import { regionData } from 'element-china-area-data';

export type RegionTree = Record<string, Record<string, string[]>>;

/** 由国家标准省市区数据构建三级树 */
function buildRegionTree(): RegionTree {
  const tree: RegionTree = {};
  for (const province of regionData) {
    const cities: Record<string, string[]> = {};
    for (const city of province.children ?? []) {
      cities[city.label] = (city.children ?? []).map((district) => district.label);
    }
    tree[province.label] = cities;
  }
  return tree;
}

export const REGION_TREE: RegionTree = buildRegionTree();

export const PROVINCES = Object.keys(REGION_TREE);

/** 三级选择「全市」选项（省/市/区列表首项） */
export const REGION_ALL = '全市';

export function getCities(province: string): string[] {
  if (province === REGION_ALL) return [];
  return Object.keys(REGION_TREE[province] ?? {});
}

export function getDistricts(province: string, city: string): string[] {
  if (province === REGION_ALL || city === REGION_ALL) return [];
  return REGION_TREE[province]?.[city] ?? [];
}

/** 省份列表（含全市） */
export function getProvincesForPicker(): string[] {
  return [...PROVINCES];
}

/** 城市列表（含全市） */
export function getCitiesForPicker(province: string): string[] {
  if (province === REGION_ALL) return [REGION_ALL];
  return [...getCities(province)];
}

/** 区县列表（含全市） */
export function getDistrictsForPicker(province: string, city: string): string[] {
  if (province === REGION_ALL || city === REGION_ALL) return [REGION_ALL];
  return [REGION_ALL, ...getDistricts(province, city)];
}

export function formatRegion(province: string, city: string, district: string): string {
  if (!province) return '';
  if (province === REGION_ALL) return REGION_ALL;
  if (city === REGION_ALL) return `${province} ${REGION_ALL}`;
  if (district === REGION_ALL) return `${province} ${city} ${REGION_ALL}`;
  if (!city || !district) return '';
  return `${province} ${city} ${district}`;
}

/** 仅展示省、市两级（门店列表等场景） */
export function formatRegionCity(province: string, city: string): string {
  if (!province) return '';
  if (province === REGION_ALL) return REGION_ALL;
  if (city === REGION_ALL) return `${province} ${REGION_ALL}`;
  if (!city) return province;
  return `${province} ${city}`;
}

/** 门店筛选：固定为市级，不按区县过滤 */
export function toCityLevelRegion(selection: RegionSelection): RegionSelection {
  const normalized = normalizeRegionSelection(selection);
  return {
    province: normalized.province,
    city: normalized.city,
    district: REGION_ALL,
  };
}

export type RegionSelection = {
  province: string;
  city: string;
  district: string;
};

export const DEFAULT_REGION: RegionSelection = {
  province: '河南省',
  city: '郑州市',
  district: '金水区',
};

export const FALLBACK_CITY_REGION: RegionSelection = {
  province: '河南省',
  city: '郑州市',
  district: REGION_ALL,
};

export function regionFromGeo(province: string, city: string, district?: string): RegionSelection {
  const cityName = city.endsWith('市') ? city : `${city}市`;
  const provinceInTree = PROVINCES.includes(province) ? province : DEFAULT_REGION.province;
  const cities = getCities(provinceInTree);
  const matchedCity = cities.includes(cityName)
    ? cityName
    : cities.find((c) => c.replace(/市$/, '') === city.replace(/市$/, '')) ?? cityName;
  const districts = getDistricts(provinceInTree, matchedCity);
  const districtName =
    district && districts.includes(district)
      ? district
      : REGION_ALL;
  return normalizeRegionSelection({
    province: provinceInTree,
    city: cities.includes(matchedCity) ? matchedCity : matchedCity,
    district: districtName,
  });
}

/** 校验已选地区是否仍存在于数据源中 */
export function normalizeRegionSelection(selection: RegionSelection): RegionSelection {
  if (selection.province === REGION_ALL) {
    return { province: REGION_ALL, city: REGION_ALL, district: REGION_ALL };
  }

  const province = PROVINCES.includes(selection.province)
    ? selection.province
    : DEFAULT_REGION.province;

  if (selection.city === REGION_ALL) {
    return { province, city: REGION_ALL, district: REGION_ALL };
  }

  const cities = getCities(province);
  const city = cities.includes(selection.city) ? selection.city : (cities[0] ?? DEFAULT_REGION.city);

  if (selection.district === REGION_ALL) {
    return { province, city, district: REGION_ALL };
  }

  const districts = getDistricts(province, city);
  const district = districts.includes(selection.district)
    ? selection.district
    : (districts[0] ?? DEFAULT_REGION.district);

  return { province, city, district };
}