//Define Gpio pins with meaningful names
#define GAS_SENSOR_PIN 34
#define BUZZER_GPIO 26
//concentration (read via MQ135)crosses the set gas threshold value (whichis 200 in this case)
#define SAFE_LED_PIN 19
#define ALERT_LED_PIN 21

int gasthreshold = 200;

void setup() {
  // Initalize serial communication at 115200 baud rate
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");

  //Set pin modes for output devices
  pinMode(BUZZER_GPIO, OUTPUT);
  pinMode(SAFE_LED_PIN, OUTPUT);
  pinMode( ALERT_LED_PIN, OUTPUT);
}

void loop() {
  // Read analog gas sensor value from MQ-135
  int gasLevel = analogRead(GAS_SENSOR_PIN);

  //Print gas level to serial monitor for debugging
  Serial.print("Gas Level:");
  Serial.println(gasLevel);

  //Compare gas level with threshold
  if (gasLevel > gasThreshold){
    //High gas concentration detected - activate danger alters
    digitalWrite( ALERT_LED_PIN,HIGH);
    digitalWrite(SAFE_LED_PIN,LOW);
    digitalWrite(BUZZER_GPIO,HIGH);
    Serial.println("Warning! Harmful gas detected!");
  }else{
    //Gas level is safe - keep clam and glow green
    digitalWrite(ALERT_LED_PIN,LOW);
    digitalWrite(SAFE_LED_PIN,HIGH);
    digitalWrite(BUZZER_GPIO,LOW);
    tone(26, 265, 250);
    Serial.println("Air quality is safe.");
  }
  delay(1000); // Wait for 1 sec before next reading
}