#include <Adafruit_NeoPixel.h>

// led count
#define NUMPIXELS 24  // Number of pixel in strip

// data pin
#define PIN 6

Adafruit_NeoPixel strip = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

uint32_t fire_color = strip.Color(80, 35, 00);
uint32_t off_color = strip.Color(0, 0, 0);

///
/// Fire simulator
///
class NeoFire {
    Adafruit_NeoPixel& strip;
  public:

    NeoFire(Adafruit_NeoPixel&);
    void Draw();
    void Clear();
    void AddColor(uint8_t position, uint32_t color);
    void SubstractColor(uint8_t position, uint32_t color);
    uint32_t Blend(uint32_t color1, uint32_t color2);
    uint32_t Substract(uint32_t color1, uint32_t color2);
};

///
/// Constructor
///
NeoFire::NeoFire(Adafruit_NeoPixel& n_strip)
  : strip(n_strip) {
}

///
/// Set all colors
///
void NeoFire::Draw() {
  Clear();

  for (int i = 0; i < NUMPIXELS; i++) {
    AddColor(i, fire_color);
    int r = random(80);
    uint32_t diff_color = strip.Color(r, r / 2, r / 2);
    SubstractColor(i, diff_color);
  }

  strip.show();
}

///
/// Set color of LED
///
void NeoFire::AddColor(uint8_t position, uint32_t color) {
  uint32_t blended_color = Blend(strip.getPixelColor(position), color);
  strip.setPixelColor(position, blended_color);
}

///
/// Set color of LED
///
void NeoFire::SubstractColor(uint8_t position, uint32_t color) {
  uint32_t blended_color = Substract(strip.getPixelColor(position), color);
  strip.setPixelColor(position, blended_color);
}

///
/// Color blending
///
uint32_t NeoFire::Blend(uint32_t color1, uint32_t color2) {
  uint8_t r1, g1, b1;
  uint8_t r2, g2, b2;
  uint8_t r3, g3, b3;

  r1 = (uint8_t)(color1 >> 16),
  g1 = (uint8_t)(color1 >> 8),
  b1 = (uint8_t)(color1 >> 0);

  r2 = (uint8_t)(color2 >> 16),
  g2 = (uint8_t)(color2 >> 8),
  b2 = (uint8_t)(color2 >> 0);

  return strip.Color(constrain(r1 + r2, 0, 255), constrain(g1 + g2, 0, 255), constrain(b1 + b2, 0, 255));
}

///
/// Color blending
///
uint32_t NeoFire::Substract(uint32_t color1, uint32_t color2) {
  uint8_t r1, g1, b1;
  uint8_t r2, g2, b2;
  uint8_t r3, g3, b3;
  int16_t r, g, b;

  r1 = (uint8_t)(color1 >> 16),
  g1 = (uint8_t)(color1 >> 8),
  b1 = (uint8_t)(color1 >> 0);

  r2 = (uint8_t)(color2 >> 16),
  g2 = (uint8_t)(color2 >> 8),
  b2 = (uint8_t)(color2 >> 0);

  r = (int16_t)r1 - (int16_t)r2;
  g = (int16_t)g1 - (int16_t)g2;
  b = (int16_t)b1 - (int16_t)b2;
  if (r < 0) r = 0;
  if (g < 0) g = 0;
  if (b < 0) b = 0;

  return strip.Color(r, g, b);
}

///
/// Every LED to black
///
void NeoFire::Clear() {
  for (uint16_t i = 0; i < strip.numPixels(); i++)
    strip.setPixelColor(i, off_color);
}

NeoFire fire(strip);

///
/// Setup
///
void setup() {
  strip.begin();
  strip.show();  // Initialize all pixels to 'off'
}

///
/// Main loop
///
void loop() {
  fire.Draw();
  delay(random(50, 150));
}