#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);

const int redLEDPin = 16;
const int greenLEDPin = 17;
const int trigPin = 26;
const int echoPin = 25;

unsigned long duration;
float distance;

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

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("Unable to connect"));
    for (;;);
  }
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.println("Smart Door Lock System");
  display.display();

  pinMode(redLEDPin, OUTPUT);
  pinMode(greenLEDPin, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;

  display.clearDisplay();
  display.setCursor(0, 0);
  display.println("Distance: ");
  display.print(distance);
  display.println(" cm");
  display.display();

  if (distance > 100) {
    digitalWrite(redLEDPin, HIGH);
    digitalWrite(greenLEDPin, LOW);
  } else {
    digitalWrite(redLEDPin, LOW);
    digitalWrite(greenLEDPin, HIGH);
  }

  delay(500);
}