[PATCH 2/5] www: don't reread CSS files

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

With preloading, we usually read our CSS files in quick
succession so they are unlikely to change in between loads.
Thus we can save some syscalls and memory (assuming newer
Perl with CoW scalars).

Since our normal Perl code is only loaded once and ignores
changes on the FS after startup, we'll treat our CSS the
same way and assume they don't change after startup.
---
 lib/PublicInbox/WWW.pm | 48 ++++++++++++++++++++++++------------------
 1 file changed, 28 insertions(+), 20 deletions(-)

diff --git a/lib/PublicInbox/WWW.pm b/lib/PublicInbox/WWW.pm
index 32d0410c..6f7c30b9 100644
--- a/lib/PublicInbox/WWW.pm
+++ b/lib/PublicInbox/WWW.pm
@@ -565,6 +565,20 @@ sub get_attach {
 # <pre>-formatted anyways.
 our $STYLE = 'pre{white-space:pre-wrap}*{font-size:100%;font-family:monospace}';
 
+sub _read_css ($$$) {
+	my ($fh, $mini, $fn) = @_;
+	my $ctime = 0;
+	my $local = PublicInbox::IO::read_all $fh; # sets _
+	if ($local =~ /\S/) {
+		$ctime = sprintf('%x',(stat(_))[10]);
+		$local = $mini->($local);
+	}
+	# do not let BOFHs override userContent.css:
+	return ($local, $ctime) if $local !~ /!\s*important\b/i;
+	warn "W: ignoring $fn since it uses `!important'\n";
+	();
+}
+
 sub stylesheets_prepare ($$) {
 	my ($self, $upfx) = @_;
 	my $mini = eval {
@@ -575,7 +589,7 @@ sub stylesheets_prepare ($$) {
 		sub { CSS::Minifier::XS::minify($_[0]) };
 	} || sub { $_[0] };
 
-	my $css_map = {};
+	my $css_map = $self->{-css_map} //= {};
 	my $stylesheets = $self->{pi_cfg}->{css} || [];
 	my $links = [];
 	my $inline_ok = 1;
@@ -598,24 +612,17 @@ sub stylesheets_prepare ($$) {
 				warn "ignoring $fn, non-ASCII word character\n";
 				next;
 			}
-			open(my $fh, '<', $fn) or do {
+			my ($local, $ctime);
+			if (my $rec = $css_map->{$key}) { # already loaded
+				($local, $ctime) = @$rec;
+			} elsif (open(my $fh, '<', $fn)) {
+				($local, $ctime) = _read_css $fh, $mini, $fn;
+				$css_map->{$key} = [ $local, $ctime ];
+			} else {
 				warn "failed to open $fn: $!\n";
 				next;
-			};
-			my $ctime = 0;
-			my $local = PublicInbox::IO::read_all $fh; # sets _
-			if ($local =~ /\S/) {
-				$ctime = sprintf('%x',(stat(_))[10]);
-				$local = $mini->($local);
-			}
-
-			# do not let BOFHs override userContent.css:
-			if ($local =~ /!\s*important\b/i) {
-				warn "ignoring $fn since it uses `!important'\n";
-				next;
 			}
 
-			$css_map->{$key} = $local;
 			$attr->{href} = "$upfx$key.css?$ctime";
 			if (defined($attr->{title})) {
 				$inline_ok = 0;
@@ -654,7 +661,7 @@ sub stylesheets_prepare ($$) {
 	} else {
 		$self->{-style_inline} = $buf;
 	}
-	$self->{-css_map} = $css_map;
+	$css_map;
 }
 
 # returns an HTML fragment with <style> or <link> tags in them
@@ -679,11 +686,12 @@ sub get_css ($$$) {
 	my $self = $ctx->{www};
 	my $css_map = $self->{-css_map} ||
 		stylesheets_prepare($self, defined($inbox) ? '' : '+/');
-	my $css = $css_map->{$key};
-	if (!defined($css) && defined($inbox) && $key eq 'userContent') {
-		$css = PublicInbox::UserContent::sample($ctx);
+	my $rec = $css_map->{$key};
+	if (!defined($rec) && defined($inbox) && $key eq 'userContent') {
+		$rec = [ PublicInbox::UserContent::sample($ctx) ];
 	}
-	defined $css or return r404();
+	$rec // return r404();
+	my ($css, undef) = @$rec; # TODO: Last-Modified
 	my $h = [ 'Content-Length', length($css), 'Content-Type', 'text/css' ];
 	PublicInbox::GitHTTPBackend::cache_one_year($h);
 	[ 200, $h, [ $css ] ];