use crate::lock::OnceCell;

use std::thread::LocalKey;

pub struct StaticCell<T: 'static> {

inner: &'static LocalKey<OnceCell<&'static T>>,

}

fn leak<T>(x: T) -> &'static T {

Box::leak(Box::new(x))

}

impl<T> StaticCell<T> {

#[doc(hidden)]

pub const fn _from_localkey(inner: &'static LocalKey<OnceCell<&'static T>>) -> Self {

Self { inner }

}

pub fn get(&'static self) -> Option<&'static T> {

self.inner.with(|x| x.get().copied())

}

pub fn set(&'static self, value: T) -> Result<(), T> {

// thread-safe because it's a unsync::OnceCell

self.inner.with(|x| {

if x.get().is_some() {

Err(value)

} else {

// will never fail

let _ = x.set(leak(value));

Ok(())

}

})

}

pub fn get_or_init<F>(&'static self, f: F) -> &'static T

where

F: FnOnce() -> T,

{

self.inner.with(|x| *x.get_or_init(|| leak(f())))

}

pub fn get_or_try_init<F, E>(&'static self, f: F) -> Result<&'static T, E>

where

F: FnOnce() -> Result<T, E>,

{

self.inner

.with(|x| x.get_or_try_init(|| f().map(leak)).map(|&x| x))

}

}

#[macro_export]

macro_rules! static_cell {

($($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty;)+) => {

$($(#[$attr])*

$vis static $name: $crate::static_cell::StaticCell<$t> = {

::std::thread_local! {

$vis static $name: $crate::lock::OnceCell<&'static $t> = $crate::lock::OnceCell::new();

}

$crate::static_cell::StaticCell::_from_localkey(&$name)

};)+

};

}

use crate::lock::OnceCell;

pub struct StaticCell<T: 'static> {

inner: OnceCell<T>,

}

impl<T> StaticCell<T> {

#[doc(hidden)]

pub const fn _from_oncecell(inner: OnceCell<T>) -> Self {

Self { inner }

}

pub fn get(&'static self) -> Option<&'static T> {

self.inner.get()

}

pub fn set(&'static self, value: T) -> Result<(), T> {

self.inner.set(value)

}

pub fn get_or_init<F>(&'static self, f: F) -> &'static T

where

F: FnOnce() -> T,

{

self.inner.get_or_init(f)

}

pub fn get_or_try_init<F, E>(&'static self, f: F) -> Result<&'static T, E>

where

F: FnOnce() -> Result<T, E>,

{

self.inner.get_or_try_init(f)

}

}

#[macro_export]

macro_rules! static_cell {

($($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty;)+) => {

$($(#[$attr])*

$vis static $name: $crate::static_cell::StaticCell<$t> =

$crate::static_cell::StaticCell::_from_oncecell($crate::lock::OnceCell::new());)+

};

}