From fad458f8ae771a4f86e2634153c2ce50315cb089 Mon Sep 17 00:00:00 2001
From: Matthias Pfefferle <pfefferle@users.noreply.github.com>
Date: Thu, 3 Jul 2025 12:53:20 +0200
Subject: [PATCH 1/2] Initial

---
 integration/class-w3-total-cache.php | 127 +++++++++++++++++++++++++++
 integration/load.php                 |   9 ++
 2 files changed, 136 insertions(+)
 create mode 100644 integration/class-w3-total-cache.php

diff --git a/integration/class-w3-total-cache.php b/integration/class-w3-total-cache.php
new file mode 100644
index 000000000..a2587d4db
--- /dev/null
+++ b/integration/class-w3-total-cache.php
@@ -0,0 +1,127 @@
+<?php
+/**
+ * W3 Total Cache extension for ActivityPub requests.
+ */
+
+namespace Activitypub\Integration;
+
+use function Activitypub\is_activitypub_request;
+
+/**
+ * W3 Total Cache extension for ActivityPub requests.
+ */
+class W3_Total_Cache {
+
+	/**
+	 * Initialize the W3 Total Cache integration.
+	 */
+	public static function init() {
+		// Register the pagecache_page_key filter.
+		\w3tc_add_action( 'pagecache_page_key', array( self::class, 'pagecache_page_key' ) );
+		// Register additional filters to handle query strings and cache rules.
+		\w3tc_add_action( 'pagecache_extract_accept_qs', array( self::class, 'pagecache_extract_accept_qs' ) );
+		\w3tc_add_action( 'w3tc_pagecache_rules_apache_accept_qs', array( self::class, 'w3tc_pagecache_rules_accept_qs' ) );
+		\w3tc_add_action( 'w3tc_pagecache_rules_nginx_accept_qs', array( self::class, 'w3tc_pagecache_rules_accept_qs' ) );
+		\w3tc_add_action( 'w3tc_pagecache_rules_apache_accept_qs_rules', array( self::class, 'w3tc_pagecache_rules_apache_accept_qs_rules' ), 10, 2 );
+		\w3tc_add_action( 'w3tc_pagecache_rules_nginx_accept_qs_rules', array( self::class, 'w3tc_pagecache_rules_nginx_accept_qs_rules' ), 10, 2 );
+		\w3tc_add_action( 'w3tc_pagecache_rules_apache_uri_prefix', array( self::class, 'w3tc_pagecache_rules_apache_uri_prefix' ) );
+		\w3tc_add_action( 'w3tc_pagecache_rules_nginx_uri_prefix', array( self::class, 'w3tc_pagecache_rules_nginx_uri_prefix' ) );
+	}
+
+	/**
+	 * Modify the page cache key if this is an ActivityPub request.
+	 *
+	 * @param array $page_key The page cache key.
+	 *
+	 * @return array The modified page cache key.
+	 */
+	public static function pagecache_page_key( $page_key ) {
+		// Always check for ActivityPub request.
+		if ( is_activitypub_request() ) {
+			// Make the ActivityPub key more distinct by adding a prefix.
+			$page_key[0]  = 'activitypub_' . $page_key[0];
+			$page_key[1] .= '_activitypub';
+		}
+
+		return $page_key;
+	}
+
+	/**
+	 * Extract query strings that should be accepted for caching.
+	 *
+	 * @param array $query_strings The list of query strings to accept.
+	 * @return array The modified list of query strings.
+	 */
+	public static function pagecache_extract_accept_qs( $query_strings ) {
+		// Add ActivityPub-specific query parameters that should be considered for caching.
+		$query_strings[] = 'activitypub';
+		$query_strings[] = 'format';
+
+		return $query_strings;
+	}
+
+	/**
+	 * Add ActivityPub query strings to the accepted query strings for caching rules.
+	 *
+	 * @param array $query_strings The list of query strings to accept.
+	 * @return array The modified list of query strings.
+	 */
+	public static function w3tc_pagecache_rules_accept_qs( $query_strings ) {
+		$query_strings[] = 'activitypub';
+		$query_strings[] = 'format';
+
+		return $query_strings;
+	}
+
+	/**
+	 * Modify Apache caching rules for ActivityPub query strings.
+	 *
+	 * @param array  $query_rules The query rules.
+	 * @param string $query The query string.
+	 *
+	 * @return array The modified query rules.
+	 */
+	public static function w3tc_pagecache_rules_apache_accept_qs_rules( $query_rules, $query ) {
+		if ( 'activitypub' === $query || 'format' === $query ) {
+			$query_rules[1] = str_replace( '[E=', '[E=W3TC_ACTIVITYPUB:_activitypub,E=', $query_rules[1] );
+		}
+
+		return $query_rules;
+	}
+
+	/**
+	 * Modify the Apache URI prefix for ActivityPub requests.
+	 *
+	 * @param string $uri_prefix The URI prefix.
+	 * @return string The modified URI prefix.
+	 */
+	public static function w3tc_pagecache_rules_apache_uri_prefix( $uri_prefix ) {
+		return $uri_prefix . '%{ENV:W3TC_ACTIVITYPUB}';
+	}
+
+	/**
+	 * Modify Nginx caching rules for ActivityPub query strings.
+	 *
+	 * @param array $query_rules The query rules.
+	 * @param string $query The query string.
+	 * @return array The modified query rules.
+	 */
+	public static function w3tc_pagecache_rules_nginx_accept_qs_rules( $query_rules, $query ) {
+		if ( $query === 'activitypub' || $query === 'format' ) {
+			array_splice( $query_rules, 1, 0, '    set $w3tc_activitypub "_activitypub";' );
+			array_unshift( $query_rules, 'set $w3tc_activitypub "";' );
+		}
+
+		return $query_rules;
+	}
+
+	/**
+	 * Modify the Nginx URI prefix for ActivityPub requests.
+	 *
+	 * @param string $uri_prefix The URI prefix.
+	 * @return string The modified URI prefix.
+	 */
+	public static function w3tc_pagecache_rules_nginx_uri_prefix( $uri_prefix ) {
+		return $uri_prefix . '$w3tc_activitypub';
+	}
+}
diff --git a/integration/load.php b/integration/load.php
index 78b0dd6b9..0afae6129 100644
--- a/integration/load.php
+++ b/integration/load.php
@@ -182,3 +182,12 @@ function ( $post_types ) {
  * @see https://buddypress.org/
  */
 add_action( 'bp_include', array( __NAMESPACE__ . '\Buddypress', 'init' ), 0 );
+
+/**
+ * Load the W3 Total Cache integration.
+ *
+ * @see https://w3-total-cache.com/
+ */
+if ( function_exists( 'w3tc_add_action' ) ) {
+	\w3tc_add_action( 'wp_loaded', array( __NAMESPACE__ . '\W3_Total_Cache', 'init' ) );
+}

