hydrogen-web/doc/impl-thoughts/PUSH.md

Push Notifications

• we setup the app on the sygnal server, with an app_id (io.element.hydrogen.web), generating a key pair
• we create a web push subscription, passing the server pub key, and get endpoint, p256dh and auth back. We put webpush_endpoint and auth in the push data, and use p256dh as the push key?
• we call POST /_matrix/client/r0/pushers/set on the homeserver with the sygnal instance url. We pass the web push subscription as pusher data.
• the homeserver wants to send out a notification, calling sygnal on POST /_matrix/push/v1/notify with for each device the pusher data.
• we encrypt and send with the data in the data for each device in the notification
• this wakes up the service worker
• now we need to find which local session id this notification is for

Testing/development

• set up local synapse
• set up local sygnal
• write pushkin
• configure "hydrogen" app in sygnal config with a webpush pushkin
• start writing service worker code in hydrogen (we'll need to enable it for local dev)
• try to get a notification through

Questions

- do we use the `event_id_only` format?
- for e2ee rooms, are we fine with just showing "Bob sent you a message (in room if not DM)", or do we want to sync and show the actual message? perhaps former can be MVP.