export function flexible(options: { minWidth?: number }) {
  const docEl = document.documentElement;
  const dpr = window.devicePixelRatio || 1;

  function setRemUnit() {
    let cwidth = docEl.clientWidth;
    if (options.minWidth) {
      cwidth = Math.max(cwidth, options.minWidth);
    }
    const rem = cwidth / 10;
    docEl.style.fontSize = rem + "px";
  }

  setRemUnit();

  window.addEventListener("resize", setRemUnit);
  window.addEventListener("pageshow", function (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);
  }
}