import { mergeDeltaRows, type DeltaDeletedItem } from "@govoplan/core-webui";

export type AdminDeltaResponse = {
  deleted: DeltaDeletedItem[];
  watermark?: string | null;
  has_more: boolean;
  full: boolean;
};

export async function loadDeltaRows<TItem, TResponse extends AdminDeltaResponse>(
  current: TItem[],
  key: string,
  getDeltaWatermark: (key: string) => string | null,
  setDeltaWatermark: (key: string, watermark: string | null | undefined) => void,
  fetchDelta: (since: string | null) => Promise<TResponse>,
  rowsFromResponse: (response: TResponse) => TItem[],
  getKey: (item: TItem) => string,
  deletedResourceType: string,
  sort?: (left: TItem, right: TItem) => number
): Promise<TItem[]> {
  let nextWatermark = getDeltaWatermark(key);
  let merged = current;
  let hasMore = false;
  do {
    const response = await fetchDelta(nextWatermark);
    const rows = rowsFromResponse(response);
    const continuingFullSnapshot = response.full && nextWatermark?.startsWith("full:");
    merged = response.full
      ? continuingFullSnapshot
        ? mergeDeltaRows(merged, rows, [], getKey, { deletedResourceType, sort })
        : rows
      : mergeDeltaRows(merged, rows, response.deleted, getKey, { deletedResourceType, sort });
    nextWatermark = response.watermark ?? null;
    hasMore = response.has_more;
  } while (hasMore);
  setDeltaWatermark(key, nextWatermark);
  return merged;
}