Shelly 4PM expose outputs in MQTT in a simple way

shelly4pm-mqtt-outputs.js

 let CONFIG = {
  topic_prefix: "",
  output_count: 4
};
let value;

//Read mqtt topic prefix
Shelly.call("MQTT.GetConfig", null, function (config) {
  CONFIG.topic_prefix = config.topic_prefix;
  startSubscribing();
});

function getStateTopic(component){
  return CONFIG.topic_prefix + "/output/"+component+"/state";
}

function getCommandTopic(component){
  return CONFIG.topic_prefix + "/output/"+component+"/command";
}

Shelly.addEventHandler(
    function (event) {    
        if(event.info.output !== undefined){
          value = event.info.output ? "on" : "off"
          print("output changed on "+event.component+" : "+value);
          if(MQTT.isConnected()){
            MQTT.publish(getStateTopic(event.component), value);
          }else{
            print("MQTT not connected, unable to publish")
          }
        }
    }, {}
);

function outputCommandCallback(topic, message, switchId){
  print("Command received on topic "+topic+": "+JSON.stringify(message));
  if(message==="on" || message==="off"){
    let params = {id: switchId, on: message === "on"};
    Shelly.call("Switch.Set", params);
  }else{
    print("Unknown command: "+message)
  }
}

function startSubscribing(){
  if(MQTT.isConnected()){
    for(let switchId=0; switchId<CONFIG.output_count; switchId++){
      let component = "switch:"+JSON.stringify(switchId);
      print("Subscribing on topic "+getCommandTopic(component));
      MQTT.subscribe(getCommandTopic(component), outputCommandCallback, switchId);
    }
  }else{
    print("MQTT not connected, unable to subscribe")
  }
}

print("script started");