var $ = document.querySelector.bind(document)

var state = {
  theme,
  raw,
  content,
  compiler,
  html: '',
  markdown: '',
  toc: '',
  interval: null,
  ms: 1000,
}

chrome.runtime.onMessage.addListener((req, sender, sendResponse) => {
  if (req.message === 'reload') {
    location.reload(true)
  }
  else if (req.message === 'theme') {
    state.theme = req.theme
    m.redraw()
  }
  else if (req.message === 'raw') {
    state.raw = req.raw
    m.redraw()
  }
  else if (req.message === 'autoreload') {
    clearInterval(state.interval)
  }
})

var oncreate = {
  markdown: () => {
    scroll()
  },
  html: () => {
    scroll()

    if (state.content.toc && !state.toc) {
      state.toc = toc()
      m.redraw()
    }

    setTimeout(() => Prism.highlightAll(), 20)

    anchors()
  }
}

function mount () {
  $('pre').style.display = 'none'
  var md = $('pre').innerText

  m.mount($('body'), {
    oninit: () => {
      state.markdown = md
      chrome.runtime.sendMessage({
        message: 'markdown',
        compiler: state.compiler,
        markdown: state.markdown
      }, (res) => {
        state.html = state.content.emoji ? emojinator(res.html) : res.html
        m.redraw()
      })
    },
    view: () => {
      var dom = []

      if (state.raw) {
        dom.push(m('pre#_markdown', {oncreate: oncreate.markdown}, state.markdown))
        $('body').classList.remove('_toc-left', '_toc-right')
      }
      else {
        if (state.theme) {
          dom.push(m('link#_theme', {
            rel: 'stylesheet', type: 'text/css',
            href: state.theme.url,
          }))
        }
        if (state.html) {
          dom.push(m('#_html', {oncreate: oncreate.html,
            class: /github(-dark)?/.test(state.theme.name) ? 'markdown-body' : 'markdown-theme'},
            m.trust(state.html)
          ))
          if (state.content.toc && state.toc) {
            dom.push(m.trust(state.toc))
            $('body').classList.add('_toc-left')
          }
          if (state.content.mathjax) {
            dom.push(m('script', {type: 'text/x-mathjax-config'}, mathjax))
            dom.push(m('script', {
              src: 'https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.2/MathJax.js'
            }))
          }
        }
      }

      return (dom.length ? dom : m('div'))
    }
  })
}

function scroll () {
  function race (done) {
    var images = Array.from(document.querySelectorAll('img'))
    if (!images.length) {
      done()
    }
    var loaded = 0
    images.forEach((img) => {
      img.addEventListener('load', () => {
        if (++loaded === images.length) {
          done()
        }
      }, {once: true})
    })
    setTimeout(done, 100)
  }
  function init () {
    if (state.content.scroll) {
      try {
        var key = 'md-' + location.origin + location.pathname
        $('body').scrollTop = parseInt(localStorage.getItem(key))
        var timeout = null
        window.addEventListener('scroll', () => {
          clearTimeout(timeout)
          timeout = setTimeout(() => {
            localStorage.setItem(key, $('body').scrollTop)
          }, 100)
        })
      }
      catch (err) {
        var key = 'md-' + location.origin + location.pathname
        chrome.storage.local.get(key, (res) => {
          $('body').scrollTop = parseInt(res[key])
        })
        var timeout = null
        window.addEventListener('scroll', () => {
          clearTimeout(timeout)
          timeout = setTimeout(() => {
            chrome.storage.local.set({[key]: $('body').scrollTop})
          }, 100)
        })
      }
    }
    else if (location.hash && $(location.hash)) {
      $('body').scrollTop = $(location.hash).offsetTop
    }
  }
  var loaded
  race(() => {
    if (!loaded) {
      init()
      loaded = true
    }
  })
}

function anchors () {
  Array.from($('#_html').childNodes)
  .filter((node) => /h[1-6]/i.test(node.tagName))
  .forEach((node) => {
    var a = document.createElement('a')
    a.className = 'anchor'
    a.name = node.id
    a.href = '#' + node.id
    a.innerHTML = '<span class="octicon octicon-link"></span>'
    node.prepend(a)
  })
}

var toc = (
  link = (header) => '<a href="#' + header.id + '">' + header.title + '</a>') =>
  Array.from($('#_html').childNodes)
  .filter((node) => /h[1-6]/i.test(node.tagName))
  .map((node) => ({
    id: node.getAttribute('id'),
    level: parseInt(node.tagName.replace('H', '')),
    title: node.innerText
  }))
  .reduce((html, header, index, headers) => {
    if (index) {
      var prev = headers[index - 1]
    }
    if (!index || prev.level === header.level) {
      html += link(header)
    }
    else if (prev.level > header.level) {
      while (prev.level-- > header.level) {
        html += '</div>'
      }
      html += link(header)
    }
    else if (prev.level < header.level) {
      while (prev.level++ < header.level) {
        html += '<div id="_ul">'
      }
      html += link(header)
    }
    return html
  }, '<div id="_toc"><div id="_ul">') + '</div></div>'

if (document.readyState === 'complete') {
  mount()
}
else {
  var timeout = setInterval(() => {
    if (document.readyState === 'complete') {
      clearInterval(timeout)
      mount()
    }
  }, 0)
}

if (state.content.autoreload) {
  ;(() => {
    var initial = ''

    var xhr = new XMLHttpRequest()
    xhr.onreadystatechange = () => {
      if (xhr.readyState === 4) {
        if (!initial) {
          initial = xhr.responseText
        }
        else if (initial !== xhr.responseText) {
          location.reload(true)
        }
      }
    }

    var get = () => {
      xhr.open('GET', location.href + '?preventCache=' + Date.now(), true)
      try {
        xhr.send()
      }
      catch (err) {
        console.error(err)
        clearInterval(state.interval)
      }
    }

    get()
    state.interval = setInterval(get, state.ms)
  })()
}

var mathjax = `
  // TeX-AMS_HTML
  MathJax.Hub.Config({
    jax: [
      'input/TeX',
      'output/HTML-CSS',
      'output/PreviewHTML',
    ],
    extensions: [
      'tex2jax.js',
      'AssistiveMML.js',
      'a11y/accessibility-menu.js',
    ],
    TeX: {
      extensions: [
        'AMSmath.js',
        'AMSsymbols.js',
        'noErrors.js',
        'noUndefined.js',
      ]
    },
    tex2jax: {
      inlineMath: [
        ['$', '$'],
        ['\\\\(', '\\\\)'],
      ],
      displayMath: [
        ['$$', '$$'],
        ['\\\\[', '\\\\]'],
      ],
      processEscapes: true
    },
    showMathMenu: false,
    showProcessingMessages: false,
    messageStyle: 'none',
    skipStartupTypeset: true, // disable initial rendering
    positionToHash: false
  })
  // set specific container to render, can be delayed too
  MathJax.Hub.Queue(
    ['Typeset', MathJax.Hub, '_html']
  )
`