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use crate::Scene; use bevy_app::prelude::*; use bevy_asset::{AssetEvent, Assets, Handle}; use bevy_ecs::{Resources, World}; use bevy_type_registry::TypeRegistry; use std::collections::{HashMap, HashSet}; use thiserror::Error; use uuid::Uuid; struct InstanceInfo { entity_map: HashMap<u32, bevy_ecs::Entity>, } #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)] struct InstanceId(Uuid); impl InstanceId { pub fn new() -> Self { InstanceId(Uuid::new_v4()) } } #[derive(Default)] pub struct SceneSpawner { loaded_scenes: HashSet<Handle<Scene>>, spawned_scenes: HashMap<Handle<Scene>, Vec<InstanceId>>, spawned_instances: HashMap<InstanceId, InstanceInfo>, scene_asset_event_reader: EventReader<AssetEvent<Scene>>, scenes_to_spawn: Vec<Handle<Scene>>, scenes_to_load: Vec<Handle<Scene>>, } #[derive(Error, Debug)] pub enum SceneSpawnError { #[error("Scene contains an unregistered component.")] UnregisteredComponent { type_name: String }, #[error("Scene does not exist. Perhaps it is still loading?")] NonExistentScene { handle: Handle<Scene> }, } impl SceneSpawner { pub fn instance(&mut self, scene_handle: Handle<Scene>) { self.scenes_to_spawn.push(scene_handle); } pub fn load(&mut self, scene_handle: Handle<Scene>) { self.scenes_to_load.push(scene_handle); } pub fn load_sync( &mut self, world: &mut World, resources: &Resources, scene_handle: Handle<Scene>, ) -> Result<(), SceneSpawnError> { Self::load_internal(world, resources, scene_handle, None)?; self.loaded_scenes.insert(scene_handle); Ok(()) } pub fn spawn_sync( &mut self, world: &mut World, resources: &Resources, scene_handle: Handle<Scene>, ) -> Result<(), SceneSpawnError> { let instance_id = InstanceId::new(); let mut instance_info = InstanceInfo { entity_map: HashMap::default(), }; Self::load_internal(world, resources, scene_handle, Some(&mut instance_info))?; 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(()) } fn load_internal( world: &mut World, resources: &Resources, scene_handle: Handle<Scene>, mut instance_info: Option<&mut InstanceInfo>, ) -> Result<(), SceneSpawnError> { let type_registry = resources.get::<TypeRegistry>().unwrap(); let component_registry = type_registry.component.read().unwrap(); let scenes = resources.get::<Assets<Scene>>().unwrap(); let scene = scenes .get(&scene_handle) .ok_or_else(|| SceneSpawnError::NonExistentScene { handle: scene_handle, })?; for scene_entity in scene.entities.iter() { let entity = if let Some(ref mut instance_info) = instance_info { *instance_info .entity_map .entry(scene_entity.entity) .or_insert_with(|| bevy_ecs::Entity::new()) } else { bevy_ecs::Entity::from_id(scene_entity.entity) }; if world.contains(entity) { for component in scene_entity.components.iter() { let component_registration = component_registry .get_with_name(&component.type_name) .ok_or_else(|| SceneSpawnError::UnregisteredComponent { type_name: component.type_name.to_string(), })?; if component.type_name != "Camera" { component_registration.apply_component_to_entity(world, entity, component); } } } else { world.spawn_as_entity(entity, (1,)); for component in scene_entity.components.iter() { let component_registration = component_registry .get_with_name(&component.type_name) .ok_or_else(|| SceneSpawnError::UnregisteredComponent { type_name: component.type_name.to_string(), })?; component_registration.add_component_to_entity(world, resources, entity, component); } } } Ok(()) } pub fn update_spawned_scenes( &mut self, world: &mut World, resources: &Resources, scene_handles: &[Handle<Scene>], ) -> Result<(), SceneSpawnError> { for scene_handle in scene_handles { if let Some(spawned_instances) = self.spawned_scenes.get(scene_handle) { for instance_id in spawned_instances.iter() { if let Some(instance_info) = self.spawned_instances.get_mut(instance_id) { Self::load_internal(world, resources, *scene_handle, Some(instance_info))?; } } } } Ok(()) } pub fn load_queued_scenes( &mut self, world: &mut World, resources: &Resources, ) -> Result<(), SceneSpawnError> { let scenes_to_load = self.scenes_to_load.drain(..).collect::<Vec<_>>(); let mut non_existent_scenes = Vec::new(); for scene_handle in scenes_to_load { match self.load_sync(world, resources, scene_handle) { Ok(_) => {} Err(SceneSpawnError::NonExistentScene { .. }) => { non_existent_scenes.push(scene_handle) } Err(err) => return Err(err), } } self.scenes_to_load = non_existent_scenes; Ok(()) } pub fn spawn_queued_scenes( &mut self, world: &mut World, resources: &Resources, ) -> Result<(), SceneSpawnError> { let scenes_to_spawn = self.scenes_to_spawn.drain(..).collect::<Vec<_>>(); let mut non_existent_scenes = Vec::new(); for scene_handle in scenes_to_spawn { match self.spawn_sync(world, resources, scene_handle) { Ok(_) => {} Err(SceneSpawnError::NonExistentScene { .. }) => { non_existent_scenes.push(scene_handle) } Err(err) => return Err(err), } } self.scenes_to_spawn = non_existent_scenes; Ok(()) } } pub fn scene_spawner_system(world: &mut World, resources: &mut Resources) { let mut scene_spawner = resources.get_mut::<SceneSpawner>().unwrap(); let scene_asset_events = resources.get::<Events<AssetEvent<Scene>>>().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.loaded_scenes.contains(handle) { scene_spawner.load(*handle); } if scene_spawner.spawned_scenes.contains_key(handle) { updated_spawned_scenes.push(*handle); } } } scene_spawner.load_queued_scenes(world, resources).unwrap(); scene_spawner.spawn_queued_scenes(world, resources).unwrap(); scene_spawner .update_spawned_scenes(world, resources, &updated_spawned_scenes) .unwrap(); }