#include <LiquidCrystal_I2C.h>

#define TRIG 2
#define ECHO 3
#define GREEN 4
#define YELLOW 5
#define RED 6
#define BUZZER 7

// Distance thresholds (in cm)
const long DIST_SAFE = 50;
const long DIST_WARNING = 20;

LiquidCrystal_I2C lcd(0x27, 16, 2);

long readDistanceCM() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  long duration = pulseIn(ECHO, HIGH);
  return duration * 0.034 / 2;
}

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(GREEN, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(RED, OUTPUT);
  pinMode(BUZZER, OUTPUT);

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Smart Trash Bin");
  lcd.setCursor(0, 1);
  lcd.print("Initializing...");
  delay(1000);
}

void loop() {
  long distance = readDistanceCM();

  // Display distance without clearing LCD every time
  lcd.setCursor(0, 0);
  lcd.print("Distance: ");
  lcd.print(distance);
  lcd.print("cm   "); // extra spaces to overwrite previous digits

  // LED and Buzzer logic
  if (distance > DIST_SAFE) {
    digitalWrite(GREEN, HIGH);
    digitalWrite(YELLOW, LOW);
    digitalWrite(RED, LOW);
    digitalWrite(BUZZER, LOW);
    lcd.setCursor(0, 1);
    lcd.print("LID CLOSED       ");
  } 
  else if (distance > DIST_WARNING) {
    digitalWrite(GREEN, LOW);
    digitalWrite(YELLOW, HIGH);
    digitalWrite(RED, LOW);
    digitalWrite(BUZZER, LOW);
    lcd.setCursor(0, 1);
    lcd.print("Getting Close   ");
  } 
  else {
    digitalWrite(GREEN, LOW);
    digitalWrite(YELLOW, LOW);
    digitalWrite(RED, HIGH);
    digitalWrite(BUZZER, HIGH);
    lcd.setCursor(0, 1);
    lcd.print("LID OPEN        ");
  }

  delay(300); // small delay for stability
}