// John Carlo D. Martin //
// BSCPE4A //

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

const int trigPin = 9;
const int echoPin = 10;
const int buzzer = 11;
const int ledPin = 13;

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

long duration;
int distance;
int safetyDistance;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);  
  pinMode(buzzer, OUTPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600); 

  display.begin(SSD1306_SWITCHCAPVCC, 0x3C); 
  display.clearDisplay(); 
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);

  distance = duration * 0.034 / 2;

  safetyDistance = distance;
  if (safetyDistance <= 20) {
    digitalWrite(buzzer, HIGH);
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(buzzer, LOW);
    digitalWrite(ledPin, LOW);
  }

  Serial.print("Distance: ");
  Serial.println(distance);

  display.clearDisplay(); 
  display.setTextSize(1); 
  display.setTextColor(WHITE); 

  String distanceText = "Distance: " + String(distance) + " cm";
  
  int16_t textWidth = distanceText.length() * 6;
  int16_t xPos = (SCREEN_WIDTH - textWidth) / 2; 

  display.setCursor(xPos, SCREEN_HEIGHT / 2); 
  display.setTextSize(1); 
  display.print(distanceText); 

  display.display(); 
}