[WIP] Time rewinding

Cargo.toml

@@ -37,3 +37,4 @@ bevy_kira_audio = { version = "0.8", features = ["wav"] }
 heron = { version = "2.0.1", features = ["2d", "enhanced-determinism"] }
 bevy-inspector-egui = "0.8"
 rand = "0.8"
+derive_more = "0.99"

src/history.rs

@@ -0,0 +1,86 @@
+use bevy::{
+    core::FixedTimestep,
+    input::{keyboard::KeyboardInput, ElementState},
+    prelude::*,
+};
+use derive_more::{Deref, DerefMut};
+use heron::{RigidBody, Velocity};
+
+use crate::GameState;
+
+#[derive(Component, Deref, DerefMut, Default)]
+pub struct PositionHistory(Vec<Vec3>);
+
+#[derive(Component, Deref, DerefMut, Default)]
+pub struct RewindState(bool);
+
+pub struct RewindPlugin;
+
+impl Plugin for RewindPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_system_set(
+            SystemSet::on_update(GameState::Playing)
+                .with_run_criteria(FixedTimestep::steps_per_second(20.0))
+                .with_system(add_trackers)
+                .with_system(detect_rewind)
+                .with_system(tick_position_trackers),
+        )
+        .insert_resource(RewindState(false))
+        .add_system_set(
+            SystemSet::on_update(GameState::Playing)
+                .with_run_criteria(FixedTimestep::steps_per_second(60.0))
+                .with_system(rewind_system),
+        );
+    }
+}
+
+pub fn add_trackers(
+    mut commands: Commands,
+    entities: Query<Entity, (With<Velocity>, With<RigidBody>, Without<PositionHistory>)>,
+) {
+    for entity in entities.iter() {
+        commands.entity(entity).insert(PositionHistory::default());
+    }
+}
+
+pub fn tick_position_trackers(
+    mut query: Query<(&mut PositionHistory, &Transform)>,
+    rewind_state: Res<RewindState>,
+) {
+    if rewind_state.0 {
+        return;
+    }
+    for (mut history, transform) in query.iter_mut() {
+        history.push(transform.translation);
+    }
+}
+
+pub fn detect_rewind(mut input: EventReader<KeyboardInput>, mut game_state: ResMut<RewindState>) {
+    for ev in input.iter() {
+        if ev.key_code == Some(KeyCode::Space) && ev.state.is_pressed() {
+            println!("triggering rewind");
+            game_state.0 = true;
+        }
+    }
+}
+
+pub fn rewind_system(
+    mut query: Query<(&mut PositionHistory, &mut Transform)>,
+    mut game_state: ResMut<RewindState>,
+) {
+    if !game_state.0 {
+        return;
+    }
+    let mut history_left = false;
+    for (mut history, mut transform) in query.iter_mut() {
+        if let Some(position) = history.pop() {
+            history_left = true;
+            *transform = Transform::from_translation(position);
+            println!("{} iters left", history.len());
+        }
+    }
+    if !history_left {
+        println!("done with rewind");
+        game_state.0 = false;
+    }
+}

src/main.rs

@@ -13,6 +13,7 @@ use resources::audio_channels::AudioChannels;
 
 mod enemy;
 pub mod gun;
+mod history;
 mod inputs;
 mod item;
 mod levels;
@@ -50,6 +51,7 @@ fn main() {
         .add_plugin(item::ItemPlugin)
         .add_plugin(gun::GunPlugin)
         .add_plugin(enemy::EnemyPlugin)
+        .add_plugin(history::RewindPlugin)
         .add_state(GameState::MainMenu)
         .run();
 }