// Reference: https://gist.github.com/florentbr/349b1ab024ca9f3de56e6bf8af2ac69e

export function getFileUploadScript(elementId: string): string {
  return `
  var args = arguments,
    element = args[0],
    offsetX = args[1],
    offsetY = args[2],
    doc = element.ownerDocument || document;

  for (var i = 0; ; ) {
    var box = element.getBoundingClientRect(),
      clientX = box.left + (offsetX || box.width / 2),
      clientY = box.top + (offsetY || box.height / 2),
      target = doc.elementFromPoint(clientX, clientY);

    if (target && element.contains(target)) {
      break;
    }

    if (++i > 1) {
      var ex = new Error('Element not interactable');
      ex.code = 15;
      throw ex;
    }

    element.scrollIntoView({ behavior: 'instant', block: 'center', inline: 'center' });
  }

  var input = doc.createElement('INPUT');
  input.setAttribute('type', 'file');
  input.setAttribute('id','${elementId}');
  input.setAttribute('multiple', '');
  input.setAttribute('style', 'position:fixed;z-index:2147483647;left:0;top:0;');
  input.onchange = function (ev) {
    input.parentElement.removeChild(input);
    ev.stopPropagation();

    var dataTransfer = {
      constructor: DataTransfer,
      effectAllowed: 'all',
      dropEffect: 'none',
      types: ['Files'],
      files: input.files,
      setData: function setData() {},
      getData: function getData() {},
      clearData: function clearData() {},
      setDragImage: function setDragImage() {}
    };

    if (window.DataTransferItemList) {
      dataTransfer.items = Object.setPrototypeOf(
        Array.prototype.map.call(input.files, function (file) {
          return {
            constructor: DataTransferItem,
            kind: 'file',
            type: file.type,
            getAsFile: function getAsFile() {
              return file;
            },
            getAsString: function getAsString(callback) {
              var reader = new FileReader();
              reader.onload = function (ev) {
                callback(ev.target.result);
              };
              reader.readAsText(file);
            }
          };
        }),
        {
          constructor: DataTransferItemList,
          add: function add() {},
          clear: function clear() {},
          remove: function remove() {}
        }
      );
    }

    ['dragenter', 'dragover', 'drop'].forEach(function (type) {
      var event = doc.createEvent('DragEvent');
      event.initMouseEvent(
        type,
        true,
        true,
        doc.defaultView,
        0,
        0,
        0,
        clientX,
        clientY,
        false,
        false,
        false,
        false,
        0,
        null
      );

      Object.setPrototypeOf(event, null);
      event.dataTransfer = dataTransfer;
      Object.setPrototypeOf(event, DragEvent.prototype);

      target.dispatchEvent(event);
    });
  };

  doc.documentElement.appendChild(input);
  input.getBoundingClientRect(); /* force reflow for Firefox */
  return input;`;
}