1use crate::{private::Sealed, AnyBox, AppContext, Context, Entity};
2use anyhow::{anyhow, Result};
3use derive_more::{Deref, DerefMut};
4use parking_lot::{RwLock, RwLockUpgradableReadGuard};
5use slotmap::{SecondaryMap, SlotMap};
6use std::{
7 any::{type_name, TypeId},
8 fmt::{self, Display},
9 hash::{Hash, Hasher},
10 marker::PhantomData,
11 mem,
12 sync::{
13 atomic::{AtomicUsize, Ordering::SeqCst},
14 Arc, Weak,
15 },
16};
17
18slotmap::new_key_type! { pub struct EntityId; }
19
20impl EntityId {
21 pub fn as_u64(self) -> u64 {
22 self.0.as_ffi()
23 }
24}
25
26impl Display for EntityId {
27 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
28 write!(f, "{}", self)
29 }
30}
31
32pub(crate) struct EntityMap {
33 entities: SecondaryMap<EntityId, AnyBox>,
34 ref_counts: Arc<RwLock<EntityRefCounts>>,
35}
36
37struct EntityRefCounts {
38 counts: SlotMap<EntityId, AtomicUsize>,
39 dropped_entity_ids: Vec<EntityId>,
40}
41
42impl EntityMap {
43 pub fn new() -> Self {
44 Self {
45 entities: SecondaryMap::new(),
46 ref_counts: Arc::new(RwLock::new(EntityRefCounts {
47 counts: SlotMap::with_key(),
48 dropped_entity_ids: Vec::new(),
49 })),
50 }
51 }
52
53 /// Reserve a slot for an entity, which you can subsequently use with `insert`.
54 pub fn reserve<T: 'static>(&self) -> Slot<T> {
55 let id = self.ref_counts.write().counts.insert(1.into());
56 Slot(Model::new(id, Arc::downgrade(&self.ref_counts)))
57 }
58
59 /// Insert an entity into a slot obtained by calling `reserve`.
60 pub fn insert<T>(&mut self, slot: Slot<T>, entity: T) -> Model<T>
61 where
62 T: 'static + Send,
63 {
64 let model = slot.0;
65 self.entities.insert(model.entity_id, Box::new(entity));
66 model
67 }
68
69 /// Move an entity to the stack.
70 pub fn lease<'a, T>(&mut self, model: &'a Model<T>) -> Lease<'a, T> {
71 self.assert_valid_context(model);
72 let entity = Some(
73 self.entities
74 .remove(model.entity_id)
75 .expect("Circular entity lease. Is the entity already being updated?"),
76 );
77 Lease {
78 model,
79 entity,
80 entity_type: PhantomData,
81 }
82 }
83
84 /// Return an entity after moving it to the stack.
85 pub fn end_lease<T>(&mut self, mut lease: Lease<T>) {
86 self.entities
87 .insert(lease.model.entity_id, lease.entity.take().unwrap());
88 }
89
90 pub fn read<T: 'static>(&self, model: &Model<T>) -> &T {
91 self.assert_valid_context(model);
92 self.entities[model.entity_id].downcast_ref().unwrap()
93 }
94
95 fn assert_valid_context(&self, model: &AnyModel) {
96 debug_assert!(
97 Weak::ptr_eq(&model.entity_map, &Arc::downgrade(&self.ref_counts)),
98 "used a model with the wrong context"
99 );
100 }
101
102 pub fn take_dropped(&mut self) -> Vec<(EntityId, AnyBox)> {
103 let mut ref_counts = self.ref_counts.write();
104 let dropped_entity_ids = mem::take(&mut ref_counts.dropped_entity_ids);
105
106 dropped_entity_ids
107 .into_iter()
108 .map(|entity_id| {
109 ref_counts.counts.remove(entity_id);
110 (entity_id, self.entities.remove(entity_id).unwrap())
111 })
112 .collect()
113 }
114}
115
116pub struct Lease<'a, T> {
117 entity: Option<AnyBox>,
118 pub model: &'a Model<T>,
119 entity_type: PhantomData<T>,
120}
121
122impl<'a, T: 'static> core::ops::Deref for Lease<'a, T> {
123 type Target = T;
124
125 fn deref(&self) -> &Self::Target {
126 self.entity.as_ref().unwrap().downcast_ref().unwrap()
127 }
128}
129
130impl<'a, T: 'static> core::ops::DerefMut for Lease<'a, T> {
131 fn deref_mut(&mut self) -> &mut Self::Target {
132 self.entity.as_mut().unwrap().downcast_mut().unwrap()
133 }
134}
135
136impl<'a, T> Drop for Lease<'a, T> {
137 fn drop(&mut self) {
138 if self.entity.is_some() {
139 // We don't panic here, because other panics can cause us to drop the lease without ending it cleanly.
