#define table_size 91

extern  void line(int x0, int y0, int x1, int y1, uint16_t color);

int32_t spiro_xofs = 120;
int32_t spiro_yofs = 120;

/* -------------------------------------------------------------
     LookUp Table fuer Sinuswerte, Werte multipliziert mit 1000
   -------------------------------------------------------------- */

#define sin_scale 1000
const int16_t sindeg_lookup[table_size] =
{
     0,   17,   34,   52,   69,   87,  104,  121,  139,  156,
    173,  190,  207,  224,  241,  258,  275,  292,  309,  325,
    342,  358,  374,  390,  406,  422,  438,  453,  469,  484,
    500,  515,  529,  544,  559,  573,  587,  601,  615,  629,
    642,  656,  669,  681,  694,  707,  719,  731,  743,  754,
    766,  777,  788,  798,  809,  819,  829,  838,  848,  857,
    866,  874,  882,  891,  898,  906,  913,  920,  927,  933,
    939,  945,  951,  956,  961,  965,  970,  974,  978,  981,
    984,  987,  990,  992,  994,  996,  997,  998,  999,  999,
   1000
};

/*
#define sin_scale 10000
int32_t sindeg_lookup[table_size] =
{
      0,   174,   348,   523,   697,   871,  1045,  1218,  1391,  1564,
   1736,  1908,  2079,  2249,  2419,  2588,  2756,  2923,  3090,  3255,
   3420,  3583,  3746,  3907,  4067,  4226,  4383,  4539,  4694,  4848,
   5000,  5150,  5299,  5446,  5591,  5735,  5877,  6018,  6156,  6293,
   6427,  6560,  6691,  6819,  6946,  7071,  7193,  7313,  7431,  7547,
   7660,  7771,  7880,  7986,  8090,  8191,  8290,  8386,  8480,  8571,
   8660,  8746,  8829,  8910,  8987,  9063,  9135,  9205,  9271,  9335,
   9396,  9455,  9510,  9563,  9612,  9659,  9702,  9743,  9781,  9816,
   9848,  9876,  9902,  9925,  9945,  9961,  9975,  9986,  9993,  9998,
  10000
};
*/

/* -------------------------------------------------------------
                              isin

     gibt einen Sinus-Wert als int32_Integerwert * 1000 zurueck,
     Wert aus der LookUp-Table gelesen
   ------------------------------------------------------------- */
int32_t isin(int32_t deg)
{
  deg %= 360;
  if (deg < 0)
  {
    deg += 360;
  }

  if (deg < 90)
  {
    return sindeg_lookup[deg];
  }
  else
  if (deg < 180)
  {
    return sindeg_lookup[180 - deg];
  }
  else
  if (deg < 270)
  {
    return -sindeg_lookup[deg - 180];
  }
  else
  {
    return -sindeg_lookup[360 - deg];
  }
}

/* -------------------------------------------------------------
                              icos
        Kosinus aus Sinus berechnen (cos(x) = sin(x + 90))
   ------------------------------------------------------------- */
#define icos(deg)   (isin(deg + 90))

/* -------------------------------------------------------------
                            spirograph

         Spirograph ohne math.h und ohne Gleitkommazahl
   ------------------------------------------------------------- */
void ispirograph(int32_t outer_r, int32_t inner_r, int32_t dif_r, int32_t steps, uint32_t col)
{
  int32_t k, i, x,y;
  int32_t winkel1, winkel2;
  int32_t prev_x, prev_y;
  int32_t cos1, cos2, sin1, sin2;
  int32_t ratio;

  k = outer_r - inner_r;
  ratio = (k * sin_scale) / inner_r;   // = (outer - inner) / ( inner * sin_scale)

  winkel1 = 0;
  winkel2 = 0;

  prev_x = -1, prev_y = -1;

  steps = steps * inner_r;

  for (i = 0; i < steps; ++i)
  {
    cos1 = icos(winkel1);
    sin1 = isin(winkel1);
    cos2 = icos(winkel2 / sin_scale);
    sin2 = isin(winkel2 / sin_scale);

    x = (k * cos1 + dif_r * cos2) / sin_scale + spiro_xofs;
    y = (k * sin1 - dif_r * sin2) / sin_scale + spiro_yofs;

    if (prev_x != -1) line(prev_x, prev_y, x, y, col);

    prev_x = x;
    prev_y = y;

    winkel1 = (winkel1 + 1) % 360;
    winkel2 = winkel2 + ratio;            // absichtlich nicht modulieren
  }
}