/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2026 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/

#include "SDL_internal.h"

#ifdef SDL_VIDEO_DRIVER_DOSVESA

#include "../../events/SDL_events_c.h"
#include "../../events/SDL_keyboard_c.h"
#include "../../events/SDL_mouse_c.h"
#include "../SDL_sysvideo.h"
#include "SDL_dosvideo.h"

#include "../../core/dos/SDL_dos_scheduler.h"
#include "SDL_dosevents_c.h"

// PS/2 keyboard controller port
#define KBD_DATA_PORT 0x60

// Scancode byte structure
#define SCANCODE_MASK    0x7F // bits 0-6: scancode index
#define SCANCODE_RELEASE 0x80 // bit 7: key released (break code)

// Multi-byte scancode prefixes
#define SCANCODE_PREFIX_EXTENDED 0xE0 // extended key prefix
#define SCANCODE_PREFIX_PAUSE    0xE1 // pause key sequence prefix

// VGA Input Status Register 1 (for vblank detection)
#define VGA_STATUS_PORT   0x3DA
#define VGA_STATUS_VBLANK 0x08 // bit 3: vertical retrace active

// Scancode table: https://www.plantation-productions.com/Webster/www.artofasm.com/DOS/pdf/apndxc.pdf
static const SDL_Scancode DOSVESA_ScancodeMapping[] = { // index is the scancode from the IRQ1 handler bitwise-ANDed against 0x7F.
    /* 0x00 */ SDL_SCANCODE_UNKNOWN,
    /* 0x01 */ SDL_SCANCODE_ESCAPE,
    /* 0x02 */ SDL_SCANCODE_1,
    /* 0x03 */ SDL_SCANCODE_2,
    /* 0x04 */ SDL_SCANCODE_3,
    /* 0x05 */ SDL_SCANCODE_4,
    /* 0x06 */ SDL_SCANCODE_5,
    /* 0x07 */ SDL_SCANCODE_6,
    /* 0x08 */ SDL_SCANCODE_7,
    /* 0x09 */ SDL_SCANCODE_8,
    /* 0x0A */ SDL_SCANCODE_9,
    /* 0x0B */ SDL_SCANCODE_0,
    /* 0x0C */ SDL_SCANCODE_MINUS,
    /* 0x0D */ SDL_SCANCODE_EQUALS,
    /* 0x0E */ SDL_SCANCODE_BACKSPACE,
    /* 0x0F */ SDL_SCANCODE_TAB,

    /* 0x10 */ SDL_SCANCODE_Q,
    /* 0x11 */ SDL_SCANCODE_W,
    /* 0x12 */ SDL_SCANCODE_E,
    /* 0x13 */ SDL_SCANCODE_R,
    /* 0x14 */ SDL_SCANCODE_T,
    /* 0x15 */ SDL_SCANCODE_Y,
    /* 0x16 */ SDL_SCANCODE_U,
    /* 0x17 */ SDL_SCANCODE_I,
    /* 0x18 */ SDL_SCANCODE_O,
    /* 0x19 */ SDL_SCANCODE_P,
    /* 0x1A */ SDL_SCANCODE_LEFTBRACKET,
    /* 0x1B */ SDL_SCANCODE_RIGHTBRACKET,
    /* 0x1C */ SDL_SCANCODE_RETURN,
    /* 0x1D */ SDL_SCANCODE_LCTRL,
    /* 0x1E */ SDL_SCANCODE_A,
    /* 0x1F */ SDL_SCANCODE_S,

    /* 0x20 */ SDL_SCANCODE_D,
    /* 0x21 */ SDL_SCANCODE_F,
    /* 0x22 */ SDL_SCANCODE_G,
    /* 0x23 */ SDL_SCANCODE_H,
    /* 0x24 */ SDL_SCANCODE_J,
    /* 0x25 */ SDL_SCANCODE_K,
    /* 0x26 */ SDL_SCANCODE_L,
    /* 0x27 */ SDL_SCANCODE_SEMICOLON,
    /* 0x28 */ SDL_SCANCODE_APOSTROPHE,
    /* 0x29 */ SDL_SCANCODE_GRAVE,
    /* 0x2A */ SDL_SCANCODE_LSHIFT,
    /* 0x2B */ SDL_SCANCODE_BACKSLASH,
    /* 0x2C */ SDL_SCANCODE_Z,
    /* 0x2D */ SDL_SCANCODE_X,
    /* 0x2E */ SDL_SCANCODE_C,
    /* 0x2F */ SDL_SCANCODE_V,

