Change default settings based on caching behaviour (#1640)

* Change default settings based on caching behaviour

Change the default behaviour of the plugin based on the caching plugins that are installed.

This PR is an extension to #1639 and #1638

* fix phpcs issues

* seems to not properly work with the plugin

so let's wait for the first that needs it.

* fix whitespaces

* Add changelog

Author: pfefferle

.github/changelog/1640-from-description

@@ -0,0 +1,4 @@
+Significance: minor
+Type: added
+
+Adjusted the plugin's default behavior based on the caching plugins installed.

includes/class-options.php

@@ -26,6 +26,7 @@ public static function init() {
 		\add_filter( 'pre_option_activitypub_allow_likes', array( self::class, 'maybe_disable_interactions' ) );
 		\add_filter( 'pre_option_activitypub_allow_replies', array( self::class, 'maybe_disable_interactions' ) );
 
+		\add_filter( 'default_option_activitypub_negotiate_content', array( self::class, 'default_option_activitypub_negotiate_content' ) );
 		\add_filter( 'option_activitypub_max_image_attachments', array( self::class, 'default_max_image_attachments' ) );
 	}
 
@@ -114,6 +115,7 @@ public static function pre_option_activitypub_vary_header( $pre ) {
 	 * Disallow interactions if the constant is set.
 	 *
 	 * @param bool $pre The value of the option.
+	 *
 	 * @return bool|string The value of the option.
 	 */
 	public static function maybe_disable_interactions( $pre ) {
@@ -137,4 +139,31 @@ public static function default_max_image_attachments( $value ) {
 
 		return $value;
 	}
+
+	/**
+	 * Default option filter for the Content-Negotiation.
+	 *
+	 * @see https://github.com/Automattic/wordpress-activitypub/wiki/Caching
+	 *
+	 * @param string $default_value The default value of the option.
+	 *
+	 * @return string The default value of the option.
+	 */
+	public static function default_option_activitypub_negotiate_content( $default_value ) {
+		$disable_for_plugins = array(
+			'wp-optimize/wp-optimize.php',
+			'wp-rocket/wp-rocket.php',
+			'w3-total-cache/w3-total-cache.php',
+			'wp-fastest-cache/wp-fastest-cache.php',
+			'sg-cachepress/sg-cachepress.php',
+		);
+
+		foreach ( $disable_for_plugins as $plugin ) {
+			if ( \is_plugin_active( $plugin ) ) {
+				return '0';
+			}
+		}
+
+		return $default_value;
+	}
 }