concinnity-core 0.19.1

//! Runtime entity spawn: instantiate a copy of an existing placement at a new
//! transform and give it the components and (optionally) the Lifetime the copy
//! needs to live in the world.
//!
//! What a copy's draw slot is comes from a host, through the `clone_slot` /
//! `acquire_slot` seams: a slot index is a renderer's to allocate, and it is
//! the one thing here that is. Everything else -- which components a copy
//! carries, when a Spawner is due, when a Lifetime is up -- is the world's, so
//! it lives with the world.

use crate::memory::InlineVec;

use crate::components::{
    BodyDynamics, Collider, GlobalTransform, Lifetime, MeshRenderer, ModelRenderer, Pickup,
    PropInstance, RenderHandle, SkeletonPose, Spawner, Transform,
};
use crate::ecs::asset_id::AssetId;
use crate::ecs::{Entity, EntityByName, FrameVec, PipelineContext};

/// Instantiate a runtime copy of `template`'s renderable: clone each of its
/// backend draw slots at `transform` through `clone_slot`, then build a new
/// entity carrying the cloned slots, a copy of the template's renderer, the
/// placement, and an optional Lifetime.
///
/// `clone_slot(src_draw_idx, model)` returns the new backend slot index (a
/// vacated slot reused, or a freshly appended one); it is the seam a host wires
/// to its own allocator. When `name` is Some the new entity is registered under
/// it so it can later be addressed by name like an authored placement;
/// transient spawns (a Spawner's churn) pass None to avoid interning a name per
/// spawn. Returns the new entity, or None when the template has no draw slots to
/// copy or a clone fails.
pub fn spawn_from_template(
    ctx: &mut PipelineContext,
    template: Entity,
    name: Option<AssetId>,
    transform: Transform,
    lifetime: Option<f32>,
    mut clone_slot: impl FnMut(usize, [[f32; 4]; 4]) -> Option<usize>,
) -> Option<Entity> {
    let src_slots: InlineVec<u32> = ctx.get::<RenderHandle>(template).map(|h| h.draws.clone())?;
    if src_slots.is_empty() {
        return None;
    }
    let model = transform.model_matrix();
    let mut draws = InlineVec::new();
    for src in src_slots {
        let new_slot = clone_slot(src as usize, model)?;
        draws.push(new_slot as u32);
    }

    // Copy whichever renderer the template carries so the new entity is a
    // first-class renderable for every system that joins on it, plus its
    // physics components so the physics system builds it a body.
    let mesh_renderer = ctx.get::<MeshRenderer>(template).cloned();
    let model_renderer = ctx.get::<ModelRenderer>(template).cloned();
    let collider = ctx.get::<Collider>(template).cloned();
    let body_dynamics = ctx.get::<BodyDynamics>(template).copied();
    let pickup = ctx.get::<Pickup>(template).is_some();
    let prop_instance = ctx.get::<PropInstance>(template).is_some();

    let entity = ctx.components.spawn();
    ctx.insert(entity, transform);
    ctx.insert(entity, GlobalTransform(model));
    ctx.insert(entity, RenderHandle { draws });
    if let Some(renderer) = mesh_renderer {
        ctx.insert(entity, renderer);
    } else if let Some(renderer) = model_renderer {
        ctx.insert(entity, renderer);
    }
    if let Some(collider) = collider {
        ctx.insert(entity, collider);
    }
    if let Some(body_dynamics) = body_dynamics {
        ctx.insert(entity, body_dynamics);
    }
    if pickup {
        ctx.insert(entity, Pickup);
    }
    if prop_instance {
        ctx.insert(entity, PropInstance);
    }
    if let Some(secs) = lifetime {
        ctx.insert(entity, Lifetime { remaining: secs });
    }
    if let Some(name) = name
        && let Some(by_name) = ctx.resource_mut::<EntityByName>()
    {
        by_name.0.insert(name, entity);
    }
    Some(entity)
}