From 3454b9af69cd4ca8ae32e1d8c579e075bf394df8 Mon Sep 17 00:00:00 2001
From: Matthias Pfefferle <pfefferle@users.noreply.github.com>
Date: Thu, 3 Jul 2025 14:39:38 +0200
Subject: [PATCH 2/2] simplified code

---
 integration/class-w3-total-cache.php | 112 ++++++---------------------
 1 file changed, 23 insertions(+), 89 deletions(-)

diff --git a/integration/class-w3-total-cache.php b/integration/class-w3-total-cache.php
index a2587d4db..d3680569a 100644
--- a/integration/class-w3-total-cache.php
+++ b/integration/class-w3-total-cache.php
@@ -1,6 +1,8 @@
 <?php
 /**
  * W3 Total Cache extension for ActivityPub requests.
+ *
+ * @package activitypub
  */
 
 namespace Activitypub\Integration;
@@ -16,112 +18,44 @@ class W3_Total_Cache {
 	 * Initialize the W3 Total Cache integration.
 	 */
 	public static function init() {
-		// Register the pagecache_page_key filter.
 		\w3tc_add_action( 'pagecache_page_key', array( self::class, 'pagecache_page_key' ) );
-		// Register additional filters to handle query strings and cache rules.
-		\w3tc_add_action( 'pagecache_extract_accept_qs', array( self::class, 'pagecache_extract_accept_qs' ) );
-		\w3tc_add_action( 'w3tc_pagecache_rules_apache_accept_qs', array( self::class, 'w3tc_pagecache_rules_accept_qs' ) );
-		\w3tc_add_action( 'w3tc_pagecache_rules_nginx_accept_qs', array( self::class, 'w3tc_pagecache_rules_accept_qs' ) );
-		\w3tc_add_action( 'w3tc_pagecache_rules_apache_accept_qs_rules', array( self::class, 'w3tc_pagecache_rules_apache_accept_qs_rules' ), 10, 2 );
-		\w3tc_add_action( 'w3tc_pagecache_rules_nginx_accept_qs_rules', array( self::class, 'w3tc_pagecache_rules_nginx_accept_qs_rules' ), 10, 2 );
-		\w3tc_add_action( 'w3tc_pagecache_rules_apache_uri_prefix', array( self::class, 'w3tc_pagecache_rules_apache_uri_prefix' ) );
-		\w3tc_add_action( 'w3tc_pagecache_rules_nginx_uri_prefix', array( self::class, 'w3tc_pagecache_rules_nginx_uri_prefix' ) );
+		\add_filter( 'w3tc_pgcache_rules_apache_last', array( self::class, 'w3tc_pgcache_rules_apache_last' ) );
 	}
 
