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use std::any::{Any, TypeId};
use std::fmt::{Debug, Formatter};
use std::hash::{Hash, Hasher};
use bevy_reflect_derive::impl_type_path;
use crate::utility::reflect_hasher;
use crate::{
self as bevy_reflect, ApplyError, FromReflect, Reflect, ReflectKind, ReflectMut, ReflectOwned,
ReflectRef, TypeInfo, TypePath, TypePathTable,
};
/// A trait used to power [list-like] operations via [reflection].
///
/// This corresponds to types, like [`Vec`], which contain an ordered sequence
/// of elements that implement [`Reflect`].
///
/// Unlike the [`Array`](crate::Array) trait, implementors of this trait are not expected to
/// maintain a constant length.
/// Methods like [insertion](List::insert) and [removal](List::remove) explicitly allow for their
/// internal size to change.
///
/// [`push`](List::push) and [`pop`](List::pop) have default implementations,
/// however it will generally be more performant to implement them manually
/// as the default implementation uses a very naive approach to find the correct position.
///
/// This trait expects its elements to be ordered linearly from front to back.
/// The _front_ element starts at index 0 with the _back_ element ending at the largest index.
/// This contract above should be upheld by any manual implementors.
///
/// Due to the [type-erasing] nature of the reflection API as a whole,
/// this trait does not make any guarantees that the implementor's elements
/// are homogeneous (i.e. all the same type).
///
/// # Example
///
/// ```
/// use bevy_reflect::{Reflect, List};
///
/// let foo: &mut dyn List = &mut vec![123_u32, 456_u32, 789_u32];
/// assert_eq!(foo.len(), 3);
///
/// let last_field: Box<dyn Reflect> = foo.pop().unwrap();
/// assert_eq!(last_field.downcast_ref::<u32>(), Some(&789));
/// ```
///
/// [list-like]: https://doc.rust-lang.org/book/ch08-01-vectors.html
/// [reflection]: crate
/// [type-erasing]: https://doc.rust-lang.org/book/ch17-02-trait-objects.html
pub trait List: Reflect {
/// Returns a reference to the element at `index`, or `None` if out of bounds.
fn get(&self, index: usize) -> Option<&dyn Reflect>;
/// Returns a mutable reference to the element at `index`, or `None` if out of bounds.
fn get_mut(&mut self, index: usize) -> Option<&mut dyn Reflect>;
/// Inserts an element at position `index` within the list,
/// shifting all elements after it towards the back of the list.
///
/// # Panics
/// Panics if `index > len`.
fn insert(&mut self, index: usize, element: Box<dyn Reflect>);
/// Removes and returns the element at position `index` within the list,
/// shifting all elements before it towards the front of the list.
///
/// # Panics
/// Panics if `index` is out of bounds.
fn remove(&mut self, index: usize) -> Box<dyn Reflect>;
/// Appends an element to the _back_ of the list.
fn push(&mut self, value: Box<dyn Reflect>) {
self.insert(self.len(), value);
}
/// Removes the _back_ element from the list and returns it, or [`None`] if it is empty.
fn pop(&mut self) -> Option<Box<dyn Reflect>> {
if self.is_empty() {
None
} else {
Some(self.remove(self.len() - 1))
}
}
/// Returns the number of elements in the list.
fn len(&self) -> usize;
/// Returns `true` if the collection contains no elements.
fn is_empty(&self) -> bool {
self.len() == 0
}
/// Returns an iterator over the list.
fn iter(&self) -> ListIter;
/// Drain the elements of this list to get a vector of owned values.
fn drain(self: Box<Self>) -> Vec<Box<dyn Reflect>>;
/// Clones the list, producing a [`DynamicList`].
fn clone_dynamic(&self) -> DynamicList {
DynamicList {
represented_type: self.get_represented_type_info(),
values: self.iter().map(|value| value.clone_value()).collect(),
}
}
}
/// A container for compile-time list info.
