Implement directional influence (#43)

Reviewed-on: #43
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/fighter/state/hitstun.rs

@@ -1,8 +1,6 @@
 use crate::{
     fighter::{
-        animation::AnimKind,
-        attack::FighterHitReaction,
-        state::{
+        animation::AnimKind, attack::{self, FighterHitReaction}, state::{
             CollisionContext, EnterContext, ExitContext, FighterState, FighterStateImpl,
             InterruptContext, UpdateContext, air,
             fall::FallState,
@@ -10,8 +8,7 @@ use crate::{
             land::LandingType,
             wait::WaitState,
         },
-    },
-    math::int::FGi32,
+    }, math::int::FGi32,
 };
 
 #[derive(Clone, Debug, Hash)]
@@ -24,6 +21,17 @@ pub enum HitstopStateKind {
 pub struct HitstunState {
     pub hit_reaction: FighterHitReaction,
     pub hitstop_kind: HitstopStateKind,
+    knockback_applied: bool
+}
+
+impl HitstunState {
+    pub fn new(hit_reaction: FighterHitReaction, hitstop_kind: HitstopStateKind) -> Self {
+        Self {
+            hit_reaction,
+            hitstop_kind,
+            knockback_applied: false
+        }
+    }
 }
 
 impl FighterStateImpl for HitstunState {
@@ -59,6 +67,17 @@ impl FighterStateImpl for HitstunState {
     }
 
     fn update(&mut self, ctx: &mut UpdateContext) {
+        if !self.knockback_applied {
+            let launch_direction = attack::directional_influence::apply_directional_influence(
+        ctx.input.get_last_frame().movement,
+                self.hit_reaction.launch_angle,
+                ctx.game_settings.fighter_common.di_max_angle
+            );
+
+            ctx.knockback_velocity.0 = launch_direction * self.hit_reaction.launch_velocity;
+            self.knockback_applied = true;
+        }
+
         air::integrate_gravity(ctx.velocity, ctx.fighter_attributes);
 
         let speed = ctx.knockback_velocity.length();
@@ -77,7 +96,6 @@ impl FighterStateImpl for HitstunState {
             HitstopStateKind::Airborne => AnimKind::FlinchAir,
         };
         state_context.play_animation(animation, false);
-        state_context.knockback_velocity.0 = self.hit_reaction.launch_velocity;
     }
 
     fn on_exit(&mut self, _state_context: &mut ExitContext) {}