#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// defines pin numbers
const int trigPin = 9;
const int echoPin = 10;
const int buzzer = 11;
const int redLedPin = 13;
const int greenLedPin = 8;
const int stopButtonPin = 4; // Stop button pin

// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27, 16, 2);

// defines variables
long duration;
int distance;
bool stoppedManually = false; // Flag for manual stop

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzer, OUTPUT);
  pinMode(redLedPin, OUTPUT);
  pinMode(greenLedPin, OUTPUT);
  pinMode(stopButtonPin, INPUT_PULLUP); // Set the stopButtonPin as an INPUT_PULLUP
  
  // Initialize the LCD 
  lcd.init();                      
  lcd.backlight();
  
  Serial.begin(9600);
}

void loop() {
  // Read the state of the stop button
  bool stopButtonState = digitalRead(stopButtonPin) == LOW; // Active LOW button

  // Only allow the stop button to work if the distance is less than 100
  if (stopButtonState && distance <= 100) {
    stoppedManually = true;
  }

  // Clears the trigPin conditionally if not manually stopped
  if (!stoppedManually) {
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);

    // Sets the trigPin on HIGH state for 10 micro seconds
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);

    // Reads the echoPin, returns the sound wave travel time in microseconds
    duration = pulseIn(echoPin, HIGH);

    // Calculating the distance
    distance = duration * 0.034 / 2;
  }

  // Display the distance on the LCD
  lcd.setCursor(0, 0);
  lcd.print("Dist: ");
  lcd.print(distance);
  lcd.print(" cm   ");

  // Conditions to turn the LEDs and buzzer on/off based on the distance
  if (!stoppedManually && distance <= 100) {
    digitalWrite(greenLedPin, HIGH);
    digitalWrite(buzzer, HIGH);
  } else {
    digitalWrite(greenLedPin, LOW);
    digitalWrite(buzzer, LOW);
  }

  // Handle red LED and LCD message for critical distance
  if (!stoppedManually && distance > 200) {
    digitalWrite(redLedPin, HIGH);
    lcd.setCursor(0, 1);
    lcd.print("All Good!       ");
  } else {
    digitalWrite(redLedPin, LOW);
  }

  // Handle LCD message for manual stop
  if (stoppedManually) {
    lcd.setCursor(0, 1);
    lcd.print("Manual Stopped  "); // Clear the rest of the line with spaces
  } else if (distance <= 100) {
    lcd.setCursor(0, 1);
    lcd.print("Critical!       ");
  } else {
    lcd.setCursor(0, 1);
    lcd.print("                "); // Clear the second line
  }

  // Prints the distance on the Serial Monitor
  Serial.print("Distance: ");
  Serial.println(distance);
}