vel_names ),
			'default' => self::DEFAULT_DB_TRANSACTIONS_ISOLATION_LEVEL,
		);

		$settings[] = array( 'type' => 'sectionend' );

		return $settings;
	}

	/**
	 * Get the valid database transaction isolation level names.
	 *
	 * @return string[]
	 */
	public static function get_valid_transaction_isolation_levels() {
		return array(
			'REPEATABLE READ',
			'READ COMMITTED',
			'READ UNCOMMITTED',
			'SERIALIZABLE',
		);
	}

	/**
	 * Handler for the individual setting updated hook.
	 *
	 * @param string $option Setting name.
	 * @param mixed  $old_value Old value of the setting.
	 * @param mixed  $value New value of the setting.
	 */
	private function process_updated_option( $option, $old_value, $value ) {
		if ( DataSynchronizer::ORDERS_DATA_SYNC_ENABLED_OPTION === $option && 'no' === $value ) {
			$this->data_synchronizer->cleanup_synchronization_state();
		}
	}

	/**
	 * Handler for the setting pre-update hook.
	 * We use it to verify that authoritative orders table switch doesn't happen while sync is pending.
	 *
	 * @param mixed  $value New value of the setting.
	 * @param string $option Setting name.
	 * @param mixed  $old_value Old value of the setting.
	 *
	 * @throws \Exception Attempt to change the authoritative orders table while orders sync is pending.
	 */
	private function process_pre_update_option( $value, $option, $old_value ) {
		if ( self::CUSTOM_ORDERS_TABLE_USAGE_ENABLED_OPTION !== $option || $value === $old_value || false === $old_value ) {
			return $value;
		}

		/**
		 * Commenting out for better testability.
		$sync_is_pending = 0 !== $this->data_synchronizer->get_current_orders_pending_sync_count();
		if ( $sync_is_pending ) {
			throw new \Exception( "The authoritative table for orders storage can't be changed while there are orders out of sync" );
		}
		 */

		return $value;
	}

	/**
	 * Handler for the synchronization finished hook.
	 * Here we switch the authoritative table if needed.
	 */
	private function process_sync_finished() {
		if ( ! $this->auto_flip_authoritative_table_enabled() ) {
			return;
		}

		update_option( self::AUTO_FLIP_AUTHORITATIVE_TABLE_ROLES_OPTION, 'no' );

		if ( $this->custom_orders_table_usage_is_enabled() ) {
			update_option( self::CUSTOM_ORDERS_TABLE_USAGE_ENABLED_OPTION, 'no' );
		} else {
			update_option( self::CUSTOM_ORDERS_TABLE_USAGE_ENABLED_OPTION, 'yes' );
		}
	}

	/**
	 * Is the automatic authoritative table switch setting set?
	 *
	 * @return bool
	 */
	private function auto_flip_authoritative_table_enabled(): bool {
		return get_option( self::AUTO_FLIP_AUTHORITATIVE_TABLE_ROLES_OPTION ) === 'yes';
	}

	/**
	 * Handler for the all settings updated hook.
	 */
	private function process_options_updated() {
		$data_sync_is_enabled = $this->data_synchronizer->data_sync_is_enabled();

		// Disabling the sync implies disabling the automatic authoritative table switch too.
		if ( ! $data_sync_is_enabled && $this->auto_flip_authoritative_table_enabled() ) {
			update_option( self::AUTO_FLIP_AUTHORITATIVE_TABLE_ROLES_OPTION, 'no' );
		}

		// Enabling/disabling the sync implies starting/stopping it too, if needed.
		// We do this check here, and not in process_pre_update_option, so that if for some reason
		// the setting is enabled but no sync is in process, sync will start by just saving the
		// settings even without modifying them (and the opposite: sync will be stopped if for
		// some reason it was ongoing while it was disabled).
		if ( $data_sync_is_enabled ) {
			$this->batch_processing_controller->enqueue_processor( DataSynchronizer::class );
		} else {
			$this->batch_processing_controller->remove_processor( DataSynchronizer::class );
		}
	}

	/**
	 * Handle the 'woocommerce_feature_enabled_changed' action,
	 * if the custom orders table feature is enabled create the database tables if they don't exist.
	 *
	 * @param string $feature_id The id of the feature that is being enabled or disabled.
	 * @param bool   $is_enabled True if the feature is being enabled, false if it's being disabled.
	 */
	private function handle_feature_enabled_changed( $feature_id, $is_enabled ): void {
		if ( 'custom_order_tables' !== $feature_id || ! $is_enabled ) {
			return;
		}

		if ( ! $this->data_synchronizer->check_orders_table_exists() ) {
			update_option( DataSynchronizer::ORDERS_DATA_SYNC_ENABLED_OPTION, 'no' );
			$this->create_custom_orders_tables( false );
		}
	}

	/**
	 * Handler for the woocommerce_after_register_post_type post,
	 * registers the post type for placeholder orders.
	 *
	 * @return void
	 */
	private function register_post_type_for_order_placeholders(): void {
		wc_register_order_type(
			DataSynchronizer::PLACEHOLDER_ORDER_POST_TYPE,
			array(
				'public'                           => false,
				'exclude_from_search'              => true,
				'publicly_queryable'               => false,
				'show_ui'                          => false,
				'show_in_menu'                     => false,
				'show_in_nav_menus'                => false,
				'show_in_admin_bar'                => false,
				'show_in_rest'                     => false,
				'rewrite'                          => false,
				'query_var'                        => false,
				'can_export'                       => false,
				'supports'                         => array(),
				'capabilities'                     => array(),
				'exclude_from_order_count'         => true,
				'exclude_from_order_views'         => true,
				'exclude_from_order_reports'       => true,
				'exclude_from_order_sales_reports' => true,
			)
		);
	}
}