#include "portio.hpp"
#include "vgaterminal.hpp"

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <utility>

void VGATerminal::write(char c) noexcept
{
    switch (c) {
    case '\n':
        offset += Width;
        [[fallthrough]];
    case '\r':
        offset -= offset % Width;
        break;
    default:
        checkpos();
        put(c);
        updatecursor();
        break;
    }
}

void VGATerminal::put(char c) noexcept
{
    std::uint16_t cell = c
        | (std::to_underlying(foreground) << 8)
        | (std::to_underlying(background) << 12);

    auto ptr = reinterpret_cast<std::uint16_t *>(Videoram);
    ptr[offset++] = cell;
}

void VGATerminal::checkpos() noexcept
{
    if (offset >= Width * Height) {
        auto ptr = reinterpret_cast<std::uint16_t *>(Videoram);
        const auto end = ptr + Width * Height;
        std::copy(ptr + Width, end, ptr);
        std::fill(end - Width, end, 0);
        offset = Width * Height - Width;
    }
}

void VGATerminal::updatecursor() const noexcept
{
    asm volatile("cli");
    outb(0x03d4, 0x0f);
    outb(0x03d5, static_cast<std::uint8_t>(offset));
    outb(0x03d4, 0x0e);
    outb(0x03d5, static_cast<std::uint8_t>(offset >> 8));
    asm volatile("sti");
}