#include <system.h>

#define args_list char *
#define _arg_stack_size(type) (((sizeof(type)-1)/sizeof(int)+1)*sizeof(int))
#define args_start(ap, fmt) do { \
	ap = (char *)((unsigned int)&fmt + _arg_stack_size(&fmt));\
} while (0)
#define args_end(ap)
#define args_next(ap, type) (((type *)(ap+=_arg_stack_size(type)))[-1])

static char buf[1024] = {-1};
static int ptr = -1;

/*
 * Parse integer
 */
static void
parse_num(
		unsigned int value,
		unsigned int base
		) {
	unsigned int n = value / base;
	int r = value % base;
	if (r < 0) {
		r += base;
		--n;
	}
	if (value >= base) {
		parse_num(n, base);
	}
	buf[ptr++] = (r+'0');
}

/*
 * Parse hexadecimal
 */
static void
parse_hex(
		unsigned int value
		) {
	int i = 8;
	while (i-- > 0) {
		buf[ptr++] = "0123456789abcdef"[(value>>(i*4))&0xF];
	}
}

/*
 * kprintf
 * %s, %c, %x, %d, %%
 * (Kernel) Print a formatted string.
 */
void
kprintf(
		const char *fmt,
		...
	   ) {
	int i = 0;
	char *s;
	args_list args;
	args_start(args, fmt);
	ptr = 0;
	for ( ; fmt[i]; ++i) {
		if ((fmt[i] != '%') && (fmt[i] != '\\')) {
			buf[ptr++] = fmt[i];
			continue;
		} else if (fmt[i] == '\\') {
			switch (fmt[++i]) {
				case 'a': buf[ptr++] = '\a'; break;
				case 'b': buf[ptr++] = '\b'; break;
				case 't': buf[ptr++] = '\t'; break;
				case 'n': buf[ptr++] = '\n'; break;
				case 'r': buf[ptr++] = '\r'; break;
				case '\\':buf[ptr++] = '\\'; break;
			}
			continue;
		}
		/* fmt[i] == '%' */
		switch (fmt[++i]) {
			case 's':
				s = (char *)args_next(args, char *);
				while (*s) {
					buf[ptr++] = *s++;
				}
				break;
			case 'c':
				buf[ptr++] = (char)args_next(args, int);
				break;
			case 'x':
				parse_hex((unsigned long)args_next(args, unsigned long));
				break;
			case 'd':
				parse_num((unsigned long)args_next(args, unsigned long), 10);
				break;
			case '%':
				buf[ptr++] = '%';
				break;
			default:
				buf[ptr++] = fmt[i];
				break;
		}
	}
	buf[ptr] = '\0';
	args_end(args);
	puts(buf);
}