/mushroom.html");
+ok($blob =~ /^trail=meme n=snake p=badger$/m);
+ok($blob !~ /^trail=wind_in_the_willows/m);
+
+$blob = readfile("t/tmp/out/snake.html");
+ok($blob =~ /^trail=meme n= p=mushroom$/m);
+ok($blob !~ /^trail=wind_in_the_willows/m);
+
+$blob = readfile("t/tmp/out/self_referential.html");
+ok($blob =~ /^trail=self_referential n= p=$/m);
+
+$blob = readfile("t/tmp/out/add/b.html");
+ok($blob =~ /^trail=add n=add\/d p=$/m);
+$blob = readfile("t/tmp/out/add/d.html");
+ok($blob =~ /^trail=add n= p=add\/b$/m);
+ok(! -f "t/tmp/out/add/a.html");
+ok(! -f "t/tmp/out/add/c.html");
+ok(! -f "t/tmp/out/add/e.html");
+
+$blob = readfile("t/tmp/out/del/a.html");
+ok($blob =~ /^trail=del n=del\/b p=$/m);
+$blob = readfile("t/tmp/out/del/b.html");
+ok($blob =~ /^trail=del n=del\/c p=del\/a$/m);
+$blob = readfile("t/tmp/out/del/c.html");
+ok($blob =~ /^trail=del n=del\/d p=del\/b$/m);
+$blob = readfile("t/tmp/out/del/d.html");
+ok($blob =~ /^trail=del n=del\/e p=del\/c$/m);
+$blob = readfile("t/tmp/out/del/e.html");
+ok($blob =~ /^trail=del n= p=del\/d$/m);
+
+# Make some changes and refresh
+
+writefile("add/a.mdwn", "t/tmp/in", "a");
+writefile("add/c.mdwn", "t/tmp/in", "c");
+writefile("add/e.mdwn", "t/tmp/in", "e");
+ok(unlink("t/tmp/in/del/a.mdwn"));
+ok(unlink("t/tmp/in/del/c.mdwn"));
+ok(unlink("t/tmp/in/del/e.mdwn"));
+
+ok(! system("$command -refresh"));
+
+$blob = readfile("t/tmp/out/add/a.html");
+ok($blob =~ /^trail=add n=add\/b p=$/m);
+$blob = readfile("t/tmp/out/add/b.html");
+ok($blob =~ /^trail=add n=add\/c p=add\/a$/m);
+$blob = readfile("t/tmp/out/add/c.html");
+ok($blob =~ /^trail=add n=add\/d p=add\/b$/m);
+$blob = readfile("t/tmp/out/add/d.html");
+ok($blob =~ /^trail=add n=add\/e p=add\/c$/m);
+$blob = readfile("t/tmp/out/add/e.html");
+ok($blob =~ /^trail=add n= p=add\/d$/m);
+
+$blob = readfile("t/tmp/out/del/b.html");
+ok($blob =~ /^trail=del n=del\/d p=$/m);
+$blob = readfile("t/tmp/out/del/d.html");
+ok($blob =~ /^trail=del n= p=del\/b$/m);
+ok(! -f "t/tmp/out/del/a.html");
+ok(! -f "t/tmp/out/del/c.html");
+ok(! -f "t/tmp/out/del/e.html");
+
+#ok(! system("rm -rf t/tmp"));
diff --git a/templates/page.tmpl b/templates/page.tmpl
index 8659018a0..770ac2399 100644
--- a/templates/page.tmpl
+++ b/templates/page.tmpl
@@ -27,6 +27,15 @@
 <TMPL_IF FEEDLINKS><TMPL_VAR FEEDLINKS></TMPL_IF>
 <TMPL_IF RELVCS><TMPL_VAR RELVCS></TMPL_IF>
 <TMPL_IF META><TMPL_VAR META></TMPL_IF>
+<TMPL_LOOP TRAILLOOP>
+<TMPL_IF PREVPAGE>
+<link rel="prev" href="<TMPL_VAR PREVURL>" title="<TMPL_VAR PREVTITLE>" />
+</TMPL_IF>
+<link rel="up" href="<TMPL_VAR TRAILURL>" title="<TMPL_VAR TRAILTITLE>" />
+<TMPL_IF NEXTPAGE>
+<link rel="next" href="<TMPL_VAR NEXTURL>" title="<TMPL_VAR NEXTTITLE>" />
+</TMPL_IF>
+</TMPL_LOOP>
 </head>
 <body>
 
