import { laneDevices, type Db } from "@parking/db";

// Resolves a device instance id (lane_devices.id) to its lane number.
//
// Device pushes/events carry the `lane_devices` id (which device fired), not a
// lane. The event log wants the lane, so we keep a small in-memory id->lane map
// rebuilt from the DB at startup and refreshed whenever assignments change
// (assign/unassign). It's tiny (one row per device) and read on the hot path of
// every input event, so a cached map beats a per-event DB lookup.
export class LaneMap {
  readonly #db: Db;
  #byDeviceId = new Map<string, number>();

  constructor(db: Db) {
    this.#db = db;
  }

  /** (Re)load the id->lane map from the lane_devices table. */
  refresh(): void {
    const rows = this.#db.select().from(laneDevices).all();
    const next = new Map<string, number>();
    for (const r of rows) next.set(r.id, r.lane);
    this.#byDeviceId = next;
  }

  /** Lane for a device instance id, or null if the device isn't known. */
  laneFor(deviceId: string): number | null {
    return this.#byDeviceId.get(deviceId) ?? null;
  }
}