import type { WorkOrderDayGroup } from "@/domain/work-orders/types/work-order-table-row";

export const DAY_PAGE_SIZE_OPTIONS = [25, 50, 100, 200] as const;
export const DEFAULT_DAY_PAGE_SIZE = 50;

export type DayPageSize = (typeof DAY_PAGE_SIZE_OPTIONS)[number];

export type PaginatedSlice<T> = {
  visible: T[];
  pageCount: number;
  pageIndex: number;
};

export function pageIndexForItem(itemIndex: number, pageSize: number): number {
  if (itemIndex < 0) {
    return 0;
  }
  const size = pageSize > 0 ? pageSize : DEFAULT_DAY_PAGE_SIZE;
  return Math.floor(itemIndex / size);
}

export function findItemPageIndex<T extends { id: string | number }>(
  items: readonly T[],
  id: string | number,
  pageSize: number,
): number | null {
  const index = items.findIndex((item) => String(item.id) === String(id));
  if (index < 0) {
    return null;
  }
  return pageIndexForItem(index, pageSize);
}

export function totalPageCount(totalCount: number, pageSize: number): number {
  const size = pageSize > 0 ? pageSize : DEFAULT_DAY_PAGE_SIZE;
  return Math.max(1, Math.ceil(Math.max(0, totalCount) / size) || 1);
}

export function asDayPageSize(value: number): DayPageSize {
  return (DAY_PAGE_SIZE_OPTIONS as readonly number[]).includes(value)
    ? (value as DayPageSize)
    : DEFAULT_DAY_PAGE_SIZE;
}

export function paginateItems<T>(
  items: readonly T[],
  pageIndex: number,
  pageSize: number,
): PaginatedSlice<T> {
  const size = pageSize > 0 ? pageSize : DEFAULT_DAY_PAGE_SIZE;
  const pageCount = totalPageCount(items.length, size);
  const page = Math.min(Math.max(0, pageIndex), pageCount - 1);
  const start = page * size;
  return {
    visible: items.slice(start, start + size),
    pageCount,
    pageIndex: page,
  };
}

export const SEARCH_PAGER_FOOTER_LABEL = "Results";

export function shouldShowDayPagination(input: {
  flatListMode: boolean;
  isLoading: boolean;
  noSearchResults: boolean;
}): boolean {
  return !input.flatListMode && !input.isLoading && !input.noSearchResults;
}

export function shouldShowSearchPagination(input: {
  isLoading: boolean;
  hasResults: boolean;
}): boolean {
  return !input.isLoading && input.hasResults;
}

export function resolveSearchPager(input: { page: number; pageSize: number; totalCount: number }): {
  pageSize: DayPageSize;
  pageIndex: number;
  pageCount: number;
  itemCount: number;
} {
  const pageSize = asDayPageSize(input.pageSize);
  const pageCount = totalPageCount(input.totalCount, pageSize);
  return {
    pageSize,
    pageIndex: Math.min(Math.max(0, input.page), pageCount - 1),
    pageCount,
    itemCount: input.totalCount,
  };
}

export function nextSearchPageIfOutOfRange(input: {
  page: number;
  pageSize: number;
  totalCount: number;
}): number | null {
  if (input.totalCount <= 0) {
    return null;
  }
  const pageCount = totalPageCount(input.totalCount, asDayPageSize(input.pageSize));
  if (input.page < pageCount) {
    return null;
  }
  return pageCount - 1;
}

export function pickBoardPager(input: {
  advActive: boolean;
  isLoading: boolean;
  noSearchResults: boolean;
  advResultCount: number;
  search: { page: number; pageSize: number; totalCount: number };
  day: {
    pageSize: DayPageSize;
    pageIndex: number;
    pageCount: number;
    itemCount: number;
    footerLabel: string;
  };
}): {
  show: boolean;
  pageSize: DayPageSize;
  pageIndex: number;
  pageCount: number;
  itemCount: number;
  footerLabel: string;
} {
  if (input.advActive) {
    return {
      show: shouldShowSearchPagination({
        isLoading: input.isLoading,
        hasResults: input.search.totalCount > 0,
      }),
      ...resolveSearchPager(input.search),
      footerLabel: SEARCH_PAGER_FOOTER_LABEL,
    };
  }
  return {
    show: shouldShowDayPagination({
      flatListMode: false,
      isLoading: input.isLoading,
      noSearchResults: input.noSearchResults,
    }),
    ...input.day,
  };
}

export function formatDayPaginationSummary(dayLabel: string, itemCount: number): string {
  const label = dayLabel.trim().toUpperCase();
  const noun = itemCount === 1 ? "item" : "items";
  return `${label} · ${itemCount} ${noun}`;
}

export function pageSelectedDayGroups(
  dayGroups: WorkOrderDayGroup[],
  pageIndex: number,
  pageSize: number,
): { groups: WorkOrderDayGroup[]; pageIndex: number; pageCount: number; totalCount: number } {
  const group = dayGroups[0];
  if (!group) {
    return { groups: dayGroups, pageIndex: 0, pageCount: 1, totalCount: 0 };
  }
  const slice = paginateItems(group.items, pageIndex, pageSize);
  return {
    groups: [{ ...group, items: slice.visible, totalCount: group.items.length }],
    pageIndex: slice.pageIndex,
    pageCount: slice.pageCount,
    totalCount: group.items.length,
  };
}