1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
use crate::{DynamicScene, Scene};
use bevy_app::{Events, ManualEventReader};
use bevy_asset::{AssetEvent, Assets, Handle};
use bevy_ecs::{
    entity::{Entity, EntityMap},
    reflect::{ReflectComponent, ReflectMapEntities},
    world::{Mut, World},
};
use bevy_reflect::TypeRegistryArc;
use bevy_transform::prelude::Parent;
use bevy_utils::{tracing::error, HashMap};
use thiserror::Error;
use uuid::Uuid;

#[derive(Debug)]
struct InstanceInfo {
    entity_map: EntityMap,
}

#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
pub struct InstanceId(Uuid);

impl InstanceId {
    fn new() -> Self {
        InstanceId(Uuid::new_v4())
    }
}

#[derive(Default)]
pub struct SceneSpawner {
    spawned_scenes: HashMap<Handle<Scene>, Vec<InstanceId>>,
    spawned_dynamic_scenes: HashMap<Handle<DynamicScene>, Vec<InstanceId>>,
    spawned_instances: HashMap<InstanceId, InstanceInfo>,
    scene_asset_event_reader: ManualEventReader<AssetEvent<DynamicScene>>,
    dynamic_scenes_to_spawn: Vec<Handle<DynamicScene>>,
    scenes_to_spawn: Vec<(Handle<Scene>, InstanceId)>,
    scenes_to_despawn: Vec<Handle<DynamicScene>>,
    scenes_with_parent: Vec<(InstanceId, Entity)>,
}

#[derive(Error, Debug)]
pub enum SceneSpawnError {
    #[error("scene contains the unregistered component `{type_name}`. consider adding `#[reflect(Component)]` to your type")]
    UnregisteredComponent { type_name: String },
    #[error("scene contains the unregistered type `{type_name}`. consider registering the type using `app.register_type::<T>()`")]
    UnregisteredType { type_name: String },
    #[error("scene does not exist")]
    NonExistentScene { handle: Handle<DynamicScene> },
    #[error("scene does not exist")]
    NonExistentRealScene { handle: Handle<Scene> },
}

impl SceneSpawner {
    pub fn spawn_dynamic(&mut self, scene_handle: Handle<DynamicScene>) {
        self.dynamic_scenes_to_spawn.push(scene_handle);
    }

    pub fn spawn(&mut self, scene_handle: Handle<Scene>) -> InstanceId {
        let instance_id = InstanceId::new();
        self.scenes_to_spawn.push((scene_handle, instance_id));
        instance_id
    }

    pub fn spawn_as_child(&mut self, scene_handle: Handle<Scene>, parent: Entity) -> InstanceId {
        let instance_id = InstanceId::new();
        self.scenes_to_spawn.push((scene_handle, instance_id));
        self.scenes_with_parent.push((instance_id, parent));
        instance_id
    }

    pub fn despawn(&mut self, scene_handle: Handle<DynamicScene>) {
        self.scenes_to_despawn.push(scene_handle);
    }

    pub fn despawn_sync(
        &mut self,
        world: &mut World,
        scene_handle: Handle<DynamicScene>,
    ) -> Result<(), SceneSpawnError> {
        if let Some(instance_ids) = self.spawned_dynamic_scenes.get(&scene_handle) {
            for instance_id in instance_ids {
                if let Some(instance) = self.spawned_instances.get(&instance_id) {
                    for entity in instance.entity_map.values() {
                        let _ = world.despawn(entity); // Ignore the result, despawn only cares if
                                                       // it exists.
                    }
                }
            }

            self.spawned_dynamic_scenes.remove(&scene_handle);
        }
        Ok(())
    }

    pub fn spawn_dynamic_sync(
        &mut self,
        world: &mut World,
        scene_handle: &Handle<DynamicScene>,
    ) -> Result<(), SceneSpawnError> {
        let mut entity_map = EntityMap::default();
        Self::spawn_dynamic_internal(world, scene_handle, &mut entity_map)?;
        let instance_id = InstanceId::new();
        self.spawned_instances
            .insert(instance_id, InstanceInfo { entity_map });
        let spawned = self
            .spawned_dynamic_scenes
            .entry(scene_handle.clone())
            .or_insert_with(Vec::new);
        spawned.push(instance_id);
        Ok(())
    }

    fn spawn_dynamic_internal(
        world: &mut World,
        scene_handle: &Handle<DynamicScene>,
        entity_map: &mut EntityMap,
    ) -> Result<(), SceneSpawnError> {
        world.resource_scope(|world, scenes: Mut<Assets<DynamicScene>>| {
            let scene =
                scenes
                    .get(scene_handle)
                    .ok_or_else(|| SceneSpawnError::NonExistentScene {
                        handle: scene_handle.clone_weak(),
                    })?;
            scene.write_to_world(world, entity_map)
        })
    }

    pub fn spawn_sync(
        &mut self,
        world: &mut World,
        scene_handle: Handle<Scene>,
    ) -> Result<InstanceId, SceneSpawnError> {
        self.spawn_sync_internal(world, scene_handle, InstanceId::new())
    }

    fn spawn_sync_internal(
        &mut self,
        world: &mut World,
        scene_handle: Handle<Scene>,
        instance_id: InstanceId,
    ) -> Result<InstanceId, SceneSpawnError> {
        let mut instance_info = InstanceInfo {
            entity_map: EntityMap::default(),
        };
        let type_registry = world.get_resource::<TypeRegistryArc>().unwrap().clone();
        let type_registry = type_registry.read();
        world.resource_scope(|world, scenes: Mut<Assets<Scene>>| {
            let scene =
                scenes
                    .get(&scene_handle)
                    .ok_or_else(|| SceneSpawnError::NonExistentRealScene {
                        handle: scene_handle.clone(),
                    })?;

            for archetype in scene.world.archetypes().iter() {
                for scene_entity in archetype.entities() {
                    let entity = *instance_info
                        .entity_map
                        .entry(*scene_entity)
                        .or_insert_with(|| world.spawn().id());
                    for component_id in archetype.components() {
                        let component_info = scene
                            .world
                            .components()
                            .get_info(component_id)
                            .expect("component_ids in archetypes should have ComponentInfo");

