#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <WiFi.h>
#include <PubSubClient.h>

#define I2C_A_SDA 21 
#define I2C_A_SCL 22 
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
#define SCREEN_ADDRESS 0x3C
const char* ssid = "Wokwi-GUEST";
const char* password = "";

const char* mqtt_server = "YOUR_MQTT_BROKER_IP";
const char* mqttUser  = "YOUR_MQTT_USERNAME"; 
const char* mqttPassword = "YOUR_MQTT_PASSWORD"; 

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
WiFiClient espClient;
PubSubClient client(espClient);
const int ledPin = 4;

void setup() {
  Serial.begin(115200);
  pinMode(ledPin, OUTPUT);
  if (!display.begin(SSD1306_SWITCHCAPVCC, SCREEN_ADDRESS)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);
  }
  display.clearDisplay();
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println(F("ESP32 MQTT LED"));
  display.display();
}

void setup_wifi() {
  delay(10);
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("WiFi connected");
}

void callback(char* topic, byte* message, unsigned int length) {
  String messageTemp;
  for (int i = 0; i < length; i++) {
    messageTemp += (char)message[i];
  }
  if (String(topic) == "esp32/output") {
    if (messageTemp == "on") {
      digitalWrite(ledPin, HIGH);
      Serial.println("LED is ON");
      display.clearDisplay();
      display.setCursor(0, 0);
      display.println(F("ESP32 MQTT LED"));
      display.println(F("LED is ON"));
      display.display();
    } else if (messageTemp == "off") {
      digitalWrite(ledPin, LOW);
      Serial.println("LED is OFF");
      display.clearDisplay();
      display.setCursor(0, 0);
      display.println(F("ESP32 MQTT LED"));
      display.println(F("LED is OFF"));
      display.display();
    }
  }
}

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

void reconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    if (client.connect("ESP32Client", mqttUser , mqttPassword)) {
      Serial.println("connected");
      client.subscribe("esp32/output");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      delay(2000);
    }
  }
}