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import { Page } from "../core/filesystem.ts";import { isPlainObject, merge } from "../core/utils.ts";import { posix } from "../deps/path.ts";
import type { PageData, Plugin } from "../core.ts";
export interface Options {  /** The list of extensions used for this plugin */  extensions: string[];
  /** Available languages */  languages: string[];
  /** A prefix-free language */  defaultLanguage?: string;}
// Default optionsexport const defaults: Options = {  extensions: [".html"],  languages: [],};
export default function multilanguage(userOptions?: Partial<Options>): Plugin {  const options = merge(defaults, userOptions);
  return (site) => {    // Configure the merged keys    const mergedKeys = site.scopedData.get("/")?.mergedKeys || {};    options.languages.forEach((lang) => {      mergedKeys[lang] = "object";    });    site.data("mergedKeys", mergedKeys);
    // Preprocessor to setup multilanguage pages    site.preprocess(options.extensions, (page, pages) => {      const { data } = page;      const languages = data.lang as string | string[] | undefined;
      // The "lang" variable of the pages must be an array      if (!Array.isArray(languages)) {        return;      }
      // Create a new page per language      const newPages: Page[] = [];      const id: string = data.id || page.src.path.slice(1);      const basePath: string = typeof page.data.url === "string"        ? posix.dirname(page.data.url)        : "";
      for (const lang of languages) {        const newData: PageData = { ...data, lang, id };        const newPage = page.duplicate();        newPage.data = newData;        newPages.push(newPage);
        // Fix the url        const customUrl = newData[`url.${lang}`] || newData[lang]?.url;
        if (customUrl) {          newData.url = customUrl;          newData.url = site.pagePreparer.getUrl(            newPage,            basePath,          );        } else if (newData.url) {          newData.url = `/${lang}${newData.url}`;        }      }
      // Replace the current page with the multiple language versions      pages.splice(pages.indexOf(page), 1, ...newPages);    });
    // Preprocessor to (un)prefix all urls with the language code    site.preprocess(options.extensions, (page) => {      const { lang } = page.data;
      if (typeof lang !== "string") {        return;      }
      const url = page.data.url as string | undefined;
      if (!url) {        return;      }
      if (!url.startsWith(`/${lang}/`) && lang !== options.defaultLanguage) {        page.data.url = `/${lang}${url}`;      } else if (        url.startsWith(`/${lang}/`) && lang === options.defaultLanguage      ) {        page.data.url = url.slice(lang.length + 1);      }    });
    // Preprocessor to process the multilanguage data    site.preprocess(options.extensions, (page) => {      const lang = page.data.lang;
      if (typeof lang !== "string") {        return;      }
      const data = filterLanguage(        options.languages,        lang,        page.data,      ) as PageData;
      for (const key of options.languages) {        if (key in data) {          if (key === lang) {            Object.assign(data, data[key]);          }          delete data[key];        }      }
      page.data = data;    });
    // Preprocessor to build the alternates object    site.preprocess(options.extensions, (page, pages) => {      const { data } = page;      const id = data.id as string | number | undefined;
      if (data.alternates || !id) {        return;      }
      const alternates: PageData[] = [];      const alternatePages = pages.filter((page) => page.data.id == id);
      options.languages.forEach((lang) => {        const page = alternatePages.find((page) => page.data.lang === lang);
        if (page) {          alternates.push(page.data);          page.data.alternates = alternates;        }      });    });
    // Include automatically the <link rel="alternate"> elements    // with the other languages    site.process(options.extensions, (page) => {      const { document } = page;      const alternates = page.data.alternates;      const lang = page.data.lang as string | undefined;
      if (!document || !alternates || !lang) {        return;      }
      // Include <html lang="${lang}"> attribute element if it's missing      if (!document.documentElement?.getAttribute("lang")) {        document.documentElement?.setAttribute("lang", lang);      }
      // Insert the <link> elements automatically      for (const data of alternates) {        if (data.lang === lang) {          continue;        }        const meta = document.createElement("link");        meta.setAttribute("rel", "alternate");        meta.setAttribute("hreflang", data.lang);        meta.setAttribute("href", data.url);        document.head.appendChild(meta);        document.head.appendChild(document.createTextNode("\n"));      }    });  };}
/** * Remove the entries from all "langs" except the "lang" value */function filterLanguage(  langs: string[],  lang: string,  data: Record<string, unknown>,): Record<string, unknown> {  const result: Record<string, unknown> = {};
  for (const [name, value] of Object.entries(data)) {    const parts = name.match(/^(.*)\.([^.]+)$/);
    if (parts) {      const [, key, l] = parts;
      if (lang === l) {        result[key] = value;        continue;      } else if (langs.includes(l)) {        continue;      }    }
    if (name in result) {      continue;    }
    if (isPlainObject(value)) {      result[name] = filterLanguage(langs, lang, value);    } else if (Array.isArray(value)) {      result[name] = value.map((item) => {        return isPlainObject(item) ? filterLanguage(langs, lang, item) : item;      });    } else {      result[name] = value;    }  }
  return result;}