function doGet(e) {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var data = sheet.getDataRange