#include "userprog/syscall.h"
#include <stdio.h>
#include <syscall-nr.h>
#include "threads/interrupt.h"
#include "threads/thread.h"

#include "threads/init.h"
#include "filesys/filesys.h"
#include "filesys/off_t.h"

static void syscall_handler (struct intr_frame *);

void
syscall_init (void) 
{
  intr_register_int (0x30, 3, INTR_ON, syscall_handler, "syscall");
}

static void
halt (void)
{
  power_off();
}

static bool
create (const char *filename, off_t initial_size)
{
  return filesys_create (filename, initial_size);
}

static void
write (const char *buf)
{
  printf ("printf: %s", buf);
}

// cast to TYPE and deref argument N from f->esp
#define INTR_ESP(N, TYPE) *(TYPE *)(f->esp+(4*(N)))

static void
syscall_handler (struct intr_frame *f UNUSED) 
{
  int syscall_number = INTR_ESP(0, int);
  switch (syscall_number) {
    case 0:
      // halt
      halt ();
      break;
    case 1:
      // exit
      break;
    case 4:
      // create
      f->eax = create(INTR_ESP(1, char *), INTR_ESP(2, off_t));
      break;
    case 6:
      // open
      break;
    case 8:
      // read
      break;
    case 9:
      // write
      write(INTR_ESP(2, char *));
      break;
    case 12:
      // close
      break;
    default:
      printf ("kernel: unknown syscall '%d'\n", syscall_number);
      break;
  }
}