Rooms and reconciliation

backend.attach(server) registers the asset-catalog room and a resolver for editable assets. An asset room is admitted when its kind has commands.live and the catalog contains that asset under the same kind.

A host registers CatalogViewExtension (asset-catalog-view) itself, for peers that must not see the whole catalog. Its scope(identity) names one asset; the peer receives that asset and its dependency closure, no folders, and changes filtered by the closure recomputed on each catalog change. An asset linked later shows up as created, one unlinked as deleted. Every command is rejected. CatalogClient.connect(client, { room }) joins it.

A room named with a tag (counter@v1:<assetId>, see AssetRoom) holds the content of that tagged event in a state of its own. It is resolved read-only, so members receive read rights and every command is denied. It appends nothing, reads no catch-up from the event store, and keeps its snapshot when the asset changes afterwards. An unknown tag refuses the join.

Room lifetime

The room validates and arbitrates a command, appends it, then commits and broadcasts it. The event store folds the command into live state. A failed append sends rejected to the sender and leaves the room state unchanged.

A kind may also relay ephemeral messages that are neither arbitrated nor logged, such as live previews of an edit. The kind declares their schemas once, as commands.relay: inbound joins the command protocol, each schema with its own literal tag on the command discriminator, and outbound joins the notices the room may send. Typing AssetCommands with the inbound message type ties the schemas to the relay. A kind that relays nothing keeps the never default, which refuses relay schemas and types its room messages as its commands alone. The backend stores handlers of every kind as AnyAssetKindHandler. registerAssetRooms builds the room protocols of every live kind when it starts, once per declaration, so a relay tag shared with a command or with another relay message fails at startup.

Each live room keeps its own state in live().relay. A kind declares the schemas and the relay together: a room whose commands.relay and live().relay are not both present or both absent throws a TypeError when it opens. The room hands every relay message, already validated and typed, to receive(clientId, message, room), which forwards it with room.sendTo or room.broadcast, and calls leave(clientId) when a member disconnects. When live() or the restore of recorded commands throws, the room stays closed and releases the asset state.

Changes outside the backend

An external tool can edit files in AssetSource. SourceWatcher groups notifications into batches. A batch holding a file change runs Reconciler, which compares scanned paths and hashes with the last projected state; every batch then refreshes CatalogFolders. backend.reconcile() runs the same scan and refresh on demand. Part files count toward their asset, as asset parts describes.

The reconciler records detected creates, updates, renames, and deletions as system lifecycle events. Unique matching content hashes identify renames; ambiguous matches become a deletion and creation. A write already present in the source is marked projected, so it is not written back as an echo.