#include "os/syscall.hpp"

#include <bit>
#include <cstddef>
#include "os/cpu.hpp"
#include "os/segments.hpp"
#include "os/serial.hpp"
#include "os/tty.hpp"

extern "C" void __handleSyscall();

namespace baos
{
void setupSyscall() noexcept
{
    // enable syscall/sysexit
    cpu::setMSRBits(cpu::MSR::IA32_EFER, cpu::IA32_EFER_SYSTEM_CALL_EXTENSIONS_BIT);
    cpu::writeMSR(cpu::MSR::LSTAR, std::bit_cast<std::uint64_t>(&__handleSyscall));
    cpu::writeMSR(cpu::MSR::STAR, static_cast<std::uint64_t>(SEGIDX_KERNEL_CODE) << 32 | static_cast<std::uint64_t>(SEGIDX_KERNEL_DATA) << 48);
}

void sysFileRead(unsigned fileDescriptor, char* buffer, std::size_t count) noexcept
{
    // TODO
}

void sysFileWrite(unsigned fileDescriptor, const char* buffer, std::size_t count) noexcept
{
    for (std::size_t index = 0; index < count; ++index) {
        serialWrite(PORT_COM1, buffer[index]);
    }
    tty::write(buffer, count);
}
}

extern "C" void __baosSyscall(baos::Syscall cmd, std::uint64_t param0, std::uint64_t param1, std::uint64_t param2) noexcept
{
    using namespace baos;

    switch (cmd)
    {
        case Syscall::FILE_READ:
            sysFileRead(static_cast<unsigned>(param0), std::bit_cast<char*>(param1), param2);
            break;
        case Syscall::FILE_WRITE:
            sysFileWrite(static_cast<unsigned>(param0), std::bit_cast<const char*>(param1), param2);
            break;
        case Syscall::EXIT:
            break;
    }
}