const { DateTime } = require("luxon");
const fs = require("fs");
const pluginNavigation = require("@11ty/eleventy-navigation");
const pluginRss = require("@11ty/eleventy-plugin-rss");
const pluginSyntaxHighlight = require("@11ty/eleventy-plugin-syntaxhighlight");
const pluginAncestry = require("@tigersway/eleventy-plugin-ancestry");
const metagen = require('eleventy-plugin-metagen');
const pluginTOC = require('eleventy-plugin-nesting-toc');
const markdownIt = require("markdown-it");
const markdownItAnchor = require("markdown-it-anchor");
const markdownItPlantUML = require("markdown-it-plantuml");
const elasticlunr = require("elasticlunr");


module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(pluginNavigation);
  eleventyConfig.addPlugin(pluginRss);
  eleventyConfig.addPlugin(pluginSyntaxHighlight);
  eleventyConfig.addPlugin(pluginAncestry);
  eleventyConfig.addPlugin(metagen);
  eleventyConfig.addPlugin(pluginTOC, {
    tags: ['h1', 'h2', 'h3']
  });

  eleventyConfig.setDataDeepMerge(true);

  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');
  });

  // Remove trailing # in automatic generated toc, because of
  // anchors added at the end of the titles.
  eleventyConfig.addFilter('stripHash', (toc) => {
    return toc.replace(/ #\<\/a\>/g, "</a>");
  });

  // 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);
  });

  // Get the lowest in a list of numbers.
  eleventyConfig.addFilter("min", (...numbers) => {
    return Math.min.apply(null, numbers);
  });

  // Build a search index
  eleventyConfig.addFilter("search", (collection) => {
    // What fields we'd like our index to consist of
    // TODO: remove html tags from content
    var index = elasticlunr(function () {
      this.addField("title");
      this.addField("content");
      this.setRef("id");
    });

    // loop through each page and add it to the index
    collection.forEach((page) => {
      index.addDoc({
        id: page.url,
        title: page.template.frontMatter.data.title,
        content: page.template.inputContent,
      });
    });

    return index.toJSON();
  });

  eleventyConfig.addPassthroughCopy("img");
  eleventyConfig.addPassthroughCopy("css");
  eleventyConfig.addPassthroughCopy("js");

  /* Markdown Overrides */
  let markdownLibrary = markdownIt({
    html: true,
    breaks: false,
    linkify: true
  }).use(markdownItAnchor, {
    permalink: true,
    permalinkClass: "direct-link",
    permalinkSymbol: "#"
  }).use(markdownItPlantUML, {
  });
  eleventyConfig.setLibrary("md", markdownLibrary);

  // Browsersync Overrides
  eleventyConfig.setBrowserSyncConfig({
    callbacks: {
      ready: function(err, browserSync) {
        const content_404 = fs.readFileSync('_dist/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.dev/docs/filters/url/

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

    markdownTemplateEngine: "liquid",
    htmlTemplateEngine: "njk",
    dataTemplateEngine: "njk",

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