/*
 * This file controls the kernel screen.  It has several routines which can
 * output text to the debug port and the the VGA Text Monitor.  Most of these
 * functions are for logging - except the Kernel Panic routine.  Hopefully it's
 * never called.  It should probably also halt execution on all CPUs, not just
 * the local one.  This would need IPIs to be sent, which can be implemented
 * later.
 */

#include <stdarg.h>
#include "mem/mem.h"
#include "mem/vm.h"
#include "task/task.h"
#include "io.h"
#include "spinlock.h"

#define IS_DIGIT(c) ((c) >= '0' && (c) <= '9')

#define ZEROPAD	1  /* Pad with zero */
#define SIGN    2  /* Insigned/signed long */
#define PLUS    4  /* Show plus */
#define SPACE   8  /* Space if plus */
#define LEFT    16 /* Left justified */
#define SPECIAL 32 /* 0x */
#define SMALL   64 /* Use 'abcdef' instead of 'ABCDEF' */

#define DO_DIV(n,base) ({                                                     \
	int __res;                                                            \
	__asm__("divl %4":"=a" (n),"=d" (__res):"0" (n),"1" (0),"r" (base));  \
	__res;                                                                \
})

Spinlock screenLock;

/* Do not convert */
static int
skip_atoi(const char **s)
{
	int i = 0;

	while (IS_DIGIT(**s))
		i = i*10 + *((*s)++) - '0';

	return i;
}

/* Convert a number to ASCII */
static char *
number(char *str, int num, int base, int size, int precision, int type)
{
	char c, sign, tmp[36];
	const char *digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	int i;

	if (type & SMALL)
		digits = "0123456789abcdefghijklmnopqrstuvwxyz";
	if (type & LEFT)
		type &= ~ZEROPAD;
	if (base < 2 || base > 36)
		return 0;
	c = (type & ZEROPAD) ? '0' : ' ' ;
	if (type & SIGN && num < 0) {
		sign = '-';
		num = -num;
	} else {
		sign = (type & PLUS) ? '+' : ((type & SPACE) ? ' ' : 0);
	}
	if (sign)
		size--;
	if (type & SPECIAL)
		if (base == 16)
			size -= 2;
		else if (base == 8)
			size--;
	i = 0;
	if (num == 0)
		tmp[i++] = '0';
	else while (num != 0)
		tmp[i++] = digits[DO_DIV(num,base)];
	if (i > precision)
		precision = i;
	size -= precision;
	if (!(type & (ZEROPAD + LEFT)))
		while (size-- > 0)
			*str++ = ' ';
	if (sign)
		*str++ = sign;
	if (type & SPECIAL)
		if (base == 8) {
			*str++ = '0';
		} else if (base == 16) {
			*str++ = '0';
			*str++ = digits[33];
		}
	if (!(type & LEFT))
		while (size-- > 0)
			*str++ = c;
	while (i < precision--)
		*str++ = '0';
	while (i-- > 0)
		*str++ = tmp[i];
	while (size-- > 0)
		*str++ = ' ';
	return str;
}

/* Print formatted to a buffer */
static int
vsprintf(char *buf, const char *fmt, va_list args)
{
	int len, i;
	char *str, *s, *p;
	int *ip, flags;
	int field_width, precision, qualifier;

	for (str = buf; *fmt; fmt++) {
		if (*fmt != '%') {
			*str++ = *fmt;
			continue;
		}

		/* Process flags */
		flags = 0;
repeat:
		fmt++;
		switch (*fmt) {
		case '-':
			flags |= LEFT;
			goto repeat;
		case '+':
			flags |= PLUS;
			goto repeat;
		case ' ':
			flags |= SPACE;
			goto repeat;
		case '#':
			flags |= SPECIAL;
			goto repeat;
		case '0':
			flags |= ZEROPAD;
			goto repeat;
		}

		/* Get field width */
		field_width = -1;
		if (IS_DIGIT(*fmt)) {
			field_width = skip_atoi(&fmt);
		} else if (*fmt == '*') {
			field_width = va_arg(args, int);
			if (field_width < 0) {
				field_width = -field_width;
				flags |= LEFT;
			}
		}

