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enemy.rs
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enemy.rs
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use bevy::prelude::*;
use rand::{rngs::SmallRng, seq::SliceRandom, SeedableRng};
use serde::Deserialize;
use crate::{
hit_points::HitPoints,
home::Home,
movement::{MovingProgress, Speed},
particle::{ParticleBundle, ParticleKind},
pathfinding::{enemy_cost_fn, heuristic, NeighborCostIter, PathState},
settings::{DifficultySetting, ParticlesSetting},
stats::Stats,
tilemap::{AtlasHandle, Map, TilePos},
util::cleanup,
GameState,
};
use pathfinding::prelude::astar;
pub struct EnemyPlugin;
impl Plugin for EnemyPlugin {
fn build(&self, app: &mut App) {
app.add_event::<SpawnEnemyEvent>()
.init_resource::<EnemyRng>()
.add_systems(
Update,
(spawn, pathfinding, behavior, tick_cooldown, attack, die)
.run_if(in_state(GameState::Playing)),
)
.add_systems(OnExit(GameState::GameOver), cleanup::<Enemy>);
}
}
#[derive(Component, Default)]
pub struct Enemy;
#[derive(Component, Default, Deserialize, Copy, Clone)]
pub enum EnemyKind {
#[default]
Skeleton,
SkeletonTwo,
SkeletonThree,
SkeletonFour,
Ent,
EntTwo,
EntThree,
EntFour,
}
impl EnemyKind {
pub fn atlas_index(&self) -> usize {
match self {
Self::Skeleton => 103 * 9 + 36,
Self::SkeletonTwo => 103 * 9 + 37,
Self::SkeletonThree => 103 * 9 + 38,
Self::SkeletonFour => 103 * 9 + 42,
Self::Ent => 103 * 15 + 45,
Self::EntTwo => 103 * 15 + 52,
Self::EntThree => 103 * 15 + 53,
Self::EntFour => 103 * 15 + 54,
}
}
}
#[derive(Event)]
pub struct SpawnEnemyEvent {
pub kind: EnemyKind,
pub pos: TilePos,
pub hp: u32,
}
#[derive(Component, Default)]
enum Behavior {
#[default]
SeekHome,
Attack,
}
#[derive(Component)]
pub struct AttackCooldown(Timer);
impl Default for AttackCooldown {
fn default() -> Self {
Self(Timer::from_seconds(1., TimerMode::Once))
}
}
#[derive(Resource)]
pub struct EnemyRng(SmallRng);
impl Default for EnemyRng {
fn default() -> Self {
Self(SmallRng::from_entropy())
}
}
#[derive(Bundle, Default)]
pub struct EnemyBundle {
sprite: SpriteBundle,
texture: TextureAtlas,
hit_points: HitPoints,
enemy: Enemy,
kind: EnemyKind,
pos: TilePos,
moving_animation: MovingProgress,
speed: Speed,
attack_cooldown: AttackCooldown,
behavior: Behavior,
}
fn spawn(
mut commands: Commands,
mut events: EventReader<SpawnEnemyEvent>,
atlas_handle: Res<AtlasHandle>,
tilemap_query: Query<&Map>,
difficulty: Res<DifficultySetting>,
) {
for event in events.read() {
let Ok(tilemap) = tilemap_query.get_single() else {
continue;
};
let world = tilemap.pos_to_world(event.pos);
let hp = match *difficulty {
DifficultySetting::Hard => event.hp,
DifficultySetting::Normal => ((event.hp as f32 * 0.75).floor() as u32).max(1),
DifficultySetting::Impossible => ((event.hp as f32 * 1.25).floor() as u32).max(1),
};
commands.spawn((
EnemyBundle {
sprite: SpriteBundle {
texture: atlas_handle.image.clone(),
transform: Transform {
translation: world.extend(1.),
scale: crate::tilemap::SCALE.extend(1.),
..default()
},
..default()
},
texture: TextureAtlas {
layout: atlas_handle.layout.clone(),
index: event.kind.atlas_index(),
},
hit_points: HitPoints::full(hp),
kind: event.kind,
pos: event.pos,
speed: Speed(2.),
..default()
},
#[cfg(feature = "inspector")]
Name::new("Enemy"),
));
}
}
fn pathfinding(
mut commands: Commands,
query: Query<(Entity, &TilePos, &Behavior, &EnemyKind), (With<Enemy>, Without<PathState>)>,
tilemap_query: Query<&Map>,
home_query: Query<(&TilePos, &HitPoints), With<Home>>,
mut rng: ResMut<EnemyRng>,
) {
// TODO spawner should do the pathfinding and cache the result.
