(function (win, library) {
  const lib = library;
  const doc = win.document;
  const docEl = doc.documentElement;
  let metaEl = doc.querySelector('meta[name="viewport"]');
  const flexibleEl = doc.querySelector('meta[name="flexible"]');
  let dpr = 0;
  let scale = 0; // nihao
  let tid;
  const flexible = lib.flexible || (lib.flexible = {});

  if (metaEl) {
    const match = metaEl
      .getAttribute('content')
      // eslint-disable-next-line no-useless-escape
      .match(/initial\-scale=([\d\.]+)/);
    if (match) {
      scale = parseFloat(match[1]);
      dpr = parseInt(1 / scale);
    }
  } else if (flexibleEl) {
    const content = flexibleEl.getAttribute('content');
    if (content) {
      // eslint-disable-next-line no-useless-escape
      const initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
      // eslint-disable-next-line no-useless-escape
      const 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) {
    const isIPhone = win.navigator.appVersion.match(/iphone/gi);
    const { devicePixelRatio } = win;
    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 {
      const wrap = doc.createElement('div');
      wrap.appendChild(metaEl);
      doc.write(wrap.innerHTML);
    }
  }

  // 默认 1920，分成24份，每份80,也就是80px,1rem就是80px
  function refreshRem() {
    const { width } = docEl.getBoundingClientRect();
    // if (width / dpr > 540) {
    //   width = 540 * dpr;
    // }\docs\rules\no-multi-assign
    const rem = width / 24;
    docEl.style.fontSize = `${rem}px`;
    flexible.rem = win.rem = rem;
  }

  win.addEventListener(
    'resize',
    () => {
      clearTimeout(tid);
      tid = setTimeout(refreshRem, 300);
    },
    false,
  );
  win.addEventListener(
    'pageshow',
    (e) => {
      if (e.persisted) {
        clearTimeout(tid);
        tid = setTimeout(refreshRem, 300);
      }
    },
    false,
  );

  if (doc.readyState === 'complete') {
    doc.body.style.fontSize = `${12 * dpr}px`;
  } else {
    doc.addEventListener(
      'DOMContentLoaded',
      () => {
        doc.body.style.fontSize = `${12 * dpr}px`;
      },
      false,
    );
  }

  refreshRem();

  flexible.dpr = win.dpr = dpr;
  flexible.refreshRem = refreshRem;
  flexible.rem2px = function (d) {
    let val = parseFloat(d) * this.rem;
    if (typeof d === 'string' && d.match(/rem$/)) {
      val += 'px';
    }
    return val;
  };
  flexible.px2rem = function (d) {
    let val = parseFloat(d) / this.rem;
    if (typeof d === 'string' && d.match(/px$/)) {
      val += 'rem';
    }
    return val;
  };
})(window, window.lib || (window.lib = {}));
