use core::sync::atomic::{AtomicU64, Ordering};

static HHDM_OFFSET: AtomicU64 = AtomicU64::new(0);

/// Store the Higher-Half Direct Map offset obtained from the bootloader.
/// Must be called once during early boot, before any address translation.
pub fn init_hhdm(offset: u64) {
    HHDM_OFFSET.store(offset, Ordering::Release);
}

/// Return the HHDM offset (kernel virtual base for physical memory).
#[inline]
pub fn get_hhdm() -> u64 {
    HHDM_OFFSET.load(Ordering::Relaxed)
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct PhysAddr(pub u64);

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
pub struct VirtAddr(pub u64);

impl PhysAddr {
    /// Convert physical address to virtual via HHDM offset
    pub fn to_virt(self) -> VirtAddr {
        VirtAddr(self.0 + get_hhdm())
    }
    
    #[allow(dead_code)]
    pub fn is_aligned(self) -> bool { self.0 % 4096 == 0 }
    
    #[allow(dead_code)]
    pub fn align_down(self) -> Self { Self(self.0 & !0xFFF) }
    
    #[allow(dead_code)]
    pub fn align_up(self) -> Self { Self((self.0 + 4095) & !0xFFF) }
}

impl VirtAddr {
    #[allow(dead_code)]
    pub fn to_phys(self) -> Option<PhysAddr> {
        let hhdm = get_hhdm();
        if self.0 < hhdm { return None; }
        Some(PhysAddr(self.0 - hhdm))
    }

    #[allow(dead_code)]
    pub fn as_ptr<T>(self) -> *const T { self.0 as *const T }

    pub fn as_mut_ptr<T>(self) -> *mut T { self.0 as *mut T }
}