validate environment variables at build time

lib/config/constants.ts

@@ -8,10 +8,6 @@ export const AVATAR_PATH = "app/avatar.jpg";
 // maximum width of content wrapper (e.g. for images) in pixels
 export const MAX_WIDTH = 865;
 
-// same logic as metadataBase: https://nextjs.org/docs/app/api-reference/functions/generate-metadata#default-value
-export const BASE_URL =
-  process.env.NEXT_PUBLIC_VERCEL_ENV === "production" && process.env.NEXT_PUBLIC_VERCEL_PROJECT_PRODUCTION_URL
-    ? `https://${process.env.NEXT_PUBLIC_VERCEL_PROJECT_PRODUCTION_URL}`
-    : process.env.NEXT_PUBLIC_VERCEL_ENV === "preview" && process.env.NEXT_PUBLIC_VERCEL_URL
-      ? `https://${process.env.NEXT_PUBLIC_VERCEL_URL}`
-      : `http://localhost:${process.env.PORT || 3000}`;
+// defined in next.config.ts
+export const BASE_URL = process.env.NEXT_PUBLIC_BASE_URL!;
+export const RELEASE_TIMESTAMP = process.env.NEXT_PUBLIC_RELEASE_TIMESTAMP!;

lib/config/seo.ts

@@ -2,7 +2,7 @@ import * as config from ".";
 import { BASE_URL } from "./constants";
 import type { Metadata } from "next";
 
-const metadata: Metadata = {
+const defaultMetadata: Metadata = {
   metadataBase: new URL(BASE_URL),
   title: {
     template: `%s – ${config.siteName}`,
@@ -44,4 +44,4 @@ const metadata: Metadata = {
   },
 };
 
-export default metadata;
+export default defaultMetadata;

lib/env.ts

@@ -0,0 +1,34 @@
+import { createEnv } from "@t3-oss/env-nextjs";
+import { vercel } from "@t3-oss/env-nextjs/presets-valibot";
+import * as v from "valibot";
+
+export const env = createEnv({
+  extends: [vercel()],
+  server: {
+    GITHUB_TOKEN: v.optional(v.pipe(v.string(), v.startsWith("ghp_"))),
+    KV_REST_API_TOKEN: v.string(),
+    KV_REST_API_URL: v.pipe(v.string(), v.url(), v.startsWith("https://"), v.endsWith(".upstash.io")),
+    RESEND_API_KEY: v.pipe(v.string(), v.startsWith("re_")),
+    RESEND_FROM_EMAIL: v.optional(v.pipe(v.string(), v.email())),
+    RESEND_TO_EMAIL: v.pipe(v.string(), v.email()),
+    TURNSTILE_SECRET_KEY: v.optional(v.string()),
+  },
+  client: {
+    NEXT_PUBLIC_GISCUS_CATEGORY_ID: v.optional(v.string()),
+    NEXT_PUBLIC_GISCUS_REPO_ID: v.optional(v.string()),
+    NEXT_PUBLIC_ONION_DOMAIN: v.optional(v.pipe(v.string(), v.endsWith(".onion"))),
+    NEXT_PUBLIC_TURNSTILE_SITE_KEY: v.optional(v.string()),
+    NEXT_PUBLIC_UMAMI_URL: v.optional(v.pipe(v.string(), v.url())),
+    NEXT_PUBLIC_UMAMI_WEBSITE_ID: v.optional(v.string()),
+  },
+  experimental__runtimeEnv: {
+    NEXT_PUBLIC_GISCUS_CATEGORY_ID: process.env.NEXT_PUBLIC_GISCUS_CATEGORY_ID,
+    NEXT_PUBLIC_GISCUS_REPO_ID: process.env.NEXT_PUBLIC_GISCUS_REPO_ID,
+    NEXT_PUBLIC_ONION_DOMAIN: process.env.NEXT_PUBLIC_ONION_DOMAIN,
+    NEXT_PUBLIC_TURNSTILE_SITE_KEY: process.env.NEXT_PUBLIC_TURNSTILE_SITE_KEY,
+    NEXT_PUBLIC_UMAMI_URL: process.env.NEXT_PUBLIC_UMAMI_URL,
+    NEXT_PUBLIC_UMAMI_WEBSITE_ID: process.env.NEXT_PUBLIC_UMAMI_WEBSITE_ID,
+  },
+  emptyStringAsUndefined: true,
+  skipValidation: !!process.env.SKIP_ENV_VALIDATION,
+});

lib/helpers/build-feed.ts

@@ -1,7 +1,7 @@
 import { Feed } from "feed";
 import { getFrontMatter, getContent } from "./posts";
 import * as config from "../config";
-import { BASE_URL } from "../config/constants";
+import { BASE_URL, RELEASE_TIMESTAMP } from "../config/constants";
 import type { Item as FeedItem } from "feed";
 
 import ogImage from "../../app/opengraph-image.jpg";
@@ -12,12 +12,12 @@ import ogImage from "../../app/opengraph-image.jpg";
  */
 export const buildFeed = async (): Promise<Feed> => {
   const feed = new Feed({
-    id: BASE_URL,
-    link: BASE_URL,
+    id: `${BASE_URL}`,
+    link: `${BASE_URL}`,
     title: config.siteName,
     description: config.longDescription,
     copyright: config.licenseUrl,
-    updated: new Date(process.env.RELEASE_DATE || Date.now()),
+    updated: new Date(RELEASE_TIMESTAMP),
     image: `${BASE_URL}${ogImage.src}`,
     feedLinks: {
       rss: `${BASE_URL}/feed.xml`,
@@ -41,7 +41,7 @@ export const buildFeed = async (): Promise<Feed> => {
       author: [
         {
           name: config.authorName,
-          link: BASE_URL,
+          link: `${BASE_URL}`,
         },
       ],
       date: new Date(post.date),

lib/helpers/metadata.ts

@@ -1,4 +1,4 @@
-import defaultMetadata from "../config/metadata";
+import defaultMetadata from "../config/seo";
 import type { Metadata } from "next";
 
 /**