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 Image = require("@11ty/eleventy-img");
const markdownIt = require("markdown-it");
const markdownItAnchor = require("markdown-it-anchor");
const markdownItAttrs = require("markdown-it-attrs");

function hyphenize(input) {
  return input.replace(/[^\w- ]/, "").replace(/[_ ]/, "-").toLowerCase();
}

module.exports = function(eleventyConfig) {
  eleventyConfig.addPlugin(pluginRss);
  eleventyConfig.addPlugin(pluginSyntaxHighlight);
  eleventyConfig.addPlugin(pluginNavigation);

  eleventyConfig.setDataDeepMerge(true);

  //
  // Filters
  //

  eleventyConfig.addFilter("readableDate", dateObj => {
    return DateTime.fromJSDate(dateObj, {zone: 'utc'}).toFormat("dd LLL yyyy");
  });
  eleventyConfig.addFilter('htmlDateString', (dateObj) => {
    return DateTime.fromJSDate(dateObj, {zone: 'utc'}).toFormat('yyyy-LL-dd');
  });
  eleventyConfig.addFilter("head", (array, n) => n < 0 ? array.slice(n) : array.slice(0, n));
  eleventyConfig.addFilter("min", (...numbers) => Math.min.apply(null, numbers));

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

  // Build collections for the top and bottom navigation - the first one
  // contains the main sites and the latter contains legal pages.
  eleventyConfig.addCollection("topNavigation", (collection) => {
    return collection.getAll().filter(item => !(item.data.tags || []).includes('legal'));
  });
  eleventyConfig.addCollection("bottomNavigation", (collection) => {
    return collection.getAll().filter(item => (item.data.tags || []).includes('legal'));
  });

  //
  // Widgets
  //

  eleventyConfig.addPairedShortcode("section", (content, inverted) => `
<section class="page-section${inverted ? ' inverse' : ''}">
${content}
</section>
  `);

  eleventyConfig.addPairedShortcode("tabs", (content) => `
<div class="tabs-widget">
${content}
</div>
  `);
  eleventyConfig.addPairedShortcode("tab", (content, title) => {
    const hyphenizedTitle = hyphenize(title);
    return `
<div id="${hyphenizedTitle}" class="tab">
${content}
</div>
<a href="#${hyphenizedTitle}" rel="tab">${title}</a>
    `;
  });

  eleventyConfig.addPairedAsyncShortcode("banner", async (content, title, backgroundSource, backgroundAlt) => {
    const backgroundMetadata = await Image(backgroundSource, {
      widths: [1200, 1980, 4000],
      formats: ["avif", "webp", "jpeg"],
      urlPath: "/assets/img",
      outputDir: "./_site/assets/img",
    });
    const backgroundHTML = Image.generateHTML(backgroundMetadata, {
      alt: backgroundAlt,
      sizes: "100vw",
      loading: "lazy",
      decoding: "async",
      whitespaceMode: "inline",
    });

    return `
<div class="page-banner">
<div class="background">${backgroundHTML}</div>
<div class="content">
${ title ? '<div class="title">' + title + '</div>' : '' }
${
  // The '\n's here are required so that markdwon still gets rendered in the
  // content block:
  content.trim() ? '<div>\n' + content + '\n</div>' : ''
}
</div>
</div>
    `;
  });

  //
  // Templating
  //

  eleventyConfig.addLayoutAlias("page", "layouts/page.njk");
  eleventyConfig.addLayoutAlias("post", "layouts/post.njk");

  let markdownLibrary = markdownIt({
    html: true,
    breaks: false,
    linkify: true
  }).use(markdownItAnchor).use(markdownItAttrs);
  eleventyConfig.setLibrary("md", markdownLibrary);

  //
  // Build settings
  //

  eleventyConfig.addPassthroughCopy("assets");

  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
  });

  //
  // Other settings
  //

  return {
    templateFormats: [
      "md",
      "njk",
      "html",
      "liquid"
    ],

    markdownTemplateEngine: "njk",
    htmlTemplateEngine: "njk",
    dataTemplateEngine: false,
  };
};