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use std::fmt::{self, Debug, Formatter};
use std::hash::{Hash, Hasher};
use std::marker::PhantomData;
use std::ops::{Deref, DerefMut};
use typst_syntax::Span;
use crate::foundations::{Content, Label, NativeElement};
use crate::introspection::Location;
/// A packed element of a static type.
#[derive(Clone)]
#[repr(transparent)]
pub struct Packed<T: NativeElement>(
/// Invariant: Must be of type `T`.
Content,
PhantomData<T>,
);
impl<T: NativeElement> Packed<T> {
/// Pack element while retaining its static type.
pub fn new(element: T) -> Self {
// Safety: The element is known to be of type `T`.
Packed(element.pack(), PhantomData)
}
/// Try to cast type-erased content into a statically known packed element.
pub fn from_ref(content: &Content) -> Option<&Self> {
if content.is::<T>() {
// Safety:
// - We have checked the type.
// - Packed<T> is repr(transparent).
return Some(unsafe { std::mem::transmute::<&Content, &Packed<T>>(content) });
}
None
}
/// Try to cast type-erased content into a statically known packed element.
pub fn from_mut(content: &mut Content) -> Option<&mut Self> {
if content.is::<T>() {
// Safety:
// - We have checked the type.
// - Packed<T> is repr(transparent).
return Some(unsafe {
std::mem::transmute::<&mut Content, &mut Packed<T>>(content)
});
}
None
}
/// Try to cast type-erased content into a statically known packed element.
pub fn from_owned(content: Content) -> Result<Self, Content> {
if content.is::<T>() {
// Safety:
// - We have checked the type.
// - Packed<T> is repr(transparent).
return Ok(unsafe { std::mem::transmute::<Content, Packed<T>>(content) });
}
Err(content)
}
/// Pack back into content.
pub fn pack(self) -> Content {
self.0
}
/// Pack back into a reference to content.
pub fn pack_ref(&self) -> &Content {
&self.0
}
/// Pack back into a mutable reference to content.
pub fn pack_mut(&mut self) -> &mut Content {
&mut self.0
}
/// Extract the raw underlying element.
pub fn unpack(self) -> T {
// This function doesn't yet need owned self, but might in the future.
(*self).clone()
}
/// The element's span.
pub fn span(&self) -> Span {
self.0.span()
}
/// Set the span of the element.
pub fn spanned(self, span: Span) -> Self {
Self(self.0.spanned(span), PhantomData)
}
/// Accesses the label of the element.
pub fn label(&self) -> Option<Label> {
self.0.label()
}
/// Accesses the location of the element.
pub fn location(&self) -> Option<Location> {
self.0.location()
}
/// Sets the location of the element.
pub fn set_location(&mut self, location: Location) {
self.0.set_location(location);
}
}
impl<T: NativeElement> AsRef<T> for Packed<T> {
fn as_ref(&self) -> &T {
self
}
}
impl<T: NativeElement> AsMut<T> for Packed<T> {
fn as_mut(&mut self) -> &mut T {
self
}
}
impl<T: NativeElement> Deref for Packed<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
// Safety: Packed<T> guarantees that the content is of element type `T`.
unsafe { (self.0).0.data::<T>() }
}
}
impl<T: NativeElement> DerefMut for Packed<T> {
fn deref_mut(&mut self) -> &mut Self::Target {
// Safety: Packed<T> guarantees that the content is of element type `T`.
unsafe { (self.0).0.data_mut::<T>() }
}
}
impl<T: NativeElement + Debug> Debug for Packed<T> {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
self.0.fmt(f)
}
}
impl<T: NativeElement> PartialEq for Packed<T> {
fn eq(&self, other: &Self) -> bool {
self.0 == other.0
}
}
impl<T: NativeElement> Hash for Packed<T> {
fn hash<H: Hasher>(&self, state: &mut H) {
self.0.hash(state);
}
}
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