From 09fd0514f6ece247715ee17fbbf72720339df97e Mon Sep 17 00:00:00 2001
From: Dennis Kobert <dennis@kobert.dev>
Date: Mon, 4 Jan 2021 01:34:26 +0100
Subject: [PATCH] Calculate the difference between bounding boxes

---
 rask-engine/src/engine/mod.rs     | 15 +++++++++-
 rask-engine/src/engine/systems.rs | 49 ++++++++++++++++++++++++++++---
 2 files changed, 59 insertions(+), 5 deletions(-)

diff --git a/rask-engine/src/engine/mod.rs b/rask-engine/src/engine/mod.rs
index 9152c85e..97ca56c7 100644
--- a/rask-engine/src/engine/mod.rs
+++ b/rask-engine/src/engine/mod.rs
@@ -95,9 +95,22 @@ impl GameEngine for RaskEngine {
                 entity: _background,
             })
             .build();
+        let _ground = world
+            .create_entity()
+            .with(SubCollider {
+                collider: crate::boxes::AABox {
+                    pos: Vec2::new(0.0, -1.0),
+                    size: Vec2::new(2.0, 0.5),
+                }
+                .into(),
+            })
+            .with(Parent {
+                entity: _background,
+            })
+            .build();
         let _char = world
             .create_entity()
-            .with(Pos(Vec2::new(0.0, 0.8)))
+            .with(Pos(Vec2::new(0.0, 0.0)))
             .with(Vel(Vec2::new(0.0, 0.0)))
             .with(Speed(0.2))
             .with(Mass(1.0))
diff --git a/rask-engine/src/engine/systems.rs b/rask-engine/src/engine/systems.rs
index d165cd0a..3a24acb8 100644
--- a/rask-engine/src/engine/systems.rs
+++ b/rask-engine/src/engine/systems.rs
@@ -141,10 +141,12 @@ impl<'a> System<'a> for UpdateAnimationSystem {
         WriteStorage<'a, Parent>,
         ReadStorage<'a, Present>,
         ReadStorage<'a, Scale>,
-        ReadStorage<'a, Pos>,
+        WriteStorage<'a, Pos>,
+        WriteStorage<'a, Vel>,
         Entities<'a>,
         ReadExpect<'a, Hierarchy<Parent>>,
         Read<'a, ElapsedTime>,
+        Read<'a, DeltaTime>,
     );
 
     fn run(
@@ -160,18 +162,21 @@ impl<'a> System<'a> for UpdateAnimationSystem {
             mut parent,
             present,
             scale,
-            pos,
+            mut pos,
+            mut vel,
             entities,
             hierarchy,
             elapsed,
+            dt,
         ): Self::SystemData,
     ) {
         let res = &mut *resources::RESOURCE_TABLE.write();
-        for (mut animation, collider, scale, pos, entity, _) in (
+        for (mut animation, collider, scale, pos, vel, entity, _) in (
             &mut animations,
             &collider,
             &scale,
-            &pos,
+            &mut pos,
+            &mut vel,
             &entities,
             &present,
         )
@@ -257,6 +262,42 @@ impl<'a> System<'a> for UpdateAnimationSystem {
                         .flatten(),
                 );
 
+                use crate::boxes::AABox;
+                let f = |old: AABox, new: AABox, dv, c: fn(Vec2) -> f32| {
+                    let dv = c(dv) > 0.0;
+                    let (new, old) = if dv {
+                        (c(new.pos + new.size), c(old.pos + old.size))
+                    } else {
+                        (c(old.pos), c(new.pos))
+                    };
+                    if dv == (new - old > 0.0) {
+                        new - old
+                    } else {
+                        0.0
+                    }
+                };
+
+                let x = f(aabb, new_aabb, vel.0, Vec2::x);
+                let y = f(aabb, new_aabb, vel.0, Vec2::y);
+                if x.is_finite() && y.is_finite() {
+                    let diff = Vec2::new(x, y);
+                    pos.0 += diff;
+                    vel.0 -= diff / dt.0.as_secs_f32();
+                    log::debug!("x: {}, y: {}, vel: {:?}", x, y, vel.0);
+                    for e in hierarchy.children(entity) {
+                        if let Some(trans) = mat3.get_mut(*e) {
+                            trans.mat3 *= Mat3::translation(diff.x(), diff.y());
+                        }
+                        if let Some(sub) = sub.get_mut(*e) {
+                            match sub.collider {
+                                Collidable::AABox(mut a) => a.pos += diff,
+                                Collidable::RBox(mut r) => r.pos += diff,
+                                Collidable::Point(mut p) => p += diff,
+                            };
+                        }
+                    }
+                }
+
                 // modify position to avoid collisions
             }
         }