// Far beyond any realistic business use (sequence numbers are a handful of
// digits) but small enough that padStart can never be tricked into
// allocating a pathologically large string - {SEQ:999999999} in a
// carelessly typed format would otherwise try to build a ~1GB string on
// every single batch/bottling creation from then on.
const MAX_SEQUENCE_PAD_WIDTH = 20;

// Placeholders: {YYYY} 4-digit year, {YY} 2-digit year, {MM} month (01-12),
// {DD} day (01-31), {SEQ} running sequence unpadded, {SEQ:N} sequence
// zero-padded to N digits. Example matching the lastenheft's own sample
// ("WH-2026-0001"): format "WH-{YYYY}-{SEQ:4}".
// `vars` fills rule-specific placeholders, e.g. { ART: 'WA' } for {ART} in
// the raw material format; a placeholder without a value stays as typed.
export function formatGeneratedNumber(
  format: string,
  sequence: number,
  date: Date,
  vars: Record<string, string> = {},
): string {
  const yyyy = String(date.getFullYear());
  const yy = yyyy.slice(-2);
  const mm = String(date.getMonth() + 1).padStart(2, '0');
  const dd = String(date.getDate()).padStart(2, '0');

  const withVars = Object.entries(vars).reduce(
    (result, [key, value]) => result.split(`{${key}}`).join(value),
    format,
  );
  return withVars
    .replace(/\{YYYY\}/g, yyyy)
    .replace(/\{YY\}/g, yy)
    .replace(/\{MM\}/g, mm)
    .replace(/\{DD\}/g, dd)
    .replace(/\{SEQ:(\d+)\}/g, (_match, width: string) =>
      String(sequence).padStart(
        Math.min(Number(width), MAX_SEQUENCE_PAD_WIDTH),
        '0',
      ),
    )
    .replace(/\{SEQ\}/g, String(sequence));
}