fix locale middleware

Author: conico974

packages/open-next/src/core/routing/i18n/index.ts

@@ -1,5 +1,5 @@
 import { NextConfig } from "config/index.js";
-import type { i18nConfig } from "types/next-types";
+import type { DomainLocale, i18nConfig } from "types/next-types";
 import type { InternalEvent } from "types/open-next";
 
 import { debug } from "../../../adapters/logger.js";
@@ -20,6 +20,31 @@ function getLocaleFromCookie(cookies: Record<string, string>) {
     : undefined;
 }
 
+// Inspired by https://github.com/vercel/next.js/blob/canary/packages/next/src/shared/lib/i18n/detect-domain-locale.ts
+export function detectDomainLocale(
+  hostname: string,
+  i18n: i18nConfig,
+  detectedLocale?: string,
+): DomainLocale | undefined {
+  if (i18n.localeDetection === false) {
+    return;
+  }
+  if (!i18n.domains) {
+    return;
+  }
+  for (const item of i18n.domains) {
+    // We remove the port if present
+    const domainHostname = item.domain.split(":", 1)[0].toLowerCase();
+    if (
+      hostname === domainHostname ||
+      detectedLocale === item.defaultLocale.toLowerCase() ||
+      item.locales?.some((locale) => detectedLocale === locale.toLowerCase())
+    ) {
+      return item;
+    }
+  }
+}
+
 export function detectLocale(
   internalEvent: InternalEvent,
   i18n: i18nConfig,
@@ -39,9 +64,14 @@ export function detectLocale(
     defaultLocale: i18n.defaultLocale,
   });
 
-  return cookiesLocale ?? preferredLocale ?? i18n.defaultLocale;
+  const domainLocale = detectDomainLocale(internalEvent.headers.host, i18n);
 
-  // TODO: handle domain based locale detection
+  return (
+    domainLocale?.defaultLocale ??
+    cookiesLocale ??
+    preferredLocale ??
+    i18n.defaultLocale
+  );
 }
 
 export function localizePath(internalEvent: InternalEvent): string {
@@ -52,6 +82,17 @@ export function localizePath(internalEvent: InternalEvent): string {
   if (isLocalizedPath(internalEvent.rawPath)) {
     return internalEvent.rawPath;
   }
+  const preferredLocale = acceptLanguage(
+    internalEvent.headers["accept-language"],
+    i18n?.locales,
+  );
+
   const detectedLocale = detectLocale(internalEvent, i18n);
+
+  // not entirely sure if we should do that or not here
+  if (preferredLocale && preferredLocale !== detectedLocale) {
+    return `/${preferredLocale}${internalEvent.rawPath}`;
+  }
+
   return `/${detectedLocale}${internalEvent.rawPath}`;
 }

packages/open-next/src/core/routing/matcher.ts

@@ -316,6 +316,7 @@ export function handleRedirects(
   redirects: RedirectDefinition[],
 ): InternalResult | undefined {
   const trailingSlashRedirect = handleTrailingSlashRedirect(event);
+  // TODO: handle locale redirects directly from here, at the moment it's next that will handle it
   if (trailingSlashRedirect) return trailingSlashRedirect;
   const { internalEvent, __rewrite } = handleRewrites(
     event,

packages/open-next/src/types/next-types.ts

@@ -61,9 +61,17 @@ export type Header = {
   missing?: RouteHas[];
 };
 
+export interface DomainLocale {
+  defaultLocale: string;
+  domain: string;
+  http?: true;
+  locales: readonly string[];
+}
+
 export interface i18nConfig {
   locales: string[];
   defaultLocale: string;
+  domains?: Array<DomainLocale>;
   localeDetection?: false;
 }
 export interface NextConfig {