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

LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C address 0x27, 16x2 LCD

volatile bool running = false;
volatile bool lap = false;
volatile bool reset = false;
unsigned long startTime = 0;
unsigned long elapsedTime = 0;
unsigned long lapTime = 0;
bool lastButtonState = HIGH; // Pro detekci START/STOP

void setup() {
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Stopwatch: 0.0s");
  lcd.setCursor(0, 1);
  lcd.print("Lap:            ");
  
  pinMode(4, INPUT_PULLUP); // START/STOP
  pinMode(3, INPUT_PULLUP); // LAP
  pinMode(2, INPUT_PULLUP); // CLEAR
  
  interrupts();
  attachInterrupt(digitalPinToInterrupt(3), lapButton, FALLING); // LAP
  attachInterrupt(digitalPinToInterrupt(2), clear, FALLING);     // CLEAR
}

void loop() {
  // DetekceSTART/STOP na pinu 4
  bool currentButtonState = digitalRead(4);
  if (currentButtonState == LOW && lastButtonState == HIGH) {
    if (!running) {
      startTime = millis() - elapsedTime;
      running = true;
    } else {
      running = false;
    }
    delay(50);
  }
  lastButtonState = currentButtonState;

  if (reset) {
    elapsedTime = 0;
    startTime = 0;
    running = false;
    lcd.setCursor(0, 0);
    lcd.print("Stopwatch: 0.0s");
    lcd.setCursor(0, 1);
    lcd.print("Lap:            ");
    reset = false;
  }

  if (running) {
    elapsedTime = millis() - startTime;
    lcd.setCursor(0, 0);
    lcd.print("Stopwatch:      ");
    lcd.setCursor(10, 0);
    lcd.print(elapsedTime / 1000.0, 1);
    lcd.print("s");
  }

  if (lap) {
    lapTime = elapsedTime;
    lcd.setCursor(0, 1);
    lcd.print("Lap:            ");
    lcd.setCursor(5, 1);
    lcd.print(lapTime / 1000.0, 1);
    lcd.print("s");
    lap = false;
  }
}

void lapButton() {
  if (running) {
    lap = true;
  }
}

void clear() {
  reset = true;
}