Using deno to subscribe or publish realtime message via Mercure Hub

publish.ts

import { load } from "https://deno.land/std@0.214.0/dotenv/mod.ts";
import jwtEncode from "https://esm.sh/jwt-encode@1.0.1";

const env = await load();

// create jwt token for publishing
const jwtSecret = env["JWT_SECRET_KEY"];
const jwtPayload = {
  mercure: {
    publish: ["/messages/{event}"],
  },
};
const token = jwtEncode(jwtPayload, jwtSecret, { alg: "HS256" });

const params = new URLSearchParams({
  "topic": "/messages/statistics",
  "id": `/message/statistics/${crypto.randomUUID()}`,
  "data": JSON.stringify({
    registered_today: 100,
  }),
});

const res = await fetch("http://localhost:8080/.well-known/mercure", {
  method: "POST",
  body: params,
  headers: {
    "Content-Type": "application/x-www-form-urlencoded",
    "Authorization": `Bearer ${token}`,
  },
});

console.log(res.status);
console.log(await res.text());

subscribe.ts

import { load } from "https://deno.land/std@0.214.0/dotenv/mod.ts";
import polyfill from "https://esm.sh/event-source-polyfill@1.0.31";
import jwtEncode from "https://esm.sh/jwt-encode@1.0.1";

const { EventSourcePolyfill } = polyfill;

const env = await load();

// sign JWT token for Mercure hub
// DONT DO THIS IN PRODUCTION!!
// You should generate this on server side, on user login
// since we are using Deno, it is safe to do this here
const jwtSecret = env["JWT_SECRET_KEY"];
const jwtPayload = {
  mercure: {
    subscribe: ["/messages/{event}"],
  },
};
const token = jwtEncode(jwtPayload, jwtSecret, { alg: "HS256" });

// get the connection URL ready
const url = new URL("http://localhost:8080/.well-known/mercure");
url.searchParams.append("topic", "/messages/{event}");

// connect to the Mercure hub
// note that EventSourcePolyfill has built-in reconnect support and allow passing headers (which native doesn't)
const source = new EventSourcePolyfill(url.toString(), {
  headers: {
    "Authorization": `Bearer ${token}`,
  },
});

// listen for messages
source.onmessage = (event) => {
  // our data is in the event.data property
  // if we sent JSON, we can parse it
  console.log("data", JSON.parse(event.data));

  // the id of this event, useful for resuming the connection
  // we can keep track of this to resume the connection
  console.log("lastEventId", event.lastEventId);
};

This implementation based on freddie (mercure hub implementation in PHP)

git clone git@github.com:bpolaszek/freddie.git
cd freddie
composer install

# update .env and add JWT_SECRET_KEY
vim .env