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

#define LED_PIN 4    // your LED pin

// WiFi
const char* ssid = "Wokwi-GUEST";
const char* password = "";

// MQTT
const char* mqtt_server = "test.mosquitto.org";  // Public broker

WiFiClient espClient;
PubSubClient client(espClient);

// -------- Callback: when MQTT message arrives --------
void callback(char* topic, byte* message, unsigned int length) {
  Serial.print("Message arrived on topic: ");
  Serial.println(topic);

  String msg;
  for (int i = 0; i < length; i++) {
    msg += (char)message[i];
  }
  Serial.print("Message: ");
  Serial.println(msg);

  // ------- Control LED -------
  if (String(topic) == "usecase/device/control") {
    if (msg == "ON") {
      digitalWrite(LED_PIN, HIGH);
      Serial.println("LED TURNED ON");
      client.publish("usecase/device/status", "LED ON");
    }
    else if (msg == "OFF") {
      digitalWrite(LED_PIN, LOW);
      Serial.println("LED TURNED OFF");
      client.publish("usecase/device/status", "LED OFF");
    }
  }
}

// -------- Reconnect MQTT --------
void reconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    if (client.connect("ESP32Client12345")) {
      Serial.println("connected!");
      client.subscribe("usecase/device/control");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" retrying...");
      delay(2000);
    }
  }
}

void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);

  // WiFi
  Serial.println("Connecting to WiFi ....");
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nWiFi connected!");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

  // MQTT
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

void loop() {
  if (!client.connected()) {
    reconnect();
  }
  client.loop();
}