    /* 0x30 */ SDL_SCANCODE_B,
    /* 0x31 */ SDL_SCANCODE_N,
    /* 0x32 */ SDL_SCANCODE_M,
    /* 0x33 */ SDL_SCANCODE_COMMA,
    /* 0x34 */ SDL_SCANCODE_PERIOD,
    /* 0x35 */ SDL_SCANCODE_SLASH,
    /* 0x36 */ SDL_SCANCODE_RSHIFT,
    /* 0x37 */ SDL_SCANCODE_KP_MULTIPLY,
    /* 0x38 */ SDL_SCANCODE_LALT,
    /* 0x39 */ SDL_SCANCODE_SPACE,
    /* 0x3A */ SDL_SCANCODE_CAPSLOCK,
    /* 0x3B */ SDL_SCANCODE_F1,
    /* 0x3C */ SDL_SCANCODE_F2,
    /* 0x3D */ SDL_SCANCODE_F3,
    /* 0x3E */ SDL_SCANCODE_F4,
    /* 0x3F */ SDL_SCANCODE_F5,

    /* 0x040 */ SDL_SCANCODE_F6,
    /* 0x041 */ SDL_SCANCODE_F7,
    /* 0x042 */ SDL_SCANCODE_F8,
    /* 0x043 */ SDL_SCANCODE_F9,
    /* 0x044 */ SDL_SCANCODE_F10,
    /* 0x045 */ SDL_SCANCODE_NUMLOCKCLEAR,
    /* 0x046 */ SDL_SCANCODE_SCROLLLOCK,
    /* 0x047 */ SDL_SCANCODE_KP_7,
    /* 0x048 */ SDL_SCANCODE_KP_8,
    /* 0x049 */ SDL_SCANCODE_KP_9,
    /* 0x04A */ SDL_SCANCODE_KP_MINUS,
    /* 0x04B */ SDL_SCANCODE_KP_4,
    /* 0x04C */ SDL_SCANCODE_KP_5,
    /* 0x04D */ SDL_SCANCODE_KP_6,
    /* 0x04E */ SDL_SCANCODE_KP_PLUS,
    /* 0x04F */ SDL_SCANCODE_KP_1,

    /* 0x050 */ SDL_SCANCODE_KP_2,
    /* 0x051 */ SDL_SCANCODE_KP_3,
    /* 0x052 */ SDL_SCANCODE_KP_0,
    /* 0x053 */ SDL_SCANCODE_KP_PERIOD,
    /* 0x054 */ SDL_SCANCODE_UNKNOWN,
    /* 0x055 */ SDL_SCANCODE_UNKNOWN,
    /* 0x056 */ SDL_SCANCODE_UNKNOWN,
    /* 0x057 */ SDL_SCANCODE_F11,
    /* 0x058 */ SDL_SCANCODE_F12
};

// Extended scancode table for keys prefixed with 0xE0
static const SDL_Scancode DOSVESA_ExtendedScancodeMapping[] = { // index is the scancode byte following the 0xE0 prefix, masked with 0x7F.
    /* 0x00 */ SDL_SCANCODE_UNKNOWN,
    /* 0x01 */ SDL_SCANCODE_UNKNOWN,
    /* 0x02 */ SDL_SCANCODE_UNKNOWN,
    /* 0x03 */ SDL_SCANCODE_UNKNOWN,
    /* 0x04 */ SDL_SCANCODE_UNKNOWN,
    /* 0x05 */ SDL_SCANCODE_UNKNOWN,
    /* 0x06 */ SDL_SCANCODE_UNKNOWN,
    /* 0x07 */ SDL_SCANCODE_UNKNOWN,
    /* 0x08 */ SDL_SCANCODE_UNKNOWN,
    /* 0x09 */ SDL_SCANCODE_UNKNOWN,
    /* 0x0A */ SDL_SCANCODE_UNKNOWN,
    /* 0x0B */ SDL_SCANCODE_UNKNOWN,
    /* 0x0C */ SDL_SCANCODE_UNKNOWN,
    /* 0x0D */ SDL_SCANCODE_UNKNOWN,
    /* 0x0E */ SDL_SCANCODE_UNKNOWN,
    /* 0x0F */ SDL_SCANCODE_UNKNOWN,

