shinespark/src/fighter/ecb.rs

use bevy::prelude::*;

use crate::{
    fighter::{
        FighterFacingDirection, FighterSurfaceState, FighterTranslation,
        baked_animation::FighterBoneMatrices,
    }, math::{int::FGi32, vec::FGVec2},
};

/// Environment collision box: the diamond used to resolve a fighter against
/// the stage. Purely geometry — the collision response lives in
/// [`super::collision`].
#[derive(Component, Debug, Clone, Copy, Hash, Default)]
#[require(FighterPreviousECB)]
pub struct FighterECB {
    pub top: FGVec2,
    pub bottom: FGVec2,
    pub left: FGVec2,
    pub right: FGVec2,
}

#[derive(Component, Debug, Clone)]
pub struct FighterECBBoneIndices {
    pub indices: Vec<usize>,
}

#[derive(Component, Debug, Clone, Copy, Default, Hash)]
pub struct FighterPreviousECB {
    pub top: FGVec2,
    pub bottom: FGVec2,
    pub left: FGVec2,
    pub right: FGVec2,
}

impl From<FighterECB> for FighterPreviousECB {
    fn from(ecb: FighterECB) -> Self {
        Self {
            top: ecb.top,
            bottom: ecb.bottom,
            left: ecb.left,
            right: ecb.right,
        }
    }
}

pub fn snapshot_fighter_ecb(fighters: Query<(&FighterECB, &mut FighterPreviousECB)>) {
    for (ecb, mut previous_ecb) in fighters {
        *previous_ecb = (*ecb).into();
    }
}

impl FighterECB {
    pub fn to_3d_lineloop(&self, trf: Transform) -> [Vec3; 4] {
        [self.top, self.right, self.bottom, self.left]
            .map(|point| trf.transform_point(Vec3::new(point.x.to_num(), point.y.to_num(), 0.0)))
    }

    pub fn get_bottom_point(&self) -> FGVec2 {
        self.bottom
    }
}

impl FighterPreviousECB {
    pub fn to_3d_lineloop(&self, trf: Transform) -> [Vec3; 4] {
        [self.top, self.right, self.bottom, self.left]
            .map(|point| trf.transform_point(Vec3::new(point.x.to_num(), point.y.to_num(), 0.0)))
    }

    pub fn get_bottom_point(&self) -> FGVec2 {
        self.bottom
    }
}

pub fn update_ecb(
    query: Query<(
        &mut FighterECB,
        &FighterSurfaceState,
        &FighterECBBoneIndices,
        &FighterBoneMatrices,
        &FighterTranslation,
        &FighterFacingDirection,
    )>,
) {
    for (mut ecb, surface_state, bone_indices, bone_matrices, translation, facing_dir) in query {
        let trf = translation.get_3d_transform(facing_dir);

        let transformed_ecb_bones = bone_indices.indices.iter().filter_map(|idx| {
            let Some((_, bone_matrix)) = bone_matrices.get_by_idx(*idx) else {
                return None;
            };

            let pt = trf.transform_point(bone_matrix.get_translation());

            Some(FGVec2::new(pt.x, pt.y) - translation.0)
        }).collect::<Vec<_>>();

        let max_x = transformed_ecb_bones.iter().max_by(|a, b| a.x.cmp(&b.x)).map(|final_val| final_val.x).unwrap_or(FGi32::lit("0.5"));
        let min_x = transformed_ecb_bones.iter().min_by(|a, b| a.x.cmp(&b.x)).map(|final_val| final_val.x).unwrap_or(FGi32::lit("-0.5"));
        let max_y = transformed_ecb_bones.iter().max_by(|a, b| a.y.cmp(&b.y)).map(|final_val| final_val.y).unwrap_or(FGi32::lit("0.5"));
        let min_y = transformed_ecb_bones.iter().min_by(|a, b| a.y.cmp(&b.y)).map(|final_val| final_val.y).unwrap_or(FGi32::lit("-0.5"));

        let midpoint_height = (max_y + min_y) / FGi32::lit("2.0");
        let top = FGVec2::new(FGi32::ZERO, max_y);
        let bottom = FGVec2::new(FGi32::ZERO, min_y);
        let left = FGVec2::new(min_x, midpoint_height);
        let right = FGVec2::new(max_x, midpoint_height);

        let ecb_lock_frames_remaining = if let FighterSurfaceState::Airborne { ecb_lock_frames_remaining, .. } = surface_state {
            *ecb_lock_frames_remaining
        } else {
            0
        };

        ecb.top = top;

        if ecb_lock_frames_remaining == 0 {
            ecb.bottom = bottom;
        }

        ecb.left = left;
        ecb.right = right;

        if surface_state.is_grounded() {
            ecb.bottom = FGVec2::ZERO;
        }
    }
}

pub fn decrement_ecb_lockout(surface_states: Query<&mut FighterSurfaceState>) {
    for mut state in surface_states {
        state.tick_ecb_lock();
        state.tick_ignored_polygons();
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn previous_ecb_copies_current_dimensions() {
        let current = FighterECB {
            bottom: FGVec2::lit("0.0", "-0.5"),
            top: FGVec2::lit("0.0", "0.5"),
            left: FGVec2::lit("-0.5", "0.0"),
            right: FGVec2::lit("0.5", "0.0"),
        };
        let previous = FighterPreviousECB::from(current);

        assert_eq!(previous.top, current.top);
        assert_eq!(previous.bottom, current.bottom);
        assert_eq!(previous.left, current.left);
        assert_eq!(previous.right, current.right);
    }
}