eleventy.config.js

const { DateTime } = require("luxon");
const markdownItAnchor = require("markdown-it-anchor");
const TeXZilla = require("texzilla");
const pluginRss = require("@11ty/eleventy-plugin-rss");
const pluginSyntaxHighlight = require("@11ty/eleventy-plugin-syntaxhighlight");
const pluginBundle = require("@11ty/eleventy-plugin-bundle");
const pluginNavigation = require("@11ty/eleventy-navigation");
const { EleventyHtmlBasePlugin } = require("@11ty/eleventy");

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

module.exports = function(eleventyConfig) {
  // Copy the contents of the `public` folder to the output folder
  // For example, `./public/css/` ends up in `_site/css/`
  eleventyConfig.addPassthroughCopy({
	"./public/": "/",
	"./node_modules/prismjs/themes/prism-okaidia.css": "/css/prism-okaidia.css"
  });

  // Run Eleventy when these files change:
  // https://www.11ty.dev/docs/watch-serve/#add-your-own-watch-targets

  // Watch content images for the image pipeline.
  eleventyConfig.addWatchTarget("content/**/*.{svg,webp,png,jpeg}");
  eleventyConfig.addFilter("math", (latex) => {
    return TeXZilla.toMathMLString(latex, true, false, false);
  });
  // App plugins
  eleventyConfig.addPlugin(pluginDrafts);
  eleventyConfig.addPlugin(pluginImages);

  // Official plugins
  eleventyConfig.addPlugin(pluginRss);
  eleventyConfig.addPlugin(pluginSyntaxHighlight, {
	preAttributes: { tabindex: 0 }
  });
  eleventyConfig.addPlugin(pluginNavigation);
  eleventyConfig.addPlugin(EleventyHtmlBasePlugin);
  eleventyConfig.addPlugin(pluginBundle);

  // Filters
  eleventyConfig.addFilter("readableDate", (dateObj, format, zone) => {
	// Formatting tokens for Luxon: https://moment.github.io/luxon/#/formatting?id=table-of-tokens
	return DateTime.fromJSDate(dateObj, { zone: zone || "utc" }).toFormat(format || "dd LLLL yyyy");
  });

  eleventyConfig.addFilter('htmlDateString', (dateObj) => {
	// dateObj input: https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#valid-date-string
	return DateTime.fromJSDate(dateObj, {zone: 'utc'}).toFormat('yyyy-LL-dd');
  });

  // 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);
  });

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

  // Customize Markdown library settings:
  eleventyConfig.amendLibrary("md", mdLib => {
	mdLib.use(markdownItAnchor, {
	  permalink: markdownItAnchor.permalink.ariaHidden({
		placement: "after",
		class: "header-anchor",
		symbol: "#",
		ariaHidden: false,
	  }),
	  level: [1,2,3,4],
	  slugify: eleventyConfig.getFilter("slugify")
	});
  });

  // Features to make your build faster (when you need them)

  // If your passthrough copy gets heavy and cumbersome, add this line
  // to emulate the file copy on the dev server. Learn more:
  // https://www.11ty.dev/docs/copy/#emulate-passthrough-copy-during-serve

  // eleventyConfig.setServerPassthroughCopyBehavior("passthrough");

  return {
	// Control which files Eleventy will process
	// e.g.: *.md, *.njk, *.html, *.liquid
	templateFormats: [
	  "md",
	  "njk",
	  "html",
	  "liquid",
	],

	// Pre-process *.md files with: (default: `liquid`)
	markdownTemplateEngine: "njk",

	// Pre-process *.html files with: (default: `liquid`)
	htmlTemplateEngine: "njk",

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

	// -----------------------------------------------------------------
	// Optional items:
	// -----------------------------------------------------------------

	// If your site deploys to a subdirectory, change `pathPrefix`.
	// Read more: https://www.11ty.dev/docs/config/#deploy-to-a-subdirectory-with-a-path-prefix

	// When paired with the HTML <base> plugin https://www.11ty.dev/docs/plugins/html-base/
	// it will transform any absolute URLs in your HTML to include this
	// folder name and does **not** affect where things go in the output folder.
	pathPrefix: "/",
  };
};