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

#define trigPin 12
#define echoPin 13
#define ledred 14
#define ledyellow 27
#define ledgreen 26

#define DISTANCE_THRESHOLD 50
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

float duration_us, distance_cm;
String tempString;

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledred, OUTPUT);  
  pinMode(ledyellow, OUTPUT);
  pinMode(ledgreen, OUTPUT);

  if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("failed to start SSD1306 OLED"));
    while (1);
  }

  delay(2000);
  oled.clearDisplay();

  oled.setTextSize(2,2);
  oled.setTextColor(WHITE);
  oled.setCursor(0, 2);
  oled.println("Name:Dr. Sayantam");
  oled.display();

  delay(2000);
  oled.clearDisplay();
}

void oledDisplayCenter(String text) {
 int16_t x1;
 int16_t y1;
 uint16_t width;
 uint16_t height;
 oled.getTextBounds(text, 0, 0, &x1, &y1, &width, &height);
 // display on horizontal and vertical center
 oled.clearDisplay(); // clear display
 oled.setCursor((SCREEN_WIDTH - width) / 2, (SCREEN_HEIGHT - height) / 2);
 oled.println(text); // text to display
 oled.display();
}

void loop() {
 digitalWrite(trigPin, HIGH);
 delay (100);
 digitalWrite(trigPin, LOW);
 // measure duration of pulse from ECHO pin
  duration_us = pulseIn(echoPin, HIGH);// calculate the distance
  distance_cm = 0.017 * duration_us;// print the value to Serial Monitor
  
  if(distance_cm < DISTANCE_THRESHOLD)

 Serial.print("distance: ");
 Serial.print("distance_cm");
 Serial.println(" cm");
 tempString = String(distance_cm, 2); // two decimal places
 tempString += " cm";
 Serial.println(tempString); // print the temperature in Celsius to Serial Monitor
 oledDisplayCenter(tempString);

   if (distance_cm > 200){
    digitalWrite(ledgreen, HIGH);
    digitalWrite(ledred, LOW);
    digitalWrite(ledyellow, LOW);
  }
  else if (distance_cm < 200 && distance_cm > 100) {
    digitalWrite(ledyellow, HIGH);
    digitalWrite(ledred, LOW);
    digitalWrite(ledgreen, LOW);
  }
  else if (distance_cm < 100) {
    digitalWrite(ledred, HIGH);
    digitalWrite(ledyellow, LOW);
    digitalWrite(ledgreen, LOW);
  }
  else {}
}