#include <Adafruit_NeoPixel.h>
#define LED_PIN PB2

int color1[3];
int color2[3];
int color3[3];
int color4[3];
int fade_length = 300;
int frame_delay = 0;

Adafruit_NeoPixel strip = Adafruit_NeoPixel(3, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  strip.begin();
  strip.show();
  randomSeed(analogRead(A0));
  random_color( color1 );
  random_color( color2 );
  random_color( color3 );
  random_color( color4 );
}

void loop() {
  for (int i=0; i <= fade_length; i++) {
    int fade_color[3];
    color_gradient( fade_color, color1, color2, i, fade_length );
    strip.setPixelColor( 0, strip.Color( fade_color[0], fade_color[1], fade_color[2] ) );
    color_gradient( fade_color, color2, color3, i, fade_length );
    strip.setPixelColor( 1, strip.Color( fade_color[0], fade_color[1], fade_color[2] ) );
    color_gradient( fade_color, color3, color4, i, fade_length );
    strip.setPixelColor( 2, strip.Color( fade_color[0], fade_color[1], fade_color[2] ) );
    strip.show();
    delay(frame_delay);
  }
  for (int i=0; i <= 2; i++){
    color1[i] = color2[i];
    color2[i] = color3[i];
    color3[i] = color4[i];
  }
  random_color( color4 );
}

void random_color( int *color ) {
  color[0] = random( 0, 255 );
  color[1] = random( 0, 255 );
  color[2] = random( 0, 255 );
}

void color_gradient( int *out, int *in1, int *in2, int u, int t ) {
  float point = float(u) / float(t);
  for (int i=0; i <= 2; i++){
    if( in1[i] > in2[i] ) {
      out[i] = in1[i] - ( ( in1[i] - in2[i] ) * point );
    } else if ( in1[i] < in2[i]) {
      out[i] = in1[i] + ( ( in2[i] - in1[i] ) * point );
    } else {
      out[i] = in1[i];
    }
  }
}