From edbccc4468427db250de2efedd1b7c1af0d79256 Mon Sep 17 00:00:00 2001
From: emkael <emkael@tlen.pl>
Date: Sat, 21 Jul 2018 17:20:56 +0200
Subject: HTTP2 Push headers support for JS/CSS assets

---
 app/frontend/web/ClientScriptManager.php | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/app/frontend/web/ClientScriptManager.php b/app/frontend/web/ClientScriptManager.php
index fb8c9fe..a26e0d6 100644
--- a/app/frontend/web/ClientScriptManager.php
+++ b/app/frontend/web/ClientScriptManager.php
@@ -192,6 +192,7 @@ class ClientScriptManager extends TClientScriptManager {
     private function _renderLocalScriptFiles(THtmlWriter $writer, array $localFiles) {
         if ($localFiles) {
             $assetPath = $this->_compileScriptFiles($localFiles);
+            $this->_setHTTP2PushHeader($assetPath);
             $writer->write(TJavascript::renderScriptFile($assetPath));
         }
     }
@@ -200,6 +201,7 @@ class ClientScriptManager extends TClientScriptManager {
     private function _renderExternalScriptFiles(THtmlWriter $writer, array $externalFiles) {
         if ($externalFiles) {
             foreach ($externalFiles as $file) {
+                $this->_setHTTP2PushHeader($file);
                 $this->markScriptFileAsRendered($file);
                 $this->_appendRenderedScripts([$file], $file);
             }
@@ -237,6 +239,9 @@ class ClientScriptManager extends TClientScriptManager {
                 $this->_renderExternalScriptFiles($writer, $externalFiles);
             }
         } else {
+            foreach ($files as $file) {
+                $this->_setHTTP2PushHeader($file);
+            }
             parent::renderScriptFiles($writer, $files);
         }
     }
@@ -425,6 +430,7 @@ class ClientScriptManager extends TClientScriptManager {
             }
             foreach ($fileTypes as $type => $files) {
                 $assetPath = $this->_compileSheetFiles($files);
+                $this->_setHTTP2PushHeader($assetPath);
                 $this->_renderSheetFileTag($writer, $assetPath, $type);
             }
         }
@@ -435,6 +441,7 @@ class ClientScriptManager extends TClientScriptManager {
         if ($externalFiles) {
             foreach ($externalFiles as $file) {
                 $this->_appendRenderedSheets([$file], $file[0]);
+                $this->_setHTTP2PushHeader($file[0]);
                 $this->_renderSheetFileTag($writer, $file[0], $file[1] ?: 'all');
             }
         }
@@ -474,6 +481,9 @@ class ClientScriptManager extends TClientScriptManager {
                 $this->_renderExternalSheetFiles($writer, $externalFiles);
             }
         } else {
+            foreach ($this->getStyleSheetUrls() as $file) {
+                $this->_setHTTP2PushHeader($file);
+            }
             parent::renderStyleSheetFiles($writer);
         }
     }
@@ -567,6 +577,16 @@ class ClientScriptManager extends TClientScriptManager {
         return $this->registerStyleSheetFile($key, $file, $media ?: 'all');
     }
 
+    private $_pushHeaders = [];
+
+    // Set Link: header for HTTP2 Push
+    private function _setHTTP2PushHeader($file) {
+        if (!in_array($file, $this->_pushHeaders)) {
+            $this->_pushHeaders[] = $file;
+            $this->getResponse()->appendHeader('Link: "<' . $file . '>; rel=preload"', FALSE);
+        }
+    }
+
 }
 
 ?>
-- 
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