From b2fa32d1343459794e2f75e5b0b280147ff2096f Mon Sep 17 00:00:00 2001
From: Lim Chee Aun <cheeaun@gmail.com>
Date: Sat, 24 Aug 2024 16:36:52 +0800
Subject: [PATCH] Generate alternate link tags for all languages

---
 src/locales.js |  2 +-
 vite.config.js | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/locales.js b/src/locales.js
index 74bf4bd4..b19934c6 100644
--- a/src/locales.js
+++ b/src/locales.js
@@ -15,7 +15,7 @@ const locales = [
 export const LOCALES = locales;
 
 let devLocales = [];
-if (import.meta.env.DEV || import.meta.env.PHANPY_SHOW_DEV_LOCALES) {
+if (import.meta.env?.DEV || import.meta.env?.PHANPY_SHOW_DEV_LOCALES) {
   devLocales = catalogs
     .filter(({ completion }) => completion < PERCENTAGE_THRESHOLD)
     .map(({ code }) => code);
diff --git a/vite.config.js b/vite.config.js
index 7bf25f11..98d05043 100644
--- a/vite.config.js
+++ b/vite.config.js
@@ -12,9 +12,12 @@ import { VitePWA } from 'vite-plugin-pwa';
 import removeConsole from 'vite-plugin-remove-console';
 import { run } from 'vite-plugin-run';
 
+import { ALL_LOCALES } from './src/locales';
+
 const allowedEnvPrefixes = ['VITE_', 'PHANPY_'];
 const { NODE_ENV } = process.env;
 const {
+  PHANPY_WEBSITE: WEBSITE,
   PHANPY_CLIENT_NAME: CLIENT_NAME,
   PHANPY_APP_ERROR_LOGGING: ERROR_LOGGING,
 } = loadEnv('production', process.cwd(), allowedEnvPrefixes);
@@ -83,6 +86,20 @@ export default defineConfig({
     }),
     htmlPlugin({
       headScripts: ERROR_LOGGING ? [rollbarCode] : [],
+      links: [
+        ...ALL_LOCALES.map((lang) => ({
+          rel: 'alternate',
+          hreflang: lang,
+          // *Fully-qualified* URLs
+          href: `${WEBSITE}/?lang=${lang}`,
+        })),
+        // https://developers.google.com/search/docs/specialty/international/localized-versions#xdefault
+        {
+          rel: 'alternate',
+          hreflang: 'x-default',
+          href: `${WEBSITE}`,
+        },
+      ],
     }),
     generateFile([
       {