Step five — composition layer. wireZebraMachines() returns a coherent
room:
- one CallFSM
- one SubscribeFSM
- three PublishFSMs (mic / screen / camera)
- lazy Map of RemoteTileFSMs created on first tileFor(kind, pubHex)
- tileLeft(pubHex) fans LEFT to every tile keyed by that publisher
Observers wire transitions between machines but the orchestrator
itself stays pure — no WebRTC, no DOM, no fetch. The page's runtime
layers its OWN observers on top to drive real side effects, and the
test extracts the orchestrator directly.
Cascades modelled:
- CallFSM joined (from anything except reconnecting) ── starts the sub
- CallFSM reconnecting → joined does NOT re-START (sub stayed alive)
- CallFSM leaving / booted ── stops sub AND every live publish
- RemoteTileFSMs lazy: tileFor returns the same instance per key
- tileLeft sends LEFT to every kind for that pubHex
+ 11 integration tests + 1 full end-to-end scenario walking through
host publishes mic+screen / listener joins late / listener sees the
screen / host unshares / mute+prune cycle removes the tile / listener
leaves and sub stops.
Total: 83 tests passing. The pure-FSM layer + orchestrator are now
ready to be wired into the imperative call sites in the live runtime.
That's the next step — gradually replace the firefighting code paths
(sfuPublishCamera, sfuSubscribe, role transitions) by feeding events
into these machines from the existing handlers, then observing
state changes to invoke the side effects. Tests catch regressions
on the pure layer while the QA loop catches what touches the wire.
Russell Ballestrini
d9a743a680