// ref: https://github.com/amfe/lib-flexible/blob/2.0/index.js
;(function flexible(window, document) {
  const docEl = document.documentElement
  const dpr = window.devicePixelRatio || 1

  // adjust body font size
  const setBodyFontSize = () => {
    if (document.body) {
      document.body.style.fontSize = `${12 * dpr}px`
    } else {
      document.addEventListener('DOMContentLoaded', setBodyFontSize)
    }
  }

  setBodyFontSize()

  // set 1rem = viewWidth / 10
  const setRemUnit = () => {
    const rem =
      Math.min(
        // 宽度限制在 500 内
        500,
        docEl.clientWidth
      ) / 10
    docEl.style.fontSize = `${rem}px`
  }

  setRemUnit()

  // reset rem unit on page resize
  window.addEventListener('resize', setRemUnit)
  window.addEventListener('pageshow', (e) => {
    if (e.persisted) {
      setRemUnit()
    }
  })

  // detect 0.5px supports
  if (dpr >= 2) {
    const fakeBody = document.createElement('body')
    const testElement = document.createElement('div')
    testElement.style.border = '.5px solid transparent'
    fakeBody.appendChild(testElement)
    docEl.appendChild(fakeBody)
    if (testElement.offsetHeight === 1) {
      docEl.classList.add('hairlines')
    }
    docEl.removeChild(fakeBody)
  }
})(window, document)