.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 mk = require("@traptitech/markdown-it-katex");
const anchor = require('markdown-it-anchor')
const pluginTOC = require('eleventy-plugin-toc')

const searchFilter = require("./filters/searchFilter");

module.exports = function(eleventyConfig) {
  // Add plugins
  eleventyConfig.addPlugin(pluginRss);
  eleventyConfig.addPlugin(pluginSyntaxHighlight, {
    init: function({ Prism }) {

      Prism.languages.console = Prism.languages.extend('markup', {});
      Prism.languages.terminal = Prism.languages.extend('markup', {});
  }
  });
  eleventyConfig.addPlugin(pluginNavigation);

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

  // Alias `layout: post` to `layout: layouts/post.njk`
  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);
  });

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

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

  eleventyConfig.addFilter("filterTagList", filterTagList)

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

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

  eleventyConfig.addCollection("projectList", function(collection) {
    let projectSet = new Set();
    collection.getAll().forEach(item => {
      let project = item.data.project;
      if (project) {
        projectSet.add(''+project)
      }
    });
    return [...projectSet].sort();
  });

  eleventyConfig.addCollection("journals", function(collection) {

    // Array of journal descriptors
    // A journal descriptor contains a posts array
    let journals = [];

    collection.getAll().forEach(post => {

      // Skip posts without journal keyword in frontmatter
      if (!post.data.journal) {
        return;
      }

      let journal = post.data.journal.toLowerCase();
      // Try to find journal descriptor
      let desc = journals.find(desc => desc.name === journal);

      // Create a journal descriptor if necessary
      if (!desc) {
        desc = {
          name: journal,
          project: post.data.project,
          posts: []
        };
        journals.push(desc);
      }

      // Add current post to descriptor
      desc.posts.push(post);

    });

    return journals;
  });

  eleventyConfig.addCollection("journalsPerProject", function(collection) {

    // create empty collection based on an object
    // Projects will be the keys
    // Echh project's value will be an array of journal descriptors
    // A journal descriptor contains a posts array
    let journalsPerProject = {};

    collection.getFilteredByTag('journal').forEach(post => {

      // Skip posts without journal keyword in frontmatter
      if (!post.data.journal) {
        return;
      }

      // Create Project key
      let project = post.data.project;
      if (!(project in journalsPerProject)) {
        journalsPerProject[project] = [];
      }

      let journal = post.data.journal.toLowerCase();;
      // Try to find journal descriptor
      let desc = journalsPerProject[project].find(desc => desc.name === journal);

      // Create a journal descriptor if necessary
      if (!desc) {
        desc = {
          name: journal,
          project: post.data.project,
          posts: []
        };
        journalsPerProject[project].push(desc);
      }

      // Add current post to descriptor
      desc.posts.push(post);

    });

    return journalsPerProject;
  });

  makeProjects = function(collection) {
    let projects = {};

    collection.getAllSorted().forEach(item => {
      let project = item.data.project;

      if (Array.isArray(projects[project])) {
          //  category array exists? Just push
          projects[project].push(item);
      } else {
          //  Otherwise create it and
          //  make `item` the first, uh, item.
          projects[project] = [item];
      }
    });

    return projects
  }

  eleventyConfig.addCollection("projects", makeProjects)

  // Copy the `img` and `css` folders to the output
  eleventyConfig.addPassthroughCopy("img");
  eleventyConfig.addPassthroughCopy("css");

  // Customize Markdown library and settings:
  let markdownLibrary = markdownIt({
    html: true,
    breaks: true,
    linkify: true
  }).use(anchor, {
    permalink: anchor.permalink.headerLink()
  }).use(mk,
    {"blockClass": "math-block", "errorColor" : " #cc0000"}
  );

  eleventyConfig.setLibrary("md", markdownLibrary);

  // Override Browsersync defaults (used only with --serve)
  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.writeHead(404, {"Content-Type": "text/html; charset=UTF-8"});
          res.write(content_404);
          res.end();
        });
      },
    },
    ui: false,
    ghostMode: false
  });

  eleventyConfig.addFilter("log", (...args) => {
    console.log(...args);
    return args;
  });

  eleventyConfig.addFilter("filterdash", (s) => {
    if (s) {
      return s.replace(/[\-_]/g, ' ');
    } else {
      return 'unknown string';
    }
  });


  eleventyConfig.addPassthroughCopy({"_data/img": "/img/meta"});

  eleventyConfig.addPassthroughCopy({"logs/img": "/img/posts"});

  eleventyConfig.addPassthroughCopy({
    "node_modules/elasticlunr/release/elasticlunr.min.js": "js/elasticlunr.min.js",
  });

  eleventyConfig.addPlugin(pluginTOC, {
    tags: ['h2', 'h3'],
    wrapper: 'div'
  });

  // add search
  eleventyConfig.addFilter("search", searchFilter);

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

    // -----------------------------------------------------------------
    // If your site deploys to a subdirectory, change `pathPrefix`.
    // Don’t worry about leading and trailing slashes, we normalize these.

    // 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`

    // Optional (default is shown)
    pathPrefix: "/",
    // -----------------------------------------------------------------

    // Pre-process *.md files with: (default: `liquid`)
    // markdownTemplateEngine: "njk",
    markdownTemplateEngine: false, // we don't want to preprocess markdown, because it will crash on {{ }} tags in code blocks

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

    // Opt-out of pre-processing global data JSON files: (default: `liquid`)
    dataTemplateEngine: false,

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