/*

  Forum: https://forum.arduino.cc/t/day-timer-using-an-arduino/1238757
  Wokwi: https://wokwi.com/projects/393161788734307329

*/

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 20, 4);

const unsigned long secsPerMinute  = 60;
const unsigned long secsPerHour    = 60 * secsPerMinute;
const unsigned long maxSecsPerDay  = 24 * secsPerHour;
unsigned long leftSecsPerDay;
unsigned long lastUpdate = 0;

int daysSpent = 0;
boolean countDownActive;

// Set the days to count here:
const int maxDaysSpent = 5;


void setup() {
  Serial.begin(115200);
  countDownActive = true;
  lcd.backlight();
  lcd.init();
  lcd.begin(20, 4);
  // Set a test date and time here the sketch
  // shall start with
  // E.g.: 5 days expired, at 23:59:55 hours:minutes:seconds
  setTestDateTime(5, 23, 59, 55);

}

void loop() {
  countDown();
}

void countDown() {
  if (!countDownActive) {
    return;
  }
  if (millis() - lastUpdate >= 1000) {
    lastUpdate = millis();
    leftSecsPerDay--;
    if (leftSecsPerDay == 0) {
      daysSpent++;
      leftSecsPerDay = maxSecsPerDay;
    }
    if (daysSpent > maxDaysSpent) {
      countDownActive = false;
    }
    if (countDownActive) {
      printCountDown();
    } else {
      printLCD("  0 - 00:00:00", 4, 2);
      //      Serial.println("Countdown stopped");
    }
  }
}

void printCountDown() {
  int days = maxDaysSpent - daysSpent;
  uint16_t hours = leftSecsPerDay / secsPerHour;
  uint16_t minutes = (leftSecsPerDay - hours * secsPerHour) / secsPerMinute;
  uint16_t seconds = leftSecsPerDay - hours * secsPerHour - minutes * secsPerMinute;
  char buffer[40];
  snprintf(buffer, sizeof(buffer), " %2d - %02d:%02d:%02d", days, hours, minutes, seconds);
  //  Serial.println(buffer);
  printLCD(buffer, 4, 2);
}

void printLCD(char msg[40], int col, int row) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Days left");
  lcd.setCursor(col, row);
  lcd.print(msg);
}


void setTestDateTime(int daysDone, uint16_t hourAtDayDone, uint16_t minutesAtDayDone,
                     uint16_t secondsAtDayDone)
{
  daysSpent = daysDone;
  leftSecsPerDay = maxSecsPerDay - hourAtDayDone * secsPerHour - minutesAtDayDone * secsPerMinute - secondsAtDayDone;
}