+# Copyright (C) all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+package PublicInbox::MailDiff;
+use v5.12;
+use File::Temp 0.19 (); # 0.19 for ->newdir
+use PublicInbox::ContentHash qw(content_digest);
+use PublicInbox::ContentDigestDbg;
+use Data::Dumper ();
+use PublicInbox::MsgIter qw(msg_part_text);
+
+sub write_part { # Eml->each_part callback
+ my ($ary, $self) = @_;
+ my ($part, $depth, $idx) = @$ary;
+ if ($idx ne '1' || $self->{-raw_hdr}) {
+ open my $fh, '>', "$self->{curdir}/$idx.hdr" or die "open: $!";
+ print $fh ${$part->{hdr}} or die "print $!";
+ close $fh or die "close $!";
+ }
+ my $ct = $part->content_type || 'text/plain';
+ my ($s, $err) = msg_part_text($part, $ct);
+ my $sfx = defined($s) ? 'txt' : 'bin';
+ open my $fh, '>', "$self->{curdir}/$idx.$sfx" or die "open: $!";
+ print $fh ($s // $part->body) or die "print $!";
+ close $fh or die "close $!";
+}
+
+# public
+sub dump_eml ($$$) {
+ my ($self, $dir, $eml) = @_;
+ local $self->{curdir} = $dir;
+ mkdir $dir or die "mkdir($dir): $!";
+ $eml->each_part(\&write_part, $self);
+
+ open my $fh, '>', "$dir/content_digest" or die "open: $!";
+ my $dig = PublicInbox::ContentDigestDbg->new($fh);
+ local $Data::Dumper::Useqq = 1;
+ local $Data::Dumper::Terse = 1;
+ content_digest($eml, $dig);
+ print $fh "\n", $dig->hexdigest, "\n" or die "print $!";
+ close $fh or die "close: $!";
+}
+
+# public
+sub prep_a ($$) {
+ my ($self, $eml) = @_;
+ $self->{tmp} = File::Temp->newdir('mail-diff-XXXX', TMPDIR => 1);
+ dump_eml($self, "$self->{tmp}/a", $eml);
+}
+
+1;