#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);

// Ultrasonic sensor pins
const int trigPin = 4;
const int echoPin = 13;

// Bin height (for calculating fill % if you want)
const float binHeight = 400.0; // cm

long duration;
float distance;
float fillLevel;

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

  // Initialize OLED
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)){
    Serial.println("OLED not found");
    while(1);
  }
  display.clearDisplay();
  display.display();
}

float getDistance() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH, 30000); // 30 ms timeout
  float dist = duration * 0.0343 / 2;
  return dist;
}

void loop() {
  distance = getDistance();

  // Optional: calculate fill level %
  if(distance > 0 && distance <= binHeight){
    fillLevel = ((binHeight - distance) / binHeight) * 100;
  } else {
    fillLevel = 0;
  }

  // Display on OLED
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);

  display.setCursor(0, 0);
  display.println("SMART DUSTBIN");

  display.setCursor(0, 20);
  display.print("Space Left: ");
  display.print(distance);
  display.println(" cm");

  display.setCursor(0, 35);
  display.print("Fill: ");
  display.print(fillLevel);
  display.println("%");

  // Show "READY" if distance <= 20 cm
  display.setCursor(0, 50);
  if(distance <= 20 && distance > 0){
    display.println("FULL");
  }

  display.display();
  delay(500);
}