    /* 0x10 */ SDL_SCANCODE_UNKNOWN,
    /* 0x11 */ SDL_SCANCODE_UNKNOWN,
    /* 0x12 */ SDL_SCANCODE_UNKNOWN,
    /* 0x13 */ SDL_SCANCODE_UNKNOWN,
    /* 0x14 */ SDL_SCANCODE_UNKNOWN,
    /* 0x15 */ SDL_SCANCODE_UNKNOWN,
    /* 0x16 */ SDL_SCANCODE_UNKNOWN,
    /* 0x17 */ SDL_SCANCODE_UNKNOWN,
    /* 0x18 */ SDL_SCANCODE_UNKNOWN,
    /* 0x19 */ SDL_SCANCODE_UNKNOWN,
    /* 0x1A */ SDL_SCANCODE_UNKNOWN,
    /* 0x1B */ SDL_SCANCODE_UNKNOWN,
    /* 0x1C */ SDL_SCANCODE_KP_ENTER,
    /* 0x1D */ SDL_SCANCODE_RCTRL,
    /* 0x1E */ SDL_SCANCODE_UNKNOWN,
    /* 0x1F */ SDL_SCANCODE_UNKNOWN,

    /* 0x20 */ SDL_SCANCODE_UNKNOWN,
    /* 0x21 */ SDL_SCANCODE_UNKNOWN,
    /* 0x22 */ SDL_SCANCODE_UNKNOWN,
    /* 0x23 */ SDL_SCANCODE_UNKNOWN,
    /* 0x24 */ SDL_SCANCODE_UNKNOWN,
    /* 0x25 */ SDL_SCANCODE_UNKNOWN,
    /* 0x26 */ SDL_SCANCODE_UNKNOWN,
    /* 0x27 */ SDL_SCANCODE_UNKNOWN,
    /* 0x28 */ SDL_SCANCODE_UNKNOWN,
    /* 0x29 */ SDL_SCANCODE_UNKNOWN,
    /* 0x2A */ SDL_SCANCODE_UNKNOWN, // fake left shift, ignore
    /* 0x2B */ SDL_SCANCODE_UNKNOWN,
    /* 0x2C */ SDL_SCANCODE_UNKNOWN,
    /* 0x2D */ SDL_SCANCODE_UNKNOWN,
    /* 0x2E */ SDL_SCANCODE_UNKNOWN,
    /* 0x2F */ SDL_SCANCODE_UNKNOWN,

    /* 0x30 */ SDL_SCANCODE_UNKNOWN,
    /* 0x31 */ SDL_SCANCODE_UNKNOWN,
    /* 0x32 */ SDL_SCANCODE_UNKNOWN,
    /* 0x33 */ SDL_SCANCODE_UNKNOWN,
    /* 0x34 */ SDL_SCANCODE_UNKNOWN,
    /* 0x35 */ SDL_SCANCODE_KP_DIVIDE,
    /* 0x36 */ SDL_SCANCODE_UNKNOWN, // fake right shift, ignore
    /* 0x37 */ SDL_SCANCODE_PRINTSCREEN,
    /* 0x38 */ SDL_SCANCODE_RALT,
    /* 0x39 */ SDL_SCANCODE_UNKNOWN,
    /* 0x3A */ SDL_SCANCODE_UNKNOWN,
    /* 0x3B */ SDL_SCANCODE_UNKNOWN,
    /* 0x3C */ SDL_SCANCODE_UNKNOWN,
    /* 0x3D */ SDL_SCANCODE_UNKNOWN,
    /* 0x3E */ SDL_SCANCODE_UNKNOWN,
    /* 0x3F */ SDL_SCANCODE_UNKNOWN,

    /* 0x40 */ SDL_SCANCODE_UNKNOWN,
    /* 0x41 */ SDL_SCANCODE_UNKNOWN,
    /* 0x42 */ SDL_SCANCODE_UNKNOWN,
    /* 0x43 */ SDL_SCANCODE_UNKNOWN,
    /* 0x44 */ SDL_SCANCODE_UNKNOWN,
    /* 0x45 */ SDL_SCANCODE_UNKNOWN,
    /* 0x46 */ SDL_SCANCODE_PAUSE, // Ctrl+Break sends E0 46 E0 C6
    /* 0x47 */ SDL_SCANCODE_HOME,
    /* 0x48 */ SDL_SCANCODE_UP,
    /* 0x49 */ SDL_SCANCODE_PAGEUP,
    /* 0x4A */ SDL_SCANCODE_UNKNOWN,
    /* 0x4B */ SDL_SCANCODE_LEFT,
    /* 0x4C */ SDL_SCANCODE_UNKNOWN,
    /* 0x4D */ SDL_SCANCODE_RIGHT,
    /* 0x4E */ SDL_SCANCODE_UNKNOWN,
    /* 0x4F */ SDL_SCANCODE_END,

