feat(WEB-132): add middlewares, support for seamless login and improve lang based routes

middlewares/authRequired.ts

@@ -0,0 +1,53 @@
+import { NextResponse } from "next/server"
+
+import { auth } from "@/auth"
+import { findLang } from "@/constants/languages"
+import { authRequired } from "@/constants/routes/authRequired"
+import { login } from "@/constants/routes/handleAuth"
+
+import type { NextMiddleware } from "next/server"
+
+import type { MiddlewareMatcher } from "@/types/middleware"
+
+/**
+ * AppRouteHandlerFnContext is the context that is passed to the handler as
+ * the second argument. This is only done for Route handlers (route.js) and
+ * not for middleware. Middleware`s second argument is `event` of type
+ * `NextFetchEvent`.
+ *
+ * Auth.js uses the same pattern for both Route handlers and Middleware,
+ * the auth()-wrapper:
+ *
+ *   auth((req) => { ... })
+ *
+ * But there is a difference between middleware and route handlers, route
+ * handlers get passed a context which middleware do not get (they get a
+ * NextFetchEvent instead). Using the same function for both works runtime
+ * because Auth.js handles this properly. But fails in typings as the second
+ * argument doesn't match for middleware.
+ *
+ * We want to avoid using ts-expect-error because that hides other errors
+ * not related to this typing error and ts-expect-error cannot be scoped either.
+ *
+ * So we type assert this export to NextMiddleware. The lesser of all evils.
+ *
+ * https://github.com/nextauthjs/next-auth/blob/3c035ec62f2f21d7cab65504ba83fb1a9a13be01/packages/next-auth/src/lib/index.ts#L265
+ * https://authjs.dev/reference/nextjs
+ */
+export const middleware = auth(async (request) => {
+  const { nextUrl } = request
+  const lang = findLang(nextUrl.pathname)!
+
+  const isLoggedIn = !!request.auth
+
+  if (isLoggedIn) {
+    return NextResponse.next()
+  }
+
+  const loginUrl = login[lang]
+  return NextResponse.redirect(new URL(loginUrl, request.nextUrl))
+}) as NextMiddleware // See comment above
+
+export const matcher: MiddlewareMatcher = (request) => {
+  return authRequired.includes(request.nextUrl.pathname)
+}