From fe88997cd183677e24a75ca243fa7647813c5071 Mon Sep 17 00:00:00 2001
From: zefad <zefad83@gmail.com>
Date: Fri, 18 Sep 2026 17:40:19 +0200
Subject: [PATCH] chunk logic

---
 src/world.rs | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 src/world.rs

diff --git a/src/world.rs b/src/world.rs
new file mode 100644
index 0000000..36642d7
--- /dev/null
+++ b/src/world.rs
@@ -0,0 +1,67 @@
+use bevy::prelude::*;
+
+use crate::{camera::MainCamera, player::Player};
+
+pub const CHUNK_HEIGHT: f32 = 700.0; // Height of a cunk
+const MARGIN_BELLOW: f32 = 400.0; // Height bellow the camera view it'll be gen
+const MARGIN_ABOVE: f32 = 400.0; // Height above the camera view it'll be gen
+
+#[derive(Component)]
+pub struct Chunk {
+    pub id: i64,
+}
+
+#[derive(Resource)]
+pub struct RunSeed(pub u64);
+
+fn stream_world(
+    player: Single<&Transform, With<Player>>,
+    entities: Query<(Entity, &Chunk)>,
+    mut commands: Commands,
+    camera: Single<&Camera, With<MainCamera>>,
+    run_seed: Res<RunSeed>,
+) {
+    let (min_id, max_id) = visible_chunk_range(
+        player.translation.y,
+        camera
+            .logical_viewport_size()
+            .unwrap_or(Vec2::new(1920.0, 1080.0))
+            .y,
+    );
+
+    let existing_ids: Vec<i64> = entities.iter().map(|(_, chunk)| chunk.id).collect();
+
+    for (entity, chunk) in entities {
+        // Out of bounds implies despawn
+        if chunk.id < min_id || chunk.id > max_id {
+            commands.entity(entity).despawn();
+        }
+    }
+
+    for id in min_id..=max_id {
+        if !existing_ids.contains(&id) {
+            spawn_chunk(&mut commands, id, run_seed.0);
+        }
+    }
+}
+
+// Bounds of chunk's ids to be generated
+fn visible_chunk_range(player_y: f32, camera_y: f32) -> (i64, i64) {
+    (
+        ((player_y - camera_y / 2.0 - MARGIN_BELLOW) / CHUNK_HEIGHT).floor() as i64,
+        ((player_y + camera_y / 2.0 + MARGIN_ABOVE) / CHUNK_HEIGHT).floor() as i64,
+    )
+}
+
+fn spawn_chunk(commands: &mut Commands, id: i64, run_seed: u64) {
+    crate::background::spawn_background_chunk(commands, id);
+    // TODO: obstacles
+}
+pub struct WorldPlugin;
+
+impl Plugin for WorldPlugin {
+    fn build(&self, app: &mut App) {
+        app.insert_resource(RunSeed(rand::random::<u64>()))
+            .add_systems(Update, stream_world);
+    }
+}