140 log::error!("Leases must be ended with EntityMap::end_lease")
141 }
142 }
143}
144
145#[derive(Deref, DerefMut)]
146pub struct Slot<T>(Model<T>);
147
148pub struct AnyModel {
149 pub(crate) entity_id: EntityId,
150 pub(crate) entity_type: TypeId,
151 entity_map: Weak<RwLock<EntityRefCounts>>,
152}
153
154impl AnyModel {
155 fn new(id: EntityId, entity_type: TypeId, entity_map: Weak<RwLock<EntityRefCounts>>) -> Self {
156 Self {
157 entity_id: id,
158 entity_type,
159 entity_map,
160 }
161 }
162
163 pub fn entity_id(&self) -> EntityId {
164 self.entity_id
165 }
166
167 pub fn downgrade(&self) -> AnyWeakModel {
168 AnyWeakModel {
169 entity_id: self.entity_id,
170 entity_type: self.entity_type,
171 entity_ref_counts: self.entity_map.clone(),
172 }
173 }
174
175 pub fn downcast<T: 'static>(&self) -> Option<Model<T>> {
176 if TypeId::of::<T>() == self.entity_type {
177 Some(Model {
178 any_model: self.clone(),
179 entity_type: PhantomData,
180 })
181 } else {
182 None
183 }
184 }
185}
186
187impl Clone for AnyModel {
188 fn clone(&self) -> Self {
189 if let Some(entity_map) = self.entity_map.upgrade() {
190 let entity_map = entity_map.read();
191 let count = entity_map
192 .counts
193 .get(self.entity_id)
194 .expect("detected over-release of a model");
195 let prev_count = count.fetch_add(1, SeqCst);
196 assert_ne!(prev_count, 0, "Detected over-release of a model.");
197 }
198
199 Self {
200 entity_id: self.entity_id,
201 entity_type: self.entity_type,
202 entity_map: self.entity_map.clone(),
203 }
204 }
205}
206
207impl Drop for AnyModel {
208 fn drop(&mut self) {
209 if let Some(entity_map) = self.entity_map.upgrade() {
210 let entity_map = entity_map.upgradable_read();
211 let count = entity_map
212 .counts
213 .get(self.entity_id)
214 .expect("Detected over-release of a model.");
215 let prev_count = count.fetch_sub(1, SeqCst);
216 assert_ne!(prev_count, 0, "Detected over-release of a model.");
217 if prev_count == 1 {
218 // We were the last reference to this entity, so we can remove it.
