# include <Adafruit_NeoPixel.h>

/*
  Serial Buffer Ring Demo

  Green  = bytes waiting in the serial receive buffer
  Yellow = byte position just consumed

  Try Serial Monitor at 300 baud to watch the buffer fill visibly.
*/

const byte LED_PIN = 6;
const byte LED_COUNT = 32;

const unsigned long CHARACTER_INTERVAL_MS = 333;
const unsigned long YELLOW_MS = 100;

Adafruit_NeoPixel ring(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

unsigned long lastCharacterTime = 0;
unsigned long yellowUntil = 0;

byte readPixel = 0;
byte yellowPixel = 0;

void showBufferLevel(int available)
{
  unsigned long now = millis();

  ring.clear();

  int shown = min(available, LED_COUNT);

  for (int i = 0; i < shown; i++)
  {
    byte pixel = (readPixel + i) % LED_COUNT;
    ring.setPixelColor(pixel, 0x00ff00);   // green
  }

  if (now < yellowUntil)
  {
    ring.setPixelColor(yellowPixel, 0xffff00); // yellow
  }

  ring.show();
}

void setup()
{
  Serial.begin(300);

  while (!Serial)
  {
    ;
  }

  ring.begin();
  ring.clear();
  ring.show();

  Serial.println();
  Serial.println("serial demo\n");

if (0) {
  Serial.println("Paste text. Green shows waiting bytes.");
  Serial.println("Yellow marks the byte just consumed.");
  Serial.println("Bytes are s l o w l y read");
  Serial.println();
}
}

void loop()
{
  unsigned long now = millis();

  if (Serial.available() > 0 &&
      now - lastCharacterTime >= CHARACTER_INTERVAL_MS)
  {
    int ch = Serial.read();

    yellowPixel = readPixel;
    yellowUntil = now + YELLOW_MS;

    readPixel = (readPixel + 1) % LED_COUNT;
    lastCharacterTime = now;

    Serial.print("# = ");
    Serial.print(Serial.available());
    Serial.print("'");

    if (ch >= 32 && ch <= 126)
      Serial.write((char)ch);
    else
      Serial.print('?');

    Serial.println("'");
  }

  showBufferLevel(Serial.available());
}