#define echoPin 3 // Echo Pin
#define trigPin 2 // Trigger Pin
#define LED_EMPTY 13
#define LED_FULL 11
#define LED_PENDING 12
#define BUZZER 7

void ULT(void);
void displayMessage(const char *line1, const String &line2);
void updateLcdDisplay();

int maximumRange = 200; // Maximum range needed
int minimumRange = 0;   // Minimum range needed
long duration, distance; // Duration used to calculate distance

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 14, 15); // Change the HEX address

int IR1 = 2;
int IR2 = 4;
int SmokeDetectorPin = 6; // Digital pin for the smoke detector
int BuzzerPin = 7;        // Digital pin for the buzzer

int Slot = 4;               // Set the initial available parking slots to 1
int carsParked = 0;         // Variable to count the number of cars parked
bool carDetected = false;

unsigned long lastLcdUpdate = 0;     // Variable to track the time of the last LCD update
unsigned long lcdUpdateInterval = 1000; // Update the LCD every 1000 milliseconds (1 second)

void setup()
{
  Serial.begin(115200);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(LED_EMPTY, OUTPUT);
  pinMode(LED_FULL, OUTPUT);
  pinMode(LED_PENDING, OUTPUT);
  pinMode(BUZZER, OUTPUT);

  lcd.begin(16, 2); // Initialize LCD with 16 columns and 2 rows
  lcd.backlight();
  pinMode(IR1, INPUT);
  pinMode(IR2, INPUT);
  pinMode(SmokeDetectorPin, INPUT);
  pinMode(BuzzerPin, OUTPUT);

  lcd.setCursor(0, 0);
  lcd.print("     ARDUINO    ");
  lcd.setCursor(0, 1);
  lcd.print(" PARKING SYSTEM ");
  delay(2000);
  lcd.clear();
}

void loop()
{
  ULT();
  Serial.println(distance); // Show distance

  /* vacant, out green light */
  if (distance >= 200)
  {
    digitalWrite(LED_EMPTY, HIGH);
    digitalWrite(LED_PENDING, LOW);
    digitalWrite(LED_FULL, LOW);
    Serial.println("Empty Space.");
    carDetected = false; // Reset the flag when the space is empty
  }
  /* someone is parking, out yellow light */
  else if (distance < 200 && distance >= 50)
  {
    digitalWrite(LED_EMPTY, LOW);
    digitalWrite(LED_PENDING, HIGH);
    digitalWrite(LED_FULL, LOW);
    tone(BUZZER, 800);
    delay(100);
    digitalWrite(LED_EMPTY, LOW);
    digitalWrite(LED_PENDING, LOW);
    digitalWrite(LED_FULL, LOW);
    noTone(BUZZER);
    delay(500);
    Serial.println("Car is going to park here or going out.");

    // Increment the number of cars parked
    carsParked++;
    carDetected = true; // Set the flag to true to indicate a car is detected
  }
  /* occupied, out red light */
  else
  {
    digitalWrite(LED_EMPTY, LOW);
    digitalWrite(LED_PENDING, LOW);
    digitalWrite(LED_FULL, HIGH);
    Serial.println("Car is Parking.");

    // Increment the number of cars parked
    carsParked++;
    carDetected = true; // Set the flag to true to indicate a car is detected
  }

  if (digitalRead(IR1) == LOW && !carDetected)
  {
    if (Slot > 0)
    {
      Slot--;

      // Increment the number of cars parked
      carsParked++;
      carDetected = true; // Set the flag to true to indicate a car is detected
    }
    else
    {
      displayMessage("    SORRY :(    ", "  Parking Full  ");
    }
  }

  if (digitalRead(IR2) == LOW && !carDetected)
  {
    Slot++;

    // Decrement the number of cars parked
    carsParked--;
    carDetected = true; // Set the flag to true to indicate a car is detected
  }

  // Update the LCD display with a delay
  if (millis() - lastLcdUpdate >= lcdUpdateInterval)
  {
    updateLcdDisplay();
    lastLcdUpdate = millis();
  }
}

void ULT()
{
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);

  // Calculate the distance (in cm) based on the speed of sound.
  distance = duration / 58.2;
}

void displayMessage(const char *line1, const String &line2)
{
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(line1);
  lcd.setCursor(0, 1);
  lcd.print(line2);
}

void updateLcdDisplay()
{
  if (digitalRead(SmokeDetectorPin) == HIGH)
  {
    displayMessage("   WARNING!   ", " Smoke Detected ");
    digitalWrite(BuzzerPin, HIGH); // Turn on the buzzer
  }
  else
  {
    displayMessage("    WELCOME!    ", "Slot Left: " + String(Slot));
    digitalWrite(BuzzerPin, LOW); // Turn off the buzzer
  }
}