#[derive(Clone, Debug)]
pub struct ListInfo {
type_path: TypePathTable,
type_id: TypeId,
item_type_path: TypePathTable,
item_type_id: TypeId,
#[cfg(feature = "documentation")]
docs: Option<&'static str>,
}
impl ListInfo {
/// Create a new [`ListInfo`].
pub fn new<TList: List + TypePath, TItem: FromReflect + TypePath>() -> Self {
Self {
type_path: TypePathTable::of::<TList>(),
type_id: TypeId::of::<TList>(),
item_type_path: TypePathTable::of::<TItem>(),
item_type_id: TypeId::of::<TItem>(),
#[cfg(feature = "documentation")]
docs: None,
}
}
/// Sets the docstring for this list.
#[cfg(feature = "documentation")]
pub fn with_docs(self, docs: Option<&'static str>) -> Self {
Self { docs, ..self }
}
/// A representation of the type path of the list.
///
/// Provides dynamic access to all methods on [`TypePath`].
pub fn type_path_table(&self) -> &TypePathTable {
&self.type_path
}
/// The [stable, full type path] of the list.
///
/// Use [`type_path_table`] if you need access to the other methods on [`TypePath`].
///
/// [stable, full type path]: TypePath
/// [`type_path_table`]: Self::type_path_table
pub fn type_path(&self) -> &'static str {
self.type_path_table().path()
}
/// The [`TypeId`] of the list.
pub fn type_id(&self) -> TypeId {
self.type_id
}
/// Check if the given type matches the list type.
pub fn is<T: Any>(&self) -> bool {
TypeId::of::<T>() == self.type_id
}
/// A representation of the type path of the list item.
///
/// Provides dynamic access to all methods on [`TypePath`].
pub fn item_type_path_table(&self) -> &TypePathTable {
&self.item_type_path
}
/// The [`TypeId`] of the list item.
pub fn item_type_id(&self) -> TypeId {
self.item_type_id
}
/// Check if the given type matches the list item type.
pub fn item_is<T: Any>(&self) -> bool {
TypeId::of::<T>() == self.item_type_id
}
/// The docstring of this list, if any.
#[cfg(feature = "documentation")]
pub fn docs(&self) -> Option<&'static str> {
self.docs
}
}
/// A list of reflected values.
#[derive(Default)]
pub struct DynamicList {
represented_type: Option<&'static TypeInfo>,
values: Vec<Box<dyn Reflect>>,
}
impl DynamicList {
/// Sets the [type] to be represented by this `DynamicList`.
/// # Panics
///
/// Panics if the given [type] is not a [`TypeInfo::List`].
///
/// [type]: TypeInfo
pub fn set_represented_type(&mut self, represented_type: Option<&'static TypeInfo>) {
if let Some(represented_type) = represented_type {
assert!(
matches!(represented_type, TypeInfo::List(_)),
"expected TypeInfo::List but received: {:?}",
represented_type
);
}
self.represented_type = represented_type;
}
/// Appends a typed value to the list.
pub fn push<T: Reflect>(&mut self, value: T) {
self.values.push(Box::new(value));
}
/// Appends a [`Reflect`] trait object to the list.
