1 files changed, 62 insertions, 0 deletions
diff --git a/plugins/movement/src/reducer.rs b/plugins/movement/src/reducer.rs
new file mode 100644
index 0000000..334d37e
--- /dev/null
+++ b/plugins/movement/src/reducer.rs
@@ -0,0 +1,62 @@
+use bevy::{ecs::component::Component, math::Vec3};
+
+use crate::Velocity;
+
+/// Controls how Velocity is reduced
+#[derive(Component)]
+pub enum VelocityReducer {
+    /// Sync mode, only applies the current Velocity to Position each time, does not reduce itself
+    Sync,
+
+    /// Move mode, directly zeroes out the velocity (momentum is transferred to Position)
+    Move,
+
+    /// Constant reduction mode, reduces by a fixed amount each time until it becomes Vec3::ZERO
+    Reduce(Vec3),
+
+    /// Lerp, reduces velocity using linear interpolation each time until it becomes Vec3::ZERO
+    Lerp(f32),
+
+    /// Function, calls a custom function to process velocity
+    Func(Box<dyn Fn(Vec3) -> Vec3 + Send + Sync + 'static>),
+}
+
+impl VelocityReducer {
+    /// Calculates velocity reduction, writing the result back to the Velocity component
+    pub fn calculate(&self, origin: &mut Velocity) {
+        self.calculate_vec(&mut *origin);
+    }
+
+    /// Calculates velocity reduction, writing the result back to Vec3
+    pub fn calculate_vec(&self, origin_vec: &mut Vec3) {
+        match self {
+            VelocityReducer::Sync => {
+                // DO NOTHING
+            }
+            VelocityReducer::Move => {
+                *origin_vec = Vec3::ZERO;
+            }
+            VelocityReducer::Reduce(vec3) => {
+                let mut vec = *origin_vec - *vec3;
+                // Handle direction: if sign flips, clamp to zero
+                if (origin_vec.x > 0.0 && vec.x < 0.0) || (origin_vec.x < 0.0 && vec.x > 0.0) {
+                    vec.x = 0.0;
+                }
+                if (origin_vec.y > 0.0 && vec.y < 0.0) || (origin_vec.y < 0.0 && vec.y > 0.0) {
+                    vec.y = 0.0;
+                }
+                if (origin_vec.z > 0.0 && vec.z < 0.0) || (origin_vec.z < 0.0 && vec.z > 0.0) {
+                    vec.z = 0.0;
+                }
+                *origin_vec = vec;
+            }
+            VelocityReducer::Lerp(lerp) => {
+                let lerp = lerp.clamp(0., 1.);
+                *origin_vec = origin_vec.lerp(Vec3::ZERO, lerp);
+            }
+            VelocityReducer::Func(fn_mut) => {
+                *origin_vec = fn_mut(*origin_vec);
+            }
+        }
+    }
+}