// 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)

// Right Alt, tracked apart from left Alt.
//
// They used to be the same bit, which is fine for typing -- neither is used to
// look up a character -- and wrong for chords. On a Polish layout AltGr is how
// you type a c e l n o s x z with their diacritics, and it is held constantly.
// Nothing the kernel binds may involve it.
#define RALT            (1<<7)

// 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

// Switch virtual terminal.
//
// Above 0xFF deliberately. kbdgetc returns an int and consoleintr takes one,
// and every value that fits in a byte is already either a character or a
// UTF-8 continuation byte. A chord that collided with one would be typed into
// the terminal instead of switching away from it.
//
// *Which* chord is a runtime setting, not a constant here, and that is the
// interesting part. Three separate parties have a claim on every candidate:
//
//   the HOST, which sees the keystroke first and may never pass it on
//     Alt+F4, Alt+F2            window manager
//     Ctrl+Alt+F1..F6           display manager, and it matches loosely --
//                               adding Shift does not get past it
//     Ctrl+Alt+<digit>          QEMU's own console tabs
//
//   APPLICATIONS, which lose the key permanently if the kernel eats it
//     Alt+<anything>            Meta. zsh binds Meta-digit as digit-argument
//     Ctrl+<letter>             control characters
//     Ctrl+Shift+<digit>        types a character -- Ctrl+Shift+2 is ^@
//     F1..F6 alone              help, and full-screen programs
//
//   the KEYBOARD LAYOUT
//     AltGr+<letter>            Polish diacritics, and on some setups AltGr
//                               arrives as Ctrl+Alt
//
// There is no combination that is free for everyone on every host, and the
// guest cannot find out what its host grabs -- the keystroke simply never
// arrives, which is indistinguishable from a chord nobody pressed. So the
// kernel ships a default and lets it be changed: VT_SETCHORD, and `chvt -c`
// in userspace. Setting it to no modifiers disables the chord entirely and
// leaves `chvt N` as the only way to switch, which is a legitimate choice on
// a machine whose host takes everything.
//
// The default is AltGr+F1..F6, and the "AltGr wants it" line above needs
// reading carefully: what a Polish layout wants is AltGr+*letter*. AltGr with
// a function key produces nothing on any layout, no window manager binds it,
// and no application asks for it. Right Alt being a separate modifier bit
// here is what makes the distinction expressible at all -- it used to share
// ALT, which is harmless for typing and useless for this.
#define KEY_VT_SWITCH   0x120

// Previous / next terminal, on the same modifiers as the chord above. The
// minus and equals keys, which sit together and read as - and + -- a relative
// move for when you have two terminals and do not care which number they are.
#define KEY_VT_PREV     0x130
#define KEY_VT_NEXT     0x131

#define SCAN_MINUS      0x0C      // - / _
#define SCAN_EQUALS     0x0D      // = / +

#define SCAN_F1         0x3B      // F1..F6 are scancodes 0x3B..0x40
#define SCAN_1          0x02      // 1..6 are scancodes 0x02..0x07

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

static uchar shiftcode[256] =
{
  [0x1D] CTL,
  [0x2A] SHIFT,
  [0x36] SHIFT,
  [0x38] ALT,
  [0x9D] CTL,
  [0xB8] RALT     // right Alt / AltGr -- see RALT above
};

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
};