(function(win, lib) {
    var doc = win.document
    var docEl = doc.documentElement
    var metaEl = doc.querySelector('meta[name="viewport"]')
    var flexibleEl = doc.querySelector('meta[name="flexible"]')
    var dpr = 0
    var scale = 0
    var tid
    var flexible = lib.flexible || (lib.flexible = {})
  
    if (metaEl) {
      // eslint-disable-next-line no-useless-escape
      var match = metaEl.getAttribute('content').match(/initial\-scale=([\d\.]+)/)
      if (match) {
        scale = parseFloat(match[1])
        dpr = parseInt(1 / scale)
      }
    } else if (flexibleEl) {
      var content = flexibleEl.getAttribute('content')
      if (content) {
        // eslint-disable-next-line no-useless-escape
        var initialDpr = content.match(/initial\-dpr=([\d\.]+)/)
        // eslint-disable-next-line no-useless-escape
        var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/)
        if (initialDpr) {
          dpr = parseFloat(initialDpr[1])
          scale = parseFloat((1 / dpr).toFixed(2))
        }
        if (maximumDpr) {
          dpr = parseFloat(maximumDpr[1])
          scale = parseFloat((1 / dpr).toFixed(2))
        }
      }
    }
  
    if (!dpr && !scale) {
      // eslint-disable-next-line no-unused-vars
      var isAndroid = win.navigator.appVersion.match(/android/gi)
      var isIPhone = win.navigator.appVersion.match(/iphone/gi)
      var devicePixelRatio = win.devicePixelRatio
      if (isIPhone) {
        // iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
        if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
          dpr = 3
        } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)) {
          dpr = 2
        } else {
          dpr = 1
        }
      } else {
        // 其他设备下，仍旧使用1倍的方案
        dpr = 1
      }
      scale = 1 / dpr
    }
  
    docEl.setAttribute('data-dpr', dpr)
    if (!metaEl) {
      metaEl = doc.createElement('meta')
      metaEl.setAttribute('name', 'viewport')
      metaEl.setAttribute('content', 'initial-scale=' + scale + ', maximum-scale=' + scale + ', minimum-scale=' + scale + ', user-scalable=no')
      if (docEl.firstElementChild) {
        docEl.firstElementChild.appendChild(metaEl)
      } else {
        var wrap = doc.createElement('div')
        wrap.appendChild(metaEl)
        doc.write(wrap.innerHTML)
      }
    }
  
    function refreshRem() {
      var width = docEl.getBoundingClientRect().width
      var rem = width / 10 // 适配宽度为 1920px， 分为10份 ，则 vue.config.js 中 postcss 值为 1920/10
      docEl.style.fontSize = rem + 'px'
      flexible.rem = win.rem = rem
    }
  
    win.addEventListener('resize', function() {
      clearTimeout(tid)
      tid = setTimeout(refreshRem, 300)
    }, false)
    win.addEventListener('pageshow', function(e) {
      if (e.persisted) {
        clearTimeout(tid)
        tid = setTimeout(refreshRem, 300)
      }
    }, false)
  
    if (doc.readyState === 'complete') {
      doc.body.style.fontSize = 12 * dpr + 'px'
    } else {
      doc.addEventListener('DOMContentLoaded', function() {
        doc.body.style.fontSize = 12 * dpr + 'px'
      }, false)
    }
  
    refreshRem()
  
    flexible.dpr = win.dpr = dpr
    flexible.refreshRem = refreshRem
    flexible.rem2px = function(d) {
      var val = parseFloat(d) * this.rem
      if (typeof d === 'string' && d.match(/rem$/)) {
        val += 'px'
      }
      return val
    }
    flexible.px2rem = function(d) {
      var val = parseFloat(d) / this.rem
      if (typeof d === 'string' && d.match(/px$/)) {
        val += 'rem'
      }
      return val
    }
  })(window, window.lib || (window.lib = {}))