// donut.c by Andy Sloane (@a1k0n)
// https://gist.github.com/a1k0n/8ea6516b4946ab36348fb61703dc3194
// Bruno Levy: added ANSI "pseudo-graphics", and RISC-V statistics

#define CPU_NAME "TordBoyau ULX3S" // Name of your CPU and FPGA board
#define MHZ 95                     // Frequency (without a timer we cannot guess)
#define USE_MUL                    // Define if you support RV32M 

// #define PRECISE // Define for a more accurate result (but it costs a bit)
#define START_FRAMES 20 // Number of frames without display
                        // (for accurate CPI/MIPS measurements)

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <math.h>

// 0 15 31 47 63 79 96 112 127 143 159 175 191 207 223 240 255
 
const char* colormap[34] = {
    "0",
    "8;5;232",
    "8;5;233",
    "8;5;234",
    "8;5;235",
    "8;5;236",
    "8;5;237",
    "8;5;238",
    "8;5;239",
    "8;5;240",
    "8;5;241",
    "8;5;242",
    "8;5;243",
    "8;5;244",
    "8;5;245",
    "8;5;246",
    "8;5;247",
    "8;5;248",
    "8;5;249",
    "8;5;250",
    "8;5;251",
    "8;5;252",
    "8;5;253",
    "8;5;254",
    "8;5;255",
    "7",
    "8;5;16",
    "8;5;17",
    "8;5;18",
    "8;5;19",
    "8;5;20",
    "8;5;21",
    "8;5;22",
    "8;5;23", 
};

int prev_color1=0;
int prev_color2=0;

char scanline[80];

#ifdef __linux__

uint64_t my_rdcycle() {
    return 0;
}

uint64_t my_rdinstret() {
    return 0;
}

#else

uint64_t my_rdcycle() {
    uint64_t result;
    uint32_t a0,a1,t0;
    {
        __asm__ __volatile__ ("rdcycleh %0" : "=r" (a1));
        __asm__ __volatile__ ("rdcycle %0" : "=r" (a0));
        __asm__ __volatile__ ("rdcycleh %0" : "=r" (t0));
    } while(t0 != a1);
    
    return ((uint64_t)a1 << 32) | a0;
}

uint64_t my_rdinstret() {
    uint64_t result;
    uint32_t a0,a1,t0;
    {
        __asm__ __volatile__ ("rdinstreth %0" : "=r" (a1));
        __asm__ __volatile__ ("rdinstret %0" : "=r" (a0));
        __asm__ __volatile__ ("rdinstreth %0" : "=r" (t0));
    } while(t0 != a1);
    
    return ((uint64_t)a1 << 32) | a0;
}

#endif

uint64_t stats_cycles_init = 0;
uint64_t stats_instructions_init = 0;
uint64_t stats_cycles = 0;
uint64_t stats_instructions = 0;
int stats_CPI_times_1000 = 0;

void stats_start() {
    stats_cycles_init       = my_rdcycle();
    stats_instructions_init = my_rdinstret();
}

void stats_end() {
    stats_cycles       = my_rdcycle() - stats_cycles_init;
    stats_instructions = my_rdinstret() - stats_instructions_init;
    if(stats_cycles==0) {
        stats_cycles++;
    }
    if(stats_instructions==0) {
        stats_instructions++;
    }
    stats_CPI_times_1000 = (int)((stats_cycles * 1000)/stats_instructions);
}

// Print "fixed point" number (integer/1000)
static void printk(uint64_t kx) {
    int intpart  = (int)(kx / 1000);
    int fracpart = (int)(kx % 1000);
    printf("%d.",intpart);
    if(fracpart<100) {
	printf("0");
    }
    if(fracpart<10) {
	printf("0");
    }
    printf("%d",fracpart);
}

static inline void setcolors(int fg, int bg) {
    printf("\033[4%s;3%sm",colormap[bg],colormap[fg]);
}

static inline void setpixel(int x, int y, int color) {
    if(y&1){
        int color1 = scanline[x];
        int color2 = color;
        if(color1 == color2) {
            if(prev_color1 == color1) {
                putchar(' ');
            } else {
                printf("\033[4%sm ",colormap[color1]);
                prev_color1 = color1;
            }
        } else {
            if(prev_color1 != color1 && prev_color2 != color2) {
                printf("\033[4%s;3%sm",colormap[color1],colormap[color2]);
                prev_color1 = color1;
                prev_color2 = color2;
            } else if(prev_color1 != color1) {
                printf("\033[4%sm",colormap[color1]);
                prev_color1 = color1;
            } else if(prev_color2 != color2) {
                printf("\033[3%sm",colormap[color2]);
                prev_color2 = color2;
            }
            printf("\u2583");
        }
    } else {
        scanline[x] = color;
    }
}

