export type Branch = 'askim' | 'backaplan';

export interface ValidTableId {
  valid: true;
  branch: Branch;
  tableNumber: string;
  tableIdentifier: string;
}

export interface InvalidTableId {
  valid: false;
  reason: 'missing' | 'format' | 'range';
}

export type ParsedTableId = ValidTableId | InvalidTableId;

const TABLE_ID_PATTERN = /^(backaplan|askim)-([0-9]{3})$/;
const MIN_TABLE = 1;
const MAX_TABLE = 40;

/** Domain rule: parse and validate QR table identifiers. */
export function parseTableId(raw: string | null | undefined): ParsedTableId {
  if (!raw) {
    return { valid: false, reason: 'missing' };
  }

  const match = raw.match(TABLE_ID_PATTERN);
  if (!match) {
    return { valid: false, reason: 'format' };
  }

  const branch = match[1] as Branch;
  const tableNum = parseInt(match[2], 10);

  if (tableNum < MIN_TABLE || tableNum > MAX_TABLE) {
    return { valid: false, reason: 'range' };
  }

  return {
    valid: true,
    branch,
    tableNumber: match[2],
    tableIdentifier: raw,
  };
}