pub fn push_box(&mut self, value: Box<dyn Reflect>) {
self.values.push(value);
}
}
impl List for DynamicList {
fn get(&self, index: usize) -> Option<&dyn Reflect> {
self.values.get(index).map(|value| &**value)
}
fn get_mut(&mut self, index: usize) -> Option<&mut dyn Reflect> {
self.values.get_mut(index).map(|value| &mut **value)
}
fn insert(&mut self, index: usize, element: Box<dyn Reflect>) {
self.values.insert(index, element);
}
fn remove(&mut self, index: usize) -> Box<dyn Reflect> {
self.values.remove(index)
}
fn push(&mut self, value: Box<dyn Reflect>) {
DynamicList::push_box(self, value);
}
fn pop(&mut self) -> Option<Box<dyn Reflect>> {
self.values.pop()
}
fn len(&self) -> usize {
self.values.len()
}
fn iter(&self) -> ListIter {
ListIter::new(self)
}
fn drain(self: Box<Self>) -> Vec<Box<dyn Reflect>> {
self.values
}
fn clone_dynamic(&self) -> DynamicList {
DynamicList {
represented_type: self.represented_type,
values: self
.values
.iter()
.map(|value| value.clone_value())
.collect(),
}
}
}
impl Reflect for DynamicList {
#[inline]
fn get_represented_type_info(&self) -> Option<&'static TypeInfo> {
self.represented_type
}
#[inline]
fn into_any(self: Box<Self>) -> Box<dyn Any> {
self
}
#[inline]
fn as_any(&self) -> &dyn Any {
self
}
#[inline]
fn as_any_mut(&mut self) -> &mut dyn Any {
self
}
#[inline]
fn into_reflect(self: Box<Self>) -> Box<dyn Reflect> {
self
}
#[inline]
fn as_reflect(&self) -> &dyn Reflect {
self
}
#[inline]
fn as_reflect_mut(&mut self) -> &mut dyn Reflect {
self
}
fn apply(&mut self, value: &dyn Reflect) {
list_apply(self, value);
}
fn try_apply(&mut self, value: &dyn Reflect) -> Result<(), ApplyError> {
list_try_apply(self, value)
}
#[inline]
fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> {
*self = value.take()?;
Ok(())
}
#[inline]
fn reflect_kind(&self) -> ReflectKind {
ReflectKind::List
}
#[inline]
fn reflect_ref(&self) -> ReflectRef {
ReflectRef::List(self)
}
#[inline]
fn reflect_mut(&mut self) -> ReflectMut {
ReflectMut::List(self)
}
#[inline]
fn reflect_owned(self: Box<Self>) -> ReflectOwned {
ReflectOwned::List(self)
}
#[inline]
fn clone_value(&self) -> Box<dyn Reflect> {
Box::new(self.clone_dynamic())
}
#[inline]
fn reflect_hash(&self) -> Option<u64> {
list_hash(self)
}
fn reflect_partial_eq(&self, value: &dyn Reflect) -> Option<bool> {
list_partial_eq(self, value)
}
fn debug(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
write!(f, "DynamicList(")?;
list_debug(self, f)?;
write!(f, ")")
}
#[inline]
fn is_dynamic(&self) -> bool {
true
}
}
impl_type_path!((in bevy_reflect) DynamicList);
impl Debug for DynamicList {
fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
self.debug(f)
}
}
impl IntoIterator for DynamicList {
type Item = Box<dyn Reflect>;
type IntoIter = std::vec::IntoIter<Self::Item>;
fn into_iter(self) -> Self::IntoIter {
self.values.into_iter()
}
}
/// An iterator over an [`List`].
pub struct ListIter<'a> {
list: &'a dyn List,
index: usize,
}
impl<'a> ListIter<'a> {
/// Creates a new [`ListIter`].
#[inline]
pub const fn new(list: &'a dyn List) -> ListIter {
ListIter { list, index: 0 }
}
}
impl<'a> Iterator for ListIter<'a> {
type Item = &'a dyn Reflect;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
let value = self.list.get(self.index);
self.index += value.is_some() as usize;
value
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let size = self.list.len();
(size, Some(size))
}
}
impl<'a> ExactSizeIterator for ListIter<'a> {}
/// Returns the `u64` hash of the given [list](List).
#[inline]
pub fn list_hash<L: List>(list: &L) -> Option<u64> {
let mut hasher = reflect_hasher();
Any::type_id(list).hash(&mut hasher);
list.len().hash(&mut hasher);
for value in list.iter() {
hasher.write_u64(value.reflect_hash()?);
}
Some(hasher.finish())
}
/// Applies the elements of `b` to the corresponding elements of `a`.