 	/**
-	 * Modify the page cache key if this is an ActivityPub request.
+	 * Filter: Allow adding additional rules at the end of the PGCACHE_CORE block, before the last rule.
 	 *
-	 * @param array $page_key The page cache key.
+	 * @since 2.7.1
 	 *
-	 * @return array The modified page cache key.
-	 */
-	public static function pagecache_page_key( $page_key ) {
-		// Always check for ActivityPub request.
-		if ( is_activitypub_request() ) {
-			// Make the ActivityPub key more distinct by adding a prefix.
-			$page_key[0]  = 'activitypub_' . $page_key[0];
-			$page_key[1] .= '_activitypub';
-		}
-
-		return $page_key;
-	}
-
-	/**
-	 * Extract query strings that should be accepted for caching.
-	 *
-	 * @param array $query_strings The list of query strings to accept.
-	 * @return array The modified list of query strings.
-	 */
-	public static function pagecache_extract_accept_qs( $query_strings ) {
-		// Add ActivityPub-specific query parameters that should be considered for caching.
-		$query_strings[] = 'activitypub';
-		$query_strings[] = 'format';
-
-		return $query_strings;
-	}
-
-	/**
-	 * Add ActivityPub query strings to the accepted query strings for caching rules.
-	 *
-	 * @param array $query_strings The list of query strings to accept.
-	 * @return array The modified list of query strings.
-	 */
-	public static function w3tc_pagecache_rules_accept_qs( $query_strings ) {
-		$query_strings[] = 'activitypub';
-		$query_strings[] = 'format';
-
-		return $query_strings;
-	}
-
-	/**
-	 * Modify Apache caching rules for ActivityPub query strings.
+	 * @param string $key The page key.
 	 *
-	 * @param array  $query_rules The query rules.
-	 * @param string $query The query string.
-	 *
-	 * @return array The modified query rules.
+	 * @return string The modified page key.
 	 */
-	public static function w3tc_pagecache_rules_apache_accept_qs_rules( $query_rules, $query ) {
-		if ( 'activitypub' === $query || 'format' === $query ) {
-			$query_rules[1] = str_replace( '[E=', '[E=W3TC_ACTIVITYPUB:_activitypub,E=', $query_rules[1] );
+	public static function pagecache_page_key( $key ) {
+		// Check if this is an ActivityPub request.
+		if ( is_activitypub_request() ) {
+			$key['key'][1] .= '_activitypub';
 		}
 
-		return $query_rules;
+		return $key;
 	}
 
 	/**
-	 * Modify the Apache URI prefix for ActivityPub requests.
+	 * Modify the Apache caching rules for ActivityPub requests.
 	 *
-	 * @param string $uri_prefix The URI prefix.
-	 * @return string The modified URI prefix.
-	 */
-	public static function w3tc_pagecache_rules_apache_uri_prefix( $uri_prefix ) {
-		return $uri_prefix . '%{ENV:W3TC_ACTIVITYPUB}';
-	}
-
-	/**
-	 * Modify Nginx caching rules for ActivityPub query strings.
+	 * @param array $rules The existing Apache rules.
 	 *
-	 * @param array $query_rules The query rules.
-	 * @param string $query The query string.
-	 * @return array The modified query rules.
+	 * @return array The modified Apache rules.
 	 */
-	public static function w3tc_pagecache_rules_nginx_accept_qs_rules( $query_rules, $query ) {
-		if ( $query === 'activitypub' || $query === 'format' ) {
-			array_splice( $query_rules, 1, 0, '    set $w3tc_activitypub "_activitypub";' );
-			array_unshift( $query_rules, 'set $w3tc_activitypub "";' );
-		}
+	public static function w3tc_pgcache_rules_apache_last( $rules ) {
+		// Add check for ActivityPub Accept header (Content Negotiation).
+		$rules .= 'RewriteCond %{HTTP:Accept} (application/(ld\+json|activity\+json|json)) [NC]' . PHP_EOL;
+		$rules .= 'RewriteRule .* - [E=W3TC_ACTIVITYPUB:_activitypub]' . PHP_EOL;
 
-		return $query_rules;
-	}
+		// Also set the environment variable if activitypub parameter is explicitly set.
+		$rules .= 'RewriteCond %{QUERY_STRING} (?:^|&)activitypub(?:=|&|$) [NC]' . PHP_EOL;
+		$rules .= 'RewriteRule .* - [E=W3TC_ACTIVITYPUB:_activitypub]' . PHP_EOL;
 
-	/**
-	 * Modify the Nginx URI prefix for ActivityPub requests.
-	 *
-	 * @param string $uri_prefix The URI prefix.
-	 * @return string The modified URI prefix.
-	 */
-	public static function w3tc_pagecache_rules_nginx_uri_prefix( $uri_prefix ) {
-		return $uri_prefix . '$w3tc_activitypub';
+		return $rules;
 	}
 }