cinny/src/app/utils/notifications.ts

import { MatrixClient, ReceiptType } from 'matrix-js-sdk';

export async function markAsRead(mx: MatrixClient, roomId: string, privateReceipt?: boolean) {
  const room = mx.getRoom(roomId);
  if (!room) return;

  const timeline = room.getLiveTimeline().getEvents();
  const readEventId = room.getEventReadUpTo(mx.getUserId()!);

  const getLatestValidEvent = () => {
    for (let i = timeline.length - 1; i >= 0; i -= 1) {
      const latestEvent = timeline[i];
      if (latestEvent.getId() === readEventId) return null;
      if (!latestEvent.isSending()) return latestEvent;
    }
    return null;
  };
  if (timeline.length === 0) return;
  const latestEvent = getLatestValidEvent();
  if (latestEvent === null) return;

  const latestEventId = latestEvent.getId();
  if (!latestEventId) return;

  // Set both the read receipt AND the fully_read marker
  // The fully_read marker is what persists your read position across sessions
  await mx.setRoomReadMarkers(
    roomId,
    latestEventId, // m.fully_read marker
    latestEvent,   // m.read receipt event
    privateReceipt ? { receiptType: ReceiptType.ReadPrivate } : undefined
  );
}