From fa493d7360417bf2c6ef8e6c3eaddd67d047e93b Mon Sep 17 00:00:00 2001
From: Alex Schroeder <alex@gnu.org>
Date: Mon, 21 Sep 2015 09:12:32 +0200
Subject: [PATCH] preview.pl: New module to report changes in HTML

---
 modules/preview.pl | 58 ++++++++++++++++++++++++++++++++++++++++++++++
 t/preview.t        | 37 +++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 modules/preview.pl
 create mode 100644 t/preview.t

diff --git a/modules/preview.pl b/modules/preview.pl
new file mode 100644
index 00000000..46c77be8
--- /dev/null
+++ b/modules/preview.pl
@@ -0,0 +1,58 @@
+# Copyright (C) 2015  Alex Schroeder <alex@gnu.org>
+#
+# 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/>.
+
+use strict;
+use v5.10;
+
+=head1 Preview Extension
+
+This module allows you to preview changes in HTML output. Oddmuse keeps a cache
+of the HTML produced for each wiki page. If you install new modules, the HTML
+produced for a page can change, but visitors will not see the new HTML because
+the cache still contains the old HTML. Now you have two options: 1. clear the
+HTML cache (Oddmuse will regenerate it as visitors look at the old pages), or 2.
+edit each page in order to regenerate the HTML cache. What happens in practice
+is that you add new modules and you aren't sure whether this breaks old pages
+and so you do don't dare clear the HTML cache. Let sleeping dogs lie.
+
+The Preview Extension produces a list of all the pages where the cached HTML
+differs from the HTML produced by the current set of modules. If you agree with
+the new HTML, feel free to clear the HTML cache. That's the point of this
+extension.
+
+=cut
+    
+our ($q, %Action, $UseCache);
+
+AddModuleDescription('preview.pl', 'Preview Extension');
+
+$Action{preview} = \&DoPreview;
+
+sub DoPreview {
+  print GetHeader('', T('Pages with changed HTML'));
+  print $q->start_div({-class=>'content preview'}), $q->start_p();
+  foreach my $id (AllPagesList()) {
+    OpenPage($id);
+    my $cache = ToString(\&PrintPageHtml);
+    local $UseCache = 0;
+    my $html = ToString(\&PrintPageHtml);
+    if ($cache ne $html) {
+      print GetPageLink($id), ' ',
+      ScriptLink('action=browse;id=$id;cache=0', T('Preview')),
+      $q->br();
+    }
+  }
+  print $q->end_p(), $q->end_div();
+  PrintFooter();
+}
diff --git a/t/preview.t b/t/preview.t
new file mode 100644
index 00000000..760f006d
--- /dev/null
+++ b/t/preview.t
@@ -0,0 +1,37 @@
+# Copyright (C) 2015  Alex Schroeder <alex@gnu.org>
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 3 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program. If not, see <http://www.gnu.org/licenses/>.
+
+require 't/test.pl';
+package OddMuse;
+use Test::More tests => 5;
+use utf8;
+
+# This is a page whose HTML will change when we install the Markup Extension.
+test_page(update_page('Test', 'This is *bold*.'), '\*bold\*');
+
+# This is a page whose HTML will not change.
+update_page('Boring', 'This is just text.');
+
+# New markup module installed but HTML returned is cached.
+add_module('markup.pl');
+test_page(get_page('Test'), '\*bold\*');
+
+# We can get the new HTML using cache=0.
+test_page(get_page('Test?cache=0'), '<b>bold</b>');
+
+# Install Preview Extension and see whether Test is listed and Boring is not.
+add_module('preview.pl');
+$page = get_page('action=preview');
+test_page($page, 'Test');
+test_page_negative($page, 'Boring');