// Countdown Timer with Relay Control without Countimer Library

#include <LiquidCrystal_I2C.h>  // I2C LCD library
#include <EEPROM.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);   // Adjust I2C address if needed

#define bt_set    A3
#define bt_up     A2
#define bt_down   A1
#define bt_start  A0

int time_s = 0;
int time_m = 0;
int time_h = 0;

int set = 0;
int flag2 = 0;

int relay = 5;
int buzzer = 6;

unsigned long previousMillis = 0;
const long interval = 1000; // 1-second interval

void setup() {
  Serial.begin(9600);

  pinMode(bt_set,   INPUT_PULLUP);
  pinMode(bt_up,    INPUT_PULLUP);
  pinMode(bt_down,  INPUT_PULLUP);
  pinMode(bt_start, INPUT_PULLUP);

  pinMode(relay, OUTPUT);
  pinMode(buzzer, OUTPUT);

  lcd.begin(16, 2);
  lcd.backlight();
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("   Welcome To   ");
  lcd.setCursor(0, 1);
  lcd.print("Countdown  Timer");
  delay(2000);
  lcd.clear();
  eeprom_write();
  eeprom_read();
}

void print_time() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;

    if (flag2 == 1) {
      time_s--;

      if (time_s < 0) {
        time_s = 59;
        time_m--;
      }

      if (time_m < 0) {
        time_m = 59;
        time_h--;
      }

      if (time_h < 0) {
        time_h = 0;
        time_m = 0;
        time_s = 0;
        flag2 = 0;

        // Turn off relay and trigger buzzer
        digitalWrite(relay, LOW);
        buzzer_alert();
      }
    }
  }
}

void buzzer_alert() {
  for (int i = 0; i < 3; i++) {
    tone(buzzer, 440);
    delay(1000);
    noTone(buzzer);
    delay(1000);
  }
}

void loop() {
  print_time();

  if (digitalRead(bt_set) == LOW) {
    set = (set + 1) % 4;
    delay(200);
  }

  if (digitalRead(bt_up) == LOW) {
    if (set == 1) time_s++;
    if (set == 2) time_m++;
    if (set == 3) time_h++;
    if (time_s > 59) time_s = 0;
    if (time_m > 59) time_m = 0;
    if (time_h > 99) time_h = 0;
    if (set > 0) eeprom_write();
    delay(200);
  }

  if (digitalRead(bt_down) == LOW) {
    if (set == 1) time_s--;
    if (set == 2) time_m--;
    if (set == 3) time_h--;
    if (time_s < 0) time_s = 59;
    if (time_m < 0) time_m = 59;
    if (time_h < 0) time_h = 99;
    if (set > 0) eeprom_write();
    delay(200);
  }

  if (digitalRead(bt_start) == LOW) {
    flag2 = 1;
    eeprom_read();
    digitalWrite(relay, HIGH);
    delay(200);
  }

  // Update LCD display
  lcd.setCursor(0, 0);
  if (set == 0) lcd.print("      Timer     ");
  if (set == 1) lcd.print("  Set Timer SS  ");
  if (set == 2) lcd.print("  Set Timer MM  ");
  if (set == 3) lcd.print("  Set Timer HH  ");

  lcd.setCursor(4, 1);
  if (time_h <= 9) lcd.print("0");
  lcd.print(time_h);
  lcd.print(":");
  if (time_m <= 9) lcd.print("0");
  lcd.print(time_m);
  lcd.print(":");
  if (time_s <= 9) lcd.print("0");
  lcd.print(time_s);
  lcd.print("   ");

  delay(50);
}

void eeprom_write() {
  EEPROM.write(1, time_s);
  EEPROM.write(2, time_m);
  EEPROM.write(3, time_h);
}

void eeprom_read() {
  time_s = EEPROM.read(1);
  time_m = EEPROM.read(2);
  time_h = EEPROM.read(3);
}