for (entity, pos, behavior, kind) in &query {
if !matches!(behavior, Behavior::SeekHome) {
continue;
}
let Ok(map) = tilemap_query.get_single() else {
return;
};
let goals = home_query
.iter()
.filter(|(_, hp)| !hp.is_zero())
.collect::<Vec<_>>();
let Some((goal, _)) = goals.choose(&mut rng.0) else {
return;
};
// choose a random neighbor of the goal and path directly to it,
// so when enemies are attacking it feels a bit swarmier.
let neighbors =
NeighborCostIter::new(**goal, enemy_cost_fn(map, *kind)).collect::<Vec<_>>();
let Some((goal, _)) = neighbors.choose(&mut rng.0) else {
return;
};
let Some(result) = astar(
pos,
|p| NeighborCostIter::new(*p, enemy_cost_fn(map, *kind)),
|p| heuristic(*p, *goal),
|p| *p == *goal,
) else {
warn!("Enemy unable to find path to goal.");
continue;
};
// The enemy may have died and been despawned in the same frame.
commands
.entity(entity)
.try_insert(PathState::from(result.0));
// limit the amount of pathfinding we do each frame.
break;
}
}
fn behavior(
mut removed: RemovedComponents<PathState>,
mut query: Query<&mut Behavior, (With<Enemy>, Without<PathState>)>,
) {
// just assume that we've reached the home whenever a PathState is removed.
let mut enemy_iter = query.iter_many_mut(removed.read());
while let Some(mut behavior) = enemy_iter.fetch_next() {
if matches!(*behavior, Behavior::SeekHome) {
*behavior = Behavior::Attack;
}
}
}
fn attack(
mut commands: Commands,
mut query: Query<
(Entity, &Behavior, &mut AttackCooldown, &TilePos),
(With<Enemy>, Without<PathState>),
>,
mut home_query: Query<(&mut HitPoints, &TilePos), With<Home>>,
tilemap_query: Query<&Map>,
particle_settings: Res<ParticlesSetting>,
) {
for (entity, behavior, mut cooldown, pos) in &mut query {
if !matches!(behavior, Behavior::Attack) {
continue;
}
if !cooldown.0.finished() {
continue;
}
let Some((mut home_hp, home_pos)) = home_query
.iter_mut()
.find(|(_, home_pos)| heuristic(**home_pos, *pos) == 1)
else {
warn!("Enemy could not locate a nearby home.");
continue;
};
if home_hp.is_zero() {
// Enemy may have died and been despawned
commands.entity(entity).try_insert(Behavior::SeekHome);
continue;
}
let Ok(map) = tilemap_query.get_single() else {
continue;
};
home_hp.sub(1);
let amt = if home_hp.is_zero() {
particle_settings.kill_amt()
} else {
particle_settings.hit_amt()
};
for _ in 0..amt {
commands.spawn(ParticleBundle::new(
ParticleKind::Home,
map.pos_to_world(*home_pos),
));
}
if home_hp.is_zero() {
// Enemy may have died and been despawned
commands.entity(entity).try_insert(Behavior::SeekHome);
}
cooldown.0.reset();
}
}
fn die(
mut commands: Commands,
query: Query<(Entity, &HitPoints), With<Enemy>>,
mut stats: ResMut<Stats>,
) {
for (entity, hp) in &query {
if !hp.is_zero() {
continue;
}
stats.kills += 1;
commands.entity(entity).despawn();
}
}
fn tick_cooldown(mut query: Query<&mut AttackCooldown>, time: Res<Time>) {
for mut cooldown in &mut query {
cooldown.0.tick(time.delta());
}
}