/// Instantiate a runtime copy of a skinned `template` (a SkinnedMesh's
/// SkeletonPose entity) at `transform`.
///
/// Unlike the static path, a skinned instance is not a cloned draw slot: it
/// claims one of the template's pre-reserved hidden bind-pose copies through
/// `acquire_slot`, which reveals it and returns its skinned index. The new
/// entity carries its own SkeletonPose (so an animation system drives it, keyed
/// on the shared mesh id, in lockstep with the template), a Transform (so the
/// per-frame model push can move it), and an optional Lifetime. When `name` is
/// Some the instance is registered so it can be addressed (e.g. despawned) by
/// name. Returns the new entity, or None when the template is not skinned or
/// its instance pool is exhausted.
pub fn spawn_skinned_from_template(
    ctx: &mut PipelineContext,
    template: Entity,
    name: Option<AssetId>,
    transform: Transform,
    lifetime: Option<f32>,
    mut acquire_slot: impl FnMut(usize, [[f32; 4]; 4]) -> Option<usize>,
) -> Option<Entity> {
    let template_pose = ctx.get::<SkeletonPose>(template)?;
    let model = transform.model_matrix();
    let skinned_index = acquire_slot(template_pose.skinned_index, model)?;
    let pose = template_pose.clone_for_slot(skinned_index);

    let prop_instance = ctx.get::<PropInstance>(template).is_some();

    let entity = ctx.components.spawn();
    ctx.insert(entity, transform);
    ctx.insert(entity, pose);
    if prop_instance {
        ctx.insert(entity, PropInstance);
    }
    if let Some(secs) = lifetime {
        ctx.insert(entity, Lifetime { remaining: secs });
    }
    if let Some(name) = name
        && let Some(by_name) = ctx.resource_mut::<EntityByName>()
    {
        by_name.0.insert(name, entity);
    }
    Some(entity)
}

/// One spawn a Spawner is due to emit this step: the template to copy, where to
/// place it, and how long the copy should live.
///
/// Returned by [`tick_spawners`] for the caller to route through
/// [`spawn_from_template`] with the live backend, the same way
/// [`tick_lifetimes`] returns expiries for the caller to despawn.
#[derive(Clone, Copy)]
pub struct DueSpawn {
    /// The placement to copy.
    pub template: AssetId,
    /// Where the copy is placed.
    pub transform: Transform,
    /// Seconds the copy lives for, or `None` when it is not auto-removed.
    pub lifetime: Option<f32>,
}

/// Advance every Spawner's clock by `dt` and return the spawns now due, in
/// frame scratch.
///
/// A spawner emits one copy per whole `interval` elapsed (so a long frame that
/// crosses several intervals catches up), at the spawner entity's own
/// Transform. A non-positive interval is inert (never spawns). A zero
/// `lifetime` means the copy is not auto-removed; otherwise it carries that
/// countdown.
pub fn tick_spawners<'a>(ctx: &mut PipelineContext<'a>, dt: f32) -> FrameVec<'a, DueSpawn> {
    let frame = ctx.frame;
    // Advance every spawner's clock in place, recording only the ones that
    // crossed at least one interval this step (template, lifetime, and how many
    // copies are due). Every spawner could fire, so the reservation is exact.
    let mut fired = frame.vec::<(Entity, AssetId, f32, u32)>(ctx.query::<Spawner>().len());
    for (entity, spawner) in ctx.query_mut_with_entity::<Spawner>() {
        if spawner.interval <= 0.0 {
            continue;
        }
        spawner.elapsed += dt;
        let mut count = 0;
        while spawner.elapsed >= spawner.interval {
            spawner.elapsed -= spawner.interval;
            spawner.count += 1;
            count += 1;
        }
        if count > 0 {
            fired.push((entity, spawner.template, spawner.lifetime, count));
        }
    }
    // Resolve each fired spawner's placement (its Transform) now that the mutable
    // Spawner borrow is released, and expand to one DueSpawn per copy.
    let mut due = frame.vec::<DueSpawn>(
        fired
            .iter()
            .map(|&(.., count)| count as usize)
            .sum::<usize>(),
    );
    for &(entity, template, lifetime, count) in fired.iter() {
        let transform = ctx.get::<Transform>(entity).copied().unwrap_or_default();
        for _ in 0..count {
            due.push(DueSpawn {
                template,
                transform,
                lifetime: (lifetime > 0.0).then_some(lifetime),
            });
        }
    }
    due
}

