import { MERCHANT_CATEGORY_OPTIONS } from '@/lib/domain/merchant';

export const MERCHANTS_PATH = '/system/merchants';
/** 엑셀 다운로드 — 파일 응답이라 라우트 핸들러가 받는다(기획 MCH_001 ②). */
export const MERCHANTS_EXCEL_PATH = `${MERCHANTS_PATH}/excel`;

/** 필터 셀렉트의 "전체" 값 — URL에서는 생략된다. */
export const FILTER_ALL = '';

export type MerchantSearchField = 'name' | 'businessNumber' | 'address';

export const MERCHANT_SEARCH_FIELD_OPTIONS: ReadonlyArray<{
  value: MerchantSearchField;
  label: string;
}> = [
  { value: 'name', label: '가맹점명' },
  { value: 'businessNumber', label: '사업자번호' },
  { value: 'address', label: '주소' },
];

export const MERCHANT_VISIBILITY_OPTIONS = [
  { value: 'visible', label: '노출' },
  { value: 'hidden', label: '미노출' },
] as const;

export const MERCHANT_PAGE_SIZE_OPTIONS = [10, 30, 50] as const;
export type MerchantPageSize = (typeof MERCHANT_PAGE_SIZE_OPTIONS)[number];

export const DEFAULT_MERCHANT_SEARCH_FIELD: MerchantSearchField = 'name';
export const DEFAULT_MERCHANT_PAGE_SIZE: MerchantPageSize = 10;
const DEFAULT_PAGE = 1;
const MAX_KEYWORD_LENGTH = 100;

export type MerchantQuery = {
  category: string;
  visibility: string;
  searchField: MerchantSearchField;
  keyword: string;
  page: number;
  pageSize: MerchantPageSize;
};

type RawSearchParams = Record<string, string | string[] | undefined>;

function readParam(params: RawSearchParams, key: string): string {
  const value = params[key];
  return (Array.isArray(value) ? value[0] : value) ?? '';
}

function readOneOf(
  params: RawSearchParams,
  key: string,
  allowed: readonly { value: string }[]
): string {
  const raw = readParam(params, key);
  return allowed.some((option) => option.value === raw) ? raw : FILTER_ALL;
}

function isSearchField(value: string): value is MerchantSearchField {
  return MERCHANT_SEARCH_FIELD_OPTIONS.some((option) => option.value === value);
}

function isPageSize(value: number): value is MerchantPageSize {
  return (MERCHANT_PAGE_SIZE_OPTIONS as readonly number[]).includes(value);
}

export function parseMerchantQuery(searchParams: RawSearchParams): MerchantQuery {
  const searchField = readParam(searchParams, 'searchField');
  const page = Number(readParam(searchParams, 'page'));
  const pageSize = Number(readParam(searchParams, 'pageSize'));

  return {
    category: readOneOf(searchParams, 'category', MERCHANT_CATEGORY_OPTIONS),
    visibility: readOneOf(
      searchParams,
      'visibility',
      MERCHANT_VISIBILITY_OPTIONS
    ),
    searchField: isSearchField(searchField)
      ? searchField
      : DEFAULT_MERCHANT_SEARCH_FIELD,
    keyword: readParam(searchParams, 'keyword').trim().slice(0, MAX_KEYWORD_LENGTH),
    page: Number.isInteger(page) && page > 0 ? page : DEFAULT_PAGE,
    pageSize: isPageSize(pageSize) ? pageSize : DEFAULT_MERCHANT_PAGE_SIZE,
  };
}

export function buildMerchantHref(
  query: MerchantQuery,
  overrides: Partial<MerchantQuery> = {}
): string {
  const merged = { ...query, ...overrides };
  const params = new URLSearchParams();

  if (merged.category) {
    params.set('category', merged.category);
  }
  if (merged.visibility) {
    params.set('visibility', merged.visibility);
  }
  if (merged.searchField !== DEFAULT_MERCHANT_SEARCH_FIELD) {
    params.set('searchField', merged.searchField);
  }
  if (merged.keyword) {
    params.set('keyword', merged.keyword);
  }
  if (merged.pageSize !== DEFAULT_MERCHANT_PAGE_SIZE) {
    params.set('pageSize', String(merged.pageSize));
  }
  if (merged.page !== DEFAULT_PAGE) {
    params.set('page', String(merged.page));
  }

  const queryString = params.toString();
  return queryString ? `${MERCHANTS_PATH}?${queryString}` : MERCHANTS_PATH;
}