<?php
/**
 * Keeps the link report current as posts are saved and deleted.
 *
 * @package Postlinkly
 * @since   1.18.4
 */

declare(strict_types=1);

namespace Postlinkly\Indexing;

use Postlinkly\Admin\Dashboard\DashboardStatsProvider;
use Postlinkly\Hooks\ServiceProvider;
use Postlinkly\Indexing\Stage\LinksStage;
use Postlinkly\Logging\Logger;
use WP_Post;

/**
 * Re-indexes one post's links whenever it is saved or deleted.
 *
 * The full index job builds the link report once; after that, this keeps it
 * current, so a post published, edited, scheduled to go live, unpublished or
 * deleted shows correct counts in the posts list, Link Report and Dashboard
 * straight away rather than at the next manual rebuild.
 *
 * Inbound counts need no work of their own: they are counted from other
 * posts' rows, so refreshing the saved post's outbound rows updates every
 * post it links to.
 *
 * @since 1.18.4
 */
final class LinkIndexSyncer implements ServiceProvider {

	/**
	 * @var LinksStage
	 */
	private LinksStage $links;

	/**
	 * @since 1.18.4
	 *
	 * @param LinksStage $links The stage that knows how to index one post and
	 *                          which posts are tracked.
	 */
	public function __construct( LinksStage $links ) {
		$this->links = $links;
	}

	/**
	 * @since 1.18.4
	 *
	 * @return array<int, array{0: string, 1: callable, 2?: int, 3?: int, 4?: 'action'|'filter'}>
	 */
	public function get_hooks(): array {
		return array(
			// Fires for publishing, editing, trashing, and a scheduled post
			// going live (wp_publish_post() fires it too), after the post's
			// own data is saved. Postlinkly's link inserts save through
			// wp_update_post(), so they arrive here as well.
			array( 'wp_after_insert_post', array( $this, 'on_post_saved' ), 20, 2 ),
			// Permanent deletion; trashing is a status change handled above.
			array( 'delete_post', array( $this, 'on_post_deleted' ), 10, 1 ),
		);
	}

	/**
	 * Indexes a saved post, or removes it when it is no longer tracked.
	 *
	 * @since 1.18.4
	 * @hook  wp_after_insert_post
	 *
	 * @param int     $post_id Post that was saved.
	 * @param WP_Post $post    The saved post.
	 *
	 * @return void
	 */
	public function on_post_saved( int $post_id, $post ): void {
		if ( ! $post instanceof WP_Post ) {
			return;
		}

		// Auto-drafts are the empty placeholders the editor creates when it
		// opens. Revisions and untracked types were never in the report.
		if ( 'auto-draft' === $post->post_status || ! $this->links->tracks_type( $post->post_type ) ) {
			return;
		}

		$done = $this->links->is_tracked( $post )
			? $this->links->index_post( $post )
			: $this->links->remove_post( $post_id );

		$this->after_change( $done, $post_id );
	}

	/**
	 * Removes a permanently deleted post's links from the report.
	 *
	 * @since 1.18.4
	 * @hook  delete_post
	 *
	 * @param int $post_id Post being deleted.
	 *
	 * @return void
	 */
	public function on_post_deleted( int $post_id ): void {
		// Deleting a post deletes each of its revisions too, one call each;
		// the post still exists at this point, so its type can be checked.
		$post = get_post( $post_id );
		if ( ! $post instanceof WP_Post || ! $this->links->tracks_type( $post->post_type ) ) {
			return;
		}

		$this->after_change( $this->links->remove_post( $post_id ), $post_id );
	}

	/**
	 * Refreshes the Dashboard, or records a write the database refused.
	 *
	 * A refused write leaves the post unmarked, so the next full scan retries
	 * it; the log says why its counts are out of date until then.
	 *
	 * @since 1.18.4
	 *
	 * @param bool $done    Whether the report was updated.
	 * @param int  $post_id Post concerned.
	 *
	 * @return void
	 */
	private function after_change( bool $done, int $post_id ): void {
		if ( ! $done ) {
			Logger::error( 'Could not update the link report for post %d; the next full scan will retry it.', array( $post_id ) );
			return;
		}

		DashboardStatsProvider::flush_cache();
	}
}