#include <DHT.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <RTClib.h>

// Pin Definitions
#define DHTPIN 5        // Pin connected to DATA pin of DHT22
#define DHTTYPE DHT22   // DHT 22 (AM2302)
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define OLED_RESET -1
#define BUTTON_ENTER 2  // Button 1 (Enter) pin
#define BUTTON_EXIT 3   // Button 2 (Exit) pin
#define BUTTON_RESET 4  // Button 3 (Reset) pin
#define TRIG_PIN 7      // Ultrasonic Trig pin
#define ECHO_PIN 8      // Ultrasonic Echo pin
#define BUZZER_PIN 9    // Buzzer pin
#define DISTANCE_THRESHOLD 25 // Distance in cm for buzzer activation

// Create instances of the DHT sensor, OLED display, and RTC
DHT dht(DHTPIN, DHTTYPE);
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
RTC_DS3231 rtc;

// Variables for tracking attendance and sensor data
int enterCount = 0;
int exitCount = 0;
int studentsInRoom = 0;

void setup() {
  Serial.begin(9600);

  pinMode(BUTTON_ENTER, INPUT_PULLUP);
  pinMode(BUTTON_EXIT, INPUT_PULLUP);
  pinMode(BUTTON_RESET, INPUT_PULLUP);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  dht.begin();

  // Initialize the OLED display
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    while (1); // Infinite loop
  }

  if (!rtc.begin()) {
    Serial.println(F("Couldn't find RTC"));
    while (1);
  }

  if (rtc.lostPower()) {
    Serial.println(F("RTC lost power, setting the time!"));
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println(F("Initializing..."));
  display.display();
  delay(2000);
}

void loop() {
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  if (isnan(humidity) || isnan(temperature)) {
    display.clearDisplay();
    display.setCursor(0, 0);
    display.println(F("DHT Sensor Error!"));
    display.display();
    return;
  }

  // Handle button presses
  if (digitalRead(BUTTON_ENTER) == LOW) {
    studentsInRoom++;
    enterCount++;
    delay(200);
  }
  if (digitalRead(BUTTON_EXIT) == LOW) {
    if (studentsInRoom > 0) {
      studentsInRoom--;
      exitCount++;
    }
    delay(200);
  }
  if (digitalRead(BUTTON_RESET) == LOW) {
    enterCount = 0;
    exitCount = 0;
    studentsInRoom = 0;
    delay(200);
  }

  // Trigger the ultrasonic sensor to measure distance
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  long duration = pulseIn(ECHO_PIN, HIGH);
  int distance = duration * 0.0344 / 2;

  // Activate buzzer if an object is detected within the threshold distance
  if (distance < DISTANCE_THRESHOLD) {
    digitalWrite(BUZZER_PIN, HIGH);
  } else {
    digitalWrite(BUZZER_PIN, LOW);
  }

  // Clear the display and print new data
  display.clearDisplay();
  display.setCursor(0, 0);

  DateTime now = rtc.now();
  display.print(F("Time: "));
  display.print(now.hour());
  display.print(':');
  display.print(now.minute());
  display.print(':');
  display.print(now.second());
  display.println();

  display.print(F("Temp: "));
  display.print(temperature, 1);
  display.println(F(" C"));
  display.print(F("Hum: "));
  display.print(humidity, 1);
  display.println(F(" %"));
  display.print(F("In Room: "));
  display.println(studentsInRoom);
  display.print(F("Entered: "));
  display.println(enterCount);
  display.print(F("Exited: "));
  display.println(exitCount);

  display.display();
  delay(2000);
}