#define debug(...)
//#define debug printf

// torus radii and distance from camera
// these are pretty baked-in to other constants now, so it probably won't work
// if you change them too much.
const int dz = 5, r1 = 1, r2 = 2;

// "Magic circle algorithm"? DDA? I've seen this formulation in a few places;
// first in Hal Chamberlain's Musical Applications of Microprocessors, but not
// sure what to call it, or how to justify it theoretically. It seems to
// correctly rotate around a point "near" the origin, without losing magnitude
// over long periods of time, as long as there are enough bits of precision in x
// and y. I use 14 bits here.
#define R(s,x,y) x-=(y>>s); y+=(x>>s)

// CORDIC algorithm to find magnitude of |x,y| by rotating the x,y vector onto
// the x axis. This also brings vector (x2,y2) along for the ride, and writes
// back to x2 -- this is used to rotate the lighting vector from the normal of
// the torus surface towards the camera, and thus determine the lighting amount.
// We only need to keep one of the two lighting normal coordinates.
int length_cordic(int16_t x, int16_t y, int16_t *x2_, int16_t y2) {

#ifdef PRECISE
   #define NIT 10
#else
   #define NIT 5
#endif
   
  int x2 = *x2_;
  if (x < 0) { // start in right half-plane
    x = -x;
    x2 = -x2;
  }
  for (int i = 0; i<NIT; i++) {
    int t = x;
    int t2 = x2;
    if (y < 0) {
      x -= y >> i;
      y += t >> i;
      x2 -= y2 >> i;
      y2 += t2 >> i;
    } else {
      x += y >> i;
      y -= t >> i;
      x2 += y2 >> i;
      y2 -= t2 >> i;
    }
  }
  // divide by 0.625 as a cheap approximation to the 0.607 scaling factor factor
  // introduced by this algorithm (see https://en.wikipedia.org/wiki/CORDIC)
  *x2_ = (x2 >> 1) + (x2 >> 3);
  return (x >> 1) + (x >> 3)
     #ifdef PRECISE
         - (x >> 6) // get nrearer to 0.607 [Inigo Quilez]
     #endif
       ; 
}

int main() {

   printf( "\033[48;5;16m"   // set background color black
	   "\033[38;5;15m"   // set foreground color white	   
	   "\033[H"          // home
	   "\033[?25l"       // hide cursor
           "\033[2J");       // clear screen

  int frame = 0;
   
  // high-precision rotation directions, sines and cosines and their products
  int16_t sB = 0, cB = 16384;
  int16_t sA = 11583, cA = 11583;
  int16_t sAsB = 0, cAsB = 0;
  int16_t sAcB = 11583, cAcB = 11583;

  int accurate_CPI_x_1000;
  int accurate_MIPS_x_1000;
  int CPI_x_1000;

  stats_start();
  
  for (;;) {

    int display_on = (frame > START_FRAMES);
    if(display_on) {
        stats_start();
    }
    
    int x1_16 = cAcB << 2;

    // yes this is a multiply but dz is 5 so it's (sb + (sb<<2)) >> 6 effectively
    int p0x = dz * sB >> 6;
    int p0y = dz * sAcB >> 6;
    int p0z = -dz * cAcB >> 6;

    const int r1i = r1*256;
    const int r2i = r2*256;

    int niters = 0;
    int nnormals = 0;
    int16_t yincC = (cA >> 6) + (cA >> 5);      // 12*cA >> 8;
    int16_t yincS = (sA >> 6) + (sA >> 5);      // 12*sA >> 8;
    int16_t xincX = (cB >> 7) + (cB >> 6);      // 6*cB >> 8;
    int16_t xincY = (sAsB >> 7) + (sAsB >> 6);  // 6*sAsB >> 8;
    int16_t xincZ = (cAsB >> 7) + (cAsB >> 6);  // 6*cAsB >> 8;
    int16_t ycA = -((cA >> 1) + (cA >> 4));     // -12 * yinc1 = -9*cA >> 4;
    int16_t ysA = -((sA >> 1) + (sA >> 4));     // -12 * yinc2 = -9*sA >> 4;
    //int dmin = INT_MAX, dmax = -INT_MAX;

    int xsAsB = (sAsB >> 4) - sAsB;  // -40*xincY
    int xcAsB = (cAsB >> 4) - cAsB;  // -40*xincZ;
     

    for (int j = 0; j < 46; j++, ycA += yincC>>1, ysA += yincS>>1) {

      int16_t vxi14 = (cB >> 4) - cB - sB; // -40*xincX - sB;
      int16_t vyi14 = ycA - xsAsB - sAcB;
      int16_t vzi14 = ysA + xcAsB + cAcB;

