#![no_std]
#![no_main]

mod spin;
mod vga;

use core::{arch::asm, panic::PanicInfo, fmt::Write};

#[repr(C)]
#[derive(Clone, Debug)]
struct BiosIntr {
  eax: u32,
  ebx: u32,
  ecx: u32,
  edx: u32,
  esi: u32,
  edi: u32,
  ds: u16,
  es: u16,
  eflags: u32,
}

unsafe extern "C" {
  unsafe fn _bios_call(intr: u32, args: *mut BiosIntr);
}

#[panic_handler]
fn panic(info: &PanicInfo) -> ! {
  vga_println!("panic!");
  if let Some(location) = info.location() {
    vga_println!("{}", location);
  }
  vga_println!("{}", info.message());
  hlt()
}

#[no_mangle]
pub extern "C" fn _start() -> ! {
  vga::vga_init();

  vga_println!("hello from rust");

  let mut args = BiosIntr {
    eax: 0xe820,
    ebx: 0,
    ecx: 24,
    edx: 0x534d4150,
    esi: 0,
    edi: 0x6a00,
    ds: 0,
    es: 0,
    eflags: 0,
  };

  unsafe {
    _bios_call(0x15, &raw mut args);
  }

  vga_println!("eax = {:x}", args.eax);

  hlt()
}

#[inline]
fn hlt() -> ! {
  loop {
    unsafe {
      asm!("hlt");
    }
  }
}