#include <LiquidCrystal.h>
#include <math.h>

// lcd(RS, E, D4, D5, D6, D7) pin configuration for the LCD screen
const int rs = 2, en = 3, d4 = 4, d5 = 5, d6 = 6, d7 = 7;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7); // Initialise the LCD

const int sensorPin = A0;  // Analog pin connected to the potentiometer.
const int led1 = 12;       // Pin for the first LED.
const int led2 = 11;       // Pin for the second LED.
const int led3 = 10;       // Pin for the third LED.
const int led4 = 9;        // Pin for the fourth LED.
// The 4 LEDs will indicate the tempo (in any time signature).

int sensorValue;           // Variable to store potentiometer reading.
int bpm;                // Variable to store the calculated BPM (beats per minute).
double interval;           // Time interval (in ms) between each LED flash.
int counter = 0;           // Counter to track which LED should be turned on.
int timeSignature = 4;     // Default time signature (e.g., 4/4), can be changed.

void setup() {
  pinMode(led1, OUTPUT);   // Set the first LED as output.
  pinMode(led2, OUTPUT);   // Set the second LED as output.
  pinMode(led3, OUTPUT);   // Set the third LED as output.
  pinMode(led4, OUTPUT);   // Set the fourth LED as output.
  
  lcd.begin(16, 2);        // Initialise the LCD to have 16 columns and 2 rows.
  lcd.print("BPM:");       // Print "BPM:" on the LCD to label the BPM display.
  
  Serial.begin(9600);      // Start the serial communication at 9600 baud rate.
}

void loop() {
  lcd.setCursor(5, 0);  // Move the cursor to the 6th character of the first row on the LCD.
  sensorValue = analogRead(sensorPin); // Read the current value of the potentiometer.
  bpm = map(sensorValue, 0, 1023, 60, 170); // Map the potentiometer value to a BPM range of 60 to 170.
  interval = 60000 / bpm; // Calculate the interval between beats in milliseconds.
  
  lcd.print(String(bpm)); // Display the BPM on the LCD screen.

  counter += 1; // Increment the counter to track the current beat.
  
  // Use the counter value to determine which LED should be turned on/off
  switch(counter) {
    case 1:
      digitalWrite(led1, HIGH);   // Turn on the first LED for the first beat.
      delay(interval);            // Wait for the calculated interval.
      digitalWrite(led1, LOW);    // Turn off the first LED after the delay.
      break;
      
    case 2:
      if (timeSignature >= 2) {   // Only flash the second LED if the time signature has at least 2 beats.
        digitalWrite(led2, HIGH);   // Turn on the second LED for the second beat.
        delay(interval);            // Wait for the calculated interval.
        digitalWrite(led2, LOW);    // Turn off the second LED after the delay.
      }
      break;
      
    case 3:
      if (timeSignature >= 3) {   // Only flash the third LED if the time signature has at least 3 beats.
        digitalWrite(led3, HIGH); // Turn on the third LED for the third beat.
        delay(interval);          // Wait for the calculated interval.
        digitalWrite(led3, LOW);  // Turn off the third LED after the delay.
      }
      break;
      
    case 4:
      if (timeSignature == 4) {   // Only flash the fourth LED if the time signature is 4/4 or greater.
        digitalWrite(led4, HIGH); // Turn on the fourth LED for the fourth beat.
        delay(interval);          // Wait for the calculated interval.
        digitalWrite(led4, LOW);  // Turn off the fourth LED after the delay.
      }
      break;
  }

  // Reset the counter based on the time signature
  if (counter >= timeSignature) {
    counter = 0; // Reset counter when reaching the end of the measure.
  }
}