Add Sketch asset, and a LivecodePlugin

Author: catilac

crates/processing_render/src/sketch.rs

@@ -0,0 +1,76 @@
+//! A Sketch asset represents a source file containing user code for a Processing sketch.
+//!
+//! Sketches are loaded through Bevy's asset system, which provides automatic file watching
+//! and change detection. This enables hot-reloading workflows where artists can edit their
+//! sketch code and see changes reflected immediately without restarting.
+//!
+//! This module is intentionally language-agnostic — it only handles loading source text from
+//! disk. Language-specific crates (like `processing_pyo3`) are responsible for executing the
+//! source and binding it to the Processing API.
+
+use bevy::{
+    asset::{AssetLoader, LoadContext, io::Reader},
+    prelude::*,
+};
+use std::path::PathBuf;
+
+/// Plugin that registers the Sketch asset type and its loader.
+pub struct LivecodePlugin;
+
+impl Plugin for LivecodePlugin {
+    fn build(&self, app: &mut App) {
+        app.init_asset::<Sketch>()
+            .init_asset_loader::<SketchLoader>();
+    }
+}
+
+/// A sketch source file loaded as a Bevy asset.
+///
+/// The `Sketch` asset contains the raw source code as a string. It does not interpret
+/// or execute the code — that responsibility belongs to language-specific crates.
+#[derive(Asset, TypePath, Debug)]
+pub struct Sketch {
+    /// The source code contents of the sketch file.
+    pub source: String,
+
+    /// The original file path.
+    pub path: PathBuf,
+}
+
+/// Loads sketch files from disk.
+///
+/// Currently supports `.py` files, but the loader is designed to be extended
+/// for other languages in the future.
+#[derive(Default)]
+pub struct SketchLoader;
+
+impl AssetLoader for SketchLoader {
+    type Asset = Sketch;
+    type Settings = ();
+    type Error = std::io::Error;
+
+    async fn load(
+        &self,
+        reader: &mut dyn Reader,
+        _settings: &Self::Settings,
+        load_context: &mut LoadContext<'_>,
+    ) -> Result<Self::Asset, Self::Error> {
+        let mut source = String::new();
+
+        let mut bytes = Vec::new();
+        reader.read_to_end(&mut bytes).await?;
+
+        if let Ok(utf8) = str::from_utf8(&bytes) {
+            source = utf8.to_string();
+        }
+
+        let asset_path = load_context.path();
+        let path: PathBuf = asset_path.path().to_path_buf();
+
+        Ok(Sketch { source, path })
+    }
+
+    fn extensions(&self) -> &[&str] {
+        &["py"]
+    }
+}