Implement speculative prerendering

includes/Plugin.php

@@ -140,6 +140,7 @@ class Plugin extends ServiceBasedPlugin {
 		'user_preferences'             => User\Preferences::class,
 		'remove_transients'            => Remove_Transients::class,
 		'web_stories_block'            => Block\Web_Stories_Block::class,
+		'speculative_prerendering'     => Admin\Speculative_Prerendering::class,
 	];
 
 	/**

includes/Speculative_Prerendering.php

@@ -0,0 +1,114 @@
+<?php
+/**
+ * Class Speculative_Prerendering
+ *
+ * @link      https://github.com/googleforcreators/web-stories-wp
+ *
+ * @copyright 2024 Google LLC
+ * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ */
+
+/**
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+declare(strict_types = 1);
+
+namespace Google\Web_Stories\Admin;
+
+use Google\Web_Stories\Service_Base;
+
+/**
+ * Speculative_Prerendering class.
+ */
+class Speculative_Prerendering extends Service_Base {
+
+	/**
+	 * Array defining the matches for different pages.
+	 *
+	 * @var array<string,array<string>>
+	 */
+	private array $matches = [
+		'dashboard'   => [ 'post.php?post=*&action=edit', 'post-new.php?post_type=web-story' ],
+		'all_stories' => [ 'post.php?post=*&action=edit', 'post-new.php?post_type=web-story', '/web-stories*' ],
+		'archive'     => [ '/web-stories*' ],
+	];
+
+	/**
+	 * Runs on instantiation.
+	 */
+	public function register(): void {
+		add_action( 'admin_enqueue_scripts', [ $this, 'load_rules' ] );
+	}
+
+	/**
+	 * Loads the prerendering rules based on the current page.
+	 *
+	 * @param string $hook The current page hook.
+	 */
+	public function load_rules( string $hook ): void {
+		$rules = [];
+		if ( 'web-story_page_stories-dashboard' === $hook ) {
+			$rules = $this->get_rules( 'dashboard' );
+		}
+
+		// phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Nonce verification not needed as we're just checking for the 'web-story' post type.
+		if ( 'edit.php' === $hook && isset( $_GET['post_type'] ) && 'web-story' === $_GET['post_type'] ) {
+			$rules = $this->get_rules( 'all_stories' );
+		}
+		$this->print_rules( $rules );
+	}
+
+	/**
+	 * Retrieves the prerendering rules for a specific page.
+	 *
+	 * @param string $page The page identifier.
+	 * @return array An array containing prerendering rules.
+	 */
+	public function get_rules( string $page ): array {
+		$rules = [
+			[
+				'source'    => 'document',
+				'where'     => [
+					'and' => [
+						[
+							'href_matches' => $this->matches[ $page ],
+						],
+					],
+				],
+				'eagerness' => 'moderate',
+			],
+		];
+
+		return [ 'prerender' => $rules ];
+	}
+
+	/**
+	 * Prints the prerendering rules as an inline script tag.
+	 *
+	 * @param array $rules The prerendering rules to print.
+	 */
+	public function print_rules( array $rules ): void {
+		if ( empty( $rules ) ) {
+			return;
+		}
+
+		$encoded_rules = wp_json_encode( $rules );
+
+		if ( false !== $encoded_rules ) {
+			wp_print_inline_script_tag( $encoded_rules, [ 'type' => 'speculationrules' ] );
+		}
+	}
+}