private prepareAttachmentUpdate = (attachmentToUpdate: LocalAttachment) => {
    const stateAttachments = this.attachments;
    const attachments = [...this.attachments];
    const attachmentIndex = this.getAttachmentIndex(attachmentToUpdate.localMetadata.id);

    if (attachmentIndex === -1) return null;

    const merged = mergeWithDiff<LocalAttachment>(
      stateAttachments[attachmentIndex] ?? {},
      attachmentToUpdate,
    );
    const updatesOnMerge = merged.diff && Object.keys(merged.diff.children).length;
    
    if (updatesOnMerge) {
      const localAttachment = ensureIsLocalAttachment(merged.result);
      if (localAttachment) {
        attachments.splice(attachmentIndex, 1, localAttachment);
        return attachments;
      }
    }
    return null;
  };

  updateAttachment = (attachmentToUpdate: LocalAttachment) => {
    const updatedAttachments = this.prepareAttachmentUpdate(attachmentToUpdate);
    if (updatedAttachments) {
      this.state.partialNext({ attachments: updatedAttachments });
    }
  };

  upsertAttachments = (attachmentsToUpsert: LocalAttachment[]) => {
    if (!attachmentsToUpsert.length) return;
    
    let attachments = [...this.attachments];
    let hasUpdates = false;

    attachmentsToUpsert.forEach((attachment) => {
      const updatedAttachments = this.prepareAttachmentUpdate(attachment);
      if (updatedAttachments) {
        attachments = updatedAttachments;
        hasUpdates = true;
      } else {
        const localAttachment = ensureIsLocalAttachment(attachment);
        if (localAttachment) {
          attachments.push(localAttachment);
          hasUpdates = true;
        }
      }
    });

    if (hasUpdates) {
      this.state.partialNext({ attachments });
    }
  };