#include <stdint.h>
#include <cmath>
#include <cstdio>
extern "C" {
  extern void   print_table  (void);
  extern double ComputeRed   (double);
  extern double ComputeGreen (double);
  extern double ComputeBlue  (double);
};
union Color {
  struct _c {
    uint8_t g, r, b, a;
    explicit _c (const uint8_t _r, const uint8_t _g, const uint8_t _b) noexcept :
                g(_g), r(_r), b(_b), a(0u) {}
  } c;
  uint32_t number;
  explicit Color (const uint8_t r, const uint8_t g, const uint8_t b) : c(r, g, b) {}
};
#if 0
static Color getColor (const int index) {
  const double fi = 2.0 * M_PI / 3.0;       // úhel posunu argumentu barvy
  const double ph =       M_PI / 128.0;
  double a1, a2, a3;
  uint8_t  r,g,b;                     // proměnné barvy
  // výpočet barvy - duha
  a1 = (double) index * ph;           // argument pro r
  a2 = a1 + fi;                       // argument pro g
  a3 = a2 + fi;                       // argument pro b
  r = (int)(127.0 + 127.0*sin(a1));
  g = (int)(127.0 + 127.0*sin(a2));
  b = (int)(127.0 + 127.0*sin(a3));
  Color color(r, g, b);
  return color;
}
#else
static uint8_t Gauss (const double x, const double x0) {
  const double sigma = 1.0 / 2048.0, arg = x - x0;
  double r = 256.0 * exp (-sigma * arg * arg);
  return uint8_t (r);
}
static Color getColor (const int index) {
  uint8_t  r=0,g=0,b=0;                  // proměnné barvy
  r = Gauss(index, 85.333);
  g = Gauss(index, 170.67);
  b = Gauss(index,   0.01) + Gauss(index, 256.0);
  Color color(r, g, b);
  return color;
}
#endif
double ComputeRed   (double x) {
  Color c = getColor(x);
  return double (c.c.r);
}
double ComputeGreen (double x) {
  Color c = getColor(x);
  return double (c.c.g);
}
double ComputeBlue  (double x) {
  Color c = getColor(x);
  return double (c.c.b);
}

void print_table () {
  FILE * out = fopen("../table.c","w");
  if (!out) return;
  fprintf(out, "const unsigned table [] = {");
  for (unsigned n=0u; n<256u; n++) {
    if ((n%8) == 0u) fprintf(out, "\n");
    const Color c = getColor(n);
    fprintf(out, "  0x%06X,", c.number);
  }
  fprintf(out, "\n};\n");
  fclose(out);
}