#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int LEDPins[6] = {0, 4, 16, 17, 5, 18};
const int Buttons[6] = {12, 14, 27, 26, 25, 13};
const int Buzzer = 2;
const int Start_Button = 15;

const int time_limit = 1000; // in seconds
const int active_time = 1000;
const int buzzer_time = 200;

int timer, timer_start, LED_time;
int score, currentLED;

// RESET state
bool start = false;
bool finish = false;

void setup() {
  Wire.begin(21, 22);   // SDA, SCL 
  lcd.init();
  lcd.backlight();

  pinMode(Start_Button, INPUT_PULLUP);
  pinMode(Buzzer, OUTPUT);

  for (int i = 0; i < 6; i++){
    pinMode(Buttons[i], INPUT_PULLUP);
    pinMode(LEDPins[i], OUTPUT);
    digitalWrite(LEDPins[i], LOW);
  }

  randomSeed(millis()); // for defining the seed as per the time returned by millis()
}

void loop() {
  if (!start && !finish){
    if (digitalRead(Start_Button) == LOW){
      start_game();
    }
  }
  else if (start){
    LCD_update();
    LED_update();
  }
  else if (finish){
    if (digitalRead(Start_Button) == LOW){
      finish = false; // back to RESET state
    }
  }
}
// start game (BUTTON PRESSED)

void start_game(){
  timer_start = millis();
  LED_time = millis();

  timer = 30; // The game goes on for 30 seconds
  score = 0;
  start = true;
}

void end_game(){
  start = false;
  finish = true;
}

// timer handling

void LCD_update(){
  if (millis() - timer_start < time_limit){

    // displaying time remaining
    lcd.setCursor(8, 0);
    if (timer < 10){
      lcd.print("TIME: 0");
    } else {
      lcd.print("TIME: ");
    }
    lcd.print(timer);

    lcd.setCursor(0,1);
    lcd.print("SCORE: ");
    lcd.print(score);
  }
  timer--;
}

// random LED lighting

void LED_update(){
  if (millis() - LED_time >= active_time){
    LED_time = millis();

    if (currentLED >= 0){
      digitalWrite(LEDPins[currentLED], LOW); // reset the state back to all LOW 
    }

    currentLED = random(0,6);
    digitalWrite(LEDPins[currentLED], HIGH); // turn on the currentLED
  }
}

// button checking 

void click(){
  click_time = millis();

  if (digitalRead(Buttons[currentLED]) == LOW){
    score++; // add to score
    digitalWrite(LEDPins[currentLED] == LOW); // immediately turn off the LED
    digitalWrite(Buzzer, HIGH);
  }
  
  if (millis() - click_time > buzzer_time){
    digitalWrite(Buzzer, LOW);
  }
}