text: const { DateTime } = require("luxon");
  const fs = require("fs");
  const pluginRss = require("@11ty/eleventy-plugin-rss");
  const pluginSyntaxHighlight = require("@11ty/eleventy-plugin-syntaxhighlight");
  const pluginNavigation = require("@11ty/eleventy-navigation");
  const markdownIt = require("markdown-it");
  const markdownItAnchor = require("markdown-it-anchor");
  const markdownItAttribution = require("markdown-it-attribution");
  const markdownItAbbr = require('markdown-it-abbr');
  
  module.exports = function(eleventyConfig) {
    // Add plugins
    eleventyConfig.addPlugin(pluginRss);
    eleventyConfig.addPlugin(pluginSyntaxHighlight);
    eleventyConfig.addPlugin(pluginNavigation);
  
    // https://www.11ty.dev/docs/data-deep-merge/
    eleventyConfig.setDataDeepMerge(true);
  
    // Alias `layout: post` to `layout: layouts/post.njk`
    eleventyConfig.addLayoutAlias("post", "layouts/post.njk");
  
    eleventyConfig.addFilter("readableDate", dateObj => {
      return DateTime.fromJSDate(dateObj, {zone: 'utc'}).toFormat("dd LLL yyyy");
    });
  
    // https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#valid-date-string
    eleventyConfig.addFilter('htmlDateString', (dateObj) => {
      return DateTime.fromJSDate(dateObj, {zone: 'utc'}).toFormat('yyyy-LL-dd');
    });
  
    // Get the first `n` elements of a collection.
    eleventyConfig.addFilter("head", (array, n) => {
      if( n < 0 ) {
        return array.slice(n);
      }
  
      return array.slice(0, n);
    });
  
    // Return the smallest number argument
    eleventyConfig.addFilter("min", (...numbers) => {
      return Math.min.apply(null, numbers);
    });
  
    eleventyConfig.addFilter("filterTagList", tags => {
      // should match the list in tags.njk
      return (tags || []).filter(tag => ["all", "nav", "post", "posts"].indexOf(tag) === -1);
    })
  
    // Create an array of all tags
    eleventyConfig.addCollection("tagList", function(collection) {
      let tagSet = new Set();
      collection.getAll().forEach(item => {
        (item.data.tags || []).forEach(tag => tagSet.add(tag));
      });
  
      return [...tagSet];
    });
  
    // Copy the `img` and `css` folders to the output
    eleventyConfig.addPassthroughCopy("img");
    eleventyConfig.addPassthroughCopy("css");
  
    // Customize Markdown library and settings:
    let markdownLibrary = markdownIt({
      html: true,
      breaks: true,
      linkify: true,
      typographer: true
    }).use(markdownItAnchor, {
      permalink: true,
      permalinkClass: "direct-link",
      permalinkSymbol: "#"
    }).use(markdownItAttribution, {
      removeMarker: false,
    }).use(markdownItAbbr);
    eleventyConfig.setLibrary("md", markdownLibrary);
  
    // Override Browsersync defaults (used only with --serve)
    eleventyConfig.setBrowserSyncConfig({
      callbacks: {
        ready: function(err, browserSync) {
          const content_404 = fs.readFileSync('_site/404.html');
  
          browserSync.addMiddleware("*", (req, res) => {
            // Provides the 404 content without redirect.
            res.writeHead(404, {"Content-Type": "text/html; charset=UTF-8"});
            res.write(content_404);
            res.end();
          });
        },
      },
      ui: false,
      ghostMode: false
    });
  
    return {
      // Control which files Eleventy will process
      // e.g.: *.md, *.njk, *.html, *.liquid
      templateFormats: [
        "md",
        "njk",
        "html",
        "liquid"
      ],
  
      // -----------------------------------------------------------------
      // If your site deploys to a subdirectory, change `pathPrefix`.
      // Don’t worry about leading and trailing slashes, we normalize these.
  
      // If you don’t have a subdirectory, use "" or "/" (they do the same thing)
      // This is only used for link URLs (it does not affect your file structure)
      // Best paired with the `url` filter: https://www.11ty.dev/docs/filters/url/
  
      // You can also pass this in on the command line using `--pathprefix`
  
      // Optional (default is shown)
      pathPrefix: "/",
      // -----------------------------------------------------------------
  
      // Pre-process *.md files with: (default: `liquid`)
      markdownTemplateEngine: "njk",
  
      // Pre-process *.html files with: (default: `liquid`)
      htmlTemplateEngine: "njk",
  
      // Opt-out of pre-processing global data JSON files: (default: `liquid`)
      dataTemplateEngine: false,
  
      // These are all optional (defaults are shown):
      dir: {
        input: ".",
        includes: "_includes",
        data: "_data",
        output: "_site"
      }
    };
  };
  