Using ParaglideJS with Hono

app.js

import { Hono } from "hono"
import { ParaglideHono } from "./paraglide-hono.js"
import * as runtime from "./paraglide/runtime.js"
import * as m from "./paraglide/messages.js"

// custom function that determines which language should be used based on the Context
function detecLanguage(c) {
  const pathname = new URL(c.req.url).pathname;
  const parts = pathname.split("/");
  return isAvailableLanguageTag(parts[1]) ? parts[1] : sourceLanguageTag;
}

const app = new Hono();
app.use(ParaglideHono(runtime, detecLanguage)) // register the middleware

app.get("/*", async (c) => {
  const text = m.a_translated_message() // this will return the message in the correct language
  return c.text(text);
});

paraglide-hono.js

import { AsyncLocalStorage } from "node:async_hooks";
import { createMiddleware } from "hono/factory";

/**
 * @template {string} T
 * @param {any} runtime
 * @param {(ctx: import("hono").Context) => import("./paraglide/runtime.js").AvailableLanguageTag} detectLanguage
 */
export function ParaglideHono(runtime, detectLanguage) {
  /** @type {AsyncLocalStorage<T>} */
  const localeStorage = new AsyncLocalStorage();

  const middleware = createMiddleware(async (c, next) => {
    return localeStorage.run(detectLanguage(c), next);
  });

  runtime.setLanguageTag(
    () => localeStorage.getStore() || runtime.sourceLanguageTag
  );

  return middleware;
}