		/* Get the precision */
		precision = -1;
		if (*fmt == '.') {
			fmt++;
			if (IS_DIGIT(*fmt)) {
				precision = skip_atoi(&fmt);
			} else if (*fmt == '*') {
				precision = va_arg(args, int);
			}
			if (precision < 0)
				precision = 0;
		}

		/* Get the conversion qualifier */
		qualifier = -1;
		if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') {
			qualifier = *fmt;
			fmt++;
		}

		switch (*fmt) {
		case 'c':
			if (!(flags & LEFT))
				while (--field_width > 0)
					*str++ = ' ';
			*str++ = (unsigned char) va_arg(args, int);
			while (--field_width > 0)
				*str++ = ' ';
			break;

		case 's':
			s = va_arg(args, char *);
			len = 0;
			p = s;
			while (*p++) len++;
			if (precision < 0)
				precision = len;
			else if (len > precision)
				len = precision;

			if (!(flags & LEFT))
				while (len < field_width--)
					*str++ = ' ';
			for (i = 0; i < len; ++i)
				*str++ = *s++;
			while (len < field_width--)
				*str++ = ' ';
			break;

		case 'o':
			str = number(str, va_arg(args, unsigned long), 8,
				field_width, precision, flags);
			break;

		case 'p':
			if (field_width == -1) {
				field_width = 8;
				flags |= ZEROPAD;
			}
			str = number(str,
				(unsigned long) va_arg(args, void *), 16,
				field_width, precision, flags);
			break;

		case 'x':
			flags |= SMALL;
			/* FALLTHROUGH */
		case 'X':
			str = number(str, va_arg(args, unsigned long), 16,
				field_width, precision, flags);
			break;

		case 'd': /* FALLTHROUGH */
		case 'i':
			flags |= SIGN;
			/* FALLTHROUGH */
		case 'u':
			str = number(str, va_arg(args, unsigned long), 10,
				field_width, precision, flags);
			break;

		case 'n':
			ip = va_arg(args, int *);
			*ip = (str - buf);
			break;

		default:
			if (*fmt != '%')
				*str++ = '%';
			if (*fmt)
				*str++ = *fmt;
			else
				--fmt;
			break;
		}
	}
	*str = '\0';
	return str-buf;
}

/* Format a string into a buffer */
int
sprintf(char *buf, char *fmt, ...)
{
	int ret;
	va_list args;
	va_start(args, fmt);
	ret = vsprintf(buf, fmt, args);
	va_end(args);
	return ret;
}

/* Print a character */
static inline void
print_char(char c)
{
	outb(0xE9, c);
}

/* Set the output colour */
static inline void
set_attribute(char c, char *esc)
{
	while (*esc)
		outb(0xE9, *esc++);
}

/* Kernel panic */
void
panic(char *fmt, ...)
{
	char buf[1024], *error = buf;

	/* Print error to serial port */
	acquire(&screenLock);
	set_attribute(0x04, "\033[31m");
	va_list args;
	va_start(args, fmt);
	vsprintf(buf, fmt, args);
	va_end(args);
	while (*error) print_char(*error++);
	print_char('\n');
	release(&screenLock);

	/* Hang */
	while (1) asm("hlt");
}

/* Kernel print */
void
kprintf(char *fmt, ...)
{
	char buf[1024], *error = buf;

	/* Print to debug port */
	acquire(&screenLock);
	set_attribute(0x03, "\033[36m");
	va_list args;
	va_start(args, fmt);
	vsprintf(buf, fmt, args);
	va_end(args);
	while (*error) print_char(*error++);
	print_char('\n');
	release(&screenLock);
}

/* Debug prefix print */
static void
dbgprefix(char *fmt, ...)
{
	char buf[1024], *error = buf;

	/* Print to debug port */
	set_attribute(0x0E, "\033[93;01m");
	va_list args;
	va_start(args, fmt);
	vsprintf(buf, fmt, args);
	va_end(args);
	while (*error) print_char(*error++);
}

/* Debug print */
void
dbgprintf(char *msg)
{
	size_t len = 1024;

	if (!msg)
		return;

	if (!verify_access(msg, strnlen(msg, len), PROT_READ))
		return;

	/* Print to debug port */
	acquire(&screenLock);
	dbgprefix("%s(%d:%d): ", current->name, current->tgid, current->tid);
	set_attribute(0x0F, "\033[0m");
	while (*msg && len--) print_char(*msg++);
	print_char('\n');
	release(&screenLock);
}