text: const { DateTime } = require("luxon");
  const fs = require("fs");
  const pluginRss = require("@11ty/eleventy-plugin-rss");
  const pluginSyntaxHighlight = require("@11ty/eleventy-plugin-syntaxhighlight");
  
  module.exports = function(eleventyConfig) {
    eleventyConfig.addPlugin(pluginRss);
    eleventyConfig.addPlugin(pluginSyntaxHighlight);
    eleventyConfig.setDataDeepMerge(true);
  
    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);
    });
  
    eleventyConfig.addCollection("tagList", require("./_11ty/getTagList"));
  
    eleventyConfig.addPassthroughCopy("img");
    eleventyConfig.addPassthroughCopy("css");
    eleventyConfig.addPassthroughCopy("js");
    eleventyConfig.addPassthroughCopy("_redirects");
  
    /* Markdown Plugins */
    let markdownIt = require("markdown-it");
    let markdownItAnchor = require("markdown-it-anchor");
    let options = {
      html: true,
      breaks: true,
      linkify: true
    };
    let opts = {
      permalink: true,
      permalinkClass: "direct-link",
      permalinkSymbol: "#"
    };
  
    eleventyConfig.setLibrary("md", markdownIt(options)
      .use(markdownItAnchor, opts)
    );
  
    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.write(content_404);
            res.end();
          });
        }
      }
    });
  
    return {
      templateFormats: [
        "md",
        "njk",
        "html",
        "liquid"
      ],
  
      // If your site lives in a different subdirectory, change this.
      // Leading or trailing slashes are all normalized away, so don’t worry about it.
      // If you don’t have a subdirectory, use "" or "/" (they do the same thing)
      // This is only used for URLs (it does not affect your file structure)
      pathPrefix: "/",
  
      markdownTemplateEngine: "liquid",
      htmlTemplateEngine: "njk",
      dataTemplateEngine: "njk",
      passthroughFileCopy: true,
      dir: {
        input: ".",
        includes: "_includes",
        data: "_data",
        output: "_site"
      }
    };
  };
  