/**
 * Reading the archive's saved slicer AMS-slot pick back out of `extra_data`.
 *
 * A virtual printer with "Save AMS mapping" on stores the slicer's own
 * live-resolved tray choice on the archive as
 * `extra_data.slicer_ams_mapping = { mapping, printer_id }` (written by
 * `ArchiveService.archive_print`). The tray IDs in `mapping` are global tray
 * IDs, which only mean something against the AMS layout of the one printer
 * they were resolved against — slot 3 on another printer can hold a completely
 * different spool. `printer_id` records which printer that was.
 *
 * Lives here rather than inline in the modal so the printer-scoping rule can
 * be tested on its own: it is the only thing standing between a saved mapping
 * and the wrong physical spool.
 */

/** Shape of `extra_data.slicer_ams_mapping`. Every field optional — this is
 *  free-form JSON off the wire, and older archives predate the key entirely. */
export interface SavedSlicerAmsMapping {
  mapping?: number[];
  printer_id?: number;
}

/**
 * The saved mapping, but only when it is safe to apply to `printerId`.
 *
 * Returns `undefined` — meaning "no saved mapping in scope, behave as before" —
 * when the archive has none, when the stored value is malformed, when no
 * printer is selected yet, or when the selected printer is not the one the
 * mapping was resolved against.
 */
export function resolveArchiveSlicerAmsMapping(
  extraData: Record<string, unknown> | null | undefined,
  printerId: number | null | undefined,
): number[] | undefined {
  // No printer selected means there is nothing to compare against. Bailing
  // here also stops `undefined === undefined` from reading as a match below.
  if (printerId == null) return undefined;

  const saved = extraData?.slicer_ams_mapping as SavedSlicerAmsMapping | undefined;
  if (!saved || typeof saved !== 'object') return undefined;
  if (saved.printer_id !== printerId) return undefined;
  if (!Array.isArray(saved.mapping) || saved.mapping.length === 0) return undefined;

  return saved.mapping;
}