ok-ready-go/web/js/mqtt.js

let wasm_inited_resolve;
const wasm_inited = new Promise((resolve) => {wasm_inited_resolve = resolve;});

document.addEventListener("wasm-loaded", () => {
  wasm_inited_resolve(wasm_bindgen)
});

document.addEventListener("alpine:init", () => {
  Alpine.store("mqtt", {
    connected: false,
    _client: null,
    _topic: null,
    _c: null,

    _pendingPromises: {},

    sendTime(time) {
      if (!this.connected) return null;

      const id = uuidv4();
      const promise = new Promise((resolve, reject) => {this._pendingPromises[id] = [resolve, reject]});
      this._publish({
        id: id, // used to prevent replay attacks and to identify confirm messages
        kind: "Time", // can be "time" or "confirm"
        time: time, // only used for "time"
      });

      return promise;
    },

    async connect() {
      if (this.connected) return;
      
      const password = Alpine.store("localState").password;
      const that = this;
      const brokerDomain = "broker.emqx.io";
      const url = `wss://${brokerDomain}:8084/mqtt`;

      if (!password) return false;

      const {Crypto} = await wasm_inited;

      Alpine.store("localState")._state = 5;

      // derive key from password
      this._c = new Crypto(password, brokerDomain);

      console.log("Test", this._encrypt("test"));

      this._topic = Crypto.sha256(
        this._encrypt(`org.speedclimbing.ok-ready-go.${password}`)
      ).toString();

      console.log("Connecting to MQTT broker...");
      console.log("topic:", this._topic);

      const options = {
        // Clean session
        clean: true,
        connectTimeout: 4000,
      };

      this._client = mqtt.connect(url, options);

      this._client.on("connect", () => {
        Alpine.store("localState")._state = 0;

        that._client.subscribe(that._topic);
        this.connected = true;
      });

      this._client.on("message", (topic, message) => {
        // message is Buffer
        message = that._decrypt(message.toString());
        const data = JSON.parse(message);

        if (topic !== that._topic || data.kind !== "Confirm" || Object.keys(this._pendingPromises).indexOf(data.id) === -1) return;

        console.log("<<< ", data);
        this._pendingPromises[data.id][0]();
      });
    },

    disconnect() {
      if(!this.connected) return;

      this._client.end(true);

      this._client = null;
      this.connected = false;
      this._topic = null;

      for (const promiseId in this._pendingPromises) {
        this._pendingPromises[promiseId][1]();
      }

      this._pendingPromises = {};
    },

    _publish(data) {
      const encryptedData = this._encrypt(JSON.stringify(data));
      console.log(">>> ", data);
      this._client.publish(this._topic, encryptedData, {
        qos: 1,
        retain: false,
      });
    },

    _encrypt(data) {
      return this._c.encrypt(data);
    },

    _decrypt(data) {
      return this._c.decrypt(data);
    },
  });
});