#include "NeoPixelController.h"

#include <Adafruit_NeoPixel.h>

namespace {
constexpr uint8_t kPin = 18;
constexpr uint16_t kCount = 1;
constexpr uint32_t kColors[] = {
  0xFF0000, 0xFF8000, 0xFFFF00, 0x00FF00,
  0x0000FF, 0x4B0082, 0x8F00FF
};
constexpr uint8_t kColorCount = sizeof(kColors) / sizeof(kColors[0]);

Adafruit_NeoPixel pixels(kCount, kPin, NEO_GRB + NEO_KHZ800);
}

void NeoPixelController::begin() {
  pixels.begin();
  pixels.setBrightness(255);
  pixels.setPixelColor(0, kColors[kStoppedColorIndex]);
  pixels.show();
}

void NeoPixelController::setPlaying(bool playing) {
  isPlaying_ = playing;

  if (isPlaying_) {
    transitionStart_ = millis();
    lastUpdate_ = transitionStart_;
    return;
  }

  colorIndex_ = kStoppedColorIndex;
  pixels.setPixelColor(0, kColors[colorIndex_]);
  pixels.show();
}

void NeoPixelController::update() {
  if (!isPlaying_ || millis() - lastUpdate_ < kUpdateIntervalMs) {
    return;
  }

  unsigned long now = millis();
  lastUpdate_ = now;
  unsigned long transitionElapsed = now - transitionStart_;
  if (transitionElapsed >= kTransitionMs) {
    colorIndex_ = (colorIndex_ + transitionElapsed / kTransitionMs) % kColorCount;
    transitionStart_ = now;
    transitionElapsed = 0;
  }

  uint8_t nextColorIndex = (colorIndex_ + 1) % kColorCount;
  uint32_t currentColor = kColors[colorIndex_];
  uint32_t nextColor = kColors[nextColorIndex];
  uint8_t red = ((currentColor >> 16) * (kTransitionMs - transitionElapsed)
    + (nextColor >> 16) * transitionElapsed) / kTransitionMs;
  uint8_t green = (((currentColor >> 8) & 0xFF) * (kTransitionMs - transitionElapsed)
    + ((nextColor >> 8) & 0xFF) * transitionElapsed) / kTransitionMs;
  uint8_t blue = ((currentColor & 0xFF) * (kTransitionMs - transitionElapsed)
    + (nextColor & 0xFF) * transitionElapsed) / kTransitionMs;
  pixels.setPixelColor(0, red, green, blue);
  pixels.show();
}