perf: keep heavy work off UI thread

crates/ocs_web_worker/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "ocs_web_worker"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+acadrust = { version = "0.4", features = ["serde"] }
+bincode = "1.3"
+getrandom = { version = "0.3", features = ["wasm_js"] }
+js-sys = "0.3"
+wasm-bindgen = "0.2"

crates/ocs_web_worker/src/lib.rs

@@ -0,0 +1,32 @@
+use std::io::Cursor;
+
+use acadrust::io::dwg::DwgReader;
+use acadrust::DxfReader;
+use js_sys::Uint8Array;
+use wasm_bindgen::prelude::*;
+
+/// Parse DWG/DXF on a dedicated browser worker and return a compact serialized
+/// document. The main wasm instance only deserializes and installs it, so the
+/// expensive bit/handle/object decode never occupies the browser UI thread.
+#[wasm_bindgen]
+pub fn parse_document(name: String, bytes: Uint8Array) -> Result<Uint8Array, JsValue> {
+    let bytes = bytes.to_vec();
+    let ext = name.rsplit('.').next().unwrap_or_default().to_lowercase();
+    let document = match ext.as_str() {
+        "dwg" => DwgReader::from_stream(Cursor::new(bytes))
+            .read()
+            .map_err(|error| JsValue::from_str(&error.to_string()))?,
+        "dxf" => DxfReader::from_reader(Cursor::new(bytes))
+            .map_err(|error| JsValue::from_str(&error.to_string()))?
+            .read()
+            .map_err(|error| JsValue::from_str(&error.to_string()))?,
+        _ => {
+            return Err(JsValue::from_str(&format!(
+                "Unsupported file format: .{ext}"
+            )))
+        }
+    };
+    let encoded =
+        bincode::serialize(&document).map_err(|error| JsValue::from_str(&error.to_string()))?;
+    Ok(Uint8Array::from(encoded.as_slice()))
+}