export type PageWindow = {
  start: number;
  end: number;
  page: number;
  pages: number;
  previousOffset: number | null;
  nextOffset: number | null;
};

export const pageWindow = (total: number, limit: number, offset: number): PageWindow => {
  const safeTotal = Math.max(0, Math.trunc(total));
  const safeLimit = Math.max(1, Math.trunc(limit));
  const safeOffset = Math.max(0, Math.trunc(offset));
  const end = Math.min(safeOffset + safeLimit, safeTotal);
  return {
    start: safeTotal > 0 && safeOffset < safeTotal ? safeOffset + 1 : 0,
    end,
    page: Math.floor(safeOffset / safeLimit) + 1,
    pages: Math.max(1, Math.ceil(safeTotal / safeLimit)),
    previousOffset: safeOffset > 0 ? Math.max(0, safeOffset - safeLimit) : null,
    nextOffset: end < safeTotal ? safeOffset + safeLimit : null,
  };
};

export const pageHref = (path: string, search: URLSearchParams, offset: number, anchor = "") => {
  const params = new URLSearchParams(search);
  if (offset > 0) params.set("offset", String(offset));
  else params.delete("offset");
  const query = params.toString();
  return `${path}${query ? `?${query}` : ""}${anchor}`;
};