// Define pins for LEDs and sensor
const int trigPin = 9;
const int echoPin = 10;
const int ledGreen = 3;
const int ledYellow = 4;
const int ledRed = 5;

long duration;
int distance;
unsigned long parkingStartTime = 0;
bool parkingActive = false;

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

void loop() {
  // Measure distance
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;

  // Logic for LEDs and parking timer
  if (distance > 100) {
    // Reset system
    resetLEDs();
    parkingStartTime = 0;
    parkingActive = false;
  } 
  else if (distance > 50 && distance <= 100) {
    // Medium range: Green LED
    resetLEDs();
    digitalWrite(ledGreen, HIGH);
  } 
  else if (distance > 20 && distance <= 50) {
    // Close range: Yellow LED
    resetLEDs();
    digitalWrite(ledYellow, HIGH);
  } 
  else if (distance <= 20) {
    // Very close range: Red LED blinks and start parking timer
    resetLEDs();
    blinkRedLED();

    if (parkingStartTime == 0) {
      parkingStartTime = millis();  // Start timing
    } else if (millis() - parkingStartTime >= 5000) {
      // Start parking counter after 5 seconds
      parkingActive = true;
    }
  }

  // Parking time display
  if (parkingActive) {
    unsigned long parkingTime = (millis() - parkingStartTime) / 1000;
    Serial.print("Parking Time: ");
    Serial.print(parkingTime);
    Serial.println(" seconds");
  }
}

// Helper function to reset LEDs
void resetLEDs() {
  digitalWrite(ledGreen, LOW);
  digitalWrite(ledYellow, LOW);
  digitalWrite(ledRed, LOW);
}

// Helper function to blink red LED
void blinkRedLED() {
  static bool ledState = false;
  static unsigned long lastBlinkTime = 0;

  if (millis() - lastBlinkTime >= 200) {
    ledState = !ledState;
    digitalWrite(ledRed, ledState);
    lastBlinkTime = millis();
  }
}