/// Decrement every Lifetime by `dt` and return the entities whose countdown
/// reached zero this step, in frame scratch, for the caller to despawn.
///
/// Entities still alive keep their decremented remaining. Returning the expired
/// list (rather than despawning inline, which would mutate storage
/// mid-iteration) lets the caller route each expiry through the same despawn
/// cascade a DespawnRequest uses.
pub fn tick_lifetimes<'a>(ctx: &mut PipelineContext<'a>, dt: f32) -> FrameVec<'a, Entity> {
    let mut expired = ctx.frame.vec::<Entity>(ctx.query::<Lifetime>().len());
    for (entity, life) in ctx.query_mut_with_entity::<Lifetime>() {
        life.remaining -= dt;
        if life.remaining <= 0.0 {
            expired.push(entity);
        }
    }
    expired
}

#[cfg(test)]
mod tests {
    use super::*;
    use alloc::collections::BTreeMap;
    use alloc::vec;
    use alloc::vec::Vec;

    use crate::ecs::{
        Arena, ComponentStorage, FrameContext, NoPayloads, Resources, SkinnedMeshHandle,
    };
    use crate::gfx::profile::FrameProfile;
    use crate::gfx::skeleton::Skeleton;

    // Build an isolated PipelineContext over fresh storage, mirroring the
    // despawn tests, so the spawn/despawn loop can run without a backend.
    fn run<R>(body: impl FnOnce(&mut PipelineContext) -> R) -> R {
        let mut components = ComponentStorage::default();
        let mut blob = NoPayloads;
        let mut profile = FrameProfile::default();
        let mut resources = Resources::new();
        let scratch = Arena::with_capacity(64 * 1024);
        let mut ctx = PipelineContext {
            components: &mut components,
            blob: &mut blob,
            profile: &mut profile,
            resources: &mut resources,
            frame: FrameContext::new(&scratch),
        };
        body(&mut ctx)
    }

    // A `clone_slot` seam standing in for a renderer's draw-slot allocator: it
    // pops a vacated slot before growing, which is the property the recycle
    // tests are about.
    #[derive(Default)]
    struct Slots {
        free: Vec<usize>,
        len: usize,
    }

    impl Slots {
        fn with_len(len: usize) -> Slots {
            Slots {
                free: Vec::new(),
                len,
            }
        }

        fn allocate(&mut self) -> usize {
            match self.free.pop() {
                Some(slot) => slot,
                None => {
                    self.len += 1;
                    self.len - 1
                }
            }
        }

        fn free(&mut self, slot: usize) {
            self.free.push(slot);
        }
    }

    // The `acquire_slot` seam's stand-in: the pre-reserved hidden copies a
    // skinned template owns, and which of them are currently free.
    #[derive(Default)]
    struct Pool {
        free: BTreeMap<usize, Vec<usize>>,
        owner: BTreeMap<usize, usize>,
    }

    impl Pool {
        fn reserve(&mut self, template: usize, instance: usize) {
            self.owner.insert(instance, template);
            self.free.entry(template).or_default().push(instance);
        }

        fn acquire(&mut self, template: usize) -> Option<usize> {
            self.free.get_mut(&template).and_then(|slots| slots.pop())
        }

        fn release(&mut self, instance: usize) {
            if let Some(&template) = self.owner.get(&instance) {
                self.free.entry(template).or_default().push(instance);
            }
        }
    }

    #[test]
    fn spawned_copy_carries_the_template_physics_components() {
        run(|ctx| {
            ctx.insert_resource(EntityByName::default());

            let template = ctx.components.spawn();
            ctx.insert(template, Transform::default());
            ctx.insert(
                template,
                MeshRenderer {
                    mesh: None,
                    material: None,
                    texture: None,
                    cull_distance: 0.0,
                },
            );
            ctx.insert(template, RenderHandle { draws: [0].into() });
            ctx.insert(
                template,
                Collider(crate::components::PropCollider {
                    radius: 0.4,
                    ..Default::default()
                }),
            );
            ctx.insert(
                template,
                BodyDynamics {
                    mass: 2.5,
                    ..Default::default()
                },
            );
            ctx.insert(template, Pickup);

            let mut alloc = Slots::with_len(1);
            let spawned = spawn_from_template(
                ctx,
                template,
                None,
                Transform::default(),
                None,
                |_src, _model| Some(alloc.allocate()),
            )
            .expect("spawn");

            assert_eq!(
                ctx.get::<Collider>(spawned).map(|c| c.0.radius),
                Some(0.4),
                "the collider is copied"
            );
            assert_eq!(
                ctx.get::<BodyDynamics>(spawned).map(|b| b.mass),
                Some(2.5),
                "the dynamic-body parameters are copied"
            );
            assert!(ctx.get::<Pickup>(spawned).is_some(), "the tag is copied");
        });
    }

