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

#define TRIG_PIN 5
#define ECHO_PIN 18
#define MQTT_SERVER "broker.hivemq.com"
#define MQTT_PORT 1883
#define TOPIC "distance"

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

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  Serial.begin(115200);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting to WiFi...");
  }
  Serial.println("Connected to WiFi");

  client.setServer(MQTT_SERVER, MQTT_PORT);
}

void reconnect() {
  while (!client.connected()) {
    if (client.connect("ESP32Publisher")) {
      client.subscribe(TOPIC);
    } else {
      delay(5000);
    }
  }
}

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

  long duration, distance;
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  duration = pulseIn(ECHO_PIN, HIGH);
  distance = duration * 0.034 / 2;

  char distStr[8];
  dtostrf(distance, 6, 2, distStr);
  client.publish(TOPIC, distStr);

  delay(1000);
}