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

LiquidCrystal_I2C lcd(0x27,16,2);  // set the LCD address to 0x27 for a 16 chars and 2 line display

//pins
long charger_pin = A0;
long button_pin = 7;

//time units
long second = 1000;
long minute = 60 * second;
long hour = 60 * minute;

//initial target
long target = hour;

int finished = 0;

void setup() {
  lcd.init();
  lcd.backlight();
  lcd.print("PASSED: ");
  lcd.setCursor(0,1);
  lcd.print("REMAIN: ");

  //pins
  pinMode(charger_pin, OUTPUT);
  digitalWrite(charger_pin, LOW); //turn on charger

  pinMode(button_pin, INPUT_PULLUP);
}

void loop() {
  if(!finished){
    //check for button pressed
    if(digitalRead(button_pin) == LOW){
      target += hour;
    }
    
    //check if finished
    long time_passed = millis();
    if (time_passed > target){
      finished = 1;
      lcd.clear();
      lcd.print("    " + millis_to_string(target));
      lcd.setCursor(0,1);
      lcd.print("CHARGING FINISH!");
      digitalWrite(charger_pin, HIGH);
    }else{
      lcd.setCursor(8,0);
      lcd.print(millis_to_string(time_passed));
      lcd.setCursor(8,1);
      lcd.print(millis_to_string(target - time_passed + 1000));

      
    }
  }

  delay(1000);

}

String millis_to_string(long millis){
  long time = round(millis / 1000);
  long hours = time / 3600;
  time = time - (hours * 3600);
  long minutes = time / 60;
  long seconds = time - (minutes * 60);

  String hours2 = "0" + String(hours);
  hours2 = hours2.substring(hours2.length() - 2);

  String minutes2 = "0" + String(minutes);
  minutes2 = minutes2.substring(minutes2.length() - 2);

  String seconds2 = "0" + String(seconds);
  seconds2 = seconds2.substring(seconds2.length() - 2);


  return hours2 + ":" + minutes2 + ":" + seconds2;
}