fail_safe_public.js

/**
 * Monitor an MQTT connection, and HTTP connectivity to Home Assistant
 * if either fail - trigger a fail-safe mode which turns the switch on.
 *
 */

// Config
let homeAssistantUrl = "https://x.x.x.x:8123";
// number of times the check is done before internet is considered as down.
let maxfails = 2;
// checks the internet connection every x minutes, recommended is 5 or more
let interval = 1;


let failcounter = 0;

function startMonitor() {
  print("Starting monitor.");
  Timer.set(15 * 1000, true, function() {
      print('Checking HA connectivity');
      Shelly.call("HTTP.GET", {
        url: homeAssistantUrl
      },
        function(res, error_code, error_msg, ud) {
          print('res:', res, error_code, error_msg, ud);
          print('mqttUp():', mqttUp());

          if (!mqttUp()) {
            print("mqtt fail: fan on");
            sendPushoverMessage('Shelly Fail Safe (mqtt)', 'Fan enabled - HA unreachable');
            switchOn();
          }

          if (error_code !== 0) {
            if (failcounter === maxfails) {
              sendPushoverMessage('Shelly Fail Safe (http)', 'Fan enabled - HA unreachable');
              print("failsafe: fan on");
              switchOn();
              failcounter = 0;
            } else {
              print("fail");
              failcounter++;
            }
          }
        }, null);
    }, null);
}


function sendPushoverMessage(title, message) {
  let token = 'xxx';
  let user = 'xxx';

  let postData = {
    url: "https://api.pushover.net/1/messages.json",
    body: { token: token, user: user, message: message, title: title }
  };

  Shelly.call(
      "http.post", postData,
      function (response, error_code, error_message, ud) {
          print(JSON.stringify(response));
      },
      null
  );
};

function mqttUp() {
  return MQTT.isConnected();
}

function switchOn() {
  Shelly.call("switch.set", { id: 0, on: true }, function(result, code, msg, ud) {
    print('switchOn', result, code, msg, ud);
  }, null);
}

startMonitor();