219 let mut entity_map = RwLockUpgradableReadGuard::upgrade(entity_map);
220 entity_map.dropped_entity_ids.push(self.entity_id);
221 }
222 }
223 }
224}
225
226impl<T> From<Model<T>> for AnyModel {
227 fn from(model: Model<T>) -> Self {
228 model.any_model
229 }
230}
231
232impl Hash for AnyModel {
233 fn hash<H: Hasher>(&self, state: &mut H) {
234 self.entity_id.hash(state);
235 }
236}
237
238impl PartialEq for AnyModel {
239 fn eq(&self, other: &Self) -> bool {
240 self.entity_id == other.entity_id
241 }
242}
243
244impl Eq for AnyModel {}
245
246#[derive(Deref, DerefMut)]
247pub struct Model<T> {
248 #[deref]
249 #[deref_mut]
250 pub(crate) any_model: AnyModel,
251 pub(crate) entity_type: PhantomData<T>,
252}
253
254unsafe impl<T> Send for Model<T> {}
255unsafe impl<T> Sync for Model<T> {}
256impl<T> Sealed for Model<T> {}
257
258impl<T: 'static> Entity<T> for Model<T> {
259 type Weak = WeakModel<T>;
260
261 fn entity_id(&self) -> EntityId {
262 self.any_model.entity_id
263 }
264
265 fn downgrade(&self) -> Self::Weak {
266 WeakModel {
267 any_model: self.any_model.downgrade(),
268 entity_type: self.entity_type,
269 }
270 }
271
272 fn upgrade_from(weak: &Self::Weak) -> Option<Self>
273 where
274 Self: Sized,
275 {
276 Some(Model {
277 any_model: weak.any_model.upgrade()?,
278 entity_type: weak.entity_type,
279 })
280 }
281}
282
283impl<T: 'static> Model<T> {
284 fn new(id: EntityId, entity_map: Weak<RwLock<EntityRefCounts>>) -> Self
285 where
286 T: 'static,
287 {
288 Self {
289 any_model: AnyModel::new(id, TypeId::of::<T>(), entity_map),
290 entity_type: PhantomData,
291 }
292 }
293
294 /// Downgrade the this to a weak model reference
295 pub fn downgrade(&self) -> WeakModel<T> {
296 // Delegate to the trait implementation to keep behavior in one place.
297 // This method was included to improve method resolution in the presence of
298 // the Model's deref
299 Entity::downgrade(self)
300 }
301
302 /// Convert this into a dynamically typed model.
303 pub fn into_any(self) -> AnyModel {
304 self.any_model
305 }
306
307 pub fn read<'a>(&self, cx: &'a AppContext) -> &'a T {
308 cx.entities.read(self)
309 }
310
311 /// Update the entity referenced by this model with the given function.
312 ///
313 /// The update function receives a context appropriate for its environment.
314 /// When updating in an `AppContext`, it receives a `ModelContext`.
315 /// When updating an a `WindowContext`, it receives a `ViewContext`.
316 pub fn update<C, R>(
317 &self,
318 cx: &mut C,
319 update: impl FnOnce(&mut T, &mut C::ModelContext<'_, T>) -> R,
320 ) -> C::Result<R>
321 where
322 C: Context,
323 {
324 cx.update_model(self, update)
325 }
326}
327
328impl<T> Clone for Model<T> {
329 fn clone(&self) -> Self {
330 Self {
331 any_model: self.any_model.clone(),
332 entity_type: self.entity_type,
333 }
334 }
335}
336
337impl<T> std::fmt::Debug for Model<T> {
338 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
339 write!(
340 f,
341 "Model {{ entity_id: {:?}, entity_type: {:?} }}",
342 self.any_model.entity_id,
343 type_name::<T>()
344 )
345 }
346}
347
348impl<T> Hash for Model<T> {
349 fn hash<H: Hasher>(&self, state: &mut H) {
350 self.any_model.hash(state);
351 }
352}
353
354impl<T> PartialEq for Model<T> {
355 fn eq(&self, other: &Self) -> bool {
356 self.any_model == other.any_model
357 }
358}
359
360impl<T> Eq for Model<T> {}
361
362impl<T> PartialEq<WeakModel<T>> for Model<T> {
363 fn eq(&self, other: &WeakModel<T>) -> bool {
364 self.any_model.entity_id() == other.entity_id()
365 }
366}
367
368#[derive(Clone)]
369pub struct AnyWeakModel {
370 pub(crate) entity_id: EntityId,
371 entity_type: TypeId,
372 entity_ref_counts: Weak<RwLock<EntityRefCounts>>,
373}
374
375impl AnyWeakModel {
376 pub fn entity_id(&self) -> EntityId {
377 self.entity_id
378 }
379
380 pub fn is_upgradable(&self) -> bool {
381 let ref_count = self
382 .entity_ref_counts
383 .upgrade()
384 .and_then(|ref_counts| Some(ref_counts.read().counts.get(self.entity_id)?.load(SeqCst)))
385 .unwrap_or(0);
386 ref_count > 0
387 }
388
389 pub fn upgrade(&self) -> Option<AnyModel> {
390 let entity_map = self.entity_ref_counts.upgrade()?;
391 entity_map
392 .read()
393 .counts
394 .get(self.entity_id)?
