Header/Footer: Add global-header-footer/v1/styles route for Profiles.

Profiles can't access the styles directly because it's on the BuddyPress network rather than the w.org one.

See #81

mu-plugins/blocks/global-header-footer/blocks.php

@@ -112,6 +112,21 @@ function register_routes() {
 			),
 		)
 	);
+
+	// Requesting this on another network would create an infinite loop.
+	if ( is_wporg_network() ) {
+		register_rest_route(
+			'global-header-footer/v1',
+			'styles',
+			array(
+				array(
+					'methods'             => WP_REST_Server::READABLE,
+					'callback'            => __NAMESPACE__ . '\rest_render_global_styles',
+					'permission_callback' => '__return_true',
+				),
+			)
+		);
+	}
 }
 
 /**
@@ -719,6 +734,35 @@ function render_global_footer() {
 	return $markup;
 }
 
+/**
+ * Check if the current site is part of the w.org network.
+ *
+ * These blocks are used on some sites (like profiles.w.org) that are running WP, but in a different network.
+ * In those sites, some things need to behave differently (e.g., because `switch_to_blog()` wouldn't work).
+ */
+function is_wporg_network() {
+	return 0 === strpos( $_SERVER['SCRIPT_FILENAME'], WPORGPATH );
+}
+
+/**
+ * Render the global styles via a REST request.
+ *
+ * @return string
+ */
+function rest_render_global_styles( $request ) {
+	// Serve the request as CSS.
+	add_filter( 'rest_pre_serve_request', function( $served, $result ) {
+		header( 'Content-Type: text/css' );
+		header( 'X-Robots-Tag: noindex, follow' );
+
+		echo $result->get_data();
+
+		return true;
+	}, 10, 2 );
+
+	return get_global_styles();
+}
+
 /**
  * Output just the variables generated by `theme.json` from the News site.
  *
@@ -727,20 +771,74 @@ function render_global_footer() {
  *
  * @see `wp_get_global_stylesheet()`
  */
-function render_global_styles() {
+function get_global_styles() {
+	/*
+	 * The block is used on some sites (like profiles.w.org) that are running WP, but in a different
+	 * network. On those sites, things like `switch_to_blog()` won't work, so they need to use the API.
+	 */
+	if ( ! is_wporg_network() ) {
+		return fetch_global_styles();
+	}
+
 	// Switch to `w.org/news-test` to generate correct theme properties.
 	switch_to_blog( 706 ); // TODO change this to `w.org/news` when the redesign launches.
 
 	// Clear the static `$theme` property, which is set by the current (classic theme) site.
 	WP_Theme_JSON_Resolver::clean_cached_data();
 
-	echo wp_get_global_stylesheet( [ 'variables' ] ); // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
+	$styles = wp_get_global_stylesheet( [ 'variables' ] );
 	// Also set the block-gap style, which isn't technically a theme variable.
-	echo 'body { --wp--style--block-gap: 24px; }';
+	$styles .= 'body { --wp--style--block-gap: 24px; }';
 
 	// Restore to current site.
 	restore_current_blog();
 	WP_Theme_JSON_Resolver::clean_cached_data();
+
+	return $styles;
+}
+
+/**
+ * Fetch the global styles via the API endpoint
+ *
+ * @see `get_global_styles()` for background.
+ */
+function fetch_global_styles() {
+	$cache_key = 'global_header_styles';
+	$styles    = get_transient( $cache_key );
+
+	if ( ! $styles ) {
+		$styles       = '';
+		$request_args = array();
+
+		// Route request to sandbox when testing.
+		if ( defined( 'WPORG_SANDBOXED' ) && WPORG_SANDBOXED ) {
+			$hostname                        = '127.0.0.1';
+			$request_args['headers']['host'] = 'wordpress.org';
+
+			/*
+			 * It's expected that the sandbox hostname won't be valid. This is safe because we're only connecting
+			 * to `127.0.0.1`.
+			 */
+			$request_args['sslverify'] = false;
+
+		} else {
+			$hostname = 'wordpress.org';
+		}
+
+		$response      = wp_remote_get( "https://$hostname/wp-json/global-header-footer/v1/styles", $request_args );
+		$response_code = wp_remote_retrieve_response_code( $response );
+
+		if ( is_wp_error( $response ) || 200 !== $response_code ) {
+			trigger_error( "Fetching global styles failed.", E_USER_WARNING );
+
+		} else {
+			$styles = wp_remote_retrieve_body( $response );
+
+			set_transient( $cache_key, $styles, HOUR_IN_SECONDS );
+		}
+	}
+
+	return $styles;
 }
 
 /**

mu-plugins/blocks/global-header-footer/classic-header.php

@@ -2,7 +2,7 @@
 
 namespace WordPressdotorg\MU_Plugins\Global_Header_Footer\Header;
 
-use function WordPressdotorg\MU_Plugins\Global_Header_Footer\render_global_styles;
+use function WordPressdotorg\MU_Plugins\Global_Header_Footer\{ get_global_styles };
 
 defined( 'WPINC' ) || die();
 
@@ -23,7 +23,7 @@
 		  output first, so they can be overridden if needed.
 		-->
 		<style id="global-styles-for-classic-themes">
-			<?php render_global_styles(); ?>
+			<?php echo get_global_styles(); // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped ?>
 		</style>
 
 		<?php