.eleventy.js

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 pluginBundle = require("@11ty/eleventy-plugin-bundle");
const markdownIt = require("markdown-it");
const markdownItAnchor = require("markdown-it-anchor");

const pluginDrafts = require("./eleventy.config.drafts.js");

module.exports = function (eleventyConfig) {
  eleventyConfig.addPlugin(pluginRss);
  eleventyConfig.addPlugin(pluginSyntaxHighlight);
  eleventyConfig.addPlugin(pluginNavigation);
  eleventyConfig.addPlugin(pluginBundle);

  // App plugins
  eleventyConfig.addPlugin(pluginDrafts);

  eleventyConfig.setDataDeepMerge(true);

  eleventyConfig.addLayoutAlias("post", "layouts/post.njk");

  eleventyConfig.addFilter("readableDate", dateObj => {
    return DateTime.fromJSDate(dateObj, { zone: 'utc' }).toLocaleString(DateTime.DATE_FULL)
  });

  // 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);
  });

  // Return all the tags used in a collection
  eleventyConfig.addFilter("getAllTags", collection => {
    let tagSet = new Set();
    for (let item of collection) {
      (item.data.tags || []).forEach(tag => tagSet.add(tag));
    }
    return Array.from(tagSet)
  });

  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":
              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");

  /* Markdown Overrides */
  let markdownLibrary = markdownIt({
    html: true,
    breaks: false,
    linkify: true
  }).use(markdownItAnchor, {
    permalink: false,
    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"
    ],

    // 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: "/test-pages/",

    markdownTemplateEngine: "liquid",
    htmlTemplateEngine: "njk",
    dataTemplateEngine: "njk",

    // These are all optional, defaults are shown:
    dir: {
      input: "content",
      includes: "../_includes",
      data: "../_data",
      output: "_site"
    }
  };
};