From 7e40887e8d2bef4126b4a3680594860a3b2fd67c Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Thu, 26 Jan 2017 02:09:36 +0000
Subject: [PATCH] add filter for Subject: tags

Some mailing lists add annoying tags into the Subject line which
discourages readers from doing proper mail organization on the
client side.  They also waste precious screen space and
attention span.

Remove them from our archives to reduce clutter.
---
 MANIFEST                             |  2 ++
 lib/PublicInbox/Filter/SubjectTag.pm | 33 ++++++++++++++++++++++++++++
 t/filter_subjecttag.t                | 27 +++++++++++++++++++++++
 3 files changed, 62 insertions(+)
 create mode 100644 lib/PublicInbox/Filter/SubjectTag.pm
 create mode 100644 t/filter_subjecttag.t

diff --git a/MANIFEST b/MANIFEST
index 76fd1da6..f16843a9 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -51,6 +51,7 @@ lib/PublicInbox/ExtMsg.pm
 lib/PublicInbox/Feed.pm
 lib/PublicInbox/Filter/Base.pm
 lib/PublicInbox/Filter/Mirror.pm
+lib/PublicInbox/Filter/SubjectTag.pm
 lib/PublicInbox/Filter/Vger.pm
 lib/PublicInbox/GetlineBody.pm
 lib/PublicInbox/Git.pm
@@ -127,6 +128,7 @@ t/fail-bin/spamc
 t/feed.t
 t/filter_base.t
 t/filter_mirror.t
+t/filter_subjecttag.t
 t/filter_vger.t
 t/git-http-backend.psgi
 t/git-http-backend.t
diff --git a/lib/PublicInbox/Filter/SubjectTag.pm b/lib/PublicInbox/Filter/SubjectTag.pm
new file mode 100644
index 00000000..1d281425
--- /dev/null
+++ b/lib/PublicInbox/Filter/SubjectTag.pm
@@ -0,0 +1,33 @@
+# Copyright (C) 2017 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# Filter for various [tags] in subjects
+package PublicInbox::Filter::SubjectTag;
+use strict;
+use warnings;
+use base qw(PublicInbox::Filter::Base);
+
+sub new {
+	my ($class, %opts) = @_;
+	my $tag = delete $opts{-tag};
+	die "tag not defined!\n" unless defined $tag && $tag ne '';
+	my $self = $class->SUPER::new(%opts);
+	$self->{tag_re} = qr/\A\s*(re:\s+|)\Q$tag\E\s*/i;
+	$self;
+}
+
+sub scrub {
+	my ($self, $mime) = @_;
+	my $subj = $mime->header('Subject');
+	$subj =~ s/$self->{tag_re}/$1/; # $1 is "Re: "
+	$mime->header_str_set('Subject', $subj);
+	$self->ACCEPT($mime);
+}
+
+# no suffix/article rejection for mirrors
+sub delivery {
+	my ($self, $mime) = @_;
+	$self->scrub($mime);
+}
+
+1;
diff --git a/t/filter_subjecttag.t b/t/filter_subjecttag.t
new file mode 100644
index 00000000..54a219e7
--- /dev/null
+++ b/t/filter_subjecttag.t
@@ -0,0 +1,27 @@
+# Copyright (C) 2017 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict;
+use warnings;
+use Test::More;
+use Email::MIME;
+use_ok 'PublicInbox::Filter::SubjectTag';
+
+my $f = eval { PublicInbox::Filter::SubjectTag->new };
+like($@, qr/tag not defined/, 'error without args');
+$f = PublicInbox::Filter::SubjectTag->new('-tag', '[foo]');
+is(ref $f, 'PublicInbox::Filter::SubjectTag', 'new object created');
+
+my $mime = Email::MIME->new(<<EOF);
+To: you <you\@example.com>
+Subject: =?UTF-8?B?UmU6IFtmb29dIEVsw4PCqWFub3I=?=
+
+EOF
+
+$mime = $f->delivery($mime);
+is($mime->header('Subject'), "Re: El\xc3\xa9anor", 'filtered with Re:');
+
+$mime->header_str_set('Subject', '[FOO] bar');
+$mime = $f->delivery($mime);
+is($mime->header('Subject'), 'bar', 'filtered non-reply');
+
+done_testing();
-- 
2.44.0