.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 markdownIt = require("markdown-it");
const markdownItAnchor = require("markdown-it-anchor");
const markdownItAttrs = require("markdown-it-attrs");

module.exports = function (eleventyConfig) {
  eleventyConfig.addPlugin(pluginRss);
  eleventyConfig.addPlugin(pluginSyntaxHighlight);
  eleventyConfig.addPlugin(pluginNavigation);
  eleventyConfig.setDataDeepMerge(true);
  eleventyConfig.addShortcode("excerpt", (article) => extractExcerpt(article));

  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("./src/_11ty/getTagList"));
  eleventyConfig.addPassthroughCopy("./src/img");
  eleventyConfig.addPassthroughCopy("./src/css");

  /* Markdown Overrides */
  let markdownLibrary = markdownIt({
    html: true,
    breaks: true,
    linkify: true,
  })
    .use(markdownItAnchor, {
      level: [1, 2],
      permalink: true,
      permalinkClass: "direct-link",
      permalinkSymbol: "#",
    })
    .use(markdownItAttrs);
  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.io/docs/filters/url/

    // You can also pass this in on the command line using `--pathprefix`
    // pathPrefix: "/",

    markdownTemplateEngine: "liquid",
    htmlTemplateEngine: "njk",
    dataTemplateEngine: "njk",
    dir: {
      input: "./src",
      includes: "_includes",
      data: "_data",
      output: "_site",
    },
  };
};

function extractExcerpt(article) {
  if (!article.hasOwnProperty("templateContent")) {
    console.warn(
      'Failed to extract excerpt: Document has no property "templateContent".'
    );
    return null;
  }

  let excerpt = null;
  const content = article.templateContent;

  // The start and end separators to identify the excerpt
  const separatorsList = [
    { start: "<!-- summary -->", end: "<!-- /summary -->" },
    { start: "<p>", end: "</p>" },
  ];

  separatorsList.some((separators) => {
    const startPosition = content.indexOf(separators.start);
    const endPosition = content.indexOf(separators.end);

    if (startPosition !== -1 && endPosition !== -1) {
      excerpt = content
        .substring(startPosition + separators.start.length, endPosition)
        .trim();
      return true; // Exit out of array loop on first match
    }
  });

  return excerpt;
}