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

// Pin Definitions
#define DHTPIN 4         // DHT22 data pin
#define DHTTYPE DHT22    // DHT22 sensor type
#define MQ135_BEFORE 34  // MQ135 before filter (Analog pin)
#define MQ135_AFTER 35   // MQ135 after filter (Analog pin)

// OLED Display Config
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Initialize Sensors
DHT dht(DHTPIN, DHTTYPE);

void setup() {
    Serial.begin(115200);
    
    // Initialize OLED Display
    if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
        Serial.println("SSD1306 allocation failed");
        while (1);
    }

    // Start DHT Sensor
    dht.begin();

    // Clear display
    display.clearDisplay();
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
}

void loop() {
    // Read Temperature & Humidity
    float temperature = dht.readTemperature();
    float humidity = dht.readHumidity();

    // Read MQ135 Sensor Values
    int mqBefore = analogRead(MQ135_BEFORE);
    int mqAfter = analogRead(MQ135_AFTER);

    // Calculate Filter Efficiency (optional)
    float efficiency = ((float)(mqBefore - mqAfter) / mqBefore) * 100.0;

    // Print values to Serial Monitor
    Serial.print("Temp: "); Serial.print(temperature); Serial.print("°C, ");
    Serial.print("Humidity: "); Serial.print(humidity); Serial.print("%, ");
    Serial.print("MQ Before: "); Serial.print(mqBefore); Serial.print(" ppm, ");
    Serial.print("MQ After: "); Serial.print(mqAfter); Serial.print(" ppm, ");
    Serial.print(", Efficiency: "); Serial.print(efficiency); Serial.println("%");

    // Display Data on OLED
    display.clearDisplay();
    display.setCursor(0, 0);
    display.setTextSize(1);
    
    display.println("Air Quality Monitor");
    display.println("--------------------");
    display.print("Temp: "); display.print(temperature); display.println(" C");
    display.print("Humidity: "); display.print(humidity); display.println(" %");
    display.print("MQ Before: "); display.println(mqBefore);
    display.print("MQ After: "); display.println(mqAfter);
    display.print("Efficiency: "); display.print(efficiency); display.println("%");

    display.display();

    // Wait 2 seconds before next reading
    delay(2000);
}