@@ -103,6 +112,8 @@
 <TMPL_IF HTML5></nav><TMPL_ELSE></div></TMPL_IF>
 </TMPL_IF>
 
+<TMPL_VAR TRAILS>
+
 <TMPL_IF HTML5></section><TMPL_ELSE></div></TMPL_IF>
 
 <TMPL_IF SIDEBAR>
diff --git a/templates/trails.tmpl b/templates/trails.tmpl
new file mode 100644
index 000000000..54c046043
--- /dev/null
+++ b/templates/trails.tmpl
@@ -0,0 +1,23 @@
+<TMPL_LOOP TRAILLOOP>
+<TMPL_IF __FIRST__><TMPL_IF HTML5><nav class="trails"><TMPL_ELSE><div class="trails"></TMPL_IF></TMPL_IF>
+<div class="trail">
+<TMPL_IF PREVPAGE>
+<span class="trailprev">
+<span class="trailarrow">←</span>
+<a href="<TMPL_VAR PREVURL>"><TMPL_VAR PREVTITLE></a>
+<span class="trailsep">|</span>
+</span>
+</TMPL_IF>
+<span class="trailup">
+<a href="<TMPL_VAR TRAILURL>"><TMPL_VAR TRAILTITLE></a>
+</span>
+<TMPL_IF NEXTPAGE>
+<span class="trailnext">
+<span class="trailsep">|</span>
+<a href="<TMPL_VAR NEXTURL>"><TMPL_VAR NEXTTITLE></a>
+<span class="trailarrow">→</span>
+</span>
+</TMPL_IF>
+</div>
+<TMPL_IF __LAST__><TMPL_IF HTML5></nav><TMPL_ELSE></div></TMPL_IF></TMPL_IF>
+</TMPL_LOOP>
diff --git a/themes/actiontabs/style.css b/themes/actiontabs/style.css
index 749d9b21e..26cdc1e86 100644
--- a/themes/actiontabs/style.css
+++ b/themes/actiontabs/style.css
@@ -142,3 +142,8 @@ div.recentchanges {
 	padding: 0 0 0 2ex;
 	border-color: #999;
 }
+
+.trails {
+	/* allow space for the action tabs */
+	margin-bottom: 2em;
+}
diff --git a/themes/blueview/style.css b/themes/blueview/style.css
index c07d1cdfa..32f4b32ea 100644
--- a/themes/blueview/style.css
+++ b/themes/blueview/style.css
@@ -197,18 +197,23 @@ body {
 	font-weight: bold;
 }
 
-.pageheader .header .title, .pageheader .header .parentlinks, .pageheader .actions ul li, .pageheader .header span, .pageheader #otherlanguages ul li {
+.pageheader .header .title, .pageheader .header .parentlinks, .pageheader .actions ul li, .pageheader .header span, .pageheader #otherlanguages ul li, .trailprev, .trailnext, .trailup {
 	padding: 0.25em 0.25em 0.25em 0.25em;
 	background-image: url('background_darkness.png');
 	background-repeat: repeat;
 	color: white;
 }
 
-.pageheader .header span a, .pageheader .actions ul li a, .pageheader .header .parentlinks a, .pageheader #otherlanguages ul li a {
+.pageheader .header span a, .pageheader .actions ul li a, .pageheader .header .parentlinks a, .pageheader #otherlanguages ul li a, .pageheader a {
+	font-weight: bold;
 	color: white;
 	text-decoration: none;
 }
 
+.trailprev, .trailnext, .trailup {
+	margin-top: 0.5em;
+}
+
 .pageheader .actions {
 	text-align: right;
 	vertical-align: bottom;
-- 
2.26.2