use core::mem::MaybeUninit;
use core::ops::{Deref, DerefMut};

/// Plain Old data type
pub trait Pod: Copy + 'static {
    fn uninit() -> Self { unsafe { MaybeUninit::uninit().assume_init() } }
    fn zeroed() -> Self { unsafe { MaybeUninit::zeroed().assume_init() } }
}

macro_rules! primitive {
    ($($p:ty),*) => {
        $(impl Pod for $p {})*
    }
}

primitive!(u8, u16, u32, u64, u128);
primitive!(i8, i16, i32, i64, i128);
primitive!(f32, f64, usize, isize);
primitive!(());

impl<const LEN: usize, T: Pod> Pod for [T;LEN] {}


/// Type with unsafe interior mutability
/// but also with Send+Sync
///
/// internally just wraps UnsafeCell
#[repr(transparent)]
pub struct Mut<T>(core::cell::UnsafeCell<T>);
unsafe impl<T> Sync for Mut<T> {}
unsafe impl<T> Send for Mut<T> {}

impl<T: Sized> Mut<T> {
    pub const fn new(value: T) -> Self {
        Self(core::cell::UnsafeCell::new(value))
    }
    pub const fn as_ptr(&self) -> *mut T {
        self.0.get()
    }
}

impl<T: Pod> Mut<T> {
    pub fn set(&self, value: T) { unsafe { core::ptr::write(self.as_ptr(), value) } }
    pub fn get(&self) -> T { unsafe { core::ptr::read(self.as_ptr()) } }
}
impl<T> Mut<MaybeUninit<T>> {
    pub const fn zeroed() -> Self { Self(core::cell::UnsafeCell::new(MaybeUninit::zeroed())) }
    pub const fn uninit() -> Self { Self(core::cell::UnsafeCell::new(MaybeUninit::uninit())) }
}

impl<T> Deref for Mut<T> {
    type Target = core::cell::UnsafeCell<T>;
    fn deref(&self) -> &Self::Target { &self.0 }
}