view: display redundant headers in permalink

Mail headers can contain multiple headers of any type, so ensure
we don't hide any information we're getting in the per-message
permalink views.

This means it's possible to have multiple From, Date, To, Cc,
Subject, and In-Reply-To headers displayed.

The thread indices are a special case, I guess, since we run
out of space on the line if the headers too long and tools like
mutt only show the first one.

2 files changed, 73 insertions, 31 deletions

diff --git a/lib/PublicInbox/Linkify.pm b/lib/PublicInbox/Linkify.pm
index 175f8d72..5b83742c 100644
--- a/lib/PublicInbox/Linkify.pm
+++ b/lib/PublicInbox/Linkify.pm
@@ -89,4 +89,33 @@ sub linkify_2 {
         $_[1];
 }
 
+# single pass linkification of <Message-ID@example.com> within $str
+# with $pfx being the URL prefix
+sub linkify_mids {
+        my ($self, $pfx, $str) = @_;
+        $$str =~ s!<([^>]+)>!
+                my $msgid = PublicInbox::Hval->new_msgid($1);
+                my $html = $msgid->as_html;
+                my $href = $msgid->{href};
+                $href = ascii_html($href); # for IDN
+
+                # salt this, as this could be exploited to show
+                # links in the HTML which don't show up in the raw mail.
+                my $key = sha1_hex($html . $SALT);
+                $self->{$key} = [ $href, $html ];
+                '<PI-LINK-'. $key . '>';
+                !ge;
+        $$str = ascii_html($$str);
+        $$str =~ s!\bPI-LINK-([a-f0-9]{40})\b!
+                my $key = $1;
+                my $repl = $_[0]->{$key};
+                if (defined $repl) {
+                        "<a\nhref=\"$pfx/$repl->[0]/\">$repl->[1]</a>";
+                } else {
+                        # false positive or somebody tried to mess with us
+                        $key;
+                }
+        !ge;
+}
+
 1;
diff --git a/lib/PublicInbox/View.pm b/lib/PublicInbox/View.pm
index aeb32fc8..1aa014fd 100644
--- a/lib/PublicInbox/View.pm
+++ b/lib/PublicInbox/View.pm
@@ -190,8 +190,8 @@ sub fold_addresses ($) {
 
 sub _hdr_names_html ($$) {
         my ($hdr, $field) = @_;
-        my $val = $hdr->header($field) or return '';
-        ascii_html(join(', ', PublicInbox::Address::names($val)));
+        my @vals = $hdr->header($field) or return '';
+        ascii_html(join(', ', PublicInbox::Address::names(join(',', @vals))));
 }
 
 sub nr_to_s ($$$) {
@@ -643,12 +643,11 @@ sub _msg_html_prepare {
         if ($over) {
                 $ctx->{-upfx} = '../';
         }
-        my @title;
-        my $v;
-        if (defined($v = $hdr->header('From'))) {
+        my @title; # (Subject[0], From[0])
+        for my $v ($hdr->header('From')) {
                 $v = PublicInbox::Hval->new($v);
                 my @n = PublicInbox::Address::names($v->raw);
-                $title[1] = ascii_html(join(', ', @n));
+                $title[1] //= ascii_html(join(', ', @n));
                 $v = $v->as_html;
                 if ($obfs_ibx) {
                         obfuscate_addrs($obfs_ibx, $v);
@@ -657,26 +656,31 @@ sub _msg_html_prepare {
                 $rv .= "From: $v\n" if $v ne '';
         }
         foreach my $h (qw(To Cc)) {
-                defined($v = $hdr->header($h)) or next;
-                fold_addresses($v);
-                $v = ascii_html($v);
-                obfuscate_addrs($obfs_ibx, $v) if $obfs_ibx;
-                $rv .= "$h: $v\n" if $v ne '';
+                for my $v ($hdr->header($h)) {
+                        fold_addresses($v);
+                        $v = ascii_html($v);
+                        obfuscate_addrs($obfs_ibx, $v) if $obfs_ibx;
+                        $rv .= "$h: $v\n" if $v ne '';
+                }
         }
-        if (defined($v = $hdr->header('Subject')) && ($v ne '')) {
-                $v = ascii_html($v);
-                obfuscate_addrs($obfs_ibx, $v) if $obfs_ibx;
-                if ($over) {
-                        $rv .= qq(Subject: <a\nhref="#r"\nid=t>$v</a>\n);
-                } else {
-                        $rv .= "Subject: $v\n";
+        my @subj = $hdr->header('Subject');
+        if (@subj) {
+                for my $v (@subj) {
+                        $v = ascii_html($v);
+                        obfuscate_addrs($obfs_ibx, $v) if $obfs_ibx;
+                        $rv .= 'Subject: ';
+                        if ($over) {
+                                $rv .= qq(<a\nhref="#r"\nid=t>$v</a>\n);
+                        } else {
+                                $rv .= "$v\n";
+                        }
+                        $title[0] //= $v;
                 }
-                $title[0] = $v;
         } else { # dummy anchor for thread skeleton at bottom of page
                 $rv .= qq(<a\nhref="#r"\nid=t></a>) if $over;
                 $title[0] = '(no subject)';
         }
-        if (defined($v = $hdr->header('Date'))) {
+        for my $v ($hdr->header('Date')) {
                 $v = ascii_html($v);
                 obfuscate_addrs($obfs_ibx, $v) if $obfs_ibx; # possible :P
                 $rv .= "Date: $v\n";
@@ -727,8 +731,9 @@ sub thread_skel {
         $$dst .= "$nr+ messages / $expand";
         $$dst .= qq!  <a\nhref="#b">top</a>\n!;
 
-        my $subj = $hdr->header('Subject');
-        defined $subj or $subj = '';
+        # nb: mutt only shows the first Subject in the index pane
+        # when multiple Subject: headers are present, so we follow suit:
+        my $subj = $hdr->header('Subject') // '';
         $subj = '(no subject)' if $subj eq '';
         $ctx->{prev_subj} = [ split(/ /, subject_normalized($subj)) ];
         $ctx->{cur} = $mid;
@@ -746,21 +751,29 @@ sub thread_skel {
 sub _parent_headers {
         my ($hdr, $over) = @_;
         my $rv = '';
-
-        my $refs = references($hdr);
-        my $irt = pop @$refs;
-        if (defined $irt) {
-                my $v = PublicInbox::Hval->new_msgid($irt);
-                my $html = $v->as_html;
-                my $href = $v->{href};
-                $rv .= "In-Reply-To: &lt;";
-                $rv .= "<a\nhref=\"../$href/\">$html</a>&gt;\n";
+        my @irt = $hdr->header_raw('In-Reply-To');
+        my $refs;
+        if (@irt) {
+                my $lnk = PublicInbox::Linkify->new;
+                $rv .= "In-Reply-To: $_\n" for @irt;
+                $lnk->linkify_mids('..', \$rv);
+        } else {
+                $refs = references($hdr);
+                my $irt = pop @$refs;
+                if (defined $irt) {
+                        my $v = PublicInbox::Hval->new_msgid($irt);
+                        my $html = $v->as_html;
+                        my $href = $v->{href};
+                        $rv .= "In-Reply-To: &lt;";
+                        $rv .= "<a\nhref=\"../$href/\">$html</a>&gt;\n";
+                }
         }
 
         # do not display References: if search is present,
         # we show the thread skeleton at the bottom, instead.
         return $rv if $over;
 
+        $refs //= references($hdr);
         if (@$refs) {
                 @$refs = map { linkify_ref_no_over($_) } @$refs;
                 $rv .= 'References: '. join("\n\t", @$refs) . "\n";