.eleventy.js

const htmlmin = require("html-minifier");
const markdownIt = require('markdown-it');
const pluginRss = require("@11ty/eleventy-plugin-rss");
const { DateTime } = require("luxon");

module.exports = function (eleventyConfig) {
  // PLUGINS
  eleventyConfig.addPlugin(pluginRss);
  eleventyConfig.setDataDeepMerge(true);
  // shortcode to render markdown from string => {{ STRING | markdown | safe }}
  eleventyConfig.addFilter('markdown', function(value) {
    let markdown = require('markdown-it')({
      html: true
    });
    return markdown.render(value);
  });

  // rebuild on CSS changes
  eleventyConfig.addWatchTarget('./src/_includes/css/');

  // Markdown
  eleventyConfig.setLibrary(
    'md',
    markdownIt({
      html: true,
      breaks: true,
      linkify: true,
      typographer: true
    })
  )

  //create collections
  eleventyConfig.addCollection('sections', async (collection) => {
    return collection.getFilteredByGlob('./src/sections/*.md');
  });

  // STATIC FILES
  eleventyConfig.addPassthroughCopy({ './src/static/': '/' });


  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":
              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];
  });

  // TRANSFORM -- Minify HTML Output
  eleventyConfig.addTransform("htmlmin", function(content, outputPath) {
    if( outputPath && outputPath.endsWith(".html") ) {
      let minified = htmlmin.minify(content, {
        useShortDoctype: true,
        removeComments: true,
        collapseWhitespace: true
      });
      return minified;
    }
    return content;
  });

  return {
    dir: {
      input: 'src',
      output: 'public',
      data: './_data',
      includes: './_includes',
      layouts: './_layouts'
    },
    templateFormats: [
      'md',
      'njk',
      '11ty.js'
    ],
    htmlTemplateEngine: 'njk'
  };
};