[PATCH 2/2] add filter for Subject: tags

[Eric Wong <e@80x24.org>]

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 76fd1da..f16843a 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 0000000..1d28142
--- /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 0000000..54a219e
--- /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();
-- 
EW