#![no_std]
#![no_main]

use core::{fmt::Write, mem::size_of_val};
use gba::{
  mgba::{MgbaBufferedLogger, MgbaMessageLevel},
  prelude::*,
};

#[panic_handler]
fn panic_handler(info: &core::panic::PanicInfo) -> ! {
  if let Ok(mut logger) = MgbaBufferedLogger::try_new(MgbaMessageLevel::Fatal) {
    write!(logger, "{info}").ok();
  }
  loop {}
}

// GbaCell is non-freeze, so `.data` section, so this will default to IWRAM.
static KEYS: GbaCell<KeyInput> = GbaCell::new(KeyInput::new());

// We can also put things into EWRAM if we want to.
#[link_section = ".ewram"]
static VALUE: GbaCell<u16> = GbaCell::new(0);

extern "C" fn irq_handler(_: IrqBits) {
  // just as a demo, we'll read the keys during vblank.
  KEYS.write(KEYINPUT.read());
}

#[no_mangle]
extern "C" fn main() -> ! {
  RUST_IRQ_HANDLER.write(Some(irq_handler));
  DISPSTAT.write(DisplayStatus::new().with_irq_vblank(true));
  IE.write(IrqBits::VBLANK);
  IME.write(true);

  if let Ok(mut logger) = MgbaBufferedLogger::try_new(MgbaMessageLevel::Debug) {
    writeln!(logger, "hello!").ok();
  }

  {
    // get our tile data into memory.
    //let src = ;
    let dest = CHARBLOCK0_4BPP.index(0).as_usize() as *mut u32;
    let info = BitUnpackInfo {
      src_byte_len: size_of_val(&CGA_8X8_THICK) as u16,
      src_elem_width: 1,
      dest_elem_width: 4,
      offset_and_touch_zero: 0,
    };
    unsafe { BitUnPack(CGA_8X8_THICK.as_ptr().cast::<u8>(), dest, &info) };
  }

  DISPCNT.write(DisplayControl::new().with_show_bg2(true));

  loop {
    VBlankIntrWait();

    let k = KEYS.read();
    VALUE.write((k.to_u16() + 3) / k.to_u16()); // force a runtime division
    BACKDROP_COLOR.write(Color(k.to_u16()));
  }
}