Attacking (#96)

* add Client::attack

* partially implement attack cooldowns

* attack speed modifiers

* don't care clippy

---------

Co-authored-by: mat <git@matdoes.dev>

1 files changed, 138 insertions, 0 deletions

diff --git a/azalea-client/src/attack.rs b/azalea-client/src/attack.rs
new file mode 100644
index 00000000..34083ffc
--- /dev/null
+++ b/azalea-client/src/attack.rs
@@ -0,0 +1,138 @@
+use azalea_core::GameMode;
+use azalea_entity::{
+    metadata::{ShiftKeyDown, Sprinting},
+    Attributes, Physics,
+};
+use azalea_protocol::packets::game::serverbound_interact_packet::{
+    self, ServerboundInteractPacket,
+};
+use azalea_world::MinecraftEntityId;
+use bevy_app::{App, FixedUpdate, Plugin, Update};
+use bevy_ecs::prelude::*;
+use derive_more::{Deref, DerefMut};
+
+use crate::{
+    interact::SwingArmEvent,
+    local_player::{LocalGameMode, SendPacketEvent},
+    Client,
+};
+
+pub struct AttackPlugin;
+impl Plugin for AttackPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_event::<AttackEvent>()
+            .add_systems(Update, handle_attack_event)
+            .add_systems(
+                FixedUpdate,
+                (
+                    increment_ticks_since_last_attack,
+                    update_attack_strength_scale,
+                )
+                    .chain(),
+            );
+    }
+}
+
+impl Client {
+    /// Attack the entity with the given id.
+    pub fn attack(&mut self, entity_id: MinecraftEntityId) {
+        self.ecs.lock().send_event(AttackEvent {
+            entity: self.entity,
+            target: entity_id,
+        });
+    }
+
+    /// Whether the player has an attack cooldown.
+    pub fn has_attack_cooldown(&self) -> bool {
+        let ticks_since_last_attack = *self.component::<AttackStrengthScale>();
+        ticks_since_last_attack < 1.0
+    }
+}
+
+#[derive(Event)]
+pub struct AttackEvent {
+    pub entity: Entity,
+    pub target: MinecraftEntityId,
+}
+pub fn handle_attack_event(
+    mut events: EventReader<AttackEvent>,
+    mut query: Query<(
+        &LocalGameMode,
+        &mut TicksSinceLastAttack,
+        &mut Physics,
+        &mut Sprinting,
+        &mut ShiftKeyDown,
+    )>,
+    mut send_packet_events: EventWriter<SendPacketEvent>,
+    mut swing_arm_event: EventWriter<SwingArmEvent>,
+) {
+    for event in events.iter() {
+        let (game_mode, mut ticks_since_last_attack, mut physics, mut sprinting, sneaking) =
+            query.get_mut(event.entity).unwrap();
+
+        swing_arm_event.send(SwingArmEvent {
+            entity: event.entity,
+        });
+        send_packet_events.send(SendPacketEvent {
+            entity: event.entity,
+            packet: ServerboundInteractPacket {
+                entity_id: *event.target,
+                action: serverbound_interact_packet::ActionType::Attack,
+                using_secondary_action: **sneaking,
+            }
+            .get(),
+        });
+
+        // we can't attack if we're in spectator mode but it still sends the attack
+        // packet
+        if game_mode.current == GameMode::Spectator {
+            continue;
+        };
+
+        ticks_since_last_attack.0 = 0;
+
+        physics.delta = physics.delta.multiply(0.6, 1.0, 0.6);
+        **sprinting = false;
+    }
+}
+
+#[derive(Default, Bundle)]
+pub struct AttackBundle {
+    pub ticks_since_last_attack: TicksSinceLastAttack,
+    pub attack_strength_scale: AttackStrengthScale,
+}
+
+#[derive(Default, Component, Clone, Deref, DerefMut)]
+pub struct TicksSinceLastAttack(pub u32);
+pub fn increment_ticks_since_last_attack(mut query: Query<&mut TicksSinceLastAttack>) {
+    for mut ticks_since_last_attack in query.iter_mut() {
+        **ticks_since_last_attack += 1;
+    }
+}
+
+#[derive(Default, Component, Clone, Deref, DerefMut)]
+pub struct AttackStrengthScale(pub f32);
+pub fn update_attack_strength_scale(
+    mut query: Query<(&TicksSinceLastAttack, &Attributes, &mut AttackStrengthScale)>,
+) {
+    for (ticks_since_last_attack, attributes, mut attack_strength_scale) in query.iter_mut() {
+        // look 0.5 ticks into the future because that's what vanilla does
+        **attack_strength_scale =
+            get_attack_strength_scale(ticks_since_last_attack.0, attributes, 0.5);
+    }
+}
+
+/// Returns how long it takes for the attack cooldown to reset (in ticks).
+pub fn get_attack_strength_delay(attributes: &Attributes) -> f32 {
+    ((1. / attributes.attack_speed.calculate()) * 20.) as f32
+}
+
+pub fn get_attack_strength_scale(
+    ticks_since_last_attack: u32,
+    attributes: &Attributes,
+    in_ticks: f32,
+) -> f32 {
+    let attack_strength_delay = get_attack_strength_delay(attributes);
+    let attack_strength = (ticks_since_last_attack as f32 + in_ticks) / attack_strength_delay;
+    attack_strength.clamp(0., 1.)
+}