//! Panic handler and diagnostic display.
//!
//! Prints panic information to the kernel log and displays the message on the
//! framebuffer before halting the CPU.
use core::arch::riscv64::wfi;

use alloc::{format, string::ToString};
use log::error;

use crate::{
    HEAP_INITIALIZED,
    draw::{Color, Draw, FONT_HEIGHT},
    uart::write_uart,
    vga::Vga,
};

#[panic_handler]
/// Kernel panic handler that displays the panic message on the framebuffer and halts.
fn panic(panic_info: &core::panic::PanicInfo) -> ! {
    if !HEAP_INITIALIZED.load(core::sync::atomic::Ordering::Relaxed) {
        write_uart("EARLY PANIC !");
    } else {
        error!("PANIC !");
        let mut panic_message = panic_info.message().to_string();
        if let Some(location) = panic_info.location() {
            panic_message = format!("{panic_message} at {}:{}", location.file(), location.line());
        }
        error!("{panic_message}");

        Vga.clear_screen(Color::WHITE);
        unsafe { Vga.draw_string(0, 0, "PANIC !", Color::BLACK, Color::WHITE) };
        unsafe {
            Vga.draw_string(
                0,
                FONT_HEIGHT as u16,
                panic_message,
                Color::BLACK,
                Color::WHITE,
            )
        };
    }

    loop {
        unsafe { wfi() }
    }
}