#include "keymap.h"
#include "stdio.h"
#include "type.h"
#include "x86.h"

#define KB_INBUF_SIZE 4

typedef struct kb_inbuf {
	u8*	p_head;
	u8*	p_tail;
	int	count;
	u8	buf[KB_INBUF_SIZE];
} KB_INPUT;

static KB_INPUT kb_input = {
	.p_head = kb_input.buf,
	.p_tail = kb_input.buf,
	.count = 0,
};

/*
 * 将ch这个字符放进内核的字符缓冲区
 */
void
add_keyboard_buf(u8 ch)
{
	if (kb_input.count < KB_INBUF_SIZE) {
		*(kb_input.p_head) = ch;
		kb_input.p_head ++;
		if (kb_input.p_head == kb_input.buf + KB_INBUF_SIZE) {
			kb_input.p_head = kb_input.buf;
		}
		kb_input.count ++;
	}
}

/*
 * 如果内核的字符缓冲区为空，则返回-1
 * 否则返回缓冲区队头的字符并弹出队头
 */
u8
getch(void)
{
	if (kb_input.count == 0)
		return -1;
	else {
		// disable_int();
		// in user mode, cli and sti will only cause protection exception
		u8 val = *(kb_input.p_tail);
		kb_input.p_tail ++;
		if (kb_input.p_tail == kb_input.buf + KB_INBUF_SIZE) {
			kb_input.p_tail = kb_input.buf;
		}
		kb_input.count --;
		// enable_int();
		return val;
	}
}