[PATCH 28/43] view: make /$INBOX/$MSGID/ permalink async

[Eric Wong <e@yhbt.net>]

This will allow -httpd to handle other requusts if waiting on
an HDD seek or git to decode a blob.
---
 lib/PublicInbox/View.pm      | 38 ++++++++++++++++------------------
 lib/PublicInbox/WwwStream.pm | 40 +++++++++++++++++++++++++++++++-----
 2 files changed, 53 insertions(+), 25 deletions(-)

diff --git a/lib/PublicInbox/View.pm b/lib/PublicInbox/View.pm
index 243528263..98445f0e0 100644
--- a/lib/PublicInbox/View.pm
+++ b/lib/PublicInbox/View.pm
@@ -27,24 +27,22 @@ use constant TCHILD => '` ';
 sub th_pfx ($) { $_[0] == 0 ? '' : TCHILD };
 
 sub msg_page_i {
-	my ($ctx) = @_;
-	my $cur = delete $ctx->{smsg} or return; # undef: done
-	my $nxt;
-	if (my $over = $ctx->{-inbox}->over) {
-		$nxt = $ctx->{smsg} = $over->next_by_mid(@{$ctx->{next_arg}});
+	my ($ctx, $eml) = @_;
+	if ($eml) { # called by WwwStream::async_eml or getline
+		my $smsg = $ctx->{smsg};
+		$ctx->{smsg} = $ctx->{over}->next_by_mid(@{$ctx->{next_arg}});
+		$ctx->{mhref} = ($ctx->{nr} || $ctx->{smsg}) ?
+				"../${\mid_href($smsg->{mid})}/" : '';
+		my $hdr = $eml->header_obj;
+		my $obuf = $ctx->{obuf} = _msg_page_prepare_obuf($hdr, $ctx);
+		multipart_text_as_html($eml, $ctx);
+		delete $ctx->{obuf};
+		$$obuf .= '</pre><hr>';
+		$$obuf .= html_footer($ctx, $ctx->{first_hdr}) if !$ctx->{smsg};
+		$$obuf;
+	} else { # called by WwwStream::async_next or getline
+		$ctx->{smsg}; # may be undef
 	}
-	$ctx->{mhref} = ($ctx->{nr} || $nxt) ?
-			"../${\mid_href($cur->{mid})}/" : '';
-	my $eml = $ctx->{-inbox}->smsg_eml($cur) or return;
-	my $hdr = $eml->header_obj;
-	my $obuf = $ctx->{obuf} = _msg_page_prepare_obuf($hdr, $ctx);
-	multipart_text_as_html($eml, $ctx);
-	delete $ctx->{obuf};
-	$$obuf .= '</pre><hr>';
-	# we want to at least show the message if something
-	# here crashes:
-	eval { $$obuf .= html_footer($ctx, $ctx->{first_hdr}) } if !$nxt;
-	$$obuf;
 }
 
 # /$INBOX/$MESSAGE_ID/ for unindexed v1 inboxes
@@ -74,11 +72,11 @@ sub msg_page {
 	my ($ctx) = @_;
 	my $ibx = $ctx->{-inbox};
 	$ctx->{-obfs_ibx} = $ibx->{obfuscate} ? $ibx : undef;
-	my $over = $ibx->over or return no_over_html($ctx);
+	my $over = $ctx->{over} = $ibx->over or return no_over_html($ctx);
 	my ($id, $prev);
 	my $next_arg = $ctx->{next_arg} = [ $ctx->{mid}, \$id, \$prev ];
-	$ctx->{smsg} = $over->next_by_mid(@$next_arg) or return;
-	PublicInbox::WwwStream::response($ctx, 200, \&msg_page_i);
+	$ctx->{smsg} = $over->next_by_mid(@$next_arg) or return; # undef == 404
+	PublicInbox::WwwStream::aresponse($ctx, 200, \&msg_page_i);
 }
 
 # /$INBOX/$MESSAGE_ID/#R
diff --git a/lib/PublicInbox/WwwStream.pm b/lib/PublicInbox/WwwStream.pm
index 42fb183f4..eecc27019 100644
--- a/lib/PublicInbox/WwwStream.pm
+++ b/lib/PublicInbox/WwwStream.pm
@@ -15,9 +15,6 @@ use PublicInbox::Hval qw(ascii_html prurl);
 our $TOR_URL = 'https://www.torproject.org/';
 our $CODE_URL = 'https://public-inbox.org/public-inbox.git';
 
-# noop for HTTP.pm (and any other PSGI servers)
-sub close {}
-
 sub base_url ($) {
 	my $ctx = shift;
 	my $base_url = $ctx->{-inbox}->base_url($ctx->{env});
@@ -40,6 +37,11 @@ sub response {
 	[ $code, $res_hdr, $ctx ]
 }
 
+sub async_eml { # ->{async_eml} for async_blob_cb
+	my ($ctx, $eml) = @_;
+	$ctx->{http_out}->write($ctx->translate($ctx->{cb}->($ctx, $eml)));
+}
+
 sub html_top ($) {
 	my ($ctx) = @_;
 	my $ibx = $ctx->{-inbox};
@@ -157,8 +159,14 @@ EOF
 sub getline {
 	my ($ctx) = @_;
 	my $cb = $ctx->{cb} or return;
-	if (defined(my $buf = $cb->($ctx))) {
-		return $ctx->translate($buf);
+	while (defined(my $x = $cb->($ctx))) { # x = smsg or scalar non-ref
+		if (ref($x)) { # smsg
+			my $eml = $ctx->{-inbox}->smsg_eml($x) or next;
+			$ctx->{smsg} = $x;
+			return $ctx->translate($cb->($ctx, $eml));
+		} else { # scalar
+			return $ctx->translate($x);
+		}
 	}
 	delete $ctx->{cb};
 	$ctx->zflush(_html_end($ctx));
@@ -179,4 +187,26 @@ sub html_oneshot ($$;$) {
 	[ $code, $res_hdr, \@bdy ]
 }
 
+sub async_next ($) {
+	my ($http) = @_; # PublicInbox::HTTP
+	my $ctx = $http->{forward} or return;
+	eval {
+		if (my $smsg = $ctx->{smsg} = $ctx->{cb}->($ctx)) {
+			$ctx->smsg_blob($smsg);
+		} else {
+			$ctx->{http_out}->write(
+					$ctx->translate(_html_end($ctx)));
+			$ctx->close; # GzipFilter->close
+		}
+	};
+	warn "E: $@" if $@;
+}
+
+sub aresponse {
+	my ($ctx, $code, $cb) = @_;
+	my $res_hdr = [ 'Content-Type' => 'text/html; charset=UTF-8' ];
+	init($ctx, $cb);
+	$ctx->psgi_response($code, $res_hdr, \&async_next, \&async_eml);
+}
+
 1;