#include "src/kernel/syscall.h"
#include "src/kernel/gdt.h"
#include "src/kernel/process.h"
#include "src/lib/layout.h"
#include "src/lib/util.h"

#define MSR_EFER 0xC0000080
#define MSR_STAR 0xC0000081
#define MSR_LSTAR 0xC0000082
#define MSR_FMASK 0xC0000084

static inline uint64_t rdmsr(uint32_t msr) {
  uint32_t lo, hi;
  __asm__ volatile("rdmsr" : "=a"(lo), "=d"(hi) : "c"(msr));
  return ((uint64_t)hi << 32) | lo;
}

static inline void wrmsr(uint32_t msr, uint64_t value) {
  __asm__ volatile("wrmsr" : : "c"(msr), "a"((uint32_t)value), "d"((uint32_t)(value >> 32)));
}

extern void syscall_entry();

void syscall_init() {
  wrmsr(MSR_EFER, rdmsr(MSR_EFER) | 0x01);
  wrmsr(MSR_STAR, ((uint64_t)KERNEL_DS << 48) | ((uint64_t)KERNEL_CS << 32));
  wrmsr(MSR_LSTAR, (uint64_t)syscall_entry);
  wrmsr(MSR_FMASK, 0x200);
}

static void write(uint64_t fd, uint64_t data, uint64_t bytes) {
  (void)fd;
  current_process->stdout->write(current_process->stdout, (const char *)data, bytes);
}

static void exit() {
  __asm__ volatile("mov %0, %%cr3" : : "r"(KERNEL_VIRTUAL_PML4) : "memory");

  process_destroy(current_process);
  current_process = NUL;

  while (1)
    ;

  // shutdown for now
  // outw(0x604, 0x2000);
  // __asm__ volatile("cli; hlt");
}

void syscall_dispatch(uint64_t func, uint64_t arg1, uint64_t arg2, uint64_t arg3) {
  switch (func) {
  case SYSCALL_WRITE:
    write(arg1, arg2, arg3);
    break;
  case SYSCALL_EXIT:
    exit();
    break;
  default:
    break;
  }
}