//! Physics pipeline structures.

use crate::dynamics::{JointSet, RigidBody, RigidBodyHandle, RigidBodySet};
use crate::geometry::{BroadPhase, BroadPhasePairEvent, ColliderPair, ColliderSet, NarrowPhase};
use crate::pipeline::EventHandler;

/// The collision pipeline, responsible for performing collision detection between colliders.
///
/// This structure only contains temporary data buffers. It can be dropped and replaced by a fresh
/// copy at any time. For performance reasons it is recommended to reuse the same physics pipeline
/// instance to benefit from the cached data.
// NOTE: this contains only workspace data, so there is no point in making this serializable.
pub struct CollisionPipeline {
    broadphase_collider_pairs: Vec<ColliderPair>,
    broad_phase_events: Vec<BroadPhasePairEvent>,
    empty_joints: JointSet,
}

#[allow(dead_code)]
fn check_pipeline_send_sync() {
    fn do_test<T: Sync>() {}
    do_test::<CollisionPipeline>();
}

impl CollisionPipeline {
    /// Initializes a new physics pipeline.
    pub fn new() -> CollisionPipeline {
        CollisionPipeline {
            broadphase_collider_pairs: Vec::new(),
            broad_phase_events: Vec::new(),
            empty_joints: JointSet::new(),
        }
    }

    /// Executes one step of the collision detection.
    pub fn step(
        &mut self,
        prediction_distance: f32,
        broad_phase: &mut BroadPhase,
        narrow_phase: &mut NarrowPhase,
        bodies: &mut RigidBodySet,
        colliders: &mut ColliderSet,
        events: &dyn EventHandler,
    ) {
        bodies.maintain_active_set();
        self.broadphase_collider_pairs.clear();

        broad_phase.update_aabbs(prediction_distance, bodies, colliders);

        self.broad_phase_events.clear();
        broad_phase.find_pairs(&mut self.broad_phase_events);

        narrow_phase.register_pairs(colliders, &self.broad_phase_events, events);

        narrow_phase.compute_contacts(prediction_distance, bodies, colliders, events);
        narrow_phase.compute_proximities(prediction_distance, bodies, colliders, events);

        bodies.update_active_set_with_contacts(
            colliders,
            narrow_phase.contact_graph(),
            self.empty_joints.joint_graph(),
            0,
        );

        // // Update kinematic bodies velocities.
        // bodies.foreach_active_kinematic_body_mut_internal(|_, body| {
        //     body.compute_velocity_from_predicted_position(integration_parameters.inv_dt());
        // });

        // Update colliders positions and kinematic bodies positions.
        bodies.foreach_active_body_mut_internal(|_, rb| {
            if rb.is_kinematic() {
                rb.position = rb.predicted_position;
            } else {
                rb.update_predicted_position(0.0);
            }

            for handle in &rb.colliders {
                let collider = &mut colliders[*handle];
                collider.position = rb.position * collider.delta;
                collider.predicted_position = rb.predicted_position * collider.delta;
            }
        });

        bodies.modified_inactive_set.clear();
    }

    /// Remove a rigid-body and all its associated data.
    pub fn remove_rigid_body(
        &mut self,
        handle: RigidBodyHandle,
        broad_phase: &mut BroadPhase,
        narrow_phase: &mut NarrowPhase,
        bodies: &mut RigidBodySet,
        colliders: &mut ColliderSet,
    ) -> Option<RigidBody> {
        // Remove the body.
        let body = bodies.remove_internal(handle)?;

        // Remove this rigid-body from the broad-phase and narrow-phase.
        broad_phase.remove_colliders(&body.colliders, colliders);
        narrow_phase.remove_colliders(&body.colliders, colliders, bodies);

        // Remove all colliders attached to this body.
        for collider in &body.colliders {
            colliders.remove_internal(*collider);
        }

        Some(body)
    }
}