function doPost(e) {
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  const data = JSON.parse(e.postData.contents);
  if (sheet.getLastRow() === 0) sheet.appendRow(data.headers);
  sheet.appendRow(data.values);
  return ContentService
    .createTextOutput(JSON.stringify({status:'ok'}))
    .setMimeType(ContentService.MimeType.JSON);
}
function doGet(e) {
  return ContentService
    .createTextOutput(JSON.stringify({status:'ready'}))
    .setMimeType(ContentService.MimeType.JSON);
}