// Chaos game, based on the task statement from https://rosettacode.org/wiki/Chaos_game
//
// Creates a Sierpinski triangle.
//
// ref: http://math.bu.edu/DYSYS/chaos-game/node1.html
//
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include "ppm.h"

#define SIZE 600 // image size

#define ITER 100000 // number of iterations

typedef struct { int x, y; } Point;

int main( int argc, char *argv[])
{
  srand(time(0));

  ppm a = ppm_new( SIZE, SIZE);

 // corners of a triangle
 //
  Point p[3] = { { 0, SIZE-1}, { SIZE/2, 0}, { SIZE-1, SIZE-1} };

#if 0
  int z = 0;
#else
  int z = 255;
#endif

  memset( a.r[0], z, a.rows*a.cols);
  memset( a.g[0], z, a.rows*a.cols);
  memset( a.b[0], z, a.rows*a.cols);

 // random starting point
 //
  int x = rand() % SIZE, y = rand() % SIZE, k;

  for( int iter = 0; iter < ITER; ++iter)
  {
   // random corner
   //
    k = rand() % 3;

    x += (p[k].x - x)/2; y += (p[k].y - y)/2;

#if 0 // should not happen
    if( x < 0 || x >= SIZE || y < 0 || y >= SIZE)
     { fprintf( stderr, "x or y out of range!\n"); return 1; }
#endif

#if 0
    a.r[y][x] = 255;
#else
    switch( k)
    {
      case 0: a.g[y][x] = a.b[y][x] = 0; break;
      case 1: a.r[y][x] = a.b[y][x] = 0; break;
      case 2: a.r[y][x] = a.g[y][x] = 0; break;
    }
#endif


  }

  ppm_write(a);
}