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