function mergeThreads()

in src/views/inbox-threads/inbox-threads-helper.ts [97:141]
42 lines of code
9 McCabe index (conditional complexity)

function mergeThreads(threads: InboxThread[]): InboxThread[] {
  const subscriptionThreads: InboxThread[] = threads.filter((it: InboxThread) => getThreadTypeData(it).isSubscription);
  const directThreads: InboxThread[] = threads.filter((it: InboxThread) => !getThreadTypeData(it).isSubscription);
  let mergedSubscriptionsThreads: InboxThread[] = subscriptionThreads;
  const sMap: Record<string, InboxThread> = {};
  const dMap: Record<string, InboxThread> = directThreads.reduce(
    (akk: Record<string, InboxThread>, it: InboxThread) => {
      const iTarget: InboxThreadTarget = it.subject.target;
      const iEntity = iTarget?.issue || iTarget?.article || iTarget;
      const curr = akk[iEntity.id];
      if (curr) {
        curr.messages = curr.messages.concat(it.messages);
      } else {
        akk[iEntity.id] = it;
      }
      return akk;
    }, {});

  if (directThreads.length > 0) {
    mergedSubscriptionsThreads = subscriptionThreads.reduce((akk: InboxThread[], it: InboxThread) => {
      const target: InboxThreadTarget = it.subject.target;
      const entity = target?.issue || target?.article || target;
      sMap[entity.id] = it;

      const direct: InboxThread | undefined = dMap[entity?.id];
      const inboxThreadMessages = it.messages.slice(0);
      const messages = direct ? [...inboxThreadMessages, ...direct.messages].sort(sortByTimestamp).reverse() : inboxThreadMessages;
      return [...akk, {
        ...it,
        messages,
        lastTimestamp: it.messages.slice(0, 1)[0].timestamp,
      }];
    }, [] as InboxThread[]);
  }

  const orphans = Object.keys(dMap).reduce((akk: (InboxThread & {lastTimestamp: number})[], id: string) => {
    if (!sMap[id]) {
      akk.push({...dMap[id], lastTimestamp: dMap[id].notified});
    }
    return akk;
  }, []);
  return mergedSubscriptionsThreads.concat(orphans).sort((a, b) => {
    return doSortBy(a, b, 'lastTimestamp', true);
  });
}