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

typedef struct {
	size_t len;
	char *items[10];
} truc_array;

enum dirs {
	R, /* right */
	L, /* left */
	U, /* up */
	D /* down */	
};

static __attribute((malloc)) __attribute__((nonnull)) char *get_it(truc_array const *src)
{
	char *r = mallocx(src->len, MALLOCX_ZERO);
	size_t n = 0;
	enum dirs dir = R;
	int x = 0, y = 0;

	while (src->len && (n < src->len)) {
		char c;

		while((c = src->items[y][x]) != ' ') {
			/* store */
			if (c != '*')
				r[n++] = c;

			if (n == src->len)
				break;

			/* test next one */
			int tx = x;
			int ty = y;
			switch (dir) {
				case R:
					tx++;
					break;
				case L:
					tx--;
					break;
				case U:
					ty--;
					break;
				case D:
					ty++;
					break;
				default:
					fprintf(stderr, "Bug!\n");
					break;
			}

			/* ouch */
			if (tx > 14 || tx < 0 || ty <0 || ty > 9)
				break;
			if ((c = src->items[ty][tx]) == ' ') 
				break;
			/* valid next */
			x = tx;
			y = ty;
		}

		switch (dir) {
			char c_up, c_down, c_left, c_right;
			case R:
			case L:
				/* cover up and down */
				c_up   = ' ';
				c_down = ' ';

				if (y > 1)
					c_up   = src->items[y - 1][x];
				if (y < 9)
					c_down = src->items[y + 1][x];
				if (c_up != ' ') {
					y = y - 1;
					dir = U;
				}
				else if (c_down != ' ') {
					y = y + 1;
					dir = D;
				}
				else
					return r;
				break;
			case U:
			case D:

				/* cover left and right */
				c_left   = ' ';
				c_right = ' ';

				if (x > 1)
					c_left  = src->items[y][x - 1];
				if (y < 14)
					c_right = src->items[y][x + 1];

				if (c_left != ' ') {
					x = x - 1;
					dir = L;
				}
				else if (c_right != ' ') {
					x = x + 1;
					dir = R;
				} else
					return r;
				break;
		}
	}

	return r;
}

static void print_it(truc_array src)
{
	printf("+---------------+\n");
	for (size_t j= 0; j < 10;) {
		printf("|%s|\n", src.items[j++]);
	}
	printf("+---------------+\n");
}

int main(int argc, char *argv[])
{
	truc_array a= {128, };
	char *r = NULL;

	/*            012345789ABCDEF */
	a.items[0] = "*01**          ";
	a.items[1] = "edcBA          ";
	a.items[2] = "*  *       X   ";
	a.items[3] = "*  !       *   ";
	a.items[4] = "****F**        ";
	a.items[5] = "      *  *H*   ";
	a.items[6] = "      *G** *   ";
	a.items[7] = "   X       I   ";
	a.items[8] = "   X **J****   ";
	a.items[9] = "X    Z         ";

	print_it(a);

	puts("");
	r = get_it(&a);
	printf("[ %s ]\n", r);
	dallocx(r, 0);
}