const DURATION_PATTERN = /^(\d+)(ms|s|m|h)$/;

const UNIT_MS: Record<string, number> = {
  ms: 1,
  s: 1_000,
  m: 60_000,
  h: 3_600_000,
};

export function parseDuration(value: string): number {
  const match = DURATION_PATTERN.exec(value.trim());
  if (!match) {
    throw new Error(`Invalid duration "${value}" (expected e.g. "500ms", "5s", "1m", "1h")`);
  }
  const [, amount, unit] = match;
  return Number(amount) * UNIT_MS[unit];
}