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

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

// Pin Definitions
const int trigPin = 9;
const int echoPin = 10;
const int relayPin = 12;

// Variables
bool relayState = false;      // Current state of the relay
bool objectPresent = false;   // Whether an object is currently in range
bool lastObjectPresent = false; // Previous detection state
int threshold = 350;           // Detection distance in cm

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(relayPin, OUTPUT);
  
  digitalWrite(relayPin, LOW); // Start with lights off

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    for(;;); // Don't proceed if OLED fails
  }
  
  updateDisplay("System Ready");
  delay(1000);
  updateDisplay("Lights: OFF");
}

void loop() {
  long duration;
  int distance;

  // Trigger the ultrasonic sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;

  // Check if an object is within the threshold
  if (distance > 0 && distance < threshold) {
    objectPresent = true;
  } else {
    objectPresent = false;
  }

  // Toggle Logic: Trigger only when an object first appears (State Change)
  if (objectPresent == true && lastObjectPresent == false) {
    relayState = !relayState; // Flip the state
    
    if (relayState) {
      digitalWrite(relayPin, HIGH);
      updateDisplay("Lights: ON");
    } else {
      digitalWrite(relayPin, LOW);
      updateDisplay("Lights: OFF");
    }
    
    delay(5000); // Small debounce delay to prevent double-triggering
  }

  lastObjectPresent = objectPresent; // Save the state for the next loop
  delay(50); 
}

void updateDisplay(String message) {
  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(0, 20);
  display.println(message);
  display.display();
}