Implement native sharing

[nightscape]

Closes #1090

• Call handleShareTarget method when native sharing button is used
• Return HTML to the client
• Store shared data in a target page
• Redirect user to target page
• Make target page for shared data configurable
• Allow using template variables in page name
• Make it work in offline mode

[nightscape]

@zefhemel from my side this would be ok as a first shot. As a second step, it might be nice to allow adding tags to the added entries, but that could be done in a follow-up PR as I've mostly spent the time I'm able to invest in this feature.

[nightscape]

Oh, the way it is currently implemented does not work in offline mode, which makes it 80% less useful...

[nightscape]

@zefhemel I guess just specifying env: client here is not enough to trigger handleShareTarget through an incoming http request, right?
Is there already logic to delegate http:request events to plugs on the client side?
It looks like this would need to be done in service_worker.ts which currently only handles read requests.
Do you think it's a good idea to enhance service_worker.ts with dispatchEvent logic similar to http_server.ts?

[nightscape]

@zefhemel ping 😉

[zefhemel]

RIght. Right now handling HTTP requests through a service worker (so fully locally and therefore offline) is not possible. It's technically possible to do, but it's not there at this moment.

[nightscape]

Would service_worker.ts be the right place? Do you see any issues with using a similar approach as on the server-side, i.e. checking the plugs if one of them wants to handle the URL?

[zefhemel]

Sorry for the huge delay of this.

I like this feature, but I'd implement it slightly differently, if this would work (I don't have an environment to test this on, because I think this is an Android feature only?) I'd implement the endpoint handling "hardcoded" in the service worker. That is: in the fetch event handler, decide on some URL (like /.share or something), and put the logic in the service worker directly rather than in the share plug. I feel this is functionality that deserves a place directly in the SB core, not so much in a plug (it needs to be hardcoded in the manifest anyway), and implemented in the service worker it can also be done (I think) in a way that works both in online and offline mode.

[zefhemel]

A head's up: working with service worker is a bit of a pain in terms of reload behavior. In Chrome, you can have the service worker update on every reload:

Still you probably need to reload your page a few times after every change to make sure you got the new service worker running before deciding things don't work ;)