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");
  
  module.exports = function(eleventyConfig) {
    eleventyConfig.addPlugin(pluginRss);
    eleventyConfig.addPlugin(pluginSyntaxHighlight);
    eleventyConfig.addPlugin(pluginNavigation);
  
    eleventyConfig.setDataDeepMerge(true);
  
    eleventyConfig.addLayoutAlias("post", "layouts/post.njk");
    eleventyConfig.addLayoutAlias("blog", "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.addFilter("min", (...numbers) => {
      return Math.min.apply(null, numbers);
    });
  
    eleventyConfig.addCollection("tagList", function(collection) {
      let tagSet = new Set();
      collection.getAll().forEach(function(item) {
        if( "tags" in item.data ) {
          let tags = item.data.tags;
  
          tags = tags.filter(function(item) {
            switch(item) {
              // this list should match the `filter` list in tags.njk
              case "all":
              case "nav":
              case "post":
              case "posts":
              case "blog":
                return false;
            }
  
            return true;
          });
  
          for (const tag of tags) {
            tagSet.add(tag);
          }
        }
      });
  
      // returning an array in addCollection works in Eleventy 0.5.3
      return [...tagSet];
    });
  
    eleventyConfig.addPassthroughCopy("img");
    eleventyConfig.addPassthroughCopy("css");
  
    /* Markdown Overrides */
    let markdownLibrary = markdownIt({
      html: true,
      breaks: true,
      linkify: true
    }).use(markdownItAnchor, {
      permalink: true,
      permalinkClass: "direct-link",
      permalinkSymbol: "#"
    });
    eleventyConfig.setLibrary("md", markdownLibrary);
  
    // Browsersync Overrides
    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();
          });
        },
      },
      ui: false,
      ghostMode: false
    });
  
    return {
      templateFormats: [
        "md",
        "njk",
        "html",
        "liquid",
        "yml"
      ],
  
      // If your site lives in a different subdirectory, change this.
      // Leading or trailing slashes are all normalized away, so don’t worry about those.
  
      // 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`
      // pathPrefix: "/",
  
      markdownTemplateEngine: "liquid",
      htmlTemplateEngine: "njk",
      dataTemplateEngine: "njk",
  
      // These are all optional, defaults are shown:
      dir: {
        input: ".",
        includes: "_includes",
        data: "_data",
        output: "_site"
      }
    };
  };
  