budibase/packages/client/src/render/screenRouter.js

import regexparam from "regexparam"
import { routerStore } from "../state/store"
import { initRouteStore } from "../state/store"

// TODO: refactor
export const screenRouter = ({ screens, onScreenSelected, appRootPath }) => {
  const makeRootedPath = url => {
    if (appRootPath) {
      if (url) return `${appRootPath}${url.startsWith("/") ? "" : "/"}${url}`
      return appRootPath
    }
    return url
  }

  const routes = screens.map(s => makeRootedPath(s.route))
  let fallback = routes.findIndex(([p]) => p === "*")
  if (fallback < 0) fallback = 0

  let current

  function route(url) {
    const _url = makeRootedPath(url.state || url)
    current = routes.findIndex(
      p => p !== "*" && new RegExp("^" + p + "$").test(_url)
    )

    const params = {}

    if (current === -1) {
      routes.forEach((p, i) => {
        const pm = regexparam(p)
        const matches = pm.pattern.exec(_url)

        if (!matches) return

        let j = 0
        while (j < pm.keys.length) {
          params[pm.keys[j]] = matches[++j] || null
        }

        current = i
      })
    }

    routerStore.update(state => {
      state["##routeParams"] = params
      return state
    })

    const screenIndex = current !== -1 ? current : fallback

    onScreenSelected(screens[screenIndex], _url)

    try {
      !url.state && history.pushState(_url, null, _url)
    } catch (_) {
      // ignoring an exception here as the builder runs an iframe, which does not like this
    }
  }

  addEventListener("popstate", route)
  addEventListener("pushstate", route)

  return route
}