opnform-host-nginx/client/middleware/custom-domain.global.js

import { customDomainUsed, getDomain, getHost } from "~/lib/utils.js"

/**
 * Added by Caddy when proxying to the app
 * @type {string}
 */
const customDomainHeaderName = "user-custom-domain"

/**
 * List of routes that can be used with a custom domain
 * @type {string[]}
 */
const customDomainAllowedRoutes = ["forms-slug"]

function redirectToMainDomain(details = {}) {
  console.warn("Redirecting to main domain", { reason: "unknown", ...details })
  return navigateTo(
    useRuntimeConfig().public.appUrl +
      "?utm_source=failed_custom_domain_redirect",
    { redirectCode: 301, external: true },
  )
}

export default defineNuxtRouteMiddleware((to) => {
  if (!customDomainUsed()) return

  const config = useRuntimeConfig()

  const customDomainHeaderValue = useRequestHeaders()[customDomainHeaderName]
  if (
    import.meta.server &&
    (!customDomainHeaderValue ||
      customDomainHeaderValue !== getDomain(getHost()))
  ) {
    return redirectToMainDomain({
      reason: "header_mismatch",
      customDomainHeaderValue: customDomainHeaderValue,
      host: getDomain(getHost()),
    })
  }

  if (!config.public.customDomainsEnabled) {
    // If custom domain not allowed, redirect
    return redirectToMainDomain({
      reason: "custom_domains_disabled",
    })
  }

  if (!customDomainAllowedRoutes.includes(to.name)) {
    // Custom domain only allowed for form url
    return redirectToMainDomain({
      reason: "route_not_allowed",
    })
  }
})