// https://wokwi.com/projects/385841513818337281
// https://forum.arduino.cc/t/fader-pickup-catch-mode/1206227

# include <Adafruit_NeoPixel.h>

# define N_REAL   16
# define PIN      8

# define threshold  25    // to detect new value

// Global variables for lights and CAN communication
Adafruit_NeoPixel led(N_REAL, PIN, NEO_GRB + NEO_KHZ800);

void setup()
{
  Serial.begin(115200); Serial.println("first things first");

  led.begin();
  led.setPixelColor(1,  0xff0000);
  led.show();
  delay(777);
}

bool trackA = true;

void loop()
{
  static int lastA;
  static int lastB;

  static int output;

  int valA = analogRead(A0);
  int valB = analogRead(A1);

  if (abs(lastA - valA) > threshold) {
    lastA = valA;

    if (abs(lastB - lastA) < threshold) trackA = true;
  }

  if (abs(lastB - valB) > threshold) {
    lastB = valB;

    if (abs(lastB - lastA) < threshold) trackA = false;
  }

  led.clear();
  if (trackA) {
    output = valA;
    led.setPixelColor(valA / 64, 0xc00040); 
  }
  else {
    output = valA;
    led.setPixelColor(valB / 64, 0x404080); 
  }
  led.show();
}

void message(char *theMessage)
{
  static unsigned int counter;

  Serial.print(counter); Serial.print(" ");
  Serial.println(theMessage);

  counter++;
}