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) -> Result<Model<T>, AnyModel> {
176 if TypeId::of::<T>() == self.entity_type {
177 Ok(Model {
178 any_model: self,
179 entity_type: PhantomData,
180 })
181 } else {
182 Err(self)
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
246impl std::fmt::Debug for AnyModel {
247 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
248 f.debug_struct("AnyModel")
249 .field("entity_id", &self.entity_id.as_u64())
250 .finish()
251 }
252}
253
254#[derive(Deref, DerefMut)]
255pub struct Model<T> {
256 #[deref]
257 #[deref_mut]
258 pub(crate) any_model: AnyModel,
259 pub(crate) entity_type: PhantomData<T>,
260}
261
262unsafe impl<T> Send for Model<T> {}
263unsafe impl<T> Sync for Model<T> {}
264impl<T> Sealed for Model<T> {}
265
266impl<T: 'static> Entity<T> for Model<T> {
267 type Weak = WeakModel<T>;
268
269 fn entity_id(&self) -> EntityId {
270 self.any_model.entity_id
271 }
272
273 fn downgrade(&self) -> Self::Weak {
274 WeakModel {
275 any_model: self.any_model.downgrade(),
276 entity_type: self.entity_type,
277 }
278 }
279
280 fn upgrade_from(weak: &Self::Weak) -> Option<Self>
281 where
282 Self: Sized,
283 {
284 Some(Model {
285 any_model: weak.any_model.upgrade()?,
286 entity_type: weak.entity_type,
287 })
288 }
289}
290
291impl<T: 'static> Model<T> {
292 fn new(id: EntityId, entity_map: Weak<RwLock<EntityRefCounts>>) -> Self
293 where
294 T: 'static,
295 {
296 Self {
297 any_model: AnyModel::new(id, TypeId::of::<T>(), entity_map),
298 entity_type: PhantomData,
299 }
300 }
301
302 /// Downgrade the this to a weak model reference
303 pub fn downgrade(&self) -> WeakModel<T> {
304 // Delegate to the trait implementation to keep behavior in one place.
305 // This method was included to improve method resolution in the presence of
306 // the Model's deref
307 Entity::downgrade(self)
308 }
309
310 /// Convert this into a dynamically typed model.
311 pub fn into_any(self) -> AnyModel {
312 self.any_model
313 }
314
315 pub fn read<'a>(&self, cx: &'a AppContext) -> &'a T {
316 cx.entities.read(self)
317 }
318
319 /// Update the entity referenced by this model with the given function.
320 ///
321 /// The update function receives a context appropriate for its environment.
322 /// When updating in an `AppContext`, it receives a `ModelContext`.
323 /// When updating an a `WindowContext`, it receives a `ViewContext`.
324 pub fn update<C, R>(
325 &self,
326 cx: &mut C,
327 update: impl FnOnce(&mut T, &mut C::ModelContext<'_, T>) -> R,
328 ) -> C::Result<R>
329 where
330 C: Context,
331 {
332 cx.update_model(self, update)
333 }
334}
335
336impl<T> Clone for Model<T> {
337 fn clone(&self) -> Self {
338 Self {
339 any_model: self.any_model.clone(),
340 entity_type: self.entity_type,
341 }
342 }
343}
344
345impl<T> std::fmt::Debug for Model<T> {
346 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
347 write!(
348 f,
349 "Model {{ entity_id: {:?}, entity_type: {:?} }}",
350 self.any_model.entity_id,
351 type_name::<T>()
352 )
353 }
354}
355
356impl<T> Hash for Model<T> {
357 fn hash<H: Hasher>(&self, state: &mut H) {
358 self.any_model.hash(state);
359 }
360}
361
362impl<T> PartialEq for Model<T> {
363 fn eq(&self, other: &Self) -> bool {
364 self.any_model == other.any_model
365 }
366}
367
368impl<T> Eq for Model<T> {}
369
370impl<T> PartialEq<WeakModel<T>> for Model<T> {
371 fn eq(&self, other: &WeakModel<T>) -> bool {
372 self.any_model.entity_id() == other.entity_id()
373 }
374}
375
376#[derive(Clone)]
377pub struct AnyWeakModel {
378 pub(crate) entity_id: EntityId,
379 entity_type: TypeId,
380 entity_ref_counts: Weak<RwLock<EntityRefCounts>>,
381}
382
383impl AnyWeakModel {
384 pub fn entity_id(&self) -> EntityId {
385 self.entity_id
386 }
387
388 pub fn is_upgradable(&self) -> bool {
389 let ref_count = self
390 .entity_ref_counts
391 .upgrade()
392 .and_then(|ref_counts| Some(ref_counts.read().counts.get(self.entity_id)?.load(SeqCst)))
393 .unwrap_or(0);
394 ref_count > 0
395 }
396
397 pub fn upgrade(&self) -> Option<AnyModel> {
398 let entity_map = self.entity_ref_counts.upgrade()?;
399 entity_map
400 .read()
401 .counts
402 .get(self.entity_id)?
