@livekit/components-core/src/sorting/sort-participants.ts

import type { Participant } from 'livekit-client';
import { LocalParticipant } from 'livekit-client';
import {
  sortParticipantsByAudioLevel,
  sortParticipantsByIsSpeaking,
  sortParticipantsByJoinedAt,
  sortParticipantsByLastSpokenAT,
} from './base-sort-functions';

/**
 * Default sort for participants, it'll order participants by:
 * 1. local participant
 * 2. dominant speaker (speaker with the loudest audio level)
 * 3. other speakers that are recently active
 * 4. participants with video on
 * 5. by joinedAt
 */
export function sortParticipants(participants: Participant[]): Participant[] {
  const sortedParticipants = [...participants];
  sortedParticipants.sort((a, b) => {
    // loudest speaker first
    if (a.isSpeaking && b.isSpeaking) {
      return sortParticipantsByAudioLevel(a, b);
    }

    // speaker goes first
    if (a.isSpeaking !== b.isSpeaking) {
      return sortParticipantsByIsSpeaking(a, b);
    }

    // last active speaker first
    if (a.lastSpokeAt !== b.lastSpokeAt) {
      return sortParticipantsByLastSpokenAT(a, b);
    }

    // video on
    const aVideo = a.videoTrackPublications.size > 0;
    const bVideo = b.videoTrackPublications.size > 0;
    if (aVideo !== bVideo) {
      if (aVideo) {
        return -1;
      } else {
        return 1;
      }
    }

    // joinedAt
    return sortParticipantsByJoinedAt(a, b);
  });
  const localParticipant = sortedParticipants.find((p) => p.isLocal) as LocalParticipant;
  if (localParticipant) {
    const localIdx = sortedParticipants.indexOf(localParticipant);
    if (localIdx >= 0) {
      sortedParticipants.splice(localIdx, 1);
      if (sortedParticipants.length > 0) {
        sortedParticipants.splice(0, 0, localParticipant);
      } else {
        sortedParticipants.push(localParticipant);
      }
    }
  }
  return sortedParticipants;
}