import { parseAsInteger, parseAsString, parseAsStringLiteral } from 'nuqs';

import type { Post } from '@/entities/post';

const SORT_ORDERS = ['asc', 'desc'] as const;

export type SortOrder = (typeof SORT_ORDERS)[number];

export const PAGE_SIZE = 5;

export const postSearchParsers = {
  keyword: parseAsString.withDefault(''),
  author: parseAsInteger,
  sort: parseAsStringLiteral(SORT_ORDERS),
  page: parseAsInteger.withDefault(1),
};

export const filterByAuthor = (posts: Post[], author: number | null) =>
  author === null ? posts : posts.filter((post) => post.userId === author);

export const toSortingState = (sort: SortOrder | null) =>
  sort === null ? [] : [{ id: 'title', desc: sort === 'desc' }];

export const toNextSort = (sort: SortOrder | null) => {
  // oxlint-disable-next-line unicorn/no-null -- nuqs는 URL 파라미터 제거를 null로 표현한다
  const NEXT_SORT = { asc: 'desc', desc: null } as const;
  return sort === null ? 'asc' : NEXT_SORT[sort];
};

export const toAuthorIds = (posts: Post[]) =>
  [...new Set(posts.map((post) => post.userId))].sort((a, b) => a - b);

export const toAvgBodyLength = (posts: Post[]) =>
  posts.length === 0
    ? 0
    : Math.round(
        posts.reduce((sum, post) => sum + post.body.length, 0) / posts.length
      );

export const toEmptyMessage = (filteredCount: number) =>
  filteredCount === 0
    ? '검색 결과가 없어요.'
    : '이 페이지에는 글이 없어요. 이전 페이지로 가 보세요.';