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

// --- OLED Display Settings ---
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1 // -1 because it shares the ESP32 reset pin
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// --- Pin Definitions (Matching your JSON) ---
const int gasSensorPin = 34; // Gas Sensor AOUT
const int buzzerPin = 25;    // Buzzer Signal
const int gasThreshold = 2000; // Trigger threshold (ESP32 ADC goes 0-4095)

void setup() {
  // Start the serial monitor for debugging
  Serial.begin(115200);

  // Configure pin modes
  pinMode(buzzerPin, OUTPUT);
  pinMode(gasSensorPin, INPUT); // GPIO 34 is input-only, explicitly defining it

  // Initialize the OLED display (I2C address 0x3C matches your JSON)
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed. Check wiring!"));
    for(;;); // Halt the system if display fails
  }

  // Startup Screen
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0, 20);
  display.println("Initializing...");
  display.display();
  delay(2000); // Give the sensor a brief moment to warm up
}

void loop() {
  // 1. Read the analog data from the gas sensor
  int gasValue = analogRead(gasSensorPin);
  
  // Print to Serial Monitor for debugging
  Serial.print("Current Gas Level: ");
  Serial.println(gasValue);

  // 2. Prepare the OLED Display
  display.clearDisplay();
  
  // Header Text
  display.setCursor(0, 0);
  display.setTextSize(1);
  display.println("Gas Leak Detector");
  display.drawLine(0, 10, 128, 10, WHITE); // Draw a separator line

  // Display the current sensor value
  display.setCursor(0, 20);
  display.setTextSize(2);
  display.print("Val: ");
  display.print(gasValue);

  // 3. Evaluate the Gas Level against the Threshold
  display.setCursor(0, 45);
  display.setTextSize(1);

  if (gasValue > gasThreshold) {
    digitalWrite(buzzerPin, HIGH); // Turn the buzzer ON
    display.println("! DANGER: GAS !");
  } else {
    digitalWrite(buzzerPin, LOW);  // Ensure the buzzer is OFF
    display.println("Status: Normal");
  }

  // 4. Push the drawing to the screen
  display.display();

  // Wait half a second before taking the next reading
  delay(500); 
}