#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
const int switchPin = 7;    // Change this to the pin you're using for the switch
const int buzzerPin = 8;    // Change this to the pin you're using for the buzzer

const int initialHours = 6;
const int initialMinutes = 0;
const int initialSeconds = 0; // Start from 10 seconds for testing

unsigned long countdownEndTime = 0;
bool countdownStarted = false;
bool switchState = false;
bool timeLapseRunning = false;
unsigned long timeLapseStartTime = 0;

void setup() {
  lcd.begin(20, 4);
  pinMode(switchPin, INPUT_PULLUP);
  pinMode(buzzerPin, OUTPUT);
  lcd.print("Switch OFF to start");
}

void loop() {
  switchState = digitalRead(switchPin);

  if (switchState && !countdownStarted) {
    lcd.clear();
    lcd.print("LN2 Tracking System:");
    countdownEndTime = millis() + initialHours * 3600000 + initialMinutes * 60000 + initialSeconds * 1000;
    countdownStarted = true;
  } else if (!switchState) {
    countdownStarted = false;
    timeLapseRunning = false;
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("___LN2 Monitoring___");
    lcd.setCursor(2, 1);
    lcd.print("LN2 not Detected!");
    lcd.setCursor(2, 2);
    lcd.print("Open the valve to");
    lcd.setCursor(2, 3);
    lcd.print("start monitoring");
  }

  if (countdownStarted) {
    unsigned long currentTime = millis();
    unsigned long remainingTime = countdownEndTime > currentTime ? countdownEndTime - currentTime : 0;

    int hours = remainingTime / 3600000;
    int minutes = (remainingTime % 3600000) / 60000;
    int seconds = (remainingTime % 60000) / 1000;

    lcd.setCursor(1, 1);
    lcd.print("Time Left: ");
    lcd.print(hours);
    lcd.print(":");
    if (minutes < 10) lcd.print("0");
    lcd.print(minutes);
    lcd.print(":");
    if (seconds < 10) lcd.print("0");
    lcd.print(seconds);

    if (remainingTime == 0 && !timeLapseRunning) {
      lcd.setCursor(1, 2);
      lcd.print("LN2 must be Empty!!");
      timeLapseStartTime = millis();
      timeLapseRunning = true;
      digitalWrite(buzzerPin, HIGH); // Turn on the buzzer
    }
  }

  if (timeLapseRunning) {
    unsigned long currentTime = millis();
    unsigned long elapsedTime = currentTime - timeLapseStartTime;

    int lapseHours = elapsedTime / 3600000;
    int lapseMinutes = (elapsedTime % 3600000) / 60000;
    int lapseSeconds = (elapsedTime % 60000) / 1000;

    lcd.setCursor(0, 3);
    lcd.print("Time Lapsed: ");
    lcd.print(lapseHours);
    lcd.print(":");
    if (lapseMinutes < 10) lcd.print("0");
    lcd.print(lapseMinutes);
    lcd.print(":");
    if (lapseSeconds < 10) lcd.print("0");
    lcd.print(lapseSeconds);
  }
  
  if (!timeLapseRunning) {
    digitalWrite(buzzerPin, LOW); // Turn off the buzzer
  }

  delay(1000); // Update every second
}