use spin::Once;

use x86_64::{PhysAddr, VirtAddr};

static HHDM_OFFSET: Once<u64> = Once::new();

pub fn set_hhdm_offset(offset: u64) {
    HHDM_OFFSET.call_once(|| offset);
}

#[inline]
pub fn hhdm_offset() -> u64 {
    *HHDM_OFFSET.get().expect("HHDM offset not initialized")
}

#[inline]
pub fn phys_to_virt(phys: PhysAddr) -> VirtAddr {
    VirtAddr::new(phys.as_u64() + hhdm_offset())
}

#[allow(dead_code)]
pub fn virt_to_phys(virt: VirtAddr) -> Option<PhysAddr> {
    virt.as_u64().checked_sub(hhdm_offset()).map(PhysAddr::new)
}

pub fn zero_frame(frame_phys: PhysAddr) {
    assert!(
        frame_phys.is_aligned(4096u64),
        "zero_frame: address not page-aligned"
    );
    let virt = phys_to_virt(frame_phys);
    unsafe {
        core::ptr::write_bytes(virt.as_mut_ptr::<u8>(), 0, 4096);
    }
}