Browser storage support in WebAssembly bindings

[penberg]

Currently, the Wasm binding implement I/O for Node filesystem APIs. Let's work on supporting OPFS, for example, to run limbo-wasm in the browser. One complication is that the current API is synchronous like better-sqlite3 so we either need to use synchronous OPFS or implement libSQL async-style API.

[BLucky-gh]

I just looked into it and synchronous OPFS is not that simple. There is FileSystemSyncAccessHandle that has synchronous read/write/etc functions, but 1) it is only obtainable in a web worker (to prevent blocking the main thread with sync io) and 2) you can only get it from a FilesystemFileHandle which you can only get via async means. You can still make it work with an awkward wrapper for bindings/wasm that creates a web worker, creates the sync handle, and then passes that to the Database constructor, and interfaces with the main thread with message passing, which would also incur non-insignificant overhead. So I feel like an async API would be a better option here.

Now that I'm writing this I figured there's also the option to expose an in-memory only db client, and let the API consumer just dump the db (raw bytes or sql dump) to be persisted however the consumer wants, be it OPFS, base64'd into LocalStorage, sent to a backend, or any other less than perfect option, but that is very much a bandaid solution since it would be impossible to guarantee that it gets persisted correctly and safely, among a myriad of other issues