import { useMemo } from "react";

import { UseCountriesOptions, CountryType } from "hooks";

export function getFlagEmoji(countryCode: string) {
  const codePoints = countryCode
    .toUpperCase()
    .split("")
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    .map((char) => 127397 + char.charCodeAt(undefined as any));
  return String.fromCodePoint(...codePoints);
}

/*
 * @param code The `code` to provide depends on the `type` passed to display name during creation:
 *  - If the type is `"region"`, code should be either an [ISO-3166 two letters region code](https://www.iso.org/iso-3166-country-codes.html),
 *    or a [three digits UN M49 Geographic Regions](https://unstats.un.org/unsd/methodology/m49/).
 *  - If the type is `"script"`, code should be an [ISO-15924 four letters script code](https://unicode.org/iso15924/iso15924-codes.html).
 *  - If the type is `"language"`, code should be a `languageCode` ["-" `scriptCode`] ["-" `regionCode` ] *("-" `variant` )
 *    subsequence of the unicode_language_id grammar in [UTS 35's Unicode Language and Locale Identifiers grammar](https://unicode.org/reports/tr35/#Unicode_language_identifier).
 *    `languageCode` is either a two letters ISO 639-1 language code or a three letters ISO 639-2 language code.
 *  - If the type is `"currency"`, code should be a [3-letter ISO 4217 currency code](https://www.iso.org/iso-4217-currency-codes.html).
 */

export function getCountries(lang = "en") {
  const A = 65;
  const Z = 90;
  const countryName = new Intl.DisplayNames([lang], { type: "region" });
  const countries: CountryType[] = [];
  for (let i = A; i <= Z; i += 1) {
    for (let j = A; j <= Z; j += 1) {
      const code = String.fromCharCode(i) + String.fromCharCode(j);
      const name = countryName.of(code) as string;
      const correctCountry = code !== name;
      const alreadyExist = countries.some((country) => country.name === name);
      if (correctCountry && !alreadyExist) {
        countries.push({
          code,
          name,
          emoji: getFlagEmoji(code),
        });
      }
    }
  }
  return countries;
}

let cachedCountries: CountryType[] = [];

/**
 *
 * @kind 03-Countries
 */
export const useCountries = (options: UseCountriesOptions) => {
  const { language } = options || {};

  const countries = useMemo(() => {
    if (!cachedCountries.length) {
      cachedCountries = getCountries(language);
    }
    return cachedCountries;
  }, [language]);

  return countries;
};