<html>
  <head>
    <meta charset="utf-8" />
    <script>
      window.addEventListener("message", e => {
        switch (e.data.type) {
          case "focus":
            window.focus();
            break;

          case "select": {
            const text = document.body.firstChild;
            document
              .getSelection()
              .setBaseAndExtent(text, 0, text, e.data.length);
            break;
          }

          case "selectedOffset": {
            const sel = document.getSelection();
            const text = document.body.firstChild;
            if (sel.anchorNode !== text || sel.focusNode !== text) {
              window.parent.postMessage([-1, -1], "*");
            } else {
              window.parent.postMessage(
                [sel.anchorOffset, sel.focusOffset],
                "*"
              );
            }
            break;
          }

          case "content":
            window.parent.postMessage(document.body.textContent, "*");
            break;
        }
      });
    </script>
  </head>
  <body onload="document.body.textContent = 'elit'"></body>
</html>
