function normalizePageNumber(value) {
  const pageNumber = Math.floor(Number(value) || 1);
  return Math.max(1, pageNumber);
}

function buildQueryString(query) {
  const searchParams = new URLSearchParams();
  Object.keys(query || {}).forEach(function (key) {
    const value = query[key];
    if (value === undefined || value === null || value === '') {
      return;
    }
    searchParams.set(key, String(value));
  });

  const queryString = searchParams.toString();
  return queryString ? `?${queryString}` : '';
}

function buildPagination(totalItems, currentPage, pageParam, queryState, pageSize, itemLabel, ariaLabel) {
  const normalizedPageParam = String(pageParam || 'page').trim() || 'page';
  const normalizedPageSize = Math.max(1, Number(pageSize) || 10);
  const totalPages = Math.max(1, Math.ceil(Number(totalItems) / normalizedPageSize));
  const safeCurrentPage = Math.min(normalizePageNumber(currentPage), totalPages);
  const startIndex = totalItems <= 0 ? 0 : (safeCurrentPage - 1) * normalizedPageSize;
  const endIndex = totalItems <= 0 ? 0 : Math.min(totalItems, startIndex + normalizedPageSize);
  const pages = [];

  for (let pageNumber = 1; pageNumber <= totalPages; pageNumber += 1) {
    const nextQuery = Object.assign({}, queryState, { [normalizedPageParam]: pageNumber });
    pages.push({
      number: pageNumber,
      active: pageNumber === safeCurrentPage,
      url: buildQueryString(nextQuery)
    });
  }

  const previousQuery = Object.assign({}, queryState, { [normalizedPageParam]: safeCurrentPage - 1 });
  const nextQuery = Object.assign({}, queryState, { [normalizedPageParam]: safeCurrentPage + 1 });

  return {
    currentPage: safeCurrentPage,
    totalPages: totalPages,
    totalItems: Number(totalItems) || 0,
    hasMultiplePages: totalPages > 1,
    startItem: startIndex + 1,
    endItem: endIndex,
    hasPrevious: safeCurrentPage > 1,
    hasNext: safeCurrentPage < totalPages,
    previousUrl: buildQueryString(previousQuery),
    nextUrl: buildQueryString(nextQuery),
    pages: pages,
    pageSize: normalizedPageSize,
    pageParam: normalizedPageParam,
    itemLabel: String(itemLabel || 'items'),
    ariaLabel: String(ariaLabel || 'Pagination')
  };
}

module.exports = {
  normalizePageNumber,
  buildQueryString,
  buildPagination
};