#include <stdio.h>
#include <string.h>
#include <va_list.h>

static void print_dec(unsigned int value, unsigned int width, char * buf, int * ptr, int fill_zero, int align_right) {
	unsigned int n_width = 1;
	unsigned int i = 9;

	if (value < 10UL) {
		n_width = 1;
	} else if (value < 100UL) {
		n_width = 2;
	} else if (value < 1000UL) {
		n_width = 3;
	} else if (value < 10000UL) {
		n_width = 4;
	} else if (value < 100000UL) {
		n_width = 5;
	} else if (value < 1000000UL) {
		n_width = 6;
	} else if (value < 10000000UL) {
		n_width = 7;
	} else if (value < 100000000UL) {
		n_width = 8;
	} else if (value < 1000000000UL) {
		n_width = 9;
	} else {
		n_width = 10;
	}

	int printed = 0;
	if (align_right) {
		while (n_width + printed < width) {
			buf[*ptr] = fill_zero ? '0' : ' ';
			*ptr += 1;
			printed += 1;
		}

		i = n_width;
		while (i > 0) {
			unsigned int n = value / 10;
			int r = value % 10;
			buf[*ptr + i - 1] = r + '0';
			i--;
			value = n;
		}
		*ptr += n_width;
	} else {
		i = n_width;
		while (i > 0) {
			unsigned int n = value / 10;
			int r = value % 10;
			buf[*ptr + i - 1] = r + '0';
			i--;
			value = n;
			printed++;
		}
		*ptr += n_width;
		while (printed < (int)width) {
			buf[*ptr] = fill_zero ? '0' : ' ';
			*ptr += 1;
			printed += 1;
		}
	}
}

/*
 * Hexadecimal to string
 */
static void print_hex(unsigned int value, unsigned int width, char * buf, int * ptr) {
	int i = width;

	if (i == 0) i = 8;

	unsigned int n_width = 1;
	unsigned int j = 0x0F;
	while (value > j && j < UINT32_MAX) {
		n_width += 1;
		j *= 0x10;
		j += 0x0F;
	}

	while (i > (int)n_width) {
		buf[*ptr] = '0';
		*ptr += 1;
		i--;
	}

	i = (int)n_width;
	while (i-- > 0) {
		buf[*ptr] = "0123456789abcdef"[(value>>(i*4))&0xF];
		*ptr += + 1;
	}
}

/*
 * vasprintf()
 */
size_t xvasprintf(char * buf, const char * fmt, va_list args) {
	int i = 0;
	char * s;
	char * b = buf;
	for (const char *f = fmt; *f; f++) {
		if (*f != '%') {
			*b++ = *f;
			continue;
		}
		++f;
		unsigned int arg_width = 0;
		int align = 1; /* right */
		int fill_zero = 0;
		if (*f == '-') {
			align = 0;
			++f;
		}
		if (*f == '*') {
			arg_width = (char)va_arg(args, int);
			++f;
		}
		if (*f == '0') {
			fill_zero = 1;
			++f;
		}
		while (*f >= '0' && *f <= '9') {
			arg_width *= 10;
			arg_width += *f - '0';
			++f;
		}
		/* fmt[i] == '%' */
		switch (*f) {
			case 's': /* String pointer -> String */
				{
					s = (char *)va_arg(args, char *);
					if (s == NULL) {
						s = "(null)";
					}
					size_t count = 0;
					while (*s) {
						*b++ = *s++;
						count++;
						if (arg_width && count == arg_width) break;
					}
					while (count < arg_width) {
						*b++ = ' ';
						count++;
					}
				}
				break;
			case 'c': /* Single character */
				*b++ = (char)va_arg(args, int);
				break;
			case 'x': /* Hexadecimal number */
				i = b - buf;
				print_hex((unsigned long)va_arg(args, unsigned long), arg_width, buf, &i);
				b = buf + i;
				break;
			case 'd': /* Decimal number */
				i = b - buf;
				{
					long val = (long)va_arg(args, long);
					if (val < 0) {
						*b++ = '-';
						buf++;
						val = -val;
					}
					print_dec(val, arg_width, buf, &i, fill_zero, align);
				}
				b = buf + i;
				break;
			case '%': /* Escape */
				*b++ = '%';
				break;
			default: /* Nothing at all, just dump it */
				*b++ = *f;
				break;
		}
	}
	/* Ensure the buffer ends in a null */
	*b = '\0';
	return b - buf;
}

size_t vasprintf(char ** buf, const char * fmt, va_list args) {
	char * b = malloc(1024);
	*buf = b;
	return xvasprintf(b, fmt, args);
}

int fprintf(FILE * device, char *fmt, ...) {
	va_list args;
	va_start(args, fmt);
	char * buffer;
	vasprintf(&buffer, fmt, args);
	va_end(args);

	int out = fwrite(buffer, 1, strlen(buffer), device);
	free(buffer);
	return out;
}

int printf(char *fmt, ...) {
	va_list args;
	va_start(args, fmt);
	char * buffer;
	vasprintf(&buffer, fmt, args);
	va_end(args);

	int out = fwrite(buffer, 1, strlen(buffer), stdout);
	free(buffer);
	return out;
}

int sprintf(char * buf, const char *fmt, ...) {
	va_list args;
	va_start(args, fmt);
	int out = xvasprintf(buf, fmt, args);
	va_end(args);
	return out;
}