Eleventy example config (not finished)

.eleventy.js

const { DateTime } = require("luxon");

const fs = require("fs");

const pluginRss = require("@11ty/eleventy-plugin-rss");
const pluginNavigation = require("@11ty/eleventy-navigation");

const markdownIt = require("markdown-it");
const markdownItAnchor = require("markdown-it-anchor");
const markdownItAttrs = require("markdown-it-attrs");
const markdownItFootnotes = require('markdown-it-footnote');
const markdownItPlantuml = require('markdown-it-plantuml');

const { execSync } = require("child_process");

module.exports = function(eleventyConfig) {

  eleventyConfig.addPlugin(pluginRss);
  eleventyConfig.addPlugin(pluginNavigation);

  // Customize Markdown library and settings:
  let markdownLibrary = markdownIt({
    html: true,
    breaks: false,
    linkify: true,
    highlight: function(str, lang, extra) {
      var result = "empty";

      var cmd = `chroma -f html -l ${lang} \
        --style="autumn" \
        --html-only \
        --html-prevent-surrounding-pre \
        --html-highlight=${extra}
      `;

      result = execSync(cmd, { input: str }).toString();
      // console.log('result -> ', result.toString())

      // remove \n at start and end of code blocks
      result = result.replace("\n<table class=\"lntable\">", '<table class="lntable">')
      result = result.replace("<table class=\"lntable\"><tr><td class=\"lntd\">\n(\s)*", "<table class=\"lntable\"><tr><td class=\"lntd\">")
      result = result.replace("</td></tr></table>\n", "</td></tr></table>")

      // console.log('result after-> ', result.toString())

      return result;
    },
  }).use(markdownItAnchor, {
    permalink: markdownItAnchor.permalink.ariaHidden({
      placement: "after",
      class: "direct-link",
      symbol: "#",
      level: [1,2,3,4,5],
    }),
    slugify: eleventyConfig.getFilter("slug")
  }).use(markdownItAttrs, {
  }).use(markdownItFootnotes, {
  }).use(markdownItPlantuml, {
    openMarker: '```plantuml',
    closeMarker: '```',
    render: function(tokens, idx) {
      var imageUrl = tokens[idx].attrGet('src')
      return `<div class="uml-wrapper"><img class="uml" src="${imageUrl}"></img></div>`
    }
  });

  eleventyConfig.setLibrary("md", markdownLibrary);

  // Override Browsersync defaults (used only with --serve)
  eleventyConfig.setBrowserSyncConfig({
    callbacks: {
      ready: function(err, browserSync) {
        const content_404 = fs.readFileSync('build/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
  });

  // https://www.11ty.dev/docs/data-deep-merge/
  eleventyConfig.setDataDeepMerge(true);

  eleventyConfig.addLayoutAlias("post", "post.njk");
  eleventyConfig.addLayoutAlias("application", "application.njk");

  eleventyConfig.addCollection("posts", function(collectionApi) {
    return collectionApi.getFilteredByGlob("site/posts/*.md");
  });

  eleventyConfig.addWatchTarget('./assets/')

  // eleventyConfig.addPassthroughCopy("img");
  // eleventyConfig.addPassthroughCopy("assets");

  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');
  });

  // Return the smallest number argument
  eleventyConfig.addFilter("min", (...numbers) => {
    return Math.min.apply(null, numbers);
  });

  // Get the first `n` elements of a collection.
  eleventyConfig.addFilter("head", (array, n) => {
    if(!Array.isArray(array) || array.length === 0) {
      return [];
    }
    if( n < 0 ) {
      return array.slice(n);
    }

    return array.slice(0, n);
  });

  function withoutBlacklistedTags(tags) {
    return (tags || []).filter(tag => ["all", "nav", "post", "posts"].indexOf(tag) === -1);
  }

  eleventyConfig.addFilter("withoutBlacklistedTags", withoutBlacklistedTags)

  // Create an array of all tags
  eleventyConfig.addCollection("tags", function(collection) {
    let tagSet = new Set();
    collection.getAll().forEach(item => {
      (item.data.tags || []).forEach(tag => tagSet.add(tag));
    });

    return withoutBlacklistedTags([...tagSet]);
  });

  eleventyConfig.on("afterBuild", function() {
    fs.readFile(".revision", "utf-8", (err, data) => {
      if (err) {
        console.log(".revision file read error:", err)
        return
      } else {
        var last_revision = parseInt(data)
        var new_revision = last_revision + 1

        fs.writeFile('.revision', String(new_revision), err => {
          if (err) {
            console.log(".revision file write error:", err)
            return
          }
        })
      }
    })
  })

  return {
    templateFormats: [
      "md",
      "njk",
      "html",
    ],

    markdownTemplateEngine: "njk",
    htmlTemplateEngine: "njk",
    dataTemplateEngine: false,

    // passthroughFileCopy: true,

    dir: {
      input: "./site/",
      output: "./build/",
      includes: "includes",
      layouts: "layouts",
      data: "data",
    }
  }
}