#include <Servo.h>
#include <LiquidCrystal_I2C.h> // Include the LCD Library

// --- Configuration ---
Servo distanceGauge; 

// I2C LCD Address is usually 0x27 in Wokwi
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Pin Definitions
const int echoPin = 2;
const int trigPin = 3;
const int greenPin = 5;
const int redPin   = 6;
const int servoPin = 9;
const int buzzerPin = 10;
const int potPin   = A0;

// Variables
long duration;
int distance;
int safetyLimit;

void setup() {
  Serial.begin(9600);

  // 1. Setup Pins
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);

  // 2. Attach Servo
  distanceGauge.attach(servoPin);

  // 3. Initialize LCD
  lcd.init();
  lcd.backlight();
  
  // Show a startup message
  lcd.setCursor(0, 0); // Column 0, Row 0
  lcd.print("System Starting");
  lcd.setCursor(0, 1); // Column 0, Row 1
  lcd.print("Please Wait...");
  delay(2000);
  lcd.clear();

  // Draw static labels (to prevent screen flickering)
  lcd.setCursor(0, 0);
  lcd.print("Dist:      cm"); 
  lcd.setCursor(0, 1);
  lcd.print("Limit:     cm");
}

void loop() {
  // --- A. Read Potentiometer (Limit) ---
  int potValue = analogRead(potPin);
  safetyLimit = map(potValue, 0, 1023, 10, 100);

  // --- B. Read Ultrasonic Sensor (Distance) ---
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;

  // --- C. Update Servo ---
  int angle = map(constrain(distance, 0, 200), 0, 200, 0, 180);
  distanceGauge.write(angle);

  // --- D. Update LCD ---
  // We only print the numbers to avoid clearing the whole screen (prevents flicker)
  
  // Row 0: Real Distance
  lcd.setCursor(6, 0); 
  lcd.print("   ");    // Clean previous number
  lcd.setCursor(6, 0);
  lcd.print(distance);

  // Row 1: Safety Limit
  lcd.setCursor(7, 1); 
  lcd.print("   ");    // Clean previous number
  lcd.setCursor(7, 1);
  lcd.print(safetyLimit);

  // --- E. Logic: Safe vs Danger ---
  if (distance < safetyLimit) {
    // === DANGER ===
    digitalWrite(redPin, HIGH);
    digitalWrite(greenPin, LOW);
    tone(buzzerPin, 1000); 
    
    // Optional: Show "!" on LCD to warn visually
    lcd.setCursor(15, 0);
    lcd.print("!");
  } 
  else {
    // === SAFE ===
    digitalWrite(redPin, LOW);
    digitalWrite(greenPin, HIGH);
    noTone(buzzerPin);
    
    // Clear warning
    lcd.setCursor(15, 0);
    lcd.print(" ");
  }

  delay(150); // Slightly slower update to make LCD readable
}