(function () {
  let app = document.getElementById('app')

  function httpGet (url) {
    let request = new XMLHttpRequest()
    return new Promise(function (resolve, reject) {
      request.onreadystatechange = function () {
        if (this.readyState === 4) {
          if (this.status === 200) {
            resolve(this.responseText)
          } else if (this.response == null && this.status === 0) {
            reject(new Error('The status server appears to be offile.'))
          }
        }
      }

      request.open("GET", url, true)
      request.send(null)
    })
  }

  function bytesToSize (bytes) {
    let sizes = ['Bytes', 'KB', 'MB', 'GB', 'TB']
    if (bytes == 0) return '0 Byte'
    let i = parseInt(Math.floor(Math.log(bytes) / Math.log(1024)))
    return Math.round(bytes / Math.pow(1024, i), 2) + ' ' + sizes[i]
  }

  // Add a zero in front of single-digit numbers
  function zf (v) {
    if (v > 9) {
      return '' + v
    } else {
      return '0' + v
    }
  }

  // Convert seconds into years days hours minutes seconds(.milliseconds)
  function readableTime (timems, ignoreMs) {
    var time = timems | 0
    var ms = ignoreMs ? '' : '.' + zf((timems * 100) % 100 | 0)
    if (time < 60) return zf(time) + ms + 's'
    else if (time < 3600) return zf(time / 60 | 0) + 'm ' + zf(time % 60) + ms + 's'
    else if (time < 86400) return zf(time / 3600 | 0) + 'h ' + zf((time % 3600) / 60 | 0) + 'm ' + zf((time % 3600) % 60) + ms + 's'
    else if (time < 31536000) return (time / 86400 | 0) + 'd ' + zf((time % 86400) / 3600 | 0) + 'h ' + zf((time % 3600) / 60 | 0) + 'm ' + zf((time % 3600) % 60) + 's'
    else return (time / 31536000 | 0) + 'y ' + zf((time % 31536000) / 86400 | 0) + 'd ' + zf((time % 86400) / 3600 | 0) + 'h ' + zf((time % 3600) / 60 | 0) + 'm ' + zf((time % 3600) % 60) + 's'
  }

  function e (element, content, cl) {
    let el = document.createElement(element)
    if (cl) el.className = cl
    el.innerHTML = content
    return el.outerHTML
  }

  function box (type, content) {
    return e('div', content, type)
  }

  function bar (metric, value, percentage, low, high) {
    return box('bar-outer',
      e('span', metric, 'bar-name') +
      box('bar-inner',
        '<div class="bar-progress" style="width: ' + percentage + '%;"></div>'
      ) +
      box('bar-stats',
        e('span', low, 'stat-low') +
        e('span', value, 'stat-now') +
        e('span', high, 'stat-high')
      )
    )
  }

  function renderPage (data) {
    let title = 'Welcome to ' + data.hostname + ' on ' + data.kernel
    document.title = title

    app.innerHTML = ''
    app.innerHTML += box('infobox-row',
    box('general infobox', 
      box('header',
        e('h2', 'General')
      ) +
      box('content',
        box('row',
          e('label', 'Hostname') +
          e('span', data.hostname)
        ) + box('row',
          e('label', 'Uptime') +
          e('span', readableTime(data.uptime))
        ) + box('row',
          e('label', 'Kernel version') +
          e('span', data.kernel)
        ) + box('row',
          e('label', 'Processes') +
          e('span', data.cpu.processes)
        )
      )
    ) +

    // CPU usage
    box('cpu infobox', 
      box('header',
        e('h2', 'CPU')
      ) +
      box('content',
        box('row',
          e('label', 'Num. cores') +
          e('span', data.cpu.count)
        ) +
        box('row',
          e('label', 'Usage') +
          e('span', Math.floor(data.cpu.usage) + ' %')
        ) + box('row',
          e('label', 'Load averages') +
          e('span', data.cpu.loadAverage[0].toFixed(2) + ', ' + data.cpu.loadAverage[1].toFixed(2) + ', ' + data.cpu.loadAverage[2].toFixed(2))
        )
      )
    ))

    // Memory usage
    let memuse = (data.memory.total - data.memory.free)
    app.innerHTML += box('memory infobox',
      box('header',
        e('h2', 'Memory')
      ) +
      box('content',
        bar('Memory usage', bytesToSize(memuse), memuse * 100 / data.memory.total, '0 Bytes', bytesToSize(data.memory.total))
      )
    )

    // Network interfaces
    let interfaces = ''
    for (let int in data.network) {
      if (int === 'lo') continue
      let iface = data.network[int]
      let ips = []
      for (let ip in iface.addresses) {
        ips.push(e('span', iface.addresses[ip], 'ip-addr'))
      }
      interfaces += box('interface',
        e('h3', int) +
        ips.join('') +
        e('h4', 'Bandwidth', 'sec-info') +
        box('row',
          e('label', 'Download') +
          e('span', bytesToSize(iface.download))
        ) + box('row',
          e('label', 'Upload') +
          e('span', bytesToSize(iface.upload))
        )
      )
    }

    // Disks
    let disks = ''
    for (let mount in data.disk) {
      let disk = data.disk[mount]
      disks += box('disk',
        e('h3', 'Mounted on ' + mount) +
        box('row',
          e('label', 'Free space') +
          e('span', disk.freeGb + ' GB')
        ) + 
        bar('Disk usage', disk.usedGb + ' GB', disk.usedPercentage, '0 GB', disk.totalGb + ' GB')
      )
    }

    app.innerHTML += box('infobox-row',
      box('network infobox',
        box('header',
          e('h2', 'Network Interfaces')
        ) +
        box('content',
          box('interfaces', interfaces)
        )
      )+

      box('disk infobox',
        box('header',
          e('h2', 'Disk Drives')
        ) +
        box('content',
          box('disks', disks)
        )
      )
    )
  }

  function update () {
    httpGet('/status').then(function (data) {
      try {
        renderPage(JSON.parse(data))
      } catch (e) {
        console.error(e)
      }
    }, function (e) {
      console.error(e)
    })
  }

  update()
})()