/**
 * The smart scan box grammar (09-UX §1.2): one input, no modes. Typed and
 * scanned input both land here; the caller resolves codes against the item
 * cache and scale profile.
 */
export type EntryParse =
  | { kind: 'empty' }
  | { kind: 'multiplier'; qty: number; rest: string }
  | { kind: 'barcode'; code: string }
  | { kind: 'code'; code: string }
  | { kind: 'search'; text: string }

const MULTIPLIER = /^(\d{1,4}(?:\.\d{1,3})?)\*(.*)$/

export function parseEntry(raw: string): EntryParse {
  const input = raw.trim()
  if (input === '') return { kind: 'empty' }

  const mult = MULTIPLIER.exec(input)
  if (mult !== null) {
    const qty = Number(mult[1])
    if (qty > 0) return { kind: 'multiplier', qty, rest: mult[2]!.trim() }
  }

  if (/^\d+$/.test(input)) {
    // 8–14 digits reads as a barcode/item code; shorter digits are still codes
    // (quick-key PLUs); resolution order is the caller's concern.
    return input.length >= 8 ? { kind: 'barcode', code: input } : { kind: 'code', code: input }
  }

  return { kind: 'search', text: input }
}