      for (int i = 0; i < 79; i++, vxi14 += xincX, vyi14 -= xincY, vzi14 += xincZ) {
        int t = 512; // (256 * dz) - r2i - r1i;

        int16_t px = p0x + (vxi14 >> 5); // assuming t = 512, t*vxi>>8 == vxi<<1
        int16_t py = p0y + (vyi14 >> 5);
        int16_t pz = p0z + (vzi14 >> 5);
        debug("pxyz (%+4d,%+4d,%+4d)\n", px, py, pz);
        int16_t lx0 = sB >> 2;
        int16_t ly0 = sAcB - cA >> 2;
        int16_t lz0 = -cAcB - sA >> 2;
        for (;;) {
          int t0, t1, t2, d;
          int16_t lx = lx0, ly = ly0, lz = lz0;
          debug("[%2d,%2d] (px, py) = (%d, %d), (lx, ly) = (%d, %d) -> ", j, i, px, py, lx, ly);
          t0 = length_cordic(px, py, &lx, ly);
          debug("t0=%d (lx', ly') = (%d, %d)\n", t0, lx, ly);
          t1 = t0 - r2i;
          t2 = length_cordic(pz, t1, &lz, lx);
          d = t2 - r1i;
          t += d;

          if (t > 8*256) {
            // putchar(' ');
            int N = (((j-frame)>>3)^(((i+frame)>>3)))&1;
            if(display_on) setpixel(i,j,(N<<2)+26);
            break;
          } else if (d < 2) {
            int N = lz >> 8;
	    // putchar(".,-~:;!*=#$@"[N > 0 ? N < 12 ? N : 11 : 0]);
            N = N > 0 ? N < 26 ? N : 25 : 0;
	    if(display_on) setpixel(i,j,N);
            nnormals++;
            break;
          }
          // todo: shift and add version of this

          /*
            if (d < dmin) dmin = d;
            if (d > dmax) dmax = d;
	   */

#ifdef USE_MUL	   
	   px += d*vxi14 >> 14;
	   py += d*vyi14 >> 14;
	   pz += d*vzi14 >> 14;
#else	   
          {
            // 11x1.14 fixed point 3x parallel multiply
            // only 16 bit registers needed; starts from highest bit to lowest
            // d is about 2..1100, so 11 bits are sufficient
            int16_t dx = 0, dy = 0, dz = 0;
            int16_t a = vxi14, b = vyi14, c = vzi14;
            while (d) {
              if (d&1024) {
                dx += a;
                dy += b;
                dz += c;
              }
              d = (d&1023) << 1;
              a >>= 1;
              b >>= 1;
              c >>= 1;
            }
            // we already shifted down 10 bits, so get the last four
            px += dx >> 4;
            py += dy >> 4;
            pz += dz >> 4;
          }
#endif
          niters++;
        }
      }
      if(display_on && (j&1)) puts("");
    }
    if(display_on) printf("\033[0m"); // reset colors

    stats_end();

    if(frame == START_FRAMES) {
        accurate_CPI_x_1000 = stats_CPI_times_1000;
        accurate_MIPS_x_1000 = (MHZ * 1000000) / accurate_CPI_x_1000;
    }

    CPI_x_1000 = stats_CPI_times_1000;

    uint64_t FPS_num   = (uint64_t)(MHZ) * 1000000 * 1000;
    uint64_t FPS_denom = stats_cycles;
    int FPSx1000 = (int)(FPS_num / FPS_denom);
    
    setcolors(25,33);    
#ifdef USE_MUL
    printf("%s RV32IM %dMHz ", CPU_NAME, MHZ);
#else
    printf("%s RV32I %dMHz ", CPU_NAME, MHZ);     
#endif

    setcolors(25,0);
    printf(" "); printk(FPSx1000); printf(" FPS ");
    setcolors(0,25);
    printf(" "); printk(CPI_x_1000);
    printf(" ("); printk(accurate_CPI_x_1000); printf(") CPI ");
    setcolors(25,0);
    printf(" "); printk(accurate_MIPS_x_1000); printf(" MIPS");
    /*
    setcolors(0,25);
    printf(" %d iterations ", niters);
    setcolors(0,25);
    printf(" %d lit pixels ", nnormals);
    */
    setcolors(25,0);
    printf("\x1b[K");
    
#ifdef __linux__    
    fflush(stdout);
#endif
    
    // rotate sines, cosines, and products thereof
    // this animates the torus rotation about two axes
    R(5, cA, sA);
    R(5, cAsB, sAsB);
    R(5, cAcB, sAcB);
    R(6, cB, sB);
    R(6, cAcB, cAsB);
    R(6, sAcB, sAsB);

#ifdef __linux__     
    usleep(15000);
#endif     
    printf("\r\x1b[23A");
    ++frame;
    prev_color1=-1;
    prev_color2=-1;
  }

  return 0;
}