5chan/src/hooks/use-replies.ts

import { useMemo } from 'react';
import { Comment, useAccountComments } from '@plebbit/plebbit-react-hooks';
import { flattenCommentsPages } from '@plebbit/plebbit-react-hooks/dist/lib/utils';

const useReplies = (comment: Comment) => {
  // flatten all replies including nested ones from the original comment
  const flattenedReplies = useMemo(() => flattenCommentsPages(comment?.replies), [comment?.replies]);

  // generate a Set of CIDs from flattened replies for quick lookup
  const replyCids = useMemo(() => new Set(flattenedReplies.map((reply) => reply?.cid)), [flattenedReplies]);

  const { accountComments } = useAccountComments();

  const filteredAccountComments = useMemo(() => {
    const commentMap = new Map(accountComments.map((c) => [c.cid, c]));

    return accountComments.filter((accountComment) => {
      let currentCid = accountComment.parentCid;
      while (currentCid && currentCid !== comment?.cid) {
        if (replyCids.has(currentCid)) {
          return true;
        }
        const parent = commentMap.get(currentCid);
        if (!parent) {
          return false;
        }
        currentCid = parent.parentCid;
      }
      return currentCid === comment?.cid;
    });
  }, [accountComments, comment?.cid, replyCids]);

  // the account's replies have a delay before getting published, so get them locally from accountComments instead
  const accountRepliesNotYetPublished = useMemo(() => {
    const replies = flattenedReplies || [];
    const replyCids = new Set(replies.map((reply: Comment) => reply?.cid));
    // filter out the account comments already in comment.replies, so they don't appear twice
    return filteredAccountComments.filter((accountReply) => !replyCids.has(accountReply?.cid));
  }, [flattenedReplies, filteredAccountComments]);

  const repliesAndNotYetPublishedReplies = useMemo(() => {
    const repliesSortedByPinnedAndTimestamp = [...accountRepliesNotYetPublished.reverse(), ...(flattenedReplies || [])];

    return repliesSortedByPinnedAndTimestamp.sort((a: Comment, b: Comment) => {
      // Sort by pinned status first, with pinned comments at the top
      if (a.pinned && !b.pinned) {
        return -1;
      } else if (!a.pinned && b.pinned) {
        return 1;
      }
      // If both are pinned or both are not pinned, sort by timestamp
      return a.timestamp - b.timestamp;
    });
  }, [flattenedReplies, accountRepliesNotYetPublished]);

  return repliesAndNotYetPublishedReplies;
};

export default useReplies;