    /* 0x50 */ SDL_SCANCODE_DOWN,
    /* 0x51 */ SDL_SCANCODE_PAGEDOWN,
    /* 0x52 */ SDL_SCANCODE_INSERT,
    /* 0x53 */ SDL_SCANCODE_DELETE,
    /* 0x54 */ SDL_SCANCODE_UNKNOWN,
    /* 0x55 */ SDL_SCANCODE_UNKNOWN,
    /* 0x56 */ SDL_SCANCODE_UNKNOWN,
    /* 0x57 */ SDL_SCANCODE_UNKNOWN,
    /* 0x58 */ SDL_SCANCODE_UNKNOWN,
    /* 0x59 */ SDL_SCANCODE_UNKNOWN,
    /* 0x5A */ SDL_SCANCODE_UNKNOWN,
    /* 0x5B */ SDL_SCANCODE_LGUI,
    /* 0x5C */ SDL_SCANCODE_RGUI,
    /* 0x5D */ SDL_SCANCODE_APPLICATION
};

static Uint8 keyevents_ringbuffer[256];
static int keyevents_head = 0;
static int keyevents_tail = 0;

static void DOSVESA_DrainBIOSKeyboardBuffer(void)
{
    __dpmi_regs regs;
    for (;;) {
        regs.h.ah = 0x01; // BIOS: check for keystroke
        __dpmi_int(0x16, &regs);
        if (regs.x.flags & 0x40) { // ZF set = buffer empty
            break;
        }
        regs.h.ah = 0x00; // BIOS: read keystroke (removes it)
        __dpmi_int(0x16, &regs);
    }
}

void DOSVESA_PumpEvents(SDL_VideoDevice *device)
{
    /* Give cooperative threads a chance to run.  Audio mixing now runs
       in its own cooperative thread (via SDL's normal audio thread),
       so it will execute during this yield along with loading threads
       and anything else that is runnable. */
    DOS_Yield();

    static bool is_extended = false;
    static int pause_sequence_remaining = 0;

    while (keyevents_head != keyevents_tail) {
        const Uint8 event = keyevents_ringbuffer[keyevents_tail];
        keyevents_tail = (keyevents_tail + 1) & (SDL_arraysize(keyevents_ringbuffer) - 1);

        // Handle remaining bytes of E1 Pause key sequence (E1 1D 45 E1 9D C5).
        if (pause_sequence_remaining > 0) {
            pause_sequence_remaining--;
            continue;
        }

        // Pause key sends a multi-byte sequence: E1 1D 45 E1 9D C5. Emit PAUSE press+release and consume the rest.
        if (event == SCANCODE_PREFIX_PAUSE) {
            pause_sequence_remaining = 5; // skip the next 5 bytes
            SDL_SendKeyboardKey(0, SDL_GLOBAL_KEYBOARD_ID, 0, SDL_SCANCODE_PAUSE, true);
            SDL_SendKeyboardKey(0, SDL_GLOBAL_KEYBOARD_ID, 0, SDL_SCANCODE_PAUSE, false);
            continue;
        }

        if (event == SCANCODE_PREFIX_EXTENDED) {
            is_extended = true;
            continue;
        }

        const int scancode = (int)(event & SCANCODE_MASK);
        const bool pressed = ((event & SCANCODE_RELEASE) == 0);

        SDL_Scancode sc = SDL_SCANCODE_UNKNOWN;

        if (is_extended) {
            is_extended = false;
            if (scancode < SDL_arraysize(DOSVESA_ExtendedScancodeMapping)) {
                sc = DOSVESA_ExtendedScancodeMapping[scancode];
            }
        } else {
            if (scancode < SDL_arraysize(DOSVESA_ScancodeMapping)) {
                sc = DOSVESA_ScancodeMapping[scancode];
            }
        }

        if (sc != SDL_SCANCODE_UNKNOWN) {
            SDL_SendKeyboardKey(0, SDL_GLOBAL_KEYBOARD_ID, 0, sc, pressed);

            // Generate text input events for key-down on printable characters.
            // SDL keycodes below SDLK_SCANCODE_MASK are Unicode codepoints.
            if (pressed) {
                SDL_Keymod mod = SDL_GetModState();
                if (!(mod & (SDL_KMOD_CTRL | SDL_KMOD_ALT))) {
                    SDL_Keycode keycode = SDL_GetKeyFromScancode(sc, mod, false);
                    if (keycode > 0 && keycode < SDLK_SCANCODE_MASK && !SDL_iscntrl((int)keycode)) {
                        char text[5];
                        char *end = SDL_UCS4ToUTF8((Uint32)keycode, text);
                        *end = '\0';
                        SDL_SendKeyboardText(text);
                    }
                }
            }
        }
    }

    // We chain IRQ1 to BIOS, so drain its keyboard queue continuously to prevent
    // BIOS buffer overflow beeps during long key autorepeat.
    DOSVESA_DrainBIOSKeyboardBuffer();

    SDL_Mouse *mouse = SDL_GetMouse();
    if (mouse->internal) { // if non-NULL, there's a mouse detected on the system.
        __dpmi_regs regs;

        regs.x.ax = 0x3; // read mouse buttons and position.
        __dpmi_int(0x33, &regs);
        const Uint16 buttons = (int)(Sint16)regs.x.bx;

        SDL_SendMouseButton(0, mouse->focus, SDL_DEFAULT_MOUSE_ID, SDL_BUTTON_LEFT, (buttons & (1 << 0)) != 0);
        SDL_SendMouseButton(0, mouse->focus, SDL_DEFAULT_MOUSE_ID, SDL_BUTTON_RIGHT, (buttons & (1 << 1)) != 0);
        SDL_SendMouseButton(0, mouse->focus, SDL_DEFAULT_MOUSE_ID, SDL_BUTTON_MIDDLE, (buttons & (1 << 2)) != 0);

        if (!mouse->relative_mode) {
            const int x = (int)(Sint16)regs.x.cx; // part of function 0x3's return value.
            const int y = (int)(Sint16)regs.x.dx;
            SDL_SendMouseMotion(0, mouse->focus, SDL_DEFAULT_MOUSE_ID, false, x, y);
        } else {
            regs.x.ax = 0xB; // read motion counters
            __dpmi_int(0x33, &regs);
            // values returned here are -32768 to 32767
            const SDL_VideoData *viddata = device->internal;
            const float MICKEYS_PER_HPIXEL = viddata->mickeys_per_hpixel;
            const float MICKEYS_PER_VPIXEL = viddata->mickeys_per_vpixel;
            const int mickeys_x = (int)(Sint16)regs.x.cx;
            const int mickeys_y = (int)(Sint16)regs.x.dx;
            SDL_SendMouseMotion(0, mouse->focus, SDL_DEFAULT_MOUSE_ID, true, mickeys_x / MICKEYS_PER_HPIXEL, mickeys_y / MICKEYS_PER_VPIXEL);
        }
    }
}

static void KeyboardIRQHandler(void) // this is wrapped in a thing that handles IRET, etc.
{
    keyevents_ringbuffer[keyevents_head] = inportb(KBD_DATA_PORT);
    keyevents_head = (keyevents_head + 1) & (SDL_arraysize(keyevents_ringbuffer) - 1);
    DOS_EndOfInterrupt(1);
}
static void KeyboardIRQHandler_End(void) {} // end-of-ISR label for memory locking

void DOSVESA_InitKeyboard(SDL_VideoDevice *device)
{
    SDL_VideoData *data = device->internal;

    // Lock ISR code and data to prevent page faults during interrupts
    DOS_LockCode(KeyboardIRQHandler, KeyboardIRQHandler_End);
    DOS_LockVariable(keyevents_ringbuffer);
    DOS_LockVariable(keyevents_head);
    DOS_LockVariable(keyevents_tail);

    DOS_HookInterrupt(1, KeyboardIRQHandler, &data->keyboard_interrupt_hook);
}

void DOSVESA_QuitKeyboard(SDL_VideoDevice *device)
{
    SDL_VideoData *data = device->internal;
    DOS_UnhookInterrupt(&data->keyboard_interrupt_hook, false);

    // Drain the BIOS keyboard buffer so held keys (like ESC) don't
    // bleed through to the DOS command line after we exit.
    DOSVESA_DrainBIOSKeyboardBuffer();
}

#endif // SDL_VIDEO_DRIVER_DOSVESA
