// WHICH LANE AN OPERATION RUNS ON. One function, one module.
//
// Its own file because it started as the arbiter's, and two things needed it
// while neither could import the other: the arbiter planned units against it and
// controller/operationJobs.ts reserves a queue key with it, while the arbiter
// called operationJobs to start the jobs it planned. The arbiter retired in
// slice 1.3; the module stays where it is, because a queue-key resolver is not
// dispatch's private business.

import { getSettings } from "../lib/settings";
import {
  EXTERNAL_OPERATIONS,
  getOperation,
  type Lane,
} from "../lib/operations";

// The lane an operation runs on, or null when the registry does not know it.
//
// ONE RESOLUTION, off the kind's own declaration. A kind whose lane depends on
// configuration says so with laneFor() — digest picks between the GPU-bound
// local queue and the metered network one, diarization between contending for
// the GPU and contending for cores — and a kind without one has a fixed lane.
// This used to special-case digest here, which meant the rule lived in two
// places and only digest's copy was live: diarization's laneFor was invisible
// to every caller.
//
// THE REGISTRY FIRST, THEN THE EXTERNAL DECLARATIONS — slice 1.5.
//
// This used to answer null for download and transcription, on the argument that
// a lane for them would let a caller "reserve the backfill queue for work no
// backfill operation can do". That was never what a catalog lookup would have
// done: their DECLARED lanes are `download:<platform>` and the transcription
// queue, neither of which is BACKFILL_QUEUE. What the null actually cost was the
// question every four-lane surface now asks — "which lane does this operation
// run on" — coming back unanswered for the two lanes carrying 100% of live
// dispatch.
//
// EXTERNAL_OPERATIONS only, not operationCatalog(): sync is catalogued beside
// them and is a per-CHANNEL cadence, not a per-video pipeline, so it keeps the
// null it has always had here and pauseGates.pauseLaneFor keeps saying so too.
//
// The one caller that reserves a queue key from this answer is
// controller/operationJobs.runOperationChannelJob, and it is unaffected: it is
// only ever handed a registry operation id (the /channels group buttons, the
// channel page, the video page), and an external id would already have found no
// kind to run.
export function laneForOperation(operation: string): Lane | null {
  const kind = getOperation(operation);
  if (kind) return kind.laneFor?.(getSettings()) ?? kind.lane;
  return EXTERNAL_OPERATIONS.find((op) => op.id === operation)?.lane ?? null;
}