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

#define MQ2_PIN 34       // Sensor gas analog MQ-2
#define LED_PIN 2        // LED indikator
#define BUZZER_PIN 4     // Buzzer aktif
#define BUTTON_PIN 5     // Tombol ke GND

LiquidCrystal_I2C lcd(0x27, 16, 2); // SDA = GPIO 21, SCL = GPIO 22

unsigned long waktuLED = 0;
bool statusLED = false;

unsigned long waktuBuzzer = 0;
bool statusBuzzer = false;

bool alarmDimatikan = false;
bool tombolTerakhir = HIGH;

const int ambangADC = 2000; // Ambang batas analogRead MQ-2 (0–4095)

void setup() {
  Serial.begin(115200);

  pinMode(MQ2_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP); // tombol satu kaki ke GND

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Deteksi Gas LPG");
  delay(2000);
  lcd.clear();
}

void loop() {
  // Baca tombol
  bool tombolSekarang = digitalRead(BUTTON_PIN);
  if (tombolTerakhir == HIGH && tombolSekarang == LOW) {
    alarmDimatikan = true;
    Serial.println("Alarm dimatikan manual");
    delay(200); // debounce
  }
  tombolTerakhir = tombolSekarang;

  // Baca nilai analog sensor gas
  int adcValue = analogRead(MQ2_PIN); // nilai dari 0 – 4095
  Serial.print("ADC: ");
  Serial.println(adcValue);

  // Reset alarm jika gas normal
  if (adcValue <= ambangADC) {
    alarmDimatikan = false;
  }

  // Tampilkan status di LCD
  lcd.setCursor(0, 0);
  lcd.print("Status: ");
  lcd.print((adcValue > ambangADC && !alarmDimatikan) ? "Bahaya" : "Aman  ");

  lcd.setCursor(0, 1);
  lcd.print("ADC: ");
  lcd.print(adcValue);
  lcd.print("    "); // hapus sisa karakter

  // Aktifkan alarm jika kondisi bahaya
  if (adcValue > ambangADC && !alarmDimatikan) {
    // LED berkedip
    if (millis() - waktuLED >= 500) {
      statusLED = !statusLED;
      digitalWrite(LED_PIN, statusLED);
      waktuLED = millis();
    }

    // Buzzer berbunyi putus-putus
    if (millis() - waktuBuzzer >= 500) {
      statusBuzzer = !statusBuzzer;
      if (statusBuzzer) tone(BUZZER_PIN, 1000);
      else noTone(BUZZER_PIN);
      waktuBuzzer = millis();
    }

  } else {
    // Matikan alarm
    digitalWrite(LED_PIN, LOW);
    noTone(BUZZER_PIN);
  }

  delay(100);
}