                        let reflect_component = type_registry
                            .get(component_info.type_id().unwrap())
                            .ok_or_else(|| SceneSpawnError::UnregisteredType {
                                type_name: component_info.name().to_string(),
                            })
                            .and_then(|registration| {
                                registration.data::<ReflectComponent>().ok_or_else(|| {
                                    SceneSpawnError::UnregisteredComponent {
                                        type_name: component_info.name().to_string(),
                                    }
                                })
                            })?;
                        reflect_component.copy_component(
                            &scene.world,
                            world,
                            *scene_entity,
                            entity,
                        );
                    }
                }
            }
            for registration in type_registry.iter() {
                if let Some(map_entities_reflect) = registration.data::<ReflectMapEntities>() {
                    map_entities_reflect
                        .map_entities(world, &instance_info.entity_map)
                        .unwrap();
                }
            }
            self.spawned_instances.insert(instance_id, instance_info);
            let spawned = self
                .spawned_scenes
                .entry(scene_handle)
                .or_insert_with(Vec::new);
            spawned.push(instance_id);
            Ok(instance_id)
        })
    }

    pub fn update_spawned_scenes(
        &mut self,
        world: &mut World,
        scene_handles: &[Handle<DynamicScene>],
    ) -> Result<(), SceneSpawnError> {
        for scene_handle in scene_handles {
            if let Some(spawned_instances) = self.spawned_dynamic_scenes.get(scene_handle) {
                for instance_id in spawned_instances.iter() {
                    if let Some(instance_info) = self.spawned_instances.get_mut(instance_id) {
                        Self::spawn_dynamic_internal(
                            world,
                            scene_handle,
                            &mut instance_info.entity_map,
                        )?;
                    }
                }
            }
        }
        Ok(())
    }

    pub fn despawn_queued_scenes(&mut self, world: &mut World) -> Result<(), SceneSpawnError> {
        let scenes_to_despawn = std::mem::take(&mut self.scenes_to_despawn);

        for scene_handle in scenes_to_despawn {
            self.despawn_sync(world, scene_handle)?;
        }
        Ok(())
    }

    pub fn spawn_queued_scenes(&mut self, world: &mut World) -> Result<(), SceneSpawnError> {
        let scenes_to_spawn = std::mem::take(&mut self.dynamic_scenes_to_spawn);

        for scene_handle in scenes_to_spawn {
            match self.spawn_dynamic_sync(world, &scene_handle) {
                Ok(_) => {}
                Err(SceneSpawnError::NonExistentScene { .. }) => {
                    self.dynamic_scenes_to_spawn.push(scene_handle)
                }
                Err(err) => return Err(err),
            }
        }

        let scenes_to_spawn = std::mem::take(&mut self.scenes_to_spawn);

        for (scene_handle, instance_id) in scenes_to_spawn {
            match self.spawn_sync_internal(world, scene_handle, instance_id) {
                Ok(_) => {}
                Err(SceneSpawnError::NonExistentRealScene { handle }) => {
                    self.scenes_to_spawn.push((handle, instance_id))
                }
                Err(err) => return Err(err),
            }
        }

        Ok(())
    }

    pub(crate) fn set_scene_instance_parent_sync(&mut self, world: &mut World) {
        let scenes_with_parent = std::mem::take(&mut self.scenes_with_parent);

        for (instance_id, parent) in scenes_with_parent {
            if let Some(instance) = self.spawned_instances.get(&instance_id) {
                for entity in instance.entity_map.values() {
                    if let Some(mut entity_mut) = world.get_entity_mut(entity) {
                        if !entity_mut.contains::<Parent>() {
                            entity_mut.insert(Parent(parent));
                        }
                    }
                }
            } else {
                self.scenes_with_parent.push((instance_id, parent));
            }
        }
    }

    /// Check that an scene instance spawned previously is ready to use
    pub fn instance_is_ready(&self, instance_id: InstanceId) -> bool {
        self.spawned_instances.contains_key(&instance_id)
    }

    /// Get an iterator over the entities in an instance, once it's spawned
    pub fn iter_instance_entities(
        &'_ self,
        instance_id: InstanceId,
    ) -> Option<impl Iterator<Item = Entity> + '_> {
        self.spawned_instances
            .get(&instance_id)
            .map(|instance| instance.entity_map.values())
    }
}

pub fn scene_spawner_system(world: &mut World) {
    world.resource_scope(|world, mut scene_spawner: Mut<SceneSpawner>| {
        let scene_asset_events = world
            .get_resource::<Events<AssetEvent<DynamicScene>>>()
            .unwrap();

        let mut updated_spawned_scenes = Vec::new();
        for event in scene_spawner
            .scene_asset_event_reader
            .iter(&scene_asset_events)
        {
            if let AssetEvent::Modified { handle } = event {
                if scene_spawner.spawned_dynamic_scenes.contains_key(handle) {
                    updated_spawned_scenes.push(handle.clone_weak());
                }
            }
        }

        scene_spawner.despawn_queued_scenes(world).unwrap();
        scene_spawner
            .spawn_queued_scenes(world)
            .unwrap_or_else(|err| panic!("{}", err));
        scene_spawner
            .update_spawned_scenes(world, &updated_spawned_scenes)
            .unwrap();
        scene_spawner.set_scene_instance_parent_sync(world);
    });
}