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

// Change this to use Blynk
// Since we cant use it in wokwi, it will show error
#define USE_BLYNK 1

#if USE_BLYNK
  #define BLYNK_TEMPLATE_ID "BLYNK_TEMPLATE_ID"
  #define BLYNK_TEMPLATE_NAME "Wokwi"
  #define BLYNK_AUTH_TOKEN "BLYNK_AUTH_TOKEN"
  
  #include <WiFi.h>
  #include <BlynkSimpleEsp32.h>
  
  // don't change the ssid and pass as they are the default for wokwi
  // for doing this on your own machine, change it to match the ssid and password
  char ssid[] = "Wokwi-GUEST";
  char pass[] = "";
#endif

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int PIN_LED_G   = 0;   // Green LED
const int PIN_LED_R   = 2;   // Red LED
const int PIN_MQ2     = 34;  // MQ-2 sensor analog pin
const int PIN_BUZZER  = 3;   // Buzzer pin
const int PIN_SWITCH  = 4;   // Reset button pin

const int HIGH_THRESHOLD = 2000;

bool alarmLatched = false;
bool previousState = alarmLatched;
int previousLevel = 0;

#if USE_BLYNK
BLYNK_WRITE(V0) {
  if (param.asInt() == 1) {
    resetAlarm();
    Blynk.virtualWrite(V0, 0);
  }
}
#endif

void resetAlarm() {
  alarmLatched = false;
  digitalWrite(PIN_BUZZER, LOW);
  digitalWrite(PIN_LED_G, HIGH);
  digitalWrite(PIN_LED_R, LOW);
  #if USE_BLYNK
    Blynk.virtualWrite(V1, 0);
  #endif
  Serial.println("Alarm reset.");
  lcd.setCursor(0, 1);
  lcd.print("                ");  
}

void checkSwitch() {
  if (!alarmLatched) return;
  if (digitalRead(PIN_SWITCH) == LOW) {
    resetAlarm();
  }
}

void setup() {
  Serial.begin(115200);
  
  pinMode(PIN_LED_G, OUTPUT);
  pinMode(PIN_LED_R, OUTPUT);
  pinMode(PIN_BUZZER, OUTPUT);
  pinMode(PIN_SWITCH, INPUT_PULLUP);
  
  lcd.init();
  lcd.backlight();
  
  digitalWrite(PIN_LED_G, HIGH);
  digitalWrite(PIN_LED_R, LOW);
  digitalWrite(PIN_BUZZER, LOW);
  
  #if USE_BLYNK
    Serial.println("Connecting to Wi-Fi & Blynk...");
    Blynk.begin(BLYNK_AUTH_TOKEN, ssid, pass);
  #else
    Serial.println("Running in OFFLINE mode");
  #endif
}

void loop() {
  #if USE_BLYNK
    Blynk.run();
  #endif
  
  int gas = analogRead(PIN_MQ2);
  
  #if USE_BLYNK
    Blynk.virtualWrite(V2, gas);
  #endif
  
  Serial.print("Gas Level: ");
  Serial.println(gas);
  
  #if USE_BLYNK
    Blynk.virtualWrite(V0, gas);
  #endif
  
  if (!alarmLatched && gas >= HIGH_THRESHOLD) {
    alarmLatched = true;
    digitalWrite(PIN_LED_G, LOW);
    digitalWrite(PIN_LED_R, HIGH);
    digitalWrite(PIN_BUZZER, HIGH);
    Serial.println("⚠️ High Gas Level Detected! Alarm Triggered.");
    #if USE_BLYNK
      Blynk.virtualWrite(V1, 1);
      Blynk.logEvent("gas_alert", String("High gas level: ") + gas);
    #endif
  }
  
  if (!alarmLatched) {
    digitalWrite(PIN_LED_G, HIGH);
    digitalWrite(PIN_LED_R, LOW);
    digitalWrite(PIN_BUZZER, LOW);
  }
  
  if (gas != previousLevel) {
    lcd.setCursor(0, 0);
    lcd.print("                ");
    lcd.setCursor(0, 0);
    lcd.print("Gas:");
    lcd.print(gas);
  }
  
  if (alarmLatched) {
    lcd.setCursor(0, 1);
    lcd.print("                ");
    lcd.setCursor(0, 1);
    lcd.print("!!! WARNING !!!");
    checkSwitch();
  }
  else {
    lcd.setCursor(0, 1);
    lcd.print("Safe");
  }
  
  previousLevel = gas;
  previousState = alarmLatched;
  delay(500);
}