Route HTTP status code middleware for router5

middlewares.js

import { startsWithSegment } from 'router5-helpers';
import { transitionPath } from 'router5';

// Reduces the activated routes, so the last status is used, defaulting to 200
// Reducingg instead of finding, assures that child routes determine the status codes, even when a parent has a different one.
export const statusCodeDecorator = routes => () => (toState, fromState) => {
  const status = getActivatedRoutes(routes, toState, fromState).reduce((s, route) => route.status || s, 200);
  return Promise.resolve({ ...toState, status });
};

function getActivatedRoutes(routes, toState, fromState) {
  const { toActivate } = transitionPath(toState, fromState);
  return toActivate.map(segment => getRoute(segment, routes));
}

// Recursively traverse routes, until route matching the segment is found.
// Returns route object.
// Throws error if none is found.
function getRoute(segment, routes) {
  for (let i = 0; i < routes.length; i += 1) {
    const route = routes[i];
    if (route.name === segment) {
      return route;
    }

    // Segment is child route of current route.
    if (startsWithSegment(segment, route.name) && route.children) {
      const splitSegment = segment.split('.');
      splitSegment.shift();
      if (splitSegment.length > 0) {
        return getRoute(splitSegment.join('.'), route.children);
      }
    }
  }
  throw new Error('route not found');
};

router.js

import createRouter from 'router5';
import listenersPlugin from 'router5/plugins/listeners';
import browserPlugin from 'router5/plugins/browser';

import { statusCodeDecorator } from './middlewares';

import routes from './routes';

export function configureRouter() {
  const router = createRouter(routes, {
    defaultRoute: 'main',
    trailingSlash: true,
    strictQueryParams: true,
  }).usePlugin(browserPlugin({ useHash: false }))
    .usePlugin(listenersPlugin());

  router.useMiddleware(statusCodeDecorator(routes));
  return router;
}

routes.js

export default [
  {
    path: '/',
    name: 'main',
  },
  {
    path: '/404',
    name: '404',
    status: 404,
  },
  {
    path: '/401',
    name: '401',
    status: 401,
  },
  {
    path: '/500',
    name: '500',
    status: 500,
  },
];