function doGet(e) { return handleRequest(e); }
function doPost(e) { return handleRequest(e); }
function handleRequest(e) {
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Data') || SpreadsheetApp.getActiveSpreadsheet().insertSheet('Data');
  const action = e.parameter.action;
  let result = { success: false };
  try {
    if (action === 'test') result = { success: true, message: 'OK!' };
    else if (action === 'save') { sheet.clear(); sheet.getRange(1,1).setValue(e.parameter.data); result = { success: true }; }
    else if (action === 'load') { const d = sheet.getRange(1,1).getValue(); result = { success: true, data: d || null }; }
  } catch (err) { result = { success: false, error: err.toString() }; }
  return ContentService.createTextOutput(JSON.stringify(result)).setMimeType(ContentService.MimeType.JSON);
}