/*When we publish a command in the MQTT Lens application,
 based on the command LED will turn ON and OFF in the Wokwi platform.*/


#include "WiFi.h"
#include "PubSubClient.h"   //library for MQTT connection

int led_pin = 5;
char clientId[50];   //define client-id with size=50 to store random-id in it

WiFiClient espClient;        // for establishing a connection for the network
PubSubClient client(espClient);  //client() used for requesting to publish or subscribe messages by the client.

void setup() 
{
  Serial.begin(115200);  //starts communication
  pinMode(led_pin, OUTPUT);

  WiFi.mode(WIFI_STA);   //check WiFi station where ESP32 will connect.

  WiFi.begin("Wokwi-GUEST", ""); //used to initialize the SSID and password.

  client.setServer("broker.emqx.io", 1883);  //set server hostname and port
  client.setCallback(callback); //function written below
}


void loop() 
{
  delay(10000);  //10 sec
  if (!client.connected()) //if not connected
  {
    mqttReconnect();
  }
  client.loop();
}


void mqttReconnect() 
{
  while (!client.connected()) //repeat till its not connected to MQTT
  {
    Serial.print("Attempting MQTT connection...");
    if (client.connect(clientId)) 
    {
      Serial.println("Connected");
      client.subscribe("topicName");//means every message coming from MQTT should be reflected here
    } 
    else 
    {
      Serial.print("Connection failed try again in 5 seconds");
      delay(5000);  //5 sec
    }
  }
}

void callback(char* topic, byte* message, unsigned int length) 
{
  // published message is coming from the MQTTLens and it is stored in stMessage variable
  String stMessage;   //variable
  for (int i = 0; i < length; i++) 
  {
    stMessage += (char)message[i];  //take complete input character
  }
  if(stMessage == "off")
  {
    digitalWrite(led_pin, LOW);
    Serial.print("LIGHT OFF!!");
  }
  else if (stMessage == "on")
  {
    digitalWrite(led_pin, HIGH);
    Serial.print("LIGHT ON!!");
  }
  else
  {
    Serial.print("INVALID COMMAND!!");
  }
}

//OUTPUT- when you write on or off on MQTTX then light should switch on or off.