#include <stdlib.h>
#include <string.h>

unsigned area_size(unsigned char **, unsigned, unsigned, unsigned, unsigned);
unsigned char ** copy_area(unsigned char **, unsigned, unsigned);
void destroy_area(unsigned char **);

unsigned area_size (unsigned char ** area, unsigned width, unsigned height, unsigned x, unsigned y) {
  if ((!area) || (x >= width) || (y >= height) || (!area[x][y])) return 0;
  unsigned char ** copy = copy_area(area, width, height);
  unsigned prevcount = 0, count = 1;
  copy[x][y] = 2;
  unsigned scan_area, scan_x, scan_y, neighbour_count;
  for (scan_area = 1; prevcount != count; scan_area ++) {
    prevcount = count;
    for (scan_x = (x < scan_area) ? 0 : (x - scan_area); (scan_x < width) && (scan_x <= (x + scan_area)); scan_x ++)
      for (scan_y = (y < scan_area) ? 0 : (y - scan_area); (scan_y < height) && (scan_y <= (y + scan_area)); scan_y ++) {
        if (!copy[scan_x][scan_y]) continue;
        if (
          (scan_x && (copy[scan_x - 1][scan_y] == 2)) ||
          (scan_y && (copy[scan_x][scan_y - 1] == 2)) ||
          (copy[scan_x + 1][scan_y] == 2) ||
          (copy[scan_x][scan_y + 1] == 2)
        ) {
          if (copy[scan_x][scan_y] == 1) count ++;
          copy[scan_x][scan_y] = 2;
        }
      }
  }
  destroy_area(copy);
  return count;
}

unsigned char ** copy_area (unsigned char ** area, unsigned width, unsigned height) {
  // this creates a copy of the area, and adds a surrounding border with 0s to the right and bottom to make coding easier
  unsigned char ** result = calloc(sizeof(char *), width + 2);
  unsigned x;
  for (x = 0; x < width; x ++) {
    memcpy(result[x] = malloc(height + 1), area[x], height);
    result[x][height] = 0;
  }
  memset(result[width] = malloc(height + 1), 0, height + 1);
  return result;
}

void destroy_area (unsigned char ** area) {
  // this destroys the copy of the area created previously
  unsigned x;
  for (x = 0; area[x]; x ++) free(area[x]);
  free(area);
}