Designing New File System API for WebExtensions

[lidel]

FYSA a new WebExtension File System API is being proposed/designed as a part of mozilla/libdweb#8 (comment)
It would enable js-ipfs running within browser extension context to have access to a better storage backend in Firefox.

My initial understanding is that we could create a special version of IPFSRepo - Default Browser stack for WebExtension contexts and replace default browser datastores with ones that take advantage of the new API.

I am not familiar with this area and it is unclear to me if we would want to create a totally new datastore like datastore-fs, or just a new levelup backend store for js-datastore-level.

Ideally, someone with prior experience in creating js-datastore implementation should review it and provide feedback for proposal from mozilla/libdweb#8 (comment) if anything is missing or unclear. (Update: API changed since then )

Thoughts?
Let's make sure we don't miss this opportunity.

cc @dignifiedquire @diasdavid

[dignifiedquire]

I scanned the API, and it seems to have everything needed to implement the filesystem datastore in good way. For the level datastore, we will still want to use the leveldb provided by the browser.

[lidel]

Status update:

• WebExtension FileSystem API landed as one of libdweb experiments: File System API mozilla/libdweb#8 (comment)
  • provides access to an OS file system, but restricted to a user chosen directory
  • more details including code samples and API itself:
    https://github.com/mozilla/libdweb#filesystem-api
• Virtual FileSystem API can be built on top of proprietary (Firefox-specific) IDBMutableFile API
  • it is not a WebExtensions-specific API, it can be used in user-space and is available in Firefox TODAY (including Stable), which means we could try to incorporate it as a backend for LevelJSDatastore in all Firefox contexts
  • able to avoid loading all of the file content for random read / writes at the expanse of limited runtime suport
  • more details/questions: Virtual FileSystem API mozilla/libdweb#13 (comment)

Quick thoughts:

While low priority, detecting and using IDBMutableFile could improve performance of long running node in browser context (namely, ipfs-companion). Not sure if we want to implement a separate datastore, or make current one automatically detect and use it instead of IndexedDB. Thoughts?

WebExtension FileSystem API requires user interaction and lacks watch feature, but if that missing piece lands in future it could be a venue for things like mounting and synchronizing MFS directory via browser extension.