Every save that stores new opportunities or new releases records them in a
change batch (migration 00008: opportunity_change_batches and
opportunity_change_batch_opportunities; the opportunities table is
unchanged), as does every change of marks. A batch is named by a random
SHA-256 hash, so it can't be guessed, and ordered by its created_at, which
is kept strictly increasing even if the clock goes back.
GET /api/opportunities pages now carry the newest batch, read before the
page, and GET /api/opportunities?changed_after=<batch> returns every
opportunity changed since that batch, unpaged, with the newest batch it
includes. Offset and limit can't be combined with it, and an unknown batch
is 410 Gone, telling the client to reload the whole list.
OpportunitiesUpdated now carries its save's batch, and a "large" flag: over
50 opportunities, new and updated are left empty and only the summary
counts them, so a big catch-up no longer sends tens of thousands of UUIDs.
SaveOpportunities now reports the classification codes a save brings into
use (AddedClassifications, in full) and takes out of use
(RemovedClassificationIDs), by comparing the codes in use before and after
the save inside its transaction. The fetcher publishes them as a
ClassificationsUpdated event, {"added":[codes],"removed":[ids]}, never null,
before the save's OpportunitiesUpdated, so clients can keep their list of
classifications without asking the API again.
internal/events decouples the parts of JobSearch that cause events from
the parts that react to them. bus.go has Bus: Subscribe, and a synchronous
Publish that calls each handler in turn on the publisher's goroutine, so
handlers mustn't block (the hub doesn't: it queues per client). events.go
has the event types and their payloads, starting with OpportunitiesUpdated.
With fetcher.WithEvents, a save that stores new opportunities, or new
releases of stored ones, publishes OpportunitiesUpdated with their UUIDs and
counts. An opportunity whose row is only rewritten, as when it is fetched
again from the newest stored release, isn't counted as updated, and nothing
is published when nothing changed. store.SaveResult now reports
NewOpportunity for each opportunity saved.
job-search serve subscribes its WebSocket hub to the bus, so every client
gets {"type":"event","eventType":"OpportunitiesUpdated","payload":{"new":
[...],"updated":[...],"summary":{"new":n,"updated":n}}}. The Envelope gains
an eventType field, and Hub.PushEvent and Server.PushEvent send events.
bwilliams