///
/// If the length of `b` is greater than that of `a`, the excess elements of `b`
/// are cloned and appended to `a`.
///
/// # Panics
///
/// This function panics if `b` is not a list.
#[inline]
pub fn list_apply<L: List>(a: &mut L, b: &dyn Reflect) {
if let Err(err) = list_try_apply(a, b) {
panic!("{err}");
}
}
/// Tries to apply the elements of `b` to the corresponding elements of `a` and
/// returns a Result.
///
/// If the length of `b` is greater than that of `a`, the excess elements of `b`
/// are cloned and appended to `a`.
///
/// # Errors
///
/// This function returns an [`ApplyError::MismatchedKinds`] if `b` is not a list or if
/// applying elements to each other fails.
#[inline]
pub fn list_try_apply<L: List>(a: &mut L, b: &dyn Reflect) -> Result<(), ApplyError> {
if let ReflectRef::List(list_value) = b.reflect_ref() {
for (i, value) in list_value.iter().enumerate() {
if i < a.len() {
if let Some(v) = a.get_mut(i) {
v.try_apply(value)?;
}
} else {
List::push(a, value.clone_value());
}
}
} else {
return Err(ApplyError::MismatchedKinds {
from_kind: b.reflect_kind(),
to_kind: ReflectKind::List,
});
}
Ok(())
}
/// Compares a [`List`] with a [`Reflect`] value.
///
/// Returns true if and only if all of the following are true:
/// - `b` is a list;
/// - `b` is the same length as `a`;
/// - [`Reflect::reflect_partial_eq`] returns `Some(true)` for pairwise elements of `a` and `b`.
///
/// Returns [`None`] if the comparison couldn't even be performed.
#[inline]
pub fn list_partial_eq<L: List>(a: &L, b: &dyn Reflect) -> Option<bool> {
let ReflectRef::List(list) = b.reflect_ref() else {
return Some(false);
};
if a.len() != list.len() {
return Some(false);
}
for (a_value, b_value) in a.iter().zip(list.iter()) {
let eq_result = a_value.reflect_partial_eq(b_value);
if let failed @ (Some(false) | None) = eq_result {
return failed;
}
}
Some(true)
}
/// The default debug formatter for [`List`] types.
///
/// # Example
/// ```
/// use bevy_reflect::Reflect;
///
/// let my_list: &dyn Reflect = &vec![1, 2, 3];
/// println!("{:#?}", my_list);
///
/// // Output:
///
/// // [
/// // 1,
/// // 2,
/// // 3,
/// // ]
/// ```
#[inline]
pub fn list_debug(dyn_list: &dyn List, f: &mut Formatter<'_>) -> std::fmt::Result {
let mut debug = f.debug_list();
for item in dyn_list.iter() {
debug.entry(&item as &dyn Debug);
}
debug.finish()
}
#[cfg(test)]
mod tests {
use super::DynamicList;
use crate::{Reflect, ReflectRef};
use std::assert_eq;
#[test]
fn test_into_iter() {
let mut list = DynamicList::default();
list.push(0usize);
list.push(1usize);
list.push(2usize);
let items = list.into_iter();
for (index, item) in items.into_iter().enumerate() {
let value = item.take::<usize>().expect("couldn't downcast to usize");
assert_eq!(index, value);
}
}
#[test]
fn next_index_increment() {
const SIZE: usize = if cfg!(debug_assertions) {
4
} else {
// If compiled in release mode, verify we dont overflow
usize::MAX
};
let b = Box::new(vec![(); SIZE]).into_reflect();
let ReflectRef::List(list) = b.reflect_ref() else {
panic!("Not a list...");
};
let mut iter = list.iter();
iter.index = SIZE - 1;
assert!(iter.next().is_some());
// When None we should no longer increase index
assert!(iter.next().is_none());
assert!(iter.index == SIZE);
assert!(iter.next().is_none());
assert!(iter.index == SIZE);
}
}