const { DateTime } = require('luxon')
const fs = require('fs')
const markdownIt = require('markdown-it')
const markdownItAnchor = require('markdown-it-anchor')

module.exports = function(eleventyConfig) {

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

  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)
  })

  eleventyConfig.addFilter('filterTagList', tags => {
    // should match the list in tags.njk
    return (tags || []).filter(tag => ['all', 'nav', 'post', 'posts'].indexOf(tag) === -1)
  })

  // Convert text to hex
  eleventyConfig.addFilter('toHex', (str) => {
    let hex = ''
    for(let i=0; i<str.length; i++){
      let h = str.codePointAt(i).toString(16)
      if(h.length===1) h='0'+h
      hex += h + ' '
      if( h.length>4 ) i++
    } return hex.trim()
  })

  // Fold lines
  eleventyConfig.addFilter('fold', (str, size) => {
    // https://stackoverflow.com/a/29202760/3006854
    const numChunks = Math.ceil(str.length/size)
    const chunks = new Array(numChunks)
    for (let i = 0, o = 0; i < numChunks; ++i, o += size)
      chunks[i] = str.substr(o, size)
    return chunks.join('\n')
  })

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

  // Customize Markdown library and settings:
  let markdownLibrary = markdownIt({
    html: true,
    breaks: true,
    linkify: true
  })//.use(markdownItAnchor, {
  //   permalink: true,
  //   permalinkClass: "direct-link",
  //   permalinkSymbol: "#"
  // })
  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
  })

  return {
    // Control which files Eleventy will process
    // e.g.: *.md, *.njk, *.html, *.liquid
    templateFormats: [
      "md",
      "njk",
      'html',
      'liquid',
      'css',
      'png',
      'webp',
      'jpg',
      'gif',
      'js',
      'crt',
      'pem',
      'ttf',
      'webmanifest',
    ],

    // -----------------------------------------------------------------
    // 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',

    // 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: '_src',
      includes: '_includes',
      data: '_data',
      output: '_site'
    }
  }
}