#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <unistd.h>
#include <assert.h>

static const int colortab[][3] = {
  { 0, 0, 0 },
  { 0, 0, 255 },
  { 0, 255, 0 },
  { 0, 255, 255 },
  { 255, 0, 0 },
  { 255, 0, 255 },
  { 255, 255, 0 },
  { 255, 255, 255 },
  { 0, 0, 128, },
  { 0, 128, 0, },
  { 0, 128, 128, },
  { 0, 128, 255, },
  { 0, 255, 128, },
  { 128, 0, 0, },
  { 128, 0, 128, },
  { 128, 0, 255, },
  { 128, 128, 0, },
  { 128, 128, 128, },
  { 128, 255, 0, },
  { 128, 255, 128, },
  { 128, 255, 255, },
  { 255, 0, 128, },
  { 255, 128, 0, },
  { 255, 128, 128, },
  { 255, 255, 128, },
};
#define MAXCOLORS (sizeof colortab / sizeof colortab[0])

static int width = 256, height = 256, colors = MAXCOLORS, npixels, seeds = 1;
static int *map;

#define pixel(x,y) map[height * (y) + (x)]

static inline int stop(int x, int y) {
  int c;
  if(x > 0 && (c = pixel(x - 1, y)))
    return c;
  if(x < width - 1 && (c = pixel(x + 1, y)))
    return c;
  if(y > 0 && (c = pixel(x, y - 1)))
    return c;
  if(y < height - 1 && (c = pixel(x, y + 1)))
    return c;
  return 0;
}

static void xprintf(const char *fmt, ...) {
  va_list ap;

  va_start(ap, fmt);
  if(vprintf(fmt, ap) < 0) {
    perror("ERROR: writing to stdout");
    exit(1);
  }
  va_end(ap);
}

static void xputchar(int c) {
  if(putchar(c) < 0) {
    perror("ERROR: writing to stdout");
    exit(1);
  }
}

int main(int argc, char **argv) {
  int c, n, x, y, maxnpixels;

  while((n = getopt(argc, argv, "w:h:c:s:p:")) >= 0) {
    switch(n) {
    case 'w': width = atoi(optarg); break;
    case 'h': height = atoi(optarg); break;
    case 'c': colors = atoi(optarg); break;
    case 's': seeds = atoi(optarg); break;
    case 'p': npixels = atoi(optarg); break;
    default: exit(1);
    }
  }
  if((unsigned)colors > MAXCOLORS) {
    fprintf(stderr, "ERROR: too many colors\n");
    exit(1);
  }
  if(!(map = calloc(width * height, sizeof (int)))) {
    perror("ERROR: calloc");
    exit(1);
  }
  if(!npixels)
    npixels = width * height / 2;
  maxnpixels = npixels;
  srand48((long)time(0));
  for(n = 0; n < seeds; ++n) {
    for(c = 1; c < colors; ++c) {
      /* pick a random unoccupied non-edge pixel */
      do {
	x = drand48() * (width - 2) + 1;
	y = drand48() * (height - 2) + 1;
    } while(pixel(x,y));
      pixel(x, y) = c;
      --npixels;
    }
  }
  while(npixels > 0) {
    if(npixels % 1024 == 0)
      fprintf(stderr, "\r[%d%%]", 100 - 100 * npixels / maxnpixels);
    /* pick a random unoccupied pixel */
    do {
      x = drand48() * width;
      y = drand48() * height;
    } while(pixel(x, y));
    /* wander about until we bump into an existing pixel */
    while(!(c = stop(x, y))) {
      for(;;) {
	switch((int)(drand48() * 4)) {
	case 0: if(x == 0) continue; else --x; break;
	case 1: if(x == width - 1) continue; else ++x; break;
	case 2: if(y == 0) continue; else --y; break;
	case 3: if(y == height - 1) continue; else ++y; break;
	default: assert("!reached");
	}
	break;
      }
    }
    pixel(x, y) = c;
    --npixels;
  }
  fprintf(stderr, "\r      \r");
  xprintf("P6\n%d %d %d\n", width, height, 255);
  for(y = 0; y < height; ++y) {
    for(x = 0; x < width; ++x) {
      n = pixel(x, y);
      xputchar(colortab[n][0]);
      xputchar(colortab[n][1]);
      xputchar(colortab[n][2]);
    }
  }
  return 0;
}