    #[test]
    fn freed_draw_slot_is_reused_by_the_next_spawn() {
        run(|ctx| {
            ctx.insert_resource(EntityByName::default());

            // A template placement occupying draw slot 0.
            let template = ctx.components.spawn();
            ctx.insert(template, Transform::default());
            ctx.insert(
                template,
                MeshRenderer {
                    mesh: None,
                    material: None,
                    texture: None,
                    cull_distance: 0.0,
                },
            );
            ctx.insert(template, RenderHandle { draws: [0].into() });

            // The backend starts with one live slot (the template's).
            let mut alloc = Slots::with_len(1);

            // First spawn appends a fresh slot past the template's.
            let first = spawn_from_template(
                ctx,
                template,
                Some(AssetId(1)),
                Transform::default(),
                Some(0.5),
                |_src, _model| Some(alloc.allocate()),
            )
            .expect("first spawn");
            let first_slot = ctx.get::<RenderHandle>(first).unwrap().draws.clone();
            assert_eq!(first_slot, vec![1], "first spawn appended slot 1");

            // Its Lifetime expires; the expiry frees the slot like a despawn's
            // retire -> free does, then despawns the entity.
            let expired = tick_lifetimes(ctx, 1.0);
            assert_eq!(&*expired, &[first], "the short-lived spawn expired");
            let freed: Vec<u32> = ctx.get::<RenderHandle>(first).unwrap().draws.to_vec();
            for slot in &freed {
                alloc.free(*slot as usize);
            }
            ctx.despawn(first);
            assert!(ctx.get::<RenderHandle>(first).is_none(), "first despawned");

            // The next spawn reuses the freed slot instead of growing the vec.
            let second = spawn_from_template(
                ctx,
                template,
                Some(AssetId(2)),
                Transform::default(),
                None,
                |_src, _model| Some(alloc.allocate()),
            )
            .expect("second spawn");
            let second_slot = ctx.get::<RenderHandle>(second).unwrap().draws.clone();
            assert_eq!(
                second_slot, freed,
                "the freed draw slot must be recycled by the next spawn"
            );
        });
    }

    #[test]
    fn skinned_spawn_claims_and_recycles_a_pooled_slot() {
        run(|ctx| {
            ctx.insert_resource(EntityByName::default());

            // A skinned template at draw slot 0 with two pre-reserved hidden
            // copies (slots 1 and 2) in the pool.
            let template = ctx.components.spawn();
            ctx.insert(
                template,
                SkeletonPose::new(SkinnedMeshHandle(10), 0, Skeleton::new(Vec::new())),
            );
            let mut pool = Pool::default();
            pool.reserve(0, 1);
            pool.reserve(0, 2);

            // The spawn claims a pooled copy and the new entity points at it.
            let first = spawn_skinned_from_template(
                ctx,
                template,
                Some(AssetId(11)),
                Transform::default(),
                Some(0.5),
                |template_idx, _model| pool.acquire(template_idx),
            )
            .expect("first skinned spawn");
            let first_slot = ctx.get::<SkeletonPose>(first).unwrap().skinned_index;
            assert_eq!(
                ctx.get::<SkeletonPose>(first).unwrap().mesh_id,
                SkinnedMeshHandle(10),
                "the instance shares the template's mesh id so it animates with it"
            );

            // Its Lifetime expires; the expiry releases the slot to the pool like
            // a despawn's retire does, then despawns the entity.
            let expired = tick_lifetimes(ctx, 1.0);
            assert_eq!(&*expired, &[first]);
            pool.release(first_slot);
            ctx.despawn(first);

