Pumpkin/crates/pumpkin/src/entity/combat.rs

use std::sync::atomic::Ordering;

use crate::entity::EntityBase;
use pumpkin_data::{
    attributes::Attributes,
    particle::Particle,
    sound::{Sound, SoundCategory},
};
use pumpkin_util::math::vector3::Vector3;

use crate::{
    entity::{Entity, player::Player},
    world::World,
};

use crate::net::ClientPlatform;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AttackType {
    Knockback,
    Critical,
    Sweeping,
    Strong,
    Weak,
    MaceSmash,
}

impl AttackType {
    pub async fn new(player: &Player, attack_cooldown_progress: f32) -> Self {
        let entity = &player.get_entity();

        let sprinting = entity.is_sprinting();
        let on_ground = entity.on_ground.load(Ordering::Relaxed);
        let fall_distance = player.living_entity.fall_distance.load();
        let held_item = player.inventory().held_item().await;
        let is_mace = held_item.item.id == pumpkin_data::item::Item::MACE.id;

        if is_mace && !on_ground && fall_distance > 1.5 {
            return Self::MaceSmash;
        }

        let sword = held_item.is_sword();
        let is_bedrock = matches!(player.client.as_ref(), ClientPlatform::Bedrock(_));

        let is_strong = attack_cooldown_progress > 0.9;
        if sprinting && is_strong {
            return Self::Knockback;
        }

        if is_strong && !on_ground && fall_distance > 0.0 {
            return Self::Critical;
        }

        if sword && is_strong && !is_bedrock {
            return Self::Sweeping;
        }

        if is_strong { Self::Strong } else { Self::Weak }
    }
}

/// Scales a knockback `strength` by a living entity's knockback resistance,
/// mirroring vanilla `LivingEntity.knockback`: `strength *= 1.0 - resistance`.
/// A resistance of 1.0 (iron golem, warden, ...) cancels the knockback entirely.
pub fn knockback_after_resistance(strength: f64, resistance: f64) -> f64 {
    strength * (1.0 - resistance)
}

pub fn handle_knockback(attacker: &Entity, victim: &dyn EntityBase, strength: f64) {
    let resistance = victim.get_living_entity().map_or(0.0, |living| {
        living.get_attribute_value(&Attributes::KNOCKBACK_RESISTANCE)
    });
    let strength = knockback_after_resistance(strength * 0.5, resistance);

    if strength > 0.0 {
        let yaw = attacker.yaw.load();
        victim.get_entity().knockback(
            strength,
            f64::from((yaw.to_radians()).sin()),
            f64::from(-(yaw.to_radians()).cos()),
        );
    }

    let velocity = attacker.velocity.load();
    attacker.velocity.store(velocity.multiply(0.6, 1.0, 0.6));
}

pub fn spawn_sweep_particle(attacker_entity: &Entity, world: &World, pos: &Vector3<f64>) {
    let yaw = attacker_entity.yaw.load();
    let d = -f64::from((yaw.to_radians()).sin());
    let e = f64::from((yaw.to_radians()).cos());

    let scale = 0.5;
    let body_y = f64::from(attacker_entity.height()).mul_add(scale, pos.y);

    world.spawn_particle(
        Vector3::new(pos.x + d, body_y, pos.z + e),
        Vector3::new(0.0, 0.0, 0.0),
        0.0,
        0,
        Particle::SweepAttack,
    );
}

pub async fn player_attack_sound(pos: &Vector3<f64>, world: &World, attack_type: AttackType) {
    match attack_type {
        AttackType::Knockback => {
            world.play_sound(
                Sound::EntityPlayerAttackKnockback,
                SoundCategory::Players,
                pos,
            );
        }
        AttackType::Critical => {
            world.play_sound(Sound::EntityPlayerAttackCrit, SoundCategory::Players, pos);
        }
        AttackType::Sweeping => {
            world.play_sound(Sound::EntityPlayerAttackSweep, SoundCategory::Players, pos);
        }
        AttackType::Strong => {
            world.play_sound(Sound::EntityPlayerAttackStrong, SoundCategory::Players, pos);
        }
        AttackType::Weak => {
            world.play_sound(Sound::EntityPlayerAttackWeak, SoundCategory::Players, pos);
        }
        AttackType::MaceSmash => {
            world.play_sound(Sound::ItemMaceSmashAir, SoundCategory::Players, pos);
        }
    }
}

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

    #[test]
    fn zero_resistance_keeps_full_strength() {
        assert_eq!(knockback_after_resistance(0.4, 0.0), 0.4);
    }

    #[test]
    fn full_resistance_cancels_knockback() {
        // Iron golem / warden have KNOCKBACK_RESISTANCE == 1.0.
        assert_eq!(knockback_after_resistance(0.4, 1.0), 0.0);
    }

    #[test]
    fn partial_resistance_scales_strength() {
        // Ravager has KNOCKBACK_RESISTANCE == 0.75.
        assert!((knockback_after_resistance(0.4, 0.75) - 0.1).abs() < 1e-9);
    }

    #[test]
    fn over_full_resistance_is_negative_so_callers_skip_it() {
        // Stacked armour modifiers can push resistance above 1.0; the result is
        // negative and callers guard on `strength > 0.0`.
        assert!(knockback_after_resistance(0.4, 1.2) < 0.0);
    }
}