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

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

int x = 0; // This will hold the count of state changes
int inputPin = A0; // Pin to read input from the sensor
int state = 0; // Current state of input pin

const int buzzerPin = 12; // Pin connected to the buzzer
const int ledPin = 4; // Pin connected to the LED
unsigned long previousMillis = 0; // Last time the alert was triggered
const long interval = 60000; // Interval at which to beep and blink (1 minute)
const long ledOnDuration = 1000; // Duration the LED should stay on (1 second for demonstration)
unsigned long ledTurnedOnAt = 0; // When the LED was last turned on
bool ledIsOn = false; // State of the LED

void setup() {
  lcd.init(); // Initialize the LCD
  lcd.backlight(); // Turn on the backlight
  lcd.setCursor(0, 0);
  lcd.print(" Tachometer (WC) ");
  lcd.setCursor(0, 1);
  lcd.print(x);
  lcd.print(" =RPM ");

  pinMode(buzzerPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(inputPin, INPUT);
}

void loop() {
  unsigned long currentMillis = millis();
  
  int sensorValue = digitalRead(inputPin);

  // Check for state changes and update counter
  if (state == 0 && sensorValue == HIGH) {
    state = 1;
    x += 1;
    lcd.setCursor(0, 1);
    lcd.print(x);
    lcd.print(" =RPM "); // Clear any leftover characters
  } else if (sensorValue == LOW) {
    state = 0;
  }

  // Manage timing for buzzer and LED
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    digitalWrite(buzzerPin, HIGH); // Turn on buzzer
    digitalWrite(ledPin, HIGH); // Turn on LED
    ledIsOn = true;
    ledTurnedOnAt = currentMillis;
  }

  if (ledIsOn && (currentMillis - ledTurnedOnAt >= ledOnDuration)) {
    digitalWrite(ledPin, LOW); // Turn off LED
    digitalWrite(buzzerPin, LOW); // Turn off buzzer after a short beep
    ledIsOn = false;
  }
}