<?php
/**
 * Rendered-content cache for AI Discovery Files.
 *
 * The generated files are identical between requests until the site's identity
 * settings or content change. Rendering them on every request means booting the
 * full plugin stack (page builders, etc.) just to emit a small static file —
 * several seconds of work on shared hosting.
 *
 * This cache stores the finished output of AIDF_Generator::generate() in a single
 * non-autoloaded option so the early server (AIDF_Server::maybe_serve_early) can
 * return it before the heavy stack loads. Crawler logging still runs on every
 * request, so the analytics feature is unaffected and responses stay uncached at
 * the CDN edge (s-maxage=0).
 *
 * The cache is keyed by plugin version, so a plugin upgrade transparently busts
 * it. It is invalidated when identity settings or relevant content change, and
 * the normal template_redirect path repopulates it on a miss, so a stale or
 * empty cache is always self-healing rather than a source of wrong output.
 *
 * @package AIDF
 * @since   2.1.2
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Stores and serves pre-rendered AI Discovery File content.
 */
class AIDF_File_Cache {

	/**
	 * Option name holding the cached content.
	 *
	 * @var string
	 */
	const OPTION = 'aidf_file_cache';

	/**
	 * Cron hook used to warm the cache asynchronously after a content change.
	 *
	 * @var string
	 */
	const WARM_HOOK = 'aidf_warm_file_cache';

	/**
	 * Register invalidation and warming hooks.
	 *
	 * Runs for every request (admin, front end, REST, cron) via the plugin
	 * constructor on plugins_loaded, so save_post and option changes in any
	 * context invalidate the cache.
	 *
	 * @return void
	 */
	public static function init() {
		add_action( 'update_option_aidf_settings', array( __CLASS__, 'on_settings_change' ) );
		add_action( 'add_option_aidf_settings', array( __CLASS__, 'on_settings_change' ) );
		add_action( 'save_post', array( __CLASS__, 'on_save_post' ), 10, 2 );
		add_action( 'update_option_blogname', array( __CLASS__, 'on_option_change' ) );
		add_action( 'update_option_blogdescription', array( __CLASS__, 'on_option_change' ) );
		add_action( self::WARM_HOOK, array( __CLASS__, 'warm' ) );
	}

	/**
	 * Get cached content for a file type.
	 *
	 * @param  string $file_slug File type slug (e.g. 'llms-txt').
	 * @return string|false Cached content, or false on a miss / version mismatch.
	 */
	public static function get( $file_slug ) {
		$cache = get_option( self::OPTION );

		if ( ! is_array( $cache ) || empty( $cache['v'] ) || AIDF_VERSION !== $cache['v'] ) {
			return false;
		}

		if ( ! isset( $cache['files'][ $file_slug ] ) || ! is_string( $cache['files'][ $file_slug ] ) ) {
			return false;
		}

		return $cache['files'][ $file_slug ];
	}

	/**
	 * Store rendered content for a single file type.
	 *
	 * Used by the normal template_redirect path to self-heal the cache after a
	 * miss, so the next request is served early and fast.
	 *
	 * @param  string $file_slug File type slug.
	 * @param  string $content   Rendered file content.
	 * @return void
	 */
	public static function set( $file_slug, $content ) {
		$cache = get_option( self::OPTION );

		if ( ! is_array( $cache ) || empty( $cache['v'] ) || AIDF_VERSION !== $cache['v'] || ! isset( $cache['files'] ) || ! is_array( $cache['files'] ) ) {
			$cache = array(
				'v'     => AIDF_VERSION,
				'files' => array(),
			);
		}

		$cache['files'][ $file_slug ] = $content;

		update_option( self::OPTION, $cache, false );
	}

	/**
	 * Regenerate and cache every active file type in one pass.
	 *
	 * Runs the full generation pipeline, so it must only be called in a fully
	 * loaded context (admin, cron, or the front-end template_redirect path) —
	 * never from the early plugins_loaded server.
	 *
	 * @return void
	 */
	public static function warm() {
		if ( ! class_exists( 'AIDF_Generator' ) || ! class_exists( 'AIDF_Plugin' ) ) {
			return;
		}

		$settings = AIDF_Plugin::get_settings();
		$active   = isset( $settings['active_files'] ) ? (array) $settings['active_files'] : array();
		$files    = array();

		foreach ( $active as $slug ) {
			// llm.txt is served as a 301 redirect to llms.txt; nothing to cache.
			if ( 'llm-txt' === $slug ) {
				continue;
			}

			$content = AIDF_Generator::generate( $slug );

			if ( false !== $content ) {
				$files[ $slug ] = $content;
			}
		}

		update_option(
			self::OPTION,
			array(
				'v'     => AIDF_VERSION,
				'files' => $files,
			),
			false
		);
	}

	/**
	 * Delete the cache.
	 *
	 * @return void
	 */
	public static function invalidate() {
		delete_option( self::OPTION );
	}

	/**
	 * Handle an identity-settings change: rebuild the cache immediately.
	 *
	 * A settings save is a deliberate content change made in the admin, so the
	 * small cost of warming synchronously keeps the front end permanently fast.
	 *
	 * @return void
	 */
	public static function on_settings_change() {
		self::invalidate();
		self::warm();
	}

	/**
	 * Handle a post/page save: invalidate and warm in the background.
	 *
	 * Only publish-worthy page and post edits affect generated content, so
	 * revisions, autosaves, and unrelated post types are ignored to avoid churn.
	 *
	 * @param  int          $post_id Saved post ID.
	 * @param  WP_Post|null $post    Saved post object.
	 * @return void
	 */
	public static function on_save_post( $post_id, $post = null ) {
		if ( wp_is_post_revision( $post_id ) || wp_is_post_autosave( $post_id ) ) {
			return;
		}

		if ( $post instanceof WP_Post && ! in_array( $post->post_type, array( 'page', 'post' ), true ) ) {
			return;
		}

		self::invalidate();
		self::schedule_warm();
	}

	/**
	 * Handle a relevant option change (site title / tagline).
	 *
	 * @return void
	 */
	public static function on_option_change() {
		self::invalidate();
		self::schedule_warm();
	}

	/**
	 * Queue a single background warm run if one is not already scheduled.
	 *
	 * @return void
	 */
	public static function schedule_warm() {
		if ( ! wp_next_scheduled( self::WARM_HOOK ) ) {
			wp_schedule_single_event( time() + 10, self::WARM_HOOK );
		}
	}
}