feat(web): persist browser state

Keep settings, aliases, and recent drawings across browser sessions.

Load Start-page videos from a Pages-generated snapshot.

src/io/web_recent.rs

@@ -0,0 +1,89 @@
+//! Browser-backed copies of recently opened drawings.
+//!
+//! A web file picker exposes bytes and a display name, not a reusable native
+//! path. Keep the last-opened copy in the origin-private file system (OPFS) so
+//! the Start page can reopen it without asking the user to pick it again.
+
+use wasm_bindgen::JsCast;
+use wasm_bindgen_futures::JsFuture;
+
+const RECENT_DIRECTORY: &str = "opencadstudio-recent";
+
+pub async fn store(name: &str, bytes: &[u8]) -> Result<(), String> {
+    let directory = recent_directory(true).await?;
+    let options = web_sys::FileSystemGetFileOptions::new();
+    options.set_create(true);
+    let handle = JsFuture::from(directory.get_file_handle_with_options(&cache_key(name), &options))
+        .await
+        .map_err(js_error)?
+        .dyn_into::<web_sys::FileSystemFileHandle>()
+        .map_err(js_error)?;
+    let writable = JsFuture::from(handle.create_writable())
+        .await
+        .map_err(js_error)?
+        .dyn_into::<web_sys::FileSystemWritableFileStream>()
+        .map_err(js_error)?;
+    let write = writable.write_with_u8_array(bytes).map_err(js_error)?;
+    JsFuture::from(write).await.map_err(js_error)?;
+    JsFuture::from(writable.close()).await.map_err(js_error)?;
+    Ok(())
+}
+
+pub async fn read(name: &str) -> Result<Vec<u8>, String> {
+    let directory = recent_directory(false).await?;
+    let handle = JsFuture::from(directory.get_file_handle(&cache_key(name)))
+        .await
+        .map_err(js_error)?
+        .dyn_into::<web_sys::FileSystemFileHandle>()
+        .map_err(js_error)?;
+    let file = JsFuture::from(handle.get_file())
+        .await
+        .map_err(js_error)?
+        .dyn_into::<web_sys::File>()
+        .map_err(js_error)?;
+    let buffer = JsFuture::from(file.array_buffer())
+        .await
+        .map_err(js_error)?;
+    Ok(js_sys::Uint8Array::new(&buffer).to_vec())
+}
+
+pub async fn remove(name: &str) -> Result<(), String> {
+    let directory = recent_directory(false).await?;
+    JsFuture::from(directory.remove_entry(&cache_key(name)))
+        .await
+        .map_err(js_error)?;
+    Ok(())
+}
+
+async fn recent_directory(create: bool) -> Result<web_sys::FileSystemDirectoryHandle, String> {
+    let window = web_sys::window().ok_or_else(|| "browser window unavailable".to_string())?;
+    let root = JsFuture::from(window.navigator().storage().get_directory())
+        .await
+        .map_err(js_error)?
+        .dyn_into::<web_sys::FileSystemDirectoryHandle>()
+        .map_err(js_error)?;
+    let options = web_sys::FileSystemGetDirectoryOptions::new();
+    options.set_create(create);
+    JsFuture::from(root.get_directory_handle_with_options(RECENT_DIRECTORY, &options))
+        .await
+        .map_err(js_error)?
+        .dyn_into::<web_sys::FileSystemDirectoryHandle>()
+        .map_err(js_error)
+}
+
+/// Stable, short OPFS entry name. The original display name remains in
+/// `AppConfig::recent`; only the browser-private cache uses this key.
+fn cache_key(name: &str) -> String {
+    let mut hash = 0xcbf29ce484222325_u64;
+    for byte in name.as_bytes() {
+        hash ^= u64::from(*byte);
+        hash = hash.wrapping_mul(0x100000001b3);
+    }
+    format!("{hash:016x}.cad")
+}
+
+fn js_error(value: wasm_bindgen::JsValue) -> String {
+    value
+        .as_string()
+        .unwrap_or_else(|| format!("browser storage error: {value:?}"))
+}