// Create an MQTT Connection
// TCP Connection
// import the WiFi and PubSubClient libraries
//The WiFi library allows ESP32 to establish connections with Wi-Fi networks
//The PubSubClient library enables ESP32 to connect to an MQTT broker for publishing messages and subscribing to topics.

/* we were using Mqttx website whose url is
 * https://mqttx.app/web  */

#include <WiFi.h>
#include "PubSubClient.h"
// WiFi
char ssid[]="Wokwi-GUEST";
char pass[]="";
// MQTT Broker
const char *mqtt_broker = "broker.emqx.io";//Public Broker
const char *mqtt_username = "emqx";
const char *mqtt_password = "public";
const int mqtt_port = 1883; /* this is the port if this number ever changed
                             * it would seem that we used websocket */
// App Protcol ---> Port 
const char *topic_publish = "emqx/esp32/p";//Topic ESP32 Pusblish
const char *topic_subsrcibe = "emqx/esp32/s";//Topic ESp32 Subs
const char *topic_subsrcibe2 = "emqx/esp32/s2";//Topic ESp32 Subs

WiFiClient espClient;//WIFI Opject
PubSubClient client(espClient);
 
void callback(char *topic, byte *message, unsigned int length);/*used when subscribing*/

#define LED 2
bool ledState=false;

void setup(){
   // Setting LED pin as output
    pinMode(LED, OUTPUT);
    digitalWrite(LED, LOW);  // Turn off the LED initially
    //Open a serial connection to display program results and establish a connection to the Wi-Fi network.
    // Set software serial baud to 115200;
    Serial.begin(115200);
    // Connecting to a Wi-Fi network
    WiFi.begin(ssid, pass);
    while (WiFi.status() != WL_CONNECTED) {
        delay(500);
        Serial.println("Connecting to WiFi..");
    }
        Serial.println("Connected to the Wi-Fi network");
 /********************************************************************************/

    // Utilize PubSubClient to establish a connection with the MQTT broker.
    //connecting to a mqtt broker
    Serial.println("Before Connect MQTT");

    //Broker Configuration 
    client.setServer(mqtt_broker, mqtt_port);
   
   while (!client.connected()) { /* it will not enter the if condition unless
                                  * the client is not connected to the broker
                                  * (ESP32 is not connected to the broker) */

        String client_id = "esp32-client-";
        client_id += String(WiFi.macAddress()); /* any device which is connected
                                                 * to the broker must have a unique id */
        //ESP32-ID -----> esp32-client-macaddress
        //variable.c_str()--->char [] , String
        Serial.printf("The client %s connects to the public MQTT broker\n", client_id.c_str());
        if (client.connect(client_id.c_str(), mqtt_username, mqtt_password)) {
            Serial.println("Public MQTT broker connected");
        } else {
            Serial.print("failed with state ");
            Serial.print(client.state());
            delay(2000);
        }
    }
    Serial.println("After Connect MQTT");
    client.publish(topic_publish, "Hi, I'm ESP32 ^^");
    client.subscribe(topic_subsrcibe);
    client.subscribe(topic_subsrcibe2);
    client.setCallback(callback); /*used when subscribing*/
}

void loop() {
    client.loop();
}



void callback(char* topic, byte* message, unsigned int length) {
  printPayload(topic, message, length);  /*used when subscribing*/
}

void printPayload(char* topic, byte* message, unsigned int length) {
  // Printing Received Message
  Serial.print("Message received on topic: ");
  Serial.println(topic);

  String messageTemp;
  for(int i=0; i<length; i+=1) {
    messageTemp += (char)message[i];  /* convert byte to string */
  }

  if(String(topic)/*this is typecasting in c++*/== "emqx/esp32/s")
  {
      Serial.println("OK");
      if(messageTemp=="ON")
      {
        //Serial.println("Led ON");
        digitalWrite(2,HIGH);
      }  
      else{
        digitalWrite(2,LOW);
      }
  }
  else if(String(topic) == "emqx/esp32/s2")
  {
    Serial.print("OK2");  
  }
  else
  {
    Serial.print("Any Thing");  
  }
  Serial.println(messageTemp); /* here we print the sent message from the mqttx for
                                * example (if the mqttx was the publisher and esp32 is the subscriber) */
}