class WorkflowStateTransitionOperationsAccessCheck

class WorkflowStateTransitionOperationsAccessCheck implements AccessInterface {
    
    /**
     * Checks access for operations of workflow states and transitions.
     *
     * The value of '_workflow_access' is used to check to kind of access that
     * should be applied to a route in the context of a workflow and a state or
     * transition. States and transitions can individually have access control
     * applied to them for 'add', 'update' and 'delete'. By default workflows will
     * use the admin permission 'administer workflows' for all of these
     * operations, except for delete-state which checks there is at least one
     * state, a state does not have data and it's not a required state.
     *
     * For the update and delete operations, a workflow and a state or transition
     * is required in the route for the access check to be applied. For the "add"
     * operation, only a workflow is required. The '_workflow_access' requirement
     * translates into access checks on the workflow entity type in the formats:
     *   - @code"$operation-state:$state_id"@endcode
     *   - @code"$operation-transition:$transition_id"@endcode
     *
     * For example the following route definition with the path
     * "/test-workflow/foo-state/delete" the 'delete-state:foo-state' operation
     * will be checked:
     * @code
     * path: '/{workflow}/{workflow_state}/delete'
     * requirements:
     *   _workflow_access: 'delete-state'
     * @endcode
     *
     * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
     *   The parametrized route
     * @param \Drupal\Core\Session\AccountInterface $account
     *   The currently logged in account.
     *
     * @return \Drupal\Core\Access\AccessResultInterface
     *   An access result.
     *
     * @throws \Exception
     *   Throws an exception when a route is defined with an invalid operation.
     */
    public function access(RouteMatchInterface $route_match, AccountInterface $account) {
        $workflow_operation = $this->getOperation($route_match);
        if (!preg_match('/^(?<operation>add|update|delete)-(?<type>state|transition)$/', $workflow_operation, $matches)) {
            throw new \Exception("Invalid _workflow_access operation '{$workflow_operation}' specified for route '{$route_match->getRouteName()}'.");
        }
        $parameters = $route_match->getParameters();
        $workflow = $parameters->get('workflow');
        if ($workflow && $matches['operation'] === 'add') {
            return $workflow->access($workflow_operation, $account, TRUE);
        }
        if ($workflow && ($type = $parameters->get(sprintf('workflow_%s', $matches['type'])))) {
            return $workflow->access(sprintf('%s:%s', $workflow_operation, $type), $account, TRUE);
        }
        return AccessResult::neutral();
    }
    
    /**
     * Get the operation that will be used for the access check.
     *
     * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
     *   The parametrized route
     *
     * @return string
     *   The access operation.
     */
    protected function getOperation(RouteMatchInterface $route_match) {
        return $route_match->getRouteObject()
            ->getRequirement('_workflow_access');
    }

}