// The Arduino standard library provides fundamental definitions and functions that make working with Arduino easier.
#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// Constants
const int IR_PIN = 2;  // Pin connected to the IR sensor
const int OLED_RESET_PIN = 4;  // Pin connected to the OLED reset
const int OLED_ADDRESS = 0x3C;  // I2C address of the OLED display

// Variables
volatile unsigned long pulseCount = 0;  // Number of pulses from the IR sensor
unsigned long lastPulseTime = 0;  // Time of the last pulse from the IR sensor
unsigned long lastUpdateTime = 0;  // Time of the last update to the OLED display
float speed = 0.0;  // Speed in km/h
float rpm = 0.0;  // Revolutions per minute
float batteryPercentage = 0.0;  // Battery percentage for lithium-ion battery

// Objects
Adafruit_SSD1306 display(OLED_RESET_PIN);

/*
 * Interrupt service routine for the IR sensor.
 * Increments the pulse count and updates the last pulse time.
 */
void irSensorISR() {
  pulseCount++;
  lastPulseTime = micros();
}

/*
 * Initializes the OLED display.
 */
void initializeDisplay() {
  display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDRESS);
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("Speed: 0.00 km/h");
  display.setCursor(0, 10);
  display.println("RPM: 0.00");
  display.setCursor(0, 40);
  display.println("Battery: 0.00%");
  display.display();
}

/*
 * Updates the speed, RPM, and battery percentage based on the pulse count and time.
 */
void updateData() {
  unsigned long currentTime = micros();
  unsigned long elapsedTime = currentTime - lastUpdateTime;
  
  // Calculate speed in km/h
  speed = (pulseCount * 2.25) / (elapsedTime / 1000000.0) * 3.6;
  
  // Calculate RPM
  rpm = (pulseCount * 60.0) / (elapsedTime / 1000000.0);
  
  // Calculate battery percentage (dummy calculation)
  batteryPercentage = analogRead(A0) * 100.0 / 1023.0;
  
  // Reset pulse count and update time
  pulseCount = 0;
  lastUpdateTime = currentTime;
}

/*
 * Updates the OLED display with the current speed, RPM, and battery percentage.
 */
void updateDisplay() {
  display.clearDisplay();
  display.setCursor(0, 0);
  display.print("Speed: ");
  display.print(speed, 2);
  display.println(" km/h");
  display.setCursor(0, 10);
  display.print("RPM: ");
  display.print(rpm, 2);
  display.println();
  display.setCursor(0, 40);
  display.print("Battery: ");
  display.print(batteryPercentage, 2);
  display.println("%");
  display.display();
}

void setup() {
  Serial.begin(9600);
  
  // Configure IR sensor pin as input
  pinMode(IR_PIN, INPUT);
  
  // Attach interrupt to the IR sensor pin
  attachInterrupt(digitalPinToInterrupt(IR_PIN), irSensorISR, FALLING);
  
  // Initialize OLED display
  initializeDisplay();
  
  // Set initial update time
  lastUpdateTime = micros();
}

void loop() {
  // Update data
  updateData();
  
  // Update display every 1 second
  if (millis() - lastUpdateTime >= 1000) {
    updateDisplay();
  }
}