rhusics-ecs 0.1.0

use std::fmt::Debug;

use cgmath::prelude::*;
use collision::prelude::*;
use shrev::EventChannel;
use specs::{Component, Entities, Entity, FetchMut, Join, ReadStorage, System, WriteStorage};

use core::{basic_collide, BroadPhase, CollisionData, CollisionShape, ContactEvent, GetId,
           NarrowPhase, NextFrame, Primitive};

/// Collision detection [system](https://docs.rs/specs/0.9.5/specs/trait.System.html) for use with
/// [`specs`](https://docs.rs/specs/0.9.5/specs/).
///
/// Has support for both broad phase and narrow phase collision detection. Will only do narrow phase
/// if both broad and narrow phase is activated.
///
/// Can handle any transform component type, as long as the type implements
/// [`Transform`](https://docs.rs/cgmath/0.15.0/cgmath/trait.Transform.html), and as long as the
/// storage is wrapped in a
/// [`FlaggedStorage`](https://docs.rs/specs/0.9.5/specs/struct.FlaggedStorage.html).
///
/// ### Type parameters:
///
/// - `P`: Shape primitive
/// - `T`: Transform
/// - `D`: Data accepted by broad phase
/// - `B`: Bounding volume
/// - `Y`: Shape type, see `Collider`
///
/// ### System Function:
///
/// `fn(Entities, T, NextFrame<T>, CollisionShape) -> (CollisionShape, EventChannel<ContactEvent>)`
pub struct BasicCollisionSystem<P, T, D, B, Y = ()>
where
    P: Primitive,
    B: Bound,
{
    narrow: Option<Box<NarrowPhase<P, T, B, Y>>>,
    broad: Option<Box<BroadPhase<D>>>,
}

impl<P, T, D, B, Y> BasicCollisionSystem<P, T, D, B, Y>
where
    P: Primitive + Send + Sync + 'static,
    <P::Point as EuclideanSpace>::Diff: Debug,
    T: Transform<P::Point> + Component,
    D: HasBound<Bound = B>,
    B: Bound<Point = P::Point>,
{
    /// Create a new collision detection system, with no broad or narrow phase activated.
    pub fn new() -> Self {
        Self {
            narrow: None,
            broad: None,
        }
    }

    /// Specify what narrow phase algorithm to use
    pub fn with_narrow_phase<N: NarrowPhase<P, T, B, Y> + 'static>(mut self, narrow: N) -> Self {
        self.narrow = Some(Box::new(narrow));
        self
    }

    /// Specify what broad phase algorithm to use
    pub fn with_broad_phase<V: BroadPhase<D> + 'static>(mut self, broad: V) -> Self {
        self.broad = Some(Box::new(broad));
        self
    }
}

impl<'a, P, T, Y, D, B> System<'a> for BasicCollisionSystem<P, T, D, B, Y>
where
    P: Primitive + ComputeBound<B> + Send + Sync + 'static,
    P::Point: Debug + Send + Sync + 'static,
    <P::Point as EuclideanSpace>::Scalar: Send + Sync + 'static,
    <P::Point as EuclideanSpace>::Diff: Debug + Send + Sync + 'static,
    T: Component + Transform<P::Point> + Send + Sync + Clone + 'static,
    Y: Default + Send + Sync + 'static,
    B: Bound<Point = P::Point> + Send + Sync + 'static + Union<B, Output = B> + Clone,
    D: HasBound<Bound = B> + From<(Entity, B)> + GetId<Entity>,
    for<'b: 'a> &'b T::Storage: Join<Type = &'b T>,
{
    type SystemData = (
        Entities<'a>,
        ReadStorage<'a, T>,
        ReadStorage<'a, NextFrame<T>>,
        WriteStorage<'a, CollisionShape<P, T, B, Y>>,
        FetchMut<'a, EventChannel<ContactEvent<Entity, P::Point>>>,
    );

    fn run(&mut self, system_data: Self::SystemData) {
        let (entities, poses, next_poses, mut shapes, mut event_channel) = system_data;

        if let Some(ref mut broad) = self.broad {
            for (entity, pose, shape) in (&*entities, &poses, &mut shapes).join() {
                shape.update(&pose, next_poses.get(entity).map(|p| &p.value));
            }
            event_channel.iter_write(basic_collide(
                BasicCollisionData {
                    poses: &poses,
                    shapes: &shapes,
                    next_poses: &next_poses,
                    entities: &entities,
                },
                broad,
                &self.narrow,
            ));
        }
    }
}

/// Collision data used by ECS systems
struct BasicCollisionData<'a, P, T, B, Y>
where
    P: Primitive + ComputeBound<B> + Send + Sync + 'static,
    P::Point: Debug + Send + Sync + 'static,
    <P::Point as EuclideanSpace>::Scalar: Send + Sync + 'static,
    <P::Point as EuclideanSpace>::Diff: Debug + Send + Sync + 'static,
    T: Component + Transform<P::Point> + Send + Sync + Clone + 'static,
    Y: Default + Send + Sync + 'static,
    B: Bound<Point = P::Point> + Send + Sync + 'static + Union<B, Output = B> + Clone,
{
    /// collision shapes
    pub shapes: &'a WriteStorage<'a, CollisionShape<P, T, B, Y>>,
    /// current frame poses
    pub poses: &'a ReadStorage<'a, T>,
    /// next frame poses
    pub next_poses: &'a ReadStorage<'a, NextFrame<T>>,
    /// entities
    pub entities: &'a Entities<'a>,
}

impl<'a, P, T, B, Y, D> CollisionData<Entity, P, T, B, Y, D> for BasicCollisionData<'a, P, T, B, Y>
where
    P: Primitive + ComputeBound<B> + Send + Sync + 'static,
    P::Point: Debug + Send + Sync + 'static,
    <P::Point as EuclideanSpace>::Scalar: Send + Sync + 'static,
    <P::Point as EuclideanSpace>::Diff: Debug + Send + Sync + 'static,
    T: Component + Transform<P::Point> + Send + Sync + Clone + 'static,
    Y: Default + Send + Sync + 'static,
    B: Bound<Point = P::Point> + Send + Sync + 'static + Union<B, Output = B> + Clone,
    D: HasBound<Bound = B> + From<(Entity, B)> + GetId<Entity>,
{
    fn get_broad_data(&self) -> Vec<D> {
        (&**self.entities, self.shapes)
            .join()
            .map(|(entity, shape)| (entity, shape.bound().clone()).into())
            .collect::<Vec<_>>()
    }

    fn get_shape(&self, id: Entity) -> &CollisionShape<P, T, B, Y> {
        self.shapes.get(id).unwrap()
    }

    fn get_pose(&self, id: Entity) -> &T {
        self.poses.get(id).unwrap()
    }

    fn get_next_pose(&self, id: Entity) -> Option<&T> {
        self.next_poses.get(id).as_ref().map(|p| &p.value)
    }
}