#include <Wire.h>
#include <RTClib.h>
#include <LiquidCrystal_I2C.h>

#define LCD_ADDR 0x27
#define LCD_COLUMNS 16
#define LCD_ROWS 2
LiquidCrystal_I2C lcd(LCD_ADDR, LCD_COLUMNS, LCD_ROWS);

RTC_DS3231 rtc;

const int ldrpin = 4;
int t1;
int t2;
int c = 0; 

unsigned long startTime = 0;

void setup() {

  t1=0;
  t2=0;

  Serial.begin(9600);
  
  if (!rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }
  
  if (rtc.lostPower()) {
    Serial.println("RTC lost power, let's set the time!");
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }

  startTime = millis(); // Start the stopwatch
  lcd.begin(LCD_COLUMNS, LCD_ROWS);
  lcd.init();
  lcd.backlight();

  lcd.setCursor(0, 0);
  lcd.print("Hello");
  lcd.setCursor(0, 1);
  lcd.print("LCDisStarting");
  lcd.clear();

}

void loop() {
  DateTime now = rtc.now();
  
  unsigned long elapsedTime = millis() - startTime;

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

  int ldrValue = digitalRead(ldrpin); // Read LDR value

  Serial.println(ldrValue);
  Serial.print("Elapsed time: ");
  Serial.print(hours);
  Serial.print(":");
  Serial.print(minutes);
  Serial.print(":");
  Serial.print(seconds);
  Serial.print(":");
  Serial.println(milliseconds);

  lcd.setCursor(0, 0);
  lcd.print(hours);
  lcd.print(":");
  lcd.print(minutes);
  lcd.print(":");
  lcd.print(seconds);
  lcd.print(":");
  lcd.println(milliseconds);

  if (ldrValue == 0) { // Compare LDR value to a threshold
    if(c == 0 ){
      lcd.setCursor(0, 1);
      lcd.print(hours);
      lcd.print(":");
      lcd.print(minutes);
      lcd.print(":");
      lcd.print(seconds);
      lcd.print(":");
      lcd.println(milliseconds);
      c = 1;
    }
    else if(c == 1 ){
      t2 = hours;
      Serial.println(t2);
      c = 0;
    }
  }
   // Update approximately every 100 milliseconds
}