import { useMemo } from 'react';
import type { CommunicationRequest } from 'fhir/r4';
import { isPoolThreadRequest, threadBelongsInInbox } from '../utils/messaging/poolThread';
import { isEncounterRoomThreadRequest } from '../utils/messaging/roomThread';

interface InboxThreadsDeps {
  getMessagesForRequest: (request: CommunicationRequest) => unknown[];
  getUnreadCountForRequest: (id: string) => number;
}

const latestTimestamp = (request: CommunicationRequest): number => {
  const value = request.authoredOn || request.meta?.lastUpdated;
  return value ? new Date(value).getTime() : 0;
};

// Direct threads deduplicate by counterparty; listed office and visit rooms retain their own identity.
export const useInboxThreads = (
  requests: CommunicationRequest[],
  getCounterpartyId: (request: CommunicationRequest) => string | undefined,
  { getMessagesForRequest, getUnreadCountForRequest }: InboxThreadsDeps,
) => {
  const dedupedThreads = useMemo(() => {
    const map = new Map<string, CommunicationRequest>();
    requests.forEach((request) => {
      // A room and a direct conversation can share a patient without sharing a thread.
      const id = isPoolThreadRequest(request) || isEncounterRoomThreadRequest(request)
        ? (request.id as string)
        : getCounterpartyId(request) || (request.id as string);
      if (!id) return;
      const existing = map.get(id);
      if (!existing || latestTimestamp(request) >= latestTimestamp(existing)) map.set(id, request);
    });
    return Array.from(map.values()).sort((a, b) => latestTimestamp(b) - latestTimestamp(a));
  }, [requests, getCounterpartyId]);

  const inboxThreads = useMemo(() => {
    return dedupedThreads
      .filter((request) => threadBelongsInInbox(request, getMessagesForRequest(request).length))
      .sort((a, b) => {
        const aUnread = getUnreadCountForRequest(a.id as string) > 0 ? 1 : 0;
        const bUnread = getUnreadCountForRequest(b.id as string) > 0 ? 1 : 0;
        return bUnread - aUnread;
      });
  }, [dedupedThreads, getMessagesForRequest, getUnreadCountForRequest]);

  return { dedupedThreads, inboxThreads };
};