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

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

#define MQ_BEFORE A0  // MQ sensor before filter
#define MQ_AFTER A1   // MQ sensor after filter

#define RED_LED 2    // Efficiency < 0% (Very Dirty)
#define YELLOW_LED 3  // Efficiency 25% - 50% (Polluted)
#define GREEN_LED 4   // Efficiency 50% - 70% (Normal)
#define BLUE_LED 5    // Efficiency > 90% (Very Clean)

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

  // Initialize OLED Display
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {  
    Serial.println(F("SSD1306 OLED initialization failed"));
    for (;;);
  }
  display.clearDisplay();
  display.display();

  pinMode(RED_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(GREEN_LED, OUTPUT);
  pinMode(BLUE_LED, OUTPUT);
}

void loop() {
  // Read MQ Sensor Values
  int mqBefore = analogRead(MQ_BEFORE);
  int mqAfter = analogRead(MQ_AFTER);

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

  // Print to Serial Monitor
  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("%");

  // Clear OLED display
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);

  // Display efficiency percentage
  display.setCursor(10, 10);
  display.print("Efficiency: ");
  display.print(efficiency);
  display.print("%");

  // Turn off all LEDs first
  digitalWrite(RED_LED, LOW);
  digitalWrite(YELLOW_LED, LOW);
  digitalWrite(GREEN_LED, LOW);
  digitalWrite(BLUE_LED, LOW);

  // LED and OLED Conditions (Only ONE LED ON at a time)
  if (efficiency < 0) {  // Very Dirty (Red LED)
    digitalWrite(RED_LED, HIGH);
    display.setCursor(10, 30);
    display.print("Status: Very Dirty");

  } else if (efficiency >= 25 && efficiency < 50) {  // Polluted (Yellow LED)
    digitalWrite(YELLOW_LED, HIGH);
    display.setCursor(10, 30);
    display.print("Status: Polluted");

  } else if (efficiency >= 50 && efficiency < 70) {  // Normal (Green LED)
    digitalWrite(GREEN_LED, HIGH);
    display.setCursor(10, 30);
    display.print("Status: Normal");

  } else if (efficiency > 90) {  // Very Clean (Blue LED)
    digitalWrite(BLUE_LED, HIGH);
    display.setCursor(10, 30);
    display.print("Status: Very Clean");
  }

  // Update OLED display
  display.display();

  delay(5000);  // Wait before next reading
}