// from https://github.com/rust-console/gba/blob/main/examples/hello.rs
#![no_std]
#![no_main]

use core::fmt::Write;
use gba::prelude::*;

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

#[link_section = ".ewram"]
static FRAME_KEYS: GbaCell<KeyInput> = GbaCell::new(KeyInput::new());

#[link_section = ".iwram"]
extern "C" fn irq_handler(_: IrqBits) {
    // We'll read the keys during vblank and store it for later.
    FRAME_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();

        let fx_u: Fixed<u32, 8> = Fixed::<u32, 8>::wrapping_from(7) + Fixed::<u32, 8>::from_raw(12);
        writeln!(logger, "fixed unsigned: {fx_u:?}").ok();

        let fx_i1: Fixed<i32, 8> =
            Fixed::<i32, 8>::wrapping_from(8) + Fixed::<i32, 8>::from_raw(15);
        writeln!(logger, "fixed signed positive: {fx_i1:?}").ok();

        let fx_i2: Fixed<i32, 8> = Fixed::<i32, 8>::wrapping_from(0)
            - Fixed::<i32, 8>::wrapping_from(3)
            - Fixed::<i32, 8>::from_raw(17);
        writeln!(logger, "fixed signed negative: {fx_i2:?}").ok();
    }

    {
        // get our tile data into memory.
        Cga8x8Thick.bitunpack_4bpp(CHARBLOCK0_4BPP.as_region(), 0);
    }

    {
        // set up the tilemap
        let tsb = TEXT_SCREENBLOCKS.get_frame(31).unwrap();
        for y in 0..16 {
            let row = tsb.get_row(y).unwrap();
            for (x, addr) in row.iter().enumerate().take(16) {
                let te = TextEntry::new().with_tile((y * 16 + x) as u16);
                addr.write(te);
            }
        }
    }

    {
        // Set BG0 to use the tilemap we just made, and set it to be shown.
        BG0CNT.write(BackgroundControl::new().with_screenblock(31));
        DISPCNT.write(DisplayControl::new().with_show_bg0(true));
    }

    let mut x_off = 0_u32;
    let mut y_off = 0_u32;
    let mut backdrop_color = Color(0);
    loop {
        VBlankIntrWait();
        // show current frame
        BACKDROP_COLOR.write(backdrop_color);
        BG0HOFS.write(x_off as u16);
        BG0VOFS.write(y_off as u16);

        // prep next frame
        let k = FRAME_KEYS.read();
        backdrop_color = Color(k.to_u16());
        if k.up() {
            y_off = y_off.wrapping_add(1);
        }
        if k.down() {
            y_off = y_off.wrapping_sub(1);
        }
        if k.left() {
            x_off = x_off.wrapping_add(1);
        }
        if k.right() {
            x_off = x_off.wrapping_sub(1);
        }
    }
}