#include "arch/context_switching/syscall/main.hpp"

#include "arch/context_switching/interrupt_descriptor_table/segment_selector.hpp"
#include "arch/exception_handling/assert.hpp"
#include "arch/exception_handling/panic.hpp"
#include "arch/kernel/cpu/msr.hpp"

#include <cstdint>

namespace teachos::arch::context_switching::syscall
{
  namespace
  {
    constexpr interrupt_descriptor_table::segment_selector KERNEL_CODE_SEGMENT_SELECTOR{
        1U, interrupt_descriptor_table::segment_selector::REQUEST_LEVEL_KERNEL};

    auto constexpr IA32_STAR_ADDRESS = 0xC0000081;
    auto constexpr IA32_LSTAR_ADDRESS = 0xC0000082;
    auto constexpr IA32_FMASK_ADDRESS = 0xC0000084;

  }  // namespace

  auto enable_syscall() -> void
  {
    uint64_t const syscall_function = reinterpret_cast<uint64_t>(syscall_handler);
    kernel::cpu::write_msr(IA32_LSTAR_ADDRESS, syscall_function);
    kernel::cpu::write_msr(IA32_FMASK_ADDRESS, 0U);

    uint64_t const kernel_cs = KERNEL_CODE_SEGMENT_SELECTOR;
    uint64_t const star_value = (kernel_cs << 32) | (kernel_cs << 48);
    kernel::cpu::write_msr(IA32_STAR_ADDRESS, star_value);

    kernel::cpu::set_efer_bit(kernel::cpu::efer_flags::SCE);
  }

  auto syscall(type syscall_number, arguments args) -> uint64_t
  {
    asm volatile("mov %[input], %%rax"
                 : /* no output from call */
                 : [input] "m"(syscall_number)
                 : "memory");

    asm volatile("mov %[input], %%rdi " : /* no output from call */ : [input] "m"(args.arg_0) : "memory");
    asm volatile("mov %[input], %%rsi" : /* no output from call */ : [input] "m"(args.arg_1) : "memory");
    asm volatile("mov %[input], %%rdx" : /* no output from call */ : [input] "m"(args.arg_2) : "memory");
    asm volatile("mov %[input], %%r10" : /* no output from call */ : [input] "m"(args.arg_3) : "memory");
    asm volatile("mov %[input], %%r8" : /* no output from call */ : [input] "m"(args.arg_4) : "memory");
    asm volatile("mov %[input], %%r9" : /* no output from call */ : [input] "m"(args.arg_5) : "memory");

    asm volatile("syscall");

    uint64_t error{};
    asm volatile("mov %%rax, %[output]" : [output] "=m"(error));
    return error;
  }

}  // namespace teachos::arch::context_switching::syscall