function doPost(e) {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheets()[0];
  ss.setSpreadsheetTimeZone('Asia/Seoul');
  // Parsing the POST data to get the required data
  var data = JSON.parse(e.postData.contents);
  
  var formAnswers = data.form_answers;
  var submittedAt = new Date(data.form_response.submitted_at);

  var responseId = data.form_response.response_id.slice(0,10);
  // First row: labels
  if (sheet.getLastRow() === 0) {
    var fieldLabels = formAnswers.map(function(answer) {
      if (answer.type === 'RADIO_GRID' || answer.type === 'CHECKBOX_GRID') {
        return answer.response.map(el => `${answer.label} - ${el.lineLabel}`);
      }
      return answer.label
    }).flat();
    var headers = ['Response ID', 'Time Submitted', ...fieldLabels]
    sheet.appendRow(headers);
  } 
   var rowData = formAnswers.map(field => {
      switch (field.type) {
        case 'CHECKBOX':
        case 'RADIO': {
          var isResponseArray = Array.isArray(field.response);
          if (isResponseArray) {
            return field.response.filter(el => Boolean(el)).join(', ');
          }
          return field.response || '';
        }
        case 'CHECKBOX_GRID':
        case 'RADIO_GRID': {
          var isLineResponseArray = Array.isArray(field.response.lineResponse)
          return field.response.map(el => {
            if (isLineResponseArray) {
              return el.lineResponse.filter(el => Boolean(el)).join(', ');
            }
            return el.lineResponse || '';
          })
        }
        case 'GEOLOCATION': {
          var response = field.response || {};
          var responseArray = Object.entries(response).map(el => `${el[0]}: ${el[1]}`);
          return responseArray.join(', ');
        }
        case 'HIDDEN': {
          return field.response === undefined || field.response === null
            ? ''
            : field.response;
        }
        default: {
          var response =
            field.response === undefined || field.response === null ? '' : field.response;
          if (Array.isArray(response)) {
            return response.join(', ');
          }
          return response;
        }
      }
    }).flat();
  sheet.appendRow([responseId, submittedAt, ...rowData]);
  return ContentService.createTextOutput(JSON.stringify({result: "success"})).setMimeType(ContentService.MimeType.JSON);
}