code refactoring + add locale field to user table

lib/client/getServerSideProps.ts

@@ -0,0 +1,64 @@
+import { GetServerSideProps } from "next";
+import { serverSideTranslations } from "next-i18next/serverSideTranslations";
+import { i18n } from "next-i18next.config";
+import { getToken } from "next-auth/jwt";
+import { prisma } from "../api/db";
+
+// Keep this in a separate file, it's for logged out users
+// For logged in users, we'll use their preferred language from the database (default: en)
+const getServerSideProps: GetServerSideProps = async (ctx) => {
+  const acceptLanguageHeader = ctx.req.headers["accept-language"];
+  const availableLanguages = i18n.locales;
+
+  // Check if it's a logged in user
+  // If it is, get the user's preferred language from the database
+  const token = await getToken({ req: ctx.req });
+
+  if (token) {
+    const user = await prisma.user.findUnique({
+      where: {
+        id: token.id,
+      },
+    });
+
+    if (user) {
+      return {
+        props: {
+          ...(await serverSideTranslations(user.locale, ["common"])),
+        },
+      };
+    }
+  }
+
+  // Parse the accept-language header to get an array of languages
+  const acceptedLanguages = acceptLanguageHeader
+    ?.split(",")
+    .map((lang) => lang.split(";")[0]);
+
+  // Find the best match between the accepted languages and available languages
+  let bestMatch = acceptedLanguages?.find((lang) =>
+    availableLanguages.includes(lang)
+  );
+
+  // If no direct match, find the best partial match
+  if (!bestMatch) {
+    acceptedLanguages?.some((acceptedLang) => {
+      const partialMatch = availableLanguages.find((lang) =>
+        lang.startsWith(acceptedLang)
+      );
+      if (partialMatch) {
+        bestMatch = partialMatch;
+        return true;
+      }
+      return false;
+    });
+  }
+
+  return {
+    props: {
+      ...(await serverSideTranslations(bestMatch ?? "en", ["common"])),
+    },
+  };
+};
+
+export default getServerSideProps;