import { InvalidIntervalError, NonWholeMinuteIntervalError } from "./errors.generated";

function isWholeMinute(instant: Date): boolean {
  return instant.getUTCSeconds() === 0 && instant.getUTCMilliseconds() === 0;
}

/**
 * Function: validateReportedInterval
 * Description: Shared well-formedness guard for a ReportedTimeBlock's [startAt, endAt] interval,
 * applied by every writer (manual declaration, correction, import, punch-derived formation) so the
 * same rules hold whatever the source (M08). Every block must span a positive interval
 * (endAt strictly after startAt). Declared/imported blocks additionally must sit on whole-minute
 * boundaries — punch-derived blocks carry raw device timestamps and skip that check. Returns the
 * domain error to surface, or null when the interval is valid.
 */
export function validateReportedInterval(
  identifier: string,
  startAt: Date,
  endAt: Date,
  opts: { requireWholeMinute: boolean },
):
  | InstanceType<typeof InvalidIntervalError>
  | InstanceType<typeof NonWholeMinuteIntervalError>
  | null {
  if (endAt.getTime() <= startAt.getTime()) {
    return new InvalidIntervalError(identifier);
  }
  if (opts.requireWholeMinute && (!isWholeMinute(startAt) || !isWholeMinute(endAt))) {
    return new NonWholeMinuteIntervalError(identifier);
  }
  return null;
}