<?php
/** Database-backed conversation serialization. */
namespace AISupportAssistant\Chat;

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

class SessionLock {
	private static array $held = array();

	public static function run( string $session_id, callable $callback ) {
		global $wpdb;
		$key = 'ai_sa_session_' . substr( hash( 'sha256', $wpdb->prefix . $session_id ), 0, 40 );
		if ( isset( self::$held[ $key ] ) ) {
			return $callback();
		}
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Advisory locks require a live connection query; caching a lock result would break mutual exclusion.
		if ( '1' !== (string) $wpdb->get_var( $wpdb->prepare( 'SELECT GET_LOCK(%s, 0)', $key ) ) ) {
			throw new \RuntimeException( 'A request for this conversation is already running. Please retry shortly.' );
		}
		self::$held[ $key ] = true;
		try {
			return $callback();
		} finally {
			unset( self::$held[ $key ] );
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Release the connection-owned lock immediately; this operation cannot be cached.
			$wpdb->get_var( $wpdb->prepare( 'SELECT RELEASE_LOCK(%s)', $key ) );
		}
	}
}