// xv6 x86_64 kbd.c

// PC keyboard interface constants

#define KBSTATP         0x64    // kbd controller status port(I)
#define KBS_DIB         0x01    // kbd data in buffer
#define KBDATAP         0x60    // kbd data port(I)

#define NO              0

#define SHIFT           (1<<0)
#define CTL             (1<<1)
#define ALT             (1<<2)

#define CAPSLOCK        (1<<3)
#define NUMLOCK         (1<<4)
#define SCROLLLOCK      (1<<5)

#define E0ESC           (1<<6)

// Special keycodes
#define KEY_HOME        0xE0
#define KEY_END         0xE1
#define KEY_UP          0xE2
#define KEY_DN          0xE3
#define KEY_LF          0xE4
#define KEY_RT          0xE5
#define KEY_PGUP        0xE6
#define KEY_PGDN        0xE7
#define KEY_INS         0xE8
#define KEY_DEL         0xE9

// C('A') == Control-A
#define C(x) (x - '@')

typedef unsigned char uchar;
typedef unsigned short ushort;
typedef unsigned int uint;

static inline uchar
inb(ushort port)
{
	uchar data;

	asm volatile("in %1,%0" : "=a" (data) : "d" (port));
	return data;
}

static uchar shiftcode[256] =
		{
				[0x1D] = CTL,
				[0x2A] = SHIFT,
				[0x36] = SHIFT,
				[0x38] = ALT,
				[0x9D] = CTL,
				[0xB8] = ALT
		};

static uchar togglecode[256] =
		{
				[0x3A] = CAPSLOCK,
				[0x45] = NUMLOCK,
				[0x46] = SCROLLLOCK
		};

static uchar normalmap[256] =
		{
				NO, 0x1B, '1', '2', '3', '4', '5', '6',  // 0x00
				'7', '8', '9', '0', '-', '=', '\b', '\t',
				'q', 'w', 'e', 'r', 't', 'y', 'u', 'i',  // 0x10
				'o', 'p', '[', ']', '\n', NO, 'a', 's',
				'd', 'f', 'g', 'h', 'j', 'k', 'l', ';',  // 0x20
				'\'', '`', NO, '\\', 'z', 'x', 'c', 'v',
				'b', 'n', 'm', ',', '.', '/', NO, '*',  // 0x30
				NO, ' ', NO, NO, NO, NO, NO, NO,
				NO, NO, NO, NO, NO, NO, NO, '7',  // 0x40
				'8', '9', '-', '4', '5', '6', '+', '1',
				'2', '3', '0', '.', NO, NO, NO, NO,   // 0x50
				[0x9C] = '\n',      // KP_Enter
				[0xB5] = '/',       // KP_Div
				[0xC8] = KEY_UP, [0xD0] = KEY_DN,
				[0xC9] = KEY_PGUP, [0xD1] = KEY_PGDN,
				[0xCB] = KEY_LF, [0xCD] = KEY_RT,
				[0x97] = KEY_HOME, [0xCF] = KEY_END,
				[0xD2] = KEY_INS, [0xD3] = KEY_DEL
		};

static uchar shiftmap[256] =
		{
				NO, 033, '!', '@', '#', '$', '%', '^',  // 0x00
				'&', '*', '(', ')', '_', '+', '\b', '\t',
				'Q', 'W', 'E', 'R', 'T', 'Y', 'U', 'I',  // 0x10
				'O', 'P', '{', '}', '\n', NO, 'A', 'S',
				'D', 'F', 'G', 'H', 'J', 'K', 'L', ':',  // 0x20
				'"', '~', NO, '|', 'Z', 'X', 'C', 'V',
				'B', 'N', 'M', '<', '>', '?', NO, '*',  // 0x30
				NO, ' ', NO, NO, NO, NO, NO, NO,
				NO, NO, NO, NO, NO, NO, NO, '7',  // 0x40
				'8', '9', '-', '4', '5', '6', '+', '1',
				'2', '3', '0', '.', NO, NO, NO, NO,   // 0x50
				[0x9C] = '\n',      // KP_Enter
				[0xB5] = '/',       // KP_Div
				[0xC8] = KEY_UP, [0xD0] = KEY_DN,
				[0xC9] = KEY_PGUP, [0xD1] = KEY_PGDN,
				[0xCB] = KEY_LF, [0xCD] = KEY_RT,
				[0x97] = KEY_HOME, [0xCF] = KEY_END,
				[0xD2] = KEY_INS, [0xD3] = KEY_DEL
		};

static uchar ctlmap[256] =
		{
				NO, NO, NO, NO, NO, NO, NO, NO,
				NO, NO, NO, NO, NO, NO, NO, NO,
				C('Q'), C('W'), C('E'), C('R'), C('T'), C('Y'), C('U'), C('I'),
				C('O'), C('P'), NO, NO, '\r', NO, C('A'), C('S'),
				C('D'), C('F'), C('G'), C('H'), C('J'), C('K'), C('L'), NO,
				NO, NO, NO, C('\\'), C('Z'), C('X'), C('C'), C('V'),
				C('B'), C('N'), C('M'), NO, NO, C('/'), NO, NO,
				[0x9C] = '\r',      // KP_Enter
				[0xB5] = C('/'),    // KP_Div
				[0xC8] = KEY_UP, [0xD0] = KEY_DN,
				[0xC9] = KEY_PGUP, [0xD1] = KEY_PGDN,
				[0xCB] = KEY_LF, [0xCD] = KEY_RT,
				[0x97] = KEY_HOME, [0xCF] = KEY_END,
				[0xD2] = KEY_INS, [0xD3] = KEY_DEL
		};

int
kbdgetc(void) {
	static uint shift;
	static uchar *charcode[4] = {
			normalmap, shiftmap, ctlmap, ctlmap
	};
	uint st, data, c;

	st = inb(KBSTATP);
	if ((st & KBS_DIB) == 0)
		return -1;
	data = inb(KBDATAP);

	if (data == 0xE0) {
		shift |= E0ESC;
		return 0;
	} else if (data & 0x80) {
		// Key released
		data = (shift & E0ESC ? data : data & 0x7F);
		shift &= ~(shiftcode[data] | E0ESC);
		return 0;
	} else if (shift & E0ESC) {
		// Last character was an E0 escape; or with 0x80
		data |= 0x80;
		shift &= ~E0ESC;
	}

	shift |= shiftcode[data];
	shift ^= togglecode[data];
	c = charcode[shift & (CTL | SHIFT)][data];
	if (shift & CAPSLOCK) {
		if ('a' <= c && c <= 'z')
			c += 'A' - 'a';
		else if ('A' <= c && c <= 'Z')
			c += 'a' - 'A';
	}
	return c;
}