use crate::io::vga_text::{CharState, Color, OStream};

const PANIC_SCREEN_MESSAGE_BUFFER_SIZE: usize = 2048;

struct TextBuffer<'a> {
    dst: &'a mut [u8],
    len: usize,
}

impl<'a> TextBuffer<'a> {
    fn new(dst: &'a mut [u8]) -> Self {
        Self { dst, len: 0 }
    }
    fn get(&'a mut self) -> &'a mut [u8] {
        &mut self.dst[..self.len]
    }
}

impl<'a> core::fmt::Write for TextBuffer<'a> {
    fn write_str(&mut self, s: &str) -> core::fmt::Result {
        if s.len() + self.len > self.dst.len() {
            Err(core::fmt::Error)
        } else {
            let s = s.as_bytes();
            (&mut self.dst[self.len..self.len + s.len()]).clone_from_slice(s);
            self.len += s.len();
            Ok(())
        }
    }
}

pub fn show(args: Option<&core::fmt::Arguments>) {
    let mut stderr = OStream::new();
    stderr.set_state(CharState::from_colors(Color::LightRed, Color::Red));
    stderr.clear();
    stderr.print(b"uff-os");
    stderr.set_row(10);
    stderr.set_state(CharState::from_colors(Color::White, Color::Red));
    stderr.print_centered(b"<kernel panic>");
    stderr.set_row(14);
    stderr.set_state(CharState::from_colors(Color::Cyan, Color::Red));
    stderr.set_centered(true);
    let buffer: &mut [u8] = &mut [b' '; PANIC_SCREEN_MESSAGE_BUFFER_SIZE];
    let mut tbuffer = TextBuffer::new(buffer);
    let _ = core::fmt::write(
        &mut tbuffer,
        *args.unwrap_or(&format_args!("no panic information obtainable")),
    );
    stderr.print(tbuffer.get());
    stderr.set_centered(false);
}