<?php
/**
 * Post-level cache of the converted Markdown (post meta).
 *
 * Removes the cost of DOM parsing + conversion on every bot visit.
 * Strategy: lazy fill on the first front-end request (there the_content
 * renders in the correct context — important for Elementor and dynamic
 * shortcodes), invalidation on save_post. Only the body is stored in meta
 * (without front matter) — reused by both the negotiator and the llms-full generator.
 *
 * @package ADG_AI_Markdown
 */

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

class ADG_AIM_Markdown_Cache {

	const META_KEY = '_adg_markdown_cache';

	/**
	 * Invalidation hooks.
	 */
	public static function hooks() {
		add_action( 'save_post', array( __CLASS__, 'invalidate' ) );
	}

	/**
	 * Get the post's Markdown body (from cache, otherwise convert).
	 *
	 * @param WP_Post $post  Post.
	 * @param bool    $store Whether to write the result to cache on a miss.
	 *                       true — only for the front-end negotiator (authoritative
	 *                       render context); false — for the llms generator/cron.
	 * @return string Markdown body (without front matter).
	 */
	public static function get( WP_Post $post, $store = true ) {
		$enabled = (bool) ADG_AIM_Plugin::get_setting( 'markdown_cache', true );

		if ( $enabled ) {
			$cached = get_post_meta( $post->ID, self::META_KEY, true );
			if ( is_array( $cached )
				&& isset( $cached['version'], $cached['hash'], $cached['body'] )
				&& ADG_AIM_VERSION === $cached['version']
				&& self::content_hash( $post ) === $cached['hash']
			) {
				return $cached['body'];
			}
		}

		$body = self::build( $post );

		if ( $enabled && $store ) {
			update_post_meta(
				$post->ID,
				self::META_KEY,
				array(
					'version' => ADG_AIM_VERSION,
					'hash'    => self::content_hash( $post ),
					'body'    => $body,
				)
			);
		}

		return $body;
	}

	/**
	 * Convert the post's the_content to Markdown (without cache).
	 *
	 * @param WP_Post $post Post.
	 * @return string
	 */
	private static function build( WP_Post $post ) {
		$html      = apply_filters( 'the_content', $post->post_content );
		$converter = new ADG_AIM_HTML_To_Markdown();
		return $converter->convert( $html );
	}

	/**
	 * Hash of the source content (to detect staleness even without save_post,
	 * e.g. after a programmatic post change).
	 *
	 * @param WP_Post $post Post.
	 * @return string
	 */
	private static function content_hash( WP_Post $post ) {
		return md5( $post->post_content );
	}

	/**
	 * Invalidate the post cache on save.
	 *
	 * @param int $post_id ID.
	 */
	public static function invalidate( $post_id ) {
		if ( wp_is_post_revision( $post_id ) || wp_is_post_autosave( $post_id ) ) {
			return;
		}
		delete_post_meta( $post_id, self::META_KEY );
	}

	/**
	 * Clear the entire cache (used by the "regenerate" button in the admin).
	 */
	public static function clear_all() {
		delete_post_meta_by_key( self::META_KEY );
	}
}