firebase/superstatic

/**
 * Copyright (c) 2022 Google LLC
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

import { normalizeMultiSlashes } from "./pathutils";

/**
 * Returns the list of paths to check for i18n content.
 * The path order is:
 * (1) root/language_country/path (for each language)
 * (2) root/ALL_country/path (if country is set)
 * (3) root/language_ALL/path or root/language/path (for each language)
 *
 * If i18n is *not* configured, an empty list is returned.
 * @param p requested path.
 * @param req the request object containing superstatic and i18n configuration.
 * @return list of paths to check for i18n content.
 */
export function i18nContentOptions(p: string, req: any): string[] {
  const paths: string[] = [];
  const i18n = req.superstatic.i18n;
  if (!i18n?.root) {
    return paths;
  }
  const country = getCountryCode(req.headers);
  const languages = getI18nLanguages(req.headers);
  // (1)
  if (country) {
    for (const l of languages) {
      paths.push(join(i18n.root, `${l}_${country}`, p));
    }
    // (2)
    paths.push(join(i18n.root, `ALL_${country}`, p));
  }
  // (3)
  for (const l of languages) {
    paths.push(join(i18n.root, `${l}_ALL`, p));
    paths.push(join(i18n.root, `${l}`, p));
  }
  return paths;
}

function join(...arr: string[]): string {
  arr.unshift("/");
  return normalizeMultiSlashes(arr.join("/"));
}

/**
 * Fetches the country code from the headers object.
 * @param headers headers from the request.
 * @return country code, or an empty string.
 */
function getCountryCode(headers: Record<string, string>): string {
  const overrideValue = cookieValue(
    headers.cookie,
    "firebase-country-override",
  );
  if (overrideValue) {
    return overrideValue;
  }
  return headers["x-country-code"] || "";
}

/**
 * Fetches the languages from the accept-language header.
 * @param headers headers from the request.
 * @return ordered list of languages from the header.
 */
function getI18nLanguages(headers: Record<string, string>): string[] {
  const overrideValue = cookieValue(
    headers.cookie,
    "firebase-language-override",
  );
  if (overrideValue) {
    return overrideValue.includes(",")
      ? overrideValue.split(",")
      : [overrideValue];
  }

  const acceptLanguage = headers["accept-language"];
  if (!acceptLanguage) {
    return [];
  }

  const languagesSeen = new Set<string>();
  const languagesOrdered = [];
  for (const v of acceptLanguage.split(",")) {
    const l = v.split("-")[0];
    if (!l) {
      continue;
    }
    if (!languagesSeen.has(l)) {
      languagesOrdered.push(l);
    }
    languagesSeen.add(l);
  }
  return languagesOrdered;
}

/**
 * Fetches a value from a cookie string.
 * @param cookieString full cookie string.
 * @param key key to look for.
 * @return the value, or empty string;
 */
function cookieValue(cookieString: string, key: string): string {
  if (!cookieString) {
    return "";
  }
  const cookies = cookieString.split(";").map((c) => c.trim());
  for (const cookie of cookies) {
    if (cookie.startsWith(key)) {
      const s = cookie.split("=", 2);
      return s.length === 2 ? s[1] : "";
    }
  }
  return "";
}