tomjaimz

function onOpen() {
  SpreadsheetApp.getUi().createAddonMenu().addItem('Upload', 'upload').addToUi();
}

function upload() {
  SpreadsheetApp.getUi().showModalDialog(HtmlService.createHtmlOutput(
    '<form><input type="file" name="file" onchange="var reader = new FileReader(); reader.onloadend = (e) => google.script.run.withSuccessHandler(google.script.host.close).importICS(e.target.result); reader.readAsText(this.parentNode.file.files[0]);"></form>'
  ), 'Select .ics file');
}