#include <Arduino.h>
// create an MQTT connection
// TCP connection
// import the WiFi and pubsubClient libraries
// The WiFi library allows ESP32 to establish connections with WiFi networks
// The pubsubClient library enables ESP32 to connect to an MQTT broker for publishing messages
#include <WiFi.h>
#include <PubSubClient.h>
//WiFi
const char *ssid = "Wokwi-GUEST";
const char *password = "";
//MQTT Broker
const char *mqtt_broker = "broker.emqx.io"; // public broker
const char *topic_publish = "emqx/esp32/p"; // topic esp publish
const char *topic_subscribe = "emqx/esp32/s"; // topic esp subscribe
const char *mqtt_username = "emqx";
const char *mqtt_password = "public";
const int mqtt_port = 1883;

WiFiClient espClient; //WiFi Object
PubSubClient Client(espClient);
void callback(char* topic, byte* payload, unsigned int length);
void printPayload(char* topic, byte* message, unsigned int length);
#define LED 2 
bool ledState= false;
void setup() {
   // setting LED pin as output
   pinMode(LED, OUTPUT);
   digitalWrite(LED, LOW); // turn off the LED initially
   // set software serial to 115200
   Serial.begin(115200);
   //Connecting to WiFi network
   WiFi.begin(ssid,password);
   while (WiFi.status() != WL_CONNECTED)
   {
    delay(500);
    Serial.println("Connecting to WiFi..");
   }
   Serial.println("Connected to the WiFi network");
   // utilize pubsubClient to establish a connection with the MQTT broker
   //connecting to a MQTT broker
   Serial.println("Before connect to MQTT");
   //broker configuration
   Client.setServer(mqtt_broker,mqtt_port);
   while (!Client.connected())
   {
    String client_id = "esp32.client";
    client_id += String(WiFi.macAddress());
    // 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_subscribe);
   Client.setCallback(callback);
}

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

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

void printPayload(char* topic, byte* message, unsigned int length){
  //printing recieved message
  Serial.print("Message recieved on topic: ");
  Serial.print(topic);
  String messageTemp;
  for (int i = 0; i < length; i++)
  {
    messageTemp += (char)message[i];
  }
  if(String(topic)== "emqx/esp32/s"){
      Serial.println("OK");
       if(messageTemp == "ON"){
          digitalWrite(LED , HIGH);

      }
      digitalWrite(LED , HIGH);
  }
 
  Serial.println(messageTemp);
}