403 .fetch_add(1, SeqCst);
404 Some(AnyModel {
405 entity_id: self.entity_id,
406 entity_type: self.entity_type,
407 entity_map: self.entity_ref_counts.clone(),
408 })
409 }
410}
411
412impl<T> From<WeakModel<T>> for AnyWeakModel {
413 fn from(model: WeakModel<T>) -> Self {
414 model.any_model
415 }
416}
417
418impl Hash for AnyWeakModel {
419 fn hash<H: Hasher>(&self, state: &mut H) {
420 self.entity_id.hash(state);
421 }
422}
423
424impl PartialEq for AnyWeakModel {
425 fn eq(&self, other: &Self) -> bool {
426 self.entity_id == other.entity_id
427 }
428}
429
430impl Eq for AnyWeakModel {}
431
432#[derive(Deref, DerefMut)]
433pub struct WeakModel<T> {
434 #[deref]
435 #[deref_mut]
436 any_model: AnyWeakModel,
437 entity_type: PhantomData<T>,
438}
439
440unsafe impl<T> Send for WeakModel<T> {}
441unsafe impl<T> Sync for WeakModel<T> {}
442
443impl<T> Clone for WeakModel<T> {
444 fn clone(&self) -> Self {
445 Self {
446 any_model: self.any_model.clone(),
447 entity_type: self.entity_type,
448 }
449 }
450}
451
452impl<T: 'static> WeakModel<T> {
453 /// Upgrade this weak model reference into a strong model reference
454 pub fn upgrade(&self) -> Option<Model<T>> {
455 // Delegate to the trait implementation to keep behavior in one place.
456 Model::upgrade_from(self)
457 }
458
459 /// Update the entity referenced by this model with the given function if
460 /// the referenced entity still exists. Returns an error if the entity has
461 /// been released.
462 ///
463 /// The update function receives a context appropriate for its environment.
464 /// When updating in an `AppContext`, it receives a `ModelContext`.
465 /// When updating an a `WindowContext`, it receives a `ViewContext`.
466 pub fn update<C, R>(
467 &self,
468 cx: &mut C,
469 update: impl FnOnce(&mut T, &mut C::ModelContext<'_, T>) -> R,
470 ) -> Result<R>
471 where
472 C: Context,
473 Result<C::Result<R>>: crate::Flatten<R>,
474 {
475 crate::Flatten::flatten(
476 self.upgrade()
477 .ok_or_else(|| anyhow!("entity release"))
478 .map(|this| cx.update_model(&this, update)),
479 )
480 }
481}
482
483impl<T> Hash for WeakModel<T> {
484 fn hash<H: Hasher>(&self, state: &mut H) {
485 self.any_model.hash(state);
486 }
487}
488
489impl<T> PartialEq for WeakModel<T> {
490 fn eq(&self, other: &Self) -> bool {
491 self.any_model == other.any_model
492 }
493}
494
495impl<T> Eq for WeakModel<T> {}
496
497impl<T> PartialEq<Model<T>> for WeakModel<T> {
498 fn eq(&self, other: &Model<T>) -> bool {
499 self.entity_id() == other.any_model.entity_id()
500 }
501}