Implement crouching

Reviewed-on: #61

src/fighter/animation.rs

@@ -84,6 +84,9 @@ pub enum AnimKind {
     AirDodge,
     Fall,
     Turn,
+    CrouchEnter,
+    CrouchIdle,
+    CrouchExit,
 
     FlinchGround,
     FlinchAir,

src/fighter/state/crouch.rs

@@ -0,0 +1,126 @@
+use super::{
+    CollisionContext, EnterContext, FighterStateImpl, InterruptContext, UpdateContext, ground,
+};
+use crate::fighter::animation::AnimKind;
+use crate::fighter::state::{FighterState, dash, ground_attack, turn, walk};
+use crate::fighter::state::ground::{grounded_movement_common_interrupts, grounded_movement_standstill_common_interrupts};
+
+#[derive(Debug, Clone, Hash)]
+pub enum CrouchSubState {
+    Entering,
+    Idle,
+    Exiting
+}
+
+#[derive(Debug, Clone, Hash)]
+pub struct CrouchState {
+    sub_state: CrouchSubState
+}
+
+pub fn crouch_idle_interrupts(
+    state_context: &InterruptContext,
+) -> Option<FighterState> {
+    if let Some(state) = ground_attack::check_interrupt(state_context) {
+        Some(state)
+    } else if let Some(state) = dash::check_input(state_context) {
+        Some(state)
+    } else if let Some(state) = turn::check_input(state_context) {
+        Some(state)
+    } else if let Some(state) = walk::check_input(state_context) {
+        Some(state)
+    } else {
+        None
+    }
+}
+
+pub fn crouch_entering_interrupts(
+    state_context: &InterruptContext,
+) -> Option<FighterState> {
+    if let Some(state) = ground_attack::check_interrupt(state_context) {
+        Some(state)
+    } else {
+        None
+    }
+}
+
+impl FighterStateImpl for CrouchState {
+    const NAME: &'static str = "Crouch";
+    fn check_interrupt(&self, state_context: &mut InterruptContext) -> Option<FighterState> {
+        if let Some(state) = grounded_movement_common_interrupts(state_context) {
+            return Some(state);
+        }
+
+        match self.sub_state {
+            CrouchSubState::Entering => {
+                // While entering the crouch animation we do not allow movement inputs, but we do allow attacks and jumps
+                if state_context.is_current_animation_finished() {
+                    return Some(FighterState::Crouch(
+                        CrouchState {
+                            sub_state: CrouchSubState::Idle,
+                        }
+                    ));
+                } else {
+                    return crouch_entering_interrupts(state_context);
+                }
+            },
+            CrouchSubState::Idle => {
+                if state_context.input.get_last_frame().movement.y > -state_context.game_settings.input_common.run_stick_threshold {
+                    return Some(FighterState::Crouch (
+                        CrouchState {
+                            sub_state: CrouchSubState::Exiting,
+                        }
+                    ));
+                } else {
+                    return crouch_idle_interrupts(state_context);
+                }
+            },
+            CrouchSubState::Exiting => {
+                if state_context.is_current_animation_finished() {
+                    return grounded_movement_standstill_common_interrupts(state_context);
+                } else {
+                    return crouch_idle_interrupts(state_context);
+                }
+            },
+        }
+    }
+
+    fn on_enter(&mut self, state_context: &mut EnterContext) {
+        match self.sub_state {
+            CrouchSubState::Entering => {
+                state_context.play_animation(AnimKind::CrouchEnter, false);
+            },
+            CrouchSubState::Idle => {
+                state_context.play_animation(AnimKind::CrouchIdle, true);
+            },
+            CrouchSubState::Exiting => {
+                state_context.play_animation(AnimKind::CrouchExit, false);
+            },
+        }
+    }
+
+    fn update(&mut self, state_context: &mut UpdateContext) {
+        ground::update_friction_motion(state_context);
+    }
+
+    fn check_collision_interrupt(
+        &mut self,
+        state_context: &mut CollisionContext,
+    ) -> Option<FighterState> {
+        ground::collision_interrupt(state_context, false)
+    }
+
+    fn is_visually_grounded<'a>(&'a self) -> bool {
+        true
+    }
+}
+
+pub fn check_input(state_context: &InterruptContext) -> Option<FighterState> {
+    let input_frame = state_context.input.get_last_frame();
+
+    if input_frame.movement.y <= -state_context.game_settings.input_common.run_stick_threshold {
+        return Some(FighterState::Crouch(CrouchState {
+            sub_state: CrouchSubState::Entering
+        }));
+    }
+    None
+}

src/fighter/state/ground.rs

@@ -3,8 +3,7 @@
 //! bit-for-bit deterministic for rollback.
 
 use crate::fighter::state::{
-    CollisionContext, FighterState, InterruptContext, air, dash, fall, ground_attack, turn, wait,
-    walk,
+    CollisionContext, FighterState, InterruptContext, air, crouch, dash, fall, ground_attack, turn, wait, walk,
 };
 use crate::fighter::{
     FighterAttributes, FighterPreviousTranslation, FighterTranslation, FighterVelocity,
@@ -461,6 +460,8 @@ pub fn grounded_movement_standstill_common_interrupts(
         Some(state)
     } else if let Some(state) = turn::check_input(state_context) {
         Some(state)
+    } else if let Some(state) = crouch::check_input(state_context) {
+        Some(state)
     } else if let Some(state) = walk::check_input(state_context) {
         Some(state)
     } else if let Some(state) = wait::check_input(state_context) {

src/fighter/state/mod.rs

@@ -41,6 +41,7 @@ pub mod run;
 pub mod turn;
 pub mod wait;
 pub mod walk;
+pub mod crouch;
 
 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
 pub enum SurfacePolicy {
@@ -211,6 +212,7 @@ impl CollisionContext<'_> {
 fighter_states! {
     Wait => wait::WaitState,
     Walk => walk::WalkState,
+    Crouch => crouch::CrouchState,
     Dash => dash::DashState,
     Run => run::RunState,
     Fall => fall::FallState,