From 946e961633d4a7ecdfd0241042526285ce2e5922 Mon Sep 17 00:00:00 2001
From: Michael Bradley <michaelmbrad@gmail.com>
Date: Sun, 23 Mar 2025 22:32:57 -0400
Subject: [PATCH] Make RNG seedable

---
 Cargo.lock    |  1 +
 Cargo.toml    |  1 +
 src/lib.rs    |  2 ++
 src/main.rs   | 34 ++++++++++++++++++++--------------
 src/random.rs | 33 +++++++++++++++++++++++++++++++++
 5 files changed, 57 insertions(+), 14 deletions(-)
 create mode 100644 src/lib.rs
 create mode 100644 src/random.rs

diff --git a/Cargo.lock b/Cargo.lock
index 4180317..01267cd 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1607,6 +1607,7 @@ dependencies = [
  "bevy",
  "log",
  "rand 0.9.0",
+ "rand_chacha 0.9.0",
 ]
 
 [[package]]
diff --git a/Cargo.toml b/Cargo.toml
index 68b934e..9c260e1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -34,3 +34,4 @@ log = { version = "*", features = [
 	"release_max_level_warn",
 ] }
 rand = "0.9.0"
+rand_chacha = "0.9.0"
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..d2c9234
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,2 @@
+mod random;
+pub use random::Random;
diff --git a/src/main.rs b/src/main.rs
index 7878fc1..6c51414 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -9,18 +9,26 @@ use bevy::{
     input::common_conditions::input_pressed,
     prelude::*,
 };
-use rand::Rng;
+
+use distributed_physics_test::Random;
 
 const AREA_WIDTH: f32 = 750.;
 const PLAYER_SIZE: f32 = 30.;
 
-fn main() {
+#[derive(Default)]
+struct AppSettings {
+    seed: String,
+}
+
+fn main() -> AppExit {
+    run_app(AppSettings::default())
+}
+
+fn run_app(settings: AppSettings) -> AppExit {
     App::new()
         .add_plugins((
             DefaultPlugins,
-            PhysicsPlugins::default()
-                .with_length_unit(50.0)
-                .set(PhysicsInterpolationPlugin::interpolate_all()),
+            PhysicsPlugins::default().with_length_unit(50.0),
         ))
         .add_systems(
             Startup,
@@ -31,11 +39,12 @@ fn main() {
             (move_player, quit.run_if(input_pressed(KeyCode::KeyQ))),
         )
         .insert_resource(Gravity(Vector::ZERO))
-        .run();
+        .insert_resource(Random::seed(&settings.seed))
+        .run()
 }
 
 fn setup_scene(mut commands: Commands) {
-    commands.spawn(Camera2d);
+    commands.spawn((Name::new("Camera"), Camera2d, IsDefaultUiCamera));
 }
 
 #[derive(Component, Default)]
@@ -50,19 +59,16 @@ fn setup_balls(
     mut commands: Commands,
     mut materials: ResMut<Assets<ColorMaterial>>,
     mut meshes: ResMut<Assets<Mesh>>,
+    mut rng: ResMut<Random>,
 ) {
-    let mut rng = rand::rng();
     for _ in 0..20 {
-        let circle = Circle::new(rng.random_range(10.0..(PLAYER_SIZE - 5.)));
+        let circle = Circle::new(rng.range(10.0..(PLAYER_SIZE - 5.)));
         let mut transform = Transform::from_xyz(
             0.,
-            rng.random_range((PLAYER_SIZE + 5.)..(AREA_WIDTH / 2. - PLAYER_SIZE)),
+            rng.range((PLAYER_SIZE + 5.)..(AREA_WIDTH / 2. - PLAYER_SIZE)),
             0.,
         );
-        transform.rotate_around(
-            Vec3::ZERO,
-            Quat::from_rotation_z(rng.random_range(0.0..(PI * 2.))),
-        );
+        transform.rotate_around(Vec3::ZERO, Quat::from_rotation_z(rng.range(0.0..(PI * 2.))));
         commands.spawn((
             Ball,
             Collider::from(circle),
diff --git a/src/random.rs b/src/random.rs
new file mode 100644
index 0000000..490003d
--- /dev/null
+++ b/src/random.rs
@@ -0,0 +1,33 @@
+use std::hash::{DefaultHasher, Hash, Hasher};
+
+use bevy::prelude::*;
+use rand::{
+    Rng, SeedableRng,
+    distr::uniform::{SampleRange, SampleUniform},
+};
+use rand_chacha::ChaCha8Rng;
+
+#[derive(Resource)]
+pub struct Random(ChaCha8Rng);
+
+impl Random {
+    pub fn seed(seed: &String) -> Self {
+        Random(ChaCha8Rng::seed_from_u64(
+            seed.parse::<u64>().unwrap_or_else(|_| hash_string(seed)),
+        ))
+    }
+
+    pub fn range<T, R>(&mut self, range: R) -> T
+    where
+        T: SampleUniform,
+        R: SampleRange<T>,
+    {
+        self.0.random_range(range)
+    }
+}
+
+fn hash_string(string: &String) -> u64 {
+    let mut state = DefaultHasher::new();
+    string.hash(&mut state);
+    state.finish()
+}