conveyal/modeify

/**
 * @author mrdoob / http://mrdoob.com/
 * @author jetienne / http://jetienne.com/
 * @author paulirish / http://paulirish.com/
 */
var MemoryStats = function () {
  var msMin = 100
  var msMax = 0
  var performance = window.performance

  var container = document.createElement('div')
  container.id = 'stats'
  container.style.cssText = 'width:80px;opacity:0.9;cursor:pointer'

  var msDiv = document.createElement('div')
  msDiv.id = 'ms'
  msDiv.style.cssText = 'padding:0 0 3px 3px;text-align:left;background-color:#020;'
  container.appendChild(msDiv)

  var msText = document.createElement('div')
  msText.id = 'msText'
  msText.style.cssText =
    'color:#0f0;font-family:Helvetica,Arial,sans-serif;font-size:9px;font-weight:bold;line-height:15px'
  msText.innerHTML = 'Memory'
  msDiv.appendChild(msText)

  var msGraph = document.createElement('div')
  msGraph.id = 'msGraph'
  msGraph.style.cssText = 'position:relative;width:74px;height:30px;background-color:#0f0'
  msDiv.appendChild(msGraph)

  while (msGraph.children.length < 74) {
    var bar = document.createElement('span')
    bar.style.cssText = 'width:1px;height:30px;float:left;background-color:#131'
    msGraph.appendChild(bar)
  }

  var updateGraph = function (dom, height, color) {
    var child = dom.appendChild(dom.firstChild)
    child.style.height = height + 'px'
    if (color) child.style.backgroundColor = color
  }

  // polyfill usedJSHeapSize
  if (performance && !performance.memory) {
    performance.memory = {
      usedJSHeapSize: 0
    }
  }

  // support of the API?
  if (performance.memory.totalJSHeapSize === 0) {
    console.warn('totalJSHeapSize === 0... performance.memory is only available in Chrome .')
  }

  // TODO, add a sanity check to see if values are bucketed.
  // If so, reminde user to adopt the --enable-precise-memory-info flag.
  // open -a "/Applications/Google Chrome.app" --args --enable-precise-memory-info

  var lastTime = Date.now()
  var lastUsedHeap = performance.memory.usedJSHeapSize
  return {
    domElement: container,

    update: function () {
      // refresh only 30time per second
      if (Date.now() - lastTime < 1000 / 30) return
      lastTime = Date.now()

      var delta = performance.memory.usedJSHeapSize - lastUsedHeap
      lastUsedHeap = performance.memory.usedJSHeapSize
      var color = delta < 0 ? '#830' : '#131'

      var ms = performance.memory.usedJSHeapSize
      msMin = Math.min(msMin, ms)
      msMax = Math.max(msMax, ms)
      msText.textContent = 'Mem: ' + bytesToSize(ms, 2)

      var normValue = ms / (30 * 1024 * 1024)
      var height = Math.min(30, 30 - (normValue * 30))
      updateGraph(msGraph, height, color)

      function bytesToSize (bytes, nFractDigit) {
        var sizes = ['Bytes', 'KB', 'MB', 'GB', 'TB']
        if (bytes === 0) return 'n/a'
        nFractDigit = nFractDigit !== undefined ? nFractDigit : 0
        var precision = Math.pow(10, nFractDigit)
        var i = Math.floor(Math.log(bytes) / Math.log(1024))
        return Math.round((bytes * precision / Math.pow(1024, i)) / precision) + ' ' + sizes[i]
      }
    }
  }
}

if (typeof module !== 'undefined' && module.exports) {
  module.exports = MemoryStats
}