#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// Sensor and Actuator Pins
const int gasSensorPin = A0;  // MQ-2 analog pin
const int buzzerPin = 11;     // Buzzer digital pin
const int ledPin = 2;         // Warning LED pin

// Thresholds
const int gasThreshold = 300;  // Adjust based on your sensor calibration

// Alarm timing variables
unsigned long previousAlarmMillis = 0;
const long alarmInterval = 500; // 0.5 second interval for beep/blink
bool alarmState = false;

void setup() {
  // Initialize serial for debugging
  Serial.begin(9600);
  
  // Set pin modes
  pinMode(buzzerPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  
  // Initialize OLED
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED init failed");
    while(1);
  }
  
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.println("Gas Monitor Ready");
  display.display();
  delay(2000);
}

void loop() {
  // Read gas sensor
  int gasValue = analogRead(gasSensorPin);
  
  // Clear display and show readings
  display.clearDisplay();
  display.setCursor(0,0);
  display.print("Gas Level: ");
  display.print(gasValue);
  
  // Check threshold and trigger alarms
  if(gasValue > gasThreshold) {
    unsigned long currentMillis = millis();
    
    // Toggle alarm state every interval
    if(currentMillis - previousAlarmMillis >= alarmInterval) {
      previousAlarmMillis = currentMillis;
      alarmState = !alarmState;
      
      // Beep buzzer and blink LED
      digitalWrite(buzzerPin, alarmState ? HIGH : LOW);
      digitalWrite(ledPin, alarmState ? HIGH : LOW);
    }
    
    // Display warning
    display.setCursor(0,20);
    display.print("WARNING! GAS LEAK");
    display.setCursor(0,40);
    display.print("EVACUATE AREA!");
  } else {
    // Normal operation - turn off alarms
    digitalWrite(buzzerPin, LOW);
    digitalWrite(ledPin, LOW);
    alarmState = false;
    
    display.setCursor(0,20);
    display.print("Air Quality: Normal");
  }
  
  display.display();
  delay(100); // Short delay for display stability
}