            // The next spawn recycles the freed slot instead of a fresh one.
            let second = spawn_skinned_from_template(
                ctx,
                template,
                None,
                Transform::default(),
                None,
                |template_idx, _model| pool.acquire(template_idx),
            )
            .expect("second skinned spawn");
            assert_eq!(
                ctx.get::<SkeletonPose>(second).unwrap().skinned_index,
                first_slot,
                "the freed skinned slot must be recycled by the next spawn"
            );
        });
    }

    #[test]
    fn skinned_spawn_with_exhausted_pool_returns_none() {
        run(|ctx| {
            let template = ctx.components.spawn();
            ctx.insert(
                template,
                SkeletonPose::new(SkinnedMeshHandle(10), 0, Skeleton::new(Vec::new())),
            );
            // A template that reserved no instances has nothing to claim.
            let mut pool = Pool::default();
            let spawned = spawn_skinned_from_template(
                ctx,
                template,
                None,
                Transform::default(),
                None,
                |template_idx, _model| pool.acquire(template_idx),
            );
            assert!(spawned.is_none(), "an exhausted pool drops the spawn");
        });
    }

    #[test]
    fn spawn_registers_the_instance_by_name() {
        run(|ctx| {
            ctx.insert_resource(EntityByName::default());
            let template = ctx.components.spawn();
            ctx.insert(template, Transform::default());
            ctx.insert(template, RenderHandle { draws: [0].into() });
            let mut alloc = Slots::with_len(1);

            let spawned = spawn_from_template(
                ctx,
                template,
                Some(AssetId(42)),
                Transform::default(),
                None,
                |_src, _model| Some(alloc.allocate()),
            )
            .expect("spawn");

            let by_name = ctx.resource::<EntityByName>().unwrap();
            assert_eq!(by_name.get(AssetId(42)), Some(spawned));
        });
    }

    #[test]
    fn spawner_emits_one_copy_per_interval_elapsed() {
        run(|ctx| {
            let spawner = ctx.components.spawn();
            ctx.insert(
                spawner,
                Transform {
                    position: [1.0, 2.0, 3.0],
                    ..Transform::default()
                },
            );
            ctx.insert(
                spawner,
                Spawner {
                    template: AssetId(7),
                    interval: 1.0,
                    lifetime: 2.0,
                    elapsed: 0.0,
                    count: 0,
                },
            );

            // Below the interval: nothing due, but the clock advances.
            assert!(tick_spawners(ctx, 0.5).is_empty());
            // Crossing the interval emits one, carrying the lifetime + template
            // and the spawner's own position.
            let due = tick_spawners(ctx, 0.6);
            assert_eq!(due.len(), 1);
            assert_eq!(due[0].template, AssetId(7));
            assert_eq!(due[0].lifetime, Some(2.0));
            assert_eq!(due[0].transform.position, [1.0, 2.0, 3.0]);
            // A long frame crossing several intervals catches up.
            assert_eq!(tick_spawners(ctx, 2.5).len(), 2);
            assert_eq!(ctx.get::<Spawner>(spawner).unwrap().count, 3);
        });
    }

    #[test]
    fn spawner_with_nonpositive_interval_is_inert() {
        run(|ctx| {
            let spawner = ctx.components.spawn();
            ctx.insert(spawner, Transform::default());
            ctx.insert(
                spawner,
                Spawner {
                    template: AssetId(7),
                    interval: 0.0,
                    lifetime: 0.0,
                    elapsed: 0.0,
                    count: 0,
                },
            );
            assert!(tick_spawners(ctx, 100.0).is_empty());
        });
    }

    #[test]
    fn tick_only_expires_elapsed_lifetimes() {
        run(|ctx| {
            let short = ctx.components.spawn();
            ctx.insert(short, Lifetime { remaining: 0.1 });
            let long = ctx.components.spawn();
            ctx.insert(long, Lifetime { remaining: 5.0 });

            let expired = tick_lifetimes(ctx, 0.2);
            assert_eq!(&*expired, &[short], "only the short lifetime expired");
            // The survivor's clock advanced but it is still alive.
            assert_eq!(ctx.get::<Lifetime>(long).unwrap().remaining, 4.8);
        });
    }
}