const SHEET_NAME = 'BudgetSync';

function doGet(e) {
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  let sheet = ss.getSheetByName(SHEET_NAME);
  if (!sheet) return ContentService.createTextOutput('{}');
  const data = sheet.getRange(1,1).getValue();
  return ContentService.createTextOutput(data || '{}')
    .setMimeType(ContentService.MimeType.JSON);
}

function doPost(e) {
  try {
    const payload = JSON.parse(e.postData.contents);
    if (payload.action !== 'write') return ContentService.createTextOutput('ERROR: unknown action');
    const ss = SpreadsheetApp.getActiveSpreadsheet();
    let sheet = ss.getSheetByName(SHEET_NAME);
    if (!sheet) sheet = ss.insertSheet(SHEET_NAME);
    sheet.getRange(1,1).setValue(JSON.stringify(payload.data));
    sheet.getRange(1,2).setValue(new Date().toISOString());
    return ContentService.createTextOutput('OK');
  } catch(err) {
    return ContentService.createTextOutput('ERROR: ' + err.message);
  }
}