395 .fetch_add(1, SeqCst);
396 Some(AnyModel {
397 entity_id: self.entity_id,
398 entity_type: self.entity_type,
399 entity_map: self.entity_ref_counts.clone(),
400 })
401 }
402}
403
404impl<T> From<WeakModel<T>> for AnyWeakModel {
405 fn from(model: WeakModel<T>) -> Self {
406 model.any_model
407 }
408}
409
410impl Hash for AnyWeakModel {
411 fn hash<H: Hasher>(&self, state: &mut H) {
412 self.entity_id.hash(state);
413 }
414}
415
416impl PartialEq for AnyWeakModel {
417 fn eq(&self, other: &Self) -> bool {
418 self.entity_id == other.entity_id
419 }
420}
421
422impl Eq for AnyWeakModel {}
423
424#[derive(Deref, DerefMut)]
425pub struct WeakModel<T> {
426 #[deref]
427 #[deref_mut]
428 any_model: AnyWeakModel,
429 entity_type: PhantomData<T>,
430}
431
432unsafe impl<T> Send for WeakModel<T> {}
433unsafe impl<T> Sync for WeakModel<T> {}
434
435impl<T> Clone for WeakModel<T> {
436 fn clone(&self) -> Self {
437 Self {
438 any_model: self.any_model.clone(),
439 entity_type: self.entity_type,
440 }
441 }
442}
443
444impl<T: 'static> WeakModel<T> {
445 /// Upgrade this weak model reference into a strong model reference
446 pub fn upgrade(&self) -> Option<Model<T>> {
447 // Delegate to the trait implementation to keep behavior in one place.
448 Model::upgrade_from(self)
449 }
450
451 /// Update the entity referenced by this model with the given function if
452 /// the referenced entity still exists. Returns an error if the entity has
453 /// been released.
454 ///
455 /// The update function receives a context appropriate for its environment.
456 /// When updating in an `AppContext`, it receives a `ModelContext`.
457 /// When updating an a `WindowContext`, it receives a `ViewContext`.
458 pub fn update<C, R>(
459 &self,
460 cx: &mut C,
461 update: impl FnOnce(&mut T, &mut C::ModelContext<'_, T>) -> R,
462 ) -> Result<R>
463 where
464 C: Context,
465 Result<C::Result<R>>: crate::Flatten<R>,
466 {
467 crate::Flatten::flatten(
468 self.upgrade()
469 .ok_or_else(|| anyhow!("entity release"))
470 .map(|this| cx.update_model(&this, update)),
471 )
472 }
473}
474
475impl<T> Hash for WeakModel<T> {
476 fn hash<H: Hasher>(&self, state: &mut H) {
477 self.any_model.hash(state);
478 }
479}
480
481impl<T> PartialEq for WeakModel<T> {
482 fn eq(&self, other: &Self) -> bool {
483 self.any_model == other.any_model
484 }
485}
486
487impl<T> Eq for WeakModel<T> {}
488
489impl<T> PartialEq<Model<T>> for WeakModel<T> {
490 fn eq(&self, other: &Model<T>) -> bool {
491 self.entity_id() == other.any_model.entity_id()
492 }
493}