#include <WiFi.h>
#include <WiFiClient.h>
#include <PubSubClient.h>
 
char PIN_TRIG = 33;
char PIN_ECHO = 35;
 
char led_red = 23;
char led_green = 18;
 
// Variables for the duration of the ping and the distance result
long duration;
float distance;
 
const char* ssid = "Wokwi-GUEST";
const char* password = "";
const char* hostname = "broker.hivemq.com";
 
WiFiClient espClient;
PubSubClient client(espClient);
 
const char* espClientName = "esp32Client_2593514k";
int PORTNUM = 1883;
 
void setup_wifi()
{
  WiFi.begin(ssid, password);
  while(WiFi.status() != WL_CONNECTED )
  {
    delay(1000);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("Given IP by the router to ESP32 is ");
  Serial.println(WiFi.localIP());
}
 
void connectMQTT()
{
  while(!client.connected() )
  {
    Serial.println("Connecting to MQTT ...");
    if (client.connect(espClientName) ) //, mqttUser, mqttPassword) )
    {
      Serial.println("Connected");
      MQTTSubscribe();
    }
    else
    {
      Serial.print("Failed with state ");
      Serial.print(client.state() );
      delay(1500);
    }
  }
}
 
void MQTTSubscribe()
{
  client.subscribe("DEIOT/6642092K");
}
 
void setup_MQTT()
{
  client.setServer(hostname, PORTNUM);
  //client.setCallback(callback);
}
 
void setup()
{
 
  Serial.begin(115200);
  pinMode(PIN_TRIG, OUTPUT);
  pinMode(PIN_ECHO, INPUT);
  pinMode(led_green, OUTPUT);
  pinMode(led_red, OUTPUT);
 
  setup_wifi();
  setup_MQTT();
}
 
 
void loop()
{
  if ( !client.connected() )
  {
    connectMQTT();
  }
  client.loop();
 
  digitalWrite(PIN_TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(PIN_TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(PIN_TRIG, LOW);
 
 
    duration = pulseIn(PIN_ECHO, HIGH);
    distance = (duration*.0343)/2;
    // Output the distance to the serial monitor
    Serial.print("Distance: ");
    Serial.print(distance);
    Serial.println(" cm");
 
  if (distance >= 300)
  {
    // On green LED
    digitalWrite(led_green, HIGH);
    // Off red LED
    digitalWrite(led_red, LOW);
    client.publish("IOT/CARPARK3", "Available");
  }
  else
  {
    // Off green LED
    digitalWrite(led_green, LOW);
    // On red LED
    digitalWrite(led_red, HIGH);
    client.publish("IOT/CARPARK3", "Occupied");
  }
 
  // Delay before next reading
  delay(1000);
}