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

struct entity {
	float x, y;
	char *label;
	struct entity *next;
};

static struct entity *entity_head = NULL;
int board_width = 300, board_height = 300;

static char *vaprintf(const char *fmt, va_list ap)
{
	int len;
	char scratch;
	char *ret;
	va_list ap2;
	va_copy(ap2, ap);
	len = vsnprintf(&scratch, 1, fmt, ap2);
	va_end(ap2);
	if (len < 0) {
		perror(__func__);
		return NULL;
	}
	ret = malloc(len + 1);
	vsnprintf(ret, len + 1, fmt, ap);
	return ret;
}

static struct entity *entity_create(const char *fmt, ...) __attribute__((format(printf,1,2)));
static struct entity *entity_create(const char *fmt, ...)
{
	va_list ap;
	struct entity *e;
	e = calloc(1, sizeof *e);
	va_start(ap, fmt);
	e->label = vaprintf(fmt, ap);
	va_end(ap);
	e->next = NULL;
	e->x = 0;
	e->y = 0;
	return e;
}

static void entity_move(struct entity *e, int x, int y)
{
	e->x = x;
	e->y = y;
}

static void entity_insert(struct entity **head, struct entity *e)
{
	e->next = *head;
	*head = e;
}

static void generate(void)
{
	int i, max;
	struct entity *e;

	max = rand() % 30;
	for (i = 0; i < max; i++) {
		e = entity_create("ent%03d", i);
		if (!e)
			exit(1);
		entity_insert(&entity_head, e);
		entity_move(e, rand() % board_width, rand() % board_height);
	}
}

static void svg_begin(FILE *f)
{
	fprintf(f, "<?xml version=\"1.0\" standalone=\"no\"?>\n");
	fprintf(f, "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\"\n");
	fprintf(f, "\"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n");
	fprintf(f, "<svg width=\"100%%\" height=\"100%%\" version=\"1.1\"\n");
	fprintf(f, "xmlns=\"http://www.w3.org/2000/svg\">\n");
}

static void svg_end(FILE *f)
{
	fprintf(f, "</svg>\n");
}

static void svg_rect(FILE *f, double w, double h, unsigned color)
{
	fprintf(f, "<rect width=\"%g\" height=\"%g\"\n", w, h);
	fprintf(f, "style=\"fill:rgb(%u,%u,%u);stroke-width:1;\n",
		(color >> 16) & 255, (color >> 8) & 255, color & 255);
	fprintf(f, "stroke:rgb(0,0,0)\"/>\n");
}

static void svg_circle(FILE *f, double r, double x, double y, unsigned color)
{
	fprintf(f, "<circle cx=\"%g\" cy=\"%g\" r=\"%g\" stroke=\"black\"\n",
		x, y, r);
	fprintf(f, "stroke-width=\"2\" fill=\"rgb(%u,%u,%u)\"/>\n",
		(color >> 16) & 255, (color >> 8) & 255, color & 255);

}

static void svg_text(FILE *f, double x, double y, const char *fmt, ...) __attribute__((format(printf,4,5)));
static void svg_text(FILE *f, double x, double y, const char *fmt, ...)
{
	char *buf;
	va_list ap;
	va_start(ap, fmt);
	buf = vaprintf(fmt, ap);
	va_end(ap);
	fprintf(f, "<text id=\"TextElement\" x=\"%g\" y=\"%g\"\n", x, y);
	fprintf(f, "style=\"font-family:Verdana;font-size:24\">\n");
	fprintf(f, "%s\n</text>\n", buf);
	free(buf);
}

static void svg_print(void)
{
	struct entity *e;
	FILE *f = stdout;
	double r = (board_width + board_height) / 50.;
	svg_begin(f);
	svg_rect(f, board_width, board_height, 0xff0088);
	for (e = entity_head; e; e = e->next) {
		svg_circle(f, r, e->x, e->y, 0x00ff88);
		svg_text(f, e->x, e->y + r, "%s", e->label);
	}
	svg_end(f);
}

int main()
{
	generate();
	svg_print();
	return 0;
}