Sync refactor — Part 1 (#1688)

* It's half-alive

* Wakeups largely working

* Other tweaks, typing works

* Fix bugs, add receipt stream

* Delete notifier, other tweaks

* Dedupe a bit, add a template for the invite stream

* Clean up, add templates for other streams

* Don't leak channels

* Bring forward some more PDU logic, clean up other places

* Add some more wakeups

* Use addRoomDeltaToResponse

* Log tweaks, typing fixed?

* Fix timed out syncs

* Don't reset next batch position on timeout

* Add account data stream/position

* End of day

* Fix complete sync for receipt, typing

* Streams package

* Clean up a bit

* Complete sync send-to-device

* Don't drop errors

* More lightweight notifications

* Fix typing positions

* Don't advance position on remove again unless needed

* Device list updates

* Advance account data position

* Use limit for incremental sync

* Limit fixes, amongst other things

* Remove some fmt.Println

* Tweaks

* Re-add notifier

* Fix invite position

* Fixes

* Notify account data without advancing PDU position in notifier

* Apply account data position

* Get initial position for account data

* Fix position update

* Fix complete sync positions

* Review comments @Kegsay

* Room consumer parameters

syncapi/streams/stream_invite.go

@@ -0,0 +1,64 @@
+package streams
+
+import (
+	"context"
+
+	"github.com/matrix-org/dendrite/syncapi/types"
+)
+
+type InviteStreamProvider struct {
+	StreamProvider
+}
+
+func (p *InviteStreamProvider) Setup() {
+	p.StreamProvider.Setup()
+
+	p.latestMutex.Lock()
+	defer p.latestMutex.Unlock()
+
+	id, err := p.DB.MaxStreamPositionForInvites(context.Background())
+	if err != nil {
+		panic(err)
+	}
+	p.latest = id
+}
+
+func (p *InviteStreamProvider) CompleteSync(
+	ctx context.Context,
+	req *types.SyncRequest,
+) types.StreamPosition {
+	return p.IncrementalSync(ctx, req, 0, p.LatestPosition(ctx))
+}
+
+func (p *InviteStreamProvider) IncrementalSync(
+	ctx context.Context,
+	req *types.SyncRequest,
+	from, to types.StreamPosition,
+) types.StreamPosition {
+	r := types.Range{
+		From: from,
+		To:   to,
+	}
+
+	invites, retiredInvites, err := p.DB.InviteEventsInRange(
+		ctx, req.Device.UserID, r,
+	)
+	if err != nil {
+		req.Log.WithError(err).Error("p.DB.InviteEventsInRange failed")
+		return from
+	}
+
+	for roomID, inviteEvent := range invites {
+		ir := types.NewInviteResponse(inviteEvent)
+		req.Response.Rooms.Invite[roomID] = *ir
+	}
+
+	for roomID := range retiredInvites {
+		if _, ok := req.Response.Rooms.Join[roomID]; !ok {
+			lr := types.NewLeaveResponse()
+			req.Response.Rooms.Leave[roomID] = *lr
+		}
+	}
+
+	return to
+}