Add i18n support

.example.env

@@ -38,6 +38,10 @@ LINK_LENGTH=6
 # Default value omits o, O, 0, i, I, l, 1, and j to avoid confusion when reading the URL
 LINK_CUSTOM_ALPHABET=abcdefghkmnpqrstuvwxyzABCDEFGHKLMNPQRSTUVWXYZ23456789
 
+# Optional - Allowed locales and translations Supported locales: 
+# en (English), zh_CN (Simplified Chinese), zh_TW (Traditional Chinese)
+LOCALES=en
+
 # Optional - Tells the app that it's running behind a proxy server
 # and that it should get the IP address from that proxy server
 # if you're not using a proxy server then set this to false, otherwise users can override their IP address

.gitignore

@@ -14,3 +14,6 @@ docs/api/static
 **/.DS_Store
 db/*
 !db/.gitkeep
+.history/**
+**.bak
+tags

package.json

@@ -38,6 +38,7 @@
     "geoip-lite": "1.4.10",
     "hbs": "4.2.0",
     "helmet": "7.1.0",
+    "i18n": "0.15.1",
     "ioredis": "5.4.2",
     "isbot": "5.1.19",
     "jsonwebtoken": "9.0.2",

server/env.js

@@ -1,5 +1,5 @@
 require("dotenv").config();
-const { cleanEnv, num, str, bool } = require("envalid");
+const { cleanEnv, num, str, bool, makeValidator } = require("envalid");
 const { readFileSync } = require("node:fs");
 
 const supportedDBClients = [
@@ -26,12 +26,34 @@ if (process.argv.includes("--production")) {
   process.env.NODE_ENV = "production";
 }
 
+// custom locales validator
+const allowedLocales = ["en", "zh_CN","zh_TW"];
+const localesValidator = makeValidator(function (locales) {
+  if (typeof locales !== "string") return "en";
+  return locales
+    .split(",")
+    .map(l => l.trim().toLowerCase())
+    .map(function (locale) {
+      const index = allowedLocales.findIndex(l => l.toLowerCase() === locale);
+      if (index !== -1) {
+        return allowedLocales[index];
+      } else {
+        throw new Error(
+          `Locale is not supported: ${locale}.` +
+          `Available locales: ${allowedLocales.join(", ")}`
+        );
+      }
+    })
+    .join(",");
+});
+
 const spec = {
   PORT: num({ default: 3000 }),
   SITE_NAME: str({ example: "Kutt", default: "Kutt" }),
   DEFAULT_DOMAIN: str({ example: "kutt.it", default: "localhost:3000" }),
   LINK_LENGTH: num({ default: 6 }),
   LINK_CUSTOM_ALPHABET: str({ default: "abcdefghkmnpqrstuvwxyzABCDEFGHKLMNPQRSTUVWXYZ23456789" }),
+  LOCALES: localesValidator({ default: "en,zh_CN,zh_TW" }),
   TRUST_PROXY: bool({ default: true }),
   DB_CLIENT: str({ choices: supportedDBClients, default: "better-sqlite3" }),
   DB_FILENAME: str({ default: "db/data" }),

server/handlers/helpers.handler.js

@@ -1,6 +1,7 @@
 const { RedisStore: RateLimitRedisStore } = require("rate-limit-redis");
 const { rateLimit: expressRateLimit } = require("express-rate-limit");
 const { validationResult } = require("express-validator");
+const i18n = require("i18n");
 
 const { CustomError } = require("../utils");
 const query = require("../queries");
@@ -14,7 +15,7 @@ function error(error, req, res, _next) {
     console.error(error.message);
   }
 
-  const message = error instanceof CustomError ? error.message : "An error occurred.";
+  const message = error instanceof CustomError ? error.message : i18n.__("backbone.errorMsg");
   const statusCode = error.statusCode ?? 500;
 
   if (req.isHTML && req.viewTemplate) {
@@ -25,7 +26,7 @@ function error(error, req, res, _next) {
 
   if (req.isHTML) {
     res.render("error", {
-      message: "An error occurred. Please try again later."
+      message: i18n.__("backbone.errorAndTryAgainMsg"),
     });
     return;
   }