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

import { useMemo } from 'react';
import { Comment, useAccountComments } from '@bitsocial/bitsocial-react-hooks';
import { sortRepliesForDisplay } from '../lib/utils/replies-preview-utils';

// Keep the hook on its indexed fast path when there are no reply indices to resolve.
const EMPTY_ACCOUNT_COMMENT_LOOKUP = { commentIndices: [-1] };

const useFreshReplies = (replies: Comment[] = []) => {
  const replyIndices = useMemo(
    () => Array.from(new Set(replies.map((reply) => reply?.index).filter((replyIndex): replyIndex is number => typeof replyIndex === 'number'))),
    [replies],
  );
  const replyCidsWithoutIndices = useMemo(
    () =>
      Array.from(
        new Set(
          replies
            .map((reply) => (typeof reply?.index === 'number' ? undefined : reply?.cid))
            .filter((replyCid): replyCid is string => typeof replyCid === 'string' && replyCid.length > 0),
        ),
      ),
    [replies],
  );
  const accountCommentLookupOptions = useMemo(() => (replyIndices.length > 0 ? { commentIndices: replyIndices } : EMPTY_ACCOUNT_COMMENT_LOOKUP), [replyIndices]);
  const accountCommentCidLookupOptions = useMemo(() => {
    if (replyCidsWithoutIndices.length === 0) {
      return EMPTY_ACCOUNT_COMMENT_LOOKUP;
    }

    const replyCidSet = new Set(replyCidsWithoutIndices);
    return {
      filter: (accountComment: Comment) => typeof accountComment?.cid === 'string' && replyCidSet.has(accountComment.cid),
    };
  }, [replyCidsWithoutIndices]);
  const { accountComments: accountCommentsByIndexList } = useAccountComments(accountCommentLookupOptions);
  const { accountComments: accountCommentsByCidList } = useAccountComments(accountCommentCidLookupOptions);

  return useMemo(() => {
    if (!replies.length) {
      return replies;
    }

    if (!accountCommentsByIndexList?.length && !accountCommentsByCidList?.length) {
      return sortRepliesForDisplay(replies);
    }

    const accountCommentsByIndex = new Map<number, Comment>();
    for (const accountComment of accountCommentsByIndexList) {
      if (typeof accountComment?.index === 'number') {
        accountCommentsByIndex.set(accountComment.index, accountComment);
      }
    }
    const accountCommentsByCidMap = new Map<string, Comment>();
    for (const accountComment of accountCommentsByCidList) {
      if (typeof accountComment?.cid === 'string') {
        accountCommentsByCidMap.set(accountComment.cid, accountComment);
      }
    }

    let hasFreshReplies = false;
    const nextReplies = replies.map((reply) => {
      if (typeof reply?.index !== 'number') {
        const freshReply = typeof reply?.cid === 'string' ? accountCommentsByCidMap.get(reply.cid) : undefined;
        if (!freshReply) {
          return reply;
        }

        hasFreshReplies = true;
        return freshReply;
      }

      const freshReply = accountCommentsByIndex.get(reply.index);
      if (!freshReply) {
        return reply;
      }

      hasFreshReplies = true;
      return freshReply;
    });

    if (!hasFreshReplies) {
      return sortRepliesForDisplay(replies);
    }

    const seenReplyIndices = new Set<number>();
    let hasDuplicateReplyIndices = false;
    const dedupedReplies = nextReplies.filter((reply) => {
      if (typeof reply?.index !== 'number') {
        return true;
      }

      if (seenReplyIndices.has(reply.index)) {
        hasDuplicateReplyIndices = true;
        return false;
      }

      seenReplyIndices.add(reply.index);
      return true;
    });

    return sortRepliesForDisplay(hasDuplicateReplyIndices ? dedupedReplies : nextReplies);
  }, [accountCommentsByCidList, accountCommentsByIndexList, replies]);
};

export default useFreshReplies;