<?php
/**
 * Database-session lock shared across PHP workers and object caches.
 *
 * @package Waitlistize
 */

namespace Waitlistize\Auth;

use WP_Error;

final class Mutex {
	private bool $held           = false;
	private static array $active = array();
	private string $name;

	public function __construct() {
		global $wpdb;
		$this->name = 'wlt_' . substr( hash( 'sha256', DB_NAME . ':' . $wpdb->prefix ), 0, 56 );
	}

	public function run( callable $callback, int $wait = 0 ): mixed {
		global $wpdb;
		// Reject reentry: GET_LOCK itself is reentrant on MySQL/MariaDB.
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Session locks must execute on the database; a cache cannot provide exclusion.
		if ( isset( self::$active[ $this->name ] ) || $this->held || '1' !== (string) $wpdb->get_var( $wpdb->prepare( 'SELECT GET_LOCK(%s, %d)', $this->name, $wait ) ) ) {
			return new WP_Error( 'busy', __( 'Another connection operation is running. Please retry shortly.', 'waitlistize' ), array( 'status' => 409 ) );
		}
		$this->held                  = true;
		self::$active[ $this->name ] = true;
		try {
			return $callback();
		} finally {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Release the database session lock.
			$wpdb->get_var( $wpdb->prepare( 'SELECT RELEASE_LOCK(%s)', $this->name ) );
			$this->held = false;
			unset( self::$active[ $this->name ] );
		}
	}

	/** Fail closed if wpdb transparently reconnected while an HTTP call ran. */
	public function owned(): bool {
		global $wpdb;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching -- Lock ownership must be observed from the active database session.
		return $this->held && '1' === (string) $wpdb->get_var( $wpdb->prepare( 'SELECT IS_USED_LOCK(%s) = CONNECTION_ID()', $this->name ) );
	}
}