//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Authors:    spectral`                                                     //
//              NeoX                                                          //
//                                                                            //
//  Desc:       Early terminal functions                                      //
//----------------------------------------------------------------------------//

#include <kaleid.h>

static Terminal_t vgaTerm;

//
// Initialize standard output
//
void InitTerms(void)
{
    KalAssert(!GetStdOut() && vgaTerm.initDone != INITOK);

    vgaTerm.initDone = INITOK;

    SetStdDbg(&vgaTerm);
    SetStdOut(&vgaTerm);

    ClearTerm(GetStdOut());
}

//
// Fill terminal with spaces
//
error_t ClearTerm(Terminal_t *term)
{
    error_t retcode;

    if (term == NULL) return EINVAL;
    KalAssert(term->initDone == INITOK);

    AquireLock(&term->lock);
    retcode = term->ClearTermUnlocked(term);
    ReleaseLock(&term->lock);

    return retcode;
}

//
// Change the color code
//
error_t ChTermColor(Terminal_t *term, TermColor_t fgColor, TermColor_t bgColor)
{
    if (fgColor > KTERM_COLOR_WHITE || bgColor > KTERM_COLOR_WHITE)
        return EINVAL;

    if (term == NULL)
        return EINVAL;

    AquireLock(&term->lock);

    term->fgColor = fgColor;
    term->bgColor = bgColor;

    ReleaseLock(&term->lock);

    return EOK;
}

//
// Write a single character on the terminal
//
error_t PutOnTerm(Terminal_t *term, char ch)
{
    error_t retcode;

    if (term == NULL) return EINVAL;
    KalAssert(term->initDone == INITOK);

    AquireLock(&term->lock);
    retcode = term->PutOnTermUnlocked(term, ch);
    ReleaseLock(&term->lock);

    return retcode;
}

//
// Print string on terminal
//
error_t PrintOnTerm(Terminal_t *term, const char *str)
{
    error_t retcode = EOK;

    if (term == NULL) return EINVAL;
    KalAssert(term->initDone == INITOK);

    AquireLock(&term->lock);
    while (*str && retcode == EOK) {
        retcode = term->PutOnTermUnlocked(term, *str++);
    }
    ReleaseLock(&term->lock);

    return retcode;
}

//----------------------------------------------------------//
//           Internal functions for VGA terminals           //
//           These DO NOT check input correctness           //
//----------------------------------------------------------//

//
// VGA-related macros
//
#define VGA_ComputeColorCode(fg, bg)    ((fg) | (bg) << 4)
#define VGA_ComputeOffset(term, x, y)   ((y) * (term)->width + (x))
#define VGA_ComputeEntry(ch, cl)        (((ushort)(ch)) | (ushort)(cl) << 8)

//
// Fill terminal with '\0'
//
error_t VGA_ClearTermUnlocked(Terminal_t *term)
{
    const uchar  color   = VGA_ComputeColorCode(term->fgColor, term->bgColor);
    const ushort filler  = VGA_ComputeEntry('\0', color);
    const size_t bufsize = term->width * term->height;

    // Fill the buffer
    memsetw((ushort *)term->data, filler, bufsize);

    // XXX update cursor too
    term->currentX = term->currentY = 0;

    return EOK;
}

//
// Write a single character on the terminal
//
error_t VGA_PutOnTermUnlocked(Terminal_t *term, char ch)
{
    uint i;
    size_t prevY;

    if (ch == '\r') {
        term->currentX = 0;
        return EOK;
    }

    //
    // Line feed first takes us to the very end of the line
    // Later in this function we actually do the line feed
    //
    else if (ch == '\n') {
        term->currentY = term->width - 1;
    }

    //
    // Tabulations account for "term->tabSize" spaces
    //
    else if (ch == '\t') {
        prevY = term->currentY;
        for (i = 0; i < term->tabSize; i++) {
            //
            // Make sure tabulations can't spread over two lines
            //
            if (term->currentY == prevY) {
                VGA_PutOnTermUnlocked(term, ' ');
            }
        }
    }

    else {
        ushort      *buffer  = (ushort *)term->data;
        const size_t offset = VGA_ComputeOffset(term, term->currentY, term->currentY);
        buffer[offset] = VGA_ComputeEntry(ch, VGA_ComputeColorCode(term->fgColor, term->bgColor));
    }

    //
    // Did we reach the end of line?
    //
    if (++term->currentX == term->width) {
        term->currentX = 0;

        //
        // Did we reach the buffer's end?
        //
        if (++term->currentY == term->height) {
            //
            // XXX scroll up
            //
            term->currentY = 0;
        }
    }

    //
    // Nothing can go wrong
    //
    return EOK;
}

//
// Print string on terminal
//
error_t VGA_PrintOnTermUnlocked(Terminal_t *term, const char *str)
{
    error_t retcode = EOK;

    while (*str && retcode == EOK) {
        retcode = term->PutOnTermUnlocked(term, *str++);
    }

    return retcode;
}

//
// VGA output
//
static Terminal_t vgaTerm = {
    .initDone   = FALSE,
    .lock       = INITLOCK(KLOCK_MUTEX),

    .name       = "VGA Output Terminal",
    .type       = "VGA",

    .data       = (void *)0xB8000,
    .width      = 80,
    .height     = 25,
    .currentX   = 0,
    .currentY   = 0,

    .tabSize    = KTABSIZE,
    .fgColor    = KTERM_COLOR_LGREY,
    .bgColor    = KTERM_COLOR_BLACK,

    .ClearTermUnlocked      = VGA_ClearTermUnlocked,
    .PutOnTermUnlocked      = VGA_PutOnTermUnlocked,
    .PrintOnTermUnlocked    = VGA_PrintOnTermUnlocked,
};