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

LiquidCrystal_I2C lcd(0x27, 20, 4);

const int buttonPins[] = {A0, A1, A2, A3};
const int relayPins[] = {9, 8, 7, 6};
const int ledPins[] = {5, 4, 3, 2};
const int activatorButtonPin = 11;
const int additionalLedPin = 12;
int selectedButton = 0;
unsigned long startTimes[] = {0, 0, 0, 0};
bool buttonDisabled[] = {false, false, false, false};
const unsigned long activationTime = 3600000;
unsigned long activationTimes[] = {0, 0, 0, 0};
unsigned long lastButtonPressTime = 0; 

void setup() {
  lcd.backlight();
  lcd.begin(20, 4);
  lcd.print("   CHARGING STATION");
  lcd.setCursor(0, 2);
  lcd.print("  by: Shirhan A. B.");
  delay(2000);
  lcd.clear();
  for (int i = 0; i < 4; i++) {
    pinMode(buttonPins[i], INPUT_PULLUP);
    pinMode(relayPins[i], OUTPUT);
    pinMode(ledPins[i], OUTPUT);
  }
  pinMode(activatorButtonPin, INPUT_PULLUP);
  pinMode(additionalLedPin, OUTPUT);
  digitalWrite(additionalLedPin, HIGH);
}

void loop() {
  for (int i = 0; i < 4; i++) {
    if (digitalRead(buttonPins[i]) == LOW) {
      lcd.setCursor((i < 2) ? 0 : 10, i % 2);
      lcd.print(String(i + 1) +":");
      selectedButton = i + 1;
      delay(1000);
      lastButtonPressTime = millis(); 
    }
  }

  if (digitalRead(activatorButtonPin) == LOW && selectedButton != 0) {
    activateRelayAndLed(relayPins[selectedButton - 1], ledPins[selectedButton - 1], startTimes[selectedButton - 1]);
    activationTimes[selectedButton - 1] = activationTimes[selectedButton - 1] + activationTime;
    selectedButton = 0;
  }

  if (millis() - lastButtonPressTime >= 2000) {
    digitalWrite(additionalLedPin, LOW);
  } else {
    digitalWrite(additionalLedPin, HIGH);
  }

  for (int i = 0; i < 4; i++) {
    if (startTimes[i] > 0) {
      unsigned long remainingTime = activationTimes[i] - (millis() - startTimes[i]);
      unsigned long remainingMinutes = remainingTime / 60000;
      unsigned long remainingSeconds = (remainingTime % 60000) / 1000;

      lcd.setCursor((i < 2) ? 0 : 10, i % 2);
      lcd.print(String(1 + i) + ":" + String(remainingMinutes) + "m " + String(remainingSeconds) + "s");
    }
    lcd.setCursor(0,2);
    lcd.print("  Select charger and");
    lcd.setCursor(0, 3);
    lcd.print("  insert coins...");

    if (millis() - startTimes[i] >= activationTimes[i] && digitalRead(relayPins[i]) == LOW) {
      digitalWrite(relayPins[i], HIGH);
      digitalWrite(ledPins[i], LOW);
      startTimes[i] = 0;
      activationTimes[i]=0;
      selectedButton = 0;
      buttonDisabled[i] = false;
    }
  }
}

void activateRelayAndLed(int relay, int led, unsigned long &startTime) {
  if (startTime == 0) {
    digitalWrite(relay, LOW);
    digitalWrite(led, HIGH);
    startTime = millis();
  }
}