#include <TFT_eSPI.h>
#include <SPI.h>
#include "colors.h"

TFT_eSPI tft = TFT_eSPI();
// With 1024 stars the update rate is ~65 frames per second
#define NSTARS 1024
uint8_t sx[NSTARS] = {};
uint8_t sy[NSTARS] = {};
uint8_t sz[NSTARS] = {};
uint8_t za, zb, zc, zx;
// Fast 0-255 random number generator from http://eternityforest.com/Projects/rng.php:
uint8_t __attribute__((always_inline)) rng() {
  zx++;
  za = (za ^ zc ^ zx);
  zb = (zb + za);
  zc = ((zc + (zb >> 1))^za);
  return zc;
}

void setup() {
  za = random(256);
  zb = random(256);
  zc = random(256);
  zx = random(256);
  Serial.begin(115200);
  tft.init();
  tft.setRotation(1);
  tft.fillScreen(TFT_BLACK);
  // fastSetup() must be used immediately before fastPixel() to prepare screen
  // It must be called after any other graphics drawing function call if fastPixel()
  // is to be called again
  // Prepare plot window range for fast pixel plotting
  // tft.fastSetup();
}

void loop() {
  unsigned long t0 = micros();
  uint8_t spawnDepthVariation = 255;
  for (int i = 0; i < NSTARS; ++i) {
    if (sz[i] <= 1) {
      sx[i] = 160 - 120 + rng();
      sy[i] = rng();
      sz[i] = spawnDepthVariation--;
    } else {
      int old_screen_x = ((int)sx[i] - 160) * 256 / sz[i] + 160;
      int old_screen_y = ((int)sy[i] - 120) * 256 / sz[i] + 120;
      // This is a faster pixel drawing function for occasions where many single pixels must be drawn
      tft.drawPixel(old_screen_x, old_screen_y, TFT_BLACK);
      sz[i] -= 2;
      if (sz[i] > 1) {
        int screen_x = ((int)sx[i] - 160) * 256 / sz[i] + 160;
        int screen_y = ((int)sy[i] - 120) * 256 / sz[i] + 120;
        if (screen_x >= 0 && screen_y >= 0 && screen_x < 320 && screen_y < 240) {
          uint8_t r, g, b;
          r = g = b = 255 - sz[i];
          tft.drawPixel(screen_x, screen_y, tft.color565(r, g, b));
        } else
          sz[i] = 0; // Out of screen, die
      }
    }
  }
  unsigned long t1 = micros();
  // static char timeMicros[8] = {};
  // Calculate frames per second
  Serial.println(1.0 / ((t1 - t0) / 1000000.0));
}