// https://alitan37.github.io/Esp32-mqtt-project/

#include <WiFi.h>
#include <PubSubClient.h>

const char* ssid = "Wokwi-GUEST";
const char* password = "";
const char* mqttServer = "broker.emqx.io";
const int port = 1883;
char clientId[50];

WiFiClient espClient;
PubSubClient client(espClient);

const int LED = 4;      // Main LED pin (not used)
const int pinGreen = 5; // pin for Green LED 

void setup() {
  Serial.begin(115200);
  delay(10);

  // Generate unique client ID
  snprintf(clientId, sizeof(clientId), "ESP32-%ld", random(1000000));

  // Connect WiFi
  Serial.print("Connecting to ");
  Serial.println(ssid);
  wifiConnect();

  Serial.println("WiFi connected");
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());

  client.setServer(mqttServer, port);
  client.setCallback(callback);

  // initializing pin
  pinMode(LED, OUTPUT);
  pinMode(pinGreen, OUTPUT);
  digitalWrite(pinGreen, LOW); // Make sure that the LED is off at the beginning.
}

void wifiConnect() {
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nWiFi Connected!");
}

void mqttReconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection with client ID: ");
    Serial.println(clientId);
    if (client.connect(clientId)) {
      Serial.println("connected");
      client.subscribe("role/led");
      Serial.println("Subscribed to role/led");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}

void loop() {
  if (!client.connected()) {
    mqttReconnect();
  }
  client.loop();
  delay(100);
}

void callback(char* topic, byte* message, unsigned int length) {
  String payload = "";
  for (unsigned int i = 0; i < length; i++) {
    payload += (char)message[i];
  }

  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("]: ");
  Serial.println(payload);

  if (payload == "ON") {
    digitalWrite(pinGreen, HIGH);
    Serial.println("LED ON");
  } else if (payload == "OFF") {
    digitalWrite(pinGreen, LOW);
    Serial.println("LED OFF");
  }
}