import { isUserId } from './matrix';

/** Minimal shape of a `io.lotus.call_state` participant entry we need here. */
export type SpeakingParticipant = { userId: string; speaking: boolean };

/** True when both sets contain exactly the same members. */
export const sameSet = <T>(a: Set<T>, b: Set<T>): boolean => {
  if (a === b) return true;
  if (a.size !== b.size) return false;
  for (const v of a) {
    if (!b.has(v)) return false;
  }
  return true;
};

/**
 * Derives the speaking-users set from a `io.lotus.call_state` participant
 * list. Returns `prev` unchanged (same reference) when the derived set is
 * equal to it, so callers using the functional `setState` form can bail out
 * of a re-render (#32 — the fork pushes this multiple times per second).
 */
export const nextSpeakerSet = (
  prev: Set<string>,
  participants: readonly SpeakingParticipant[],
): Set<string> => {
  const next = new Set<string>();
  participants.forEach((p) => {
    if (p.speaking && isUserId(p.userId)) next.add(p.userId);
  });
  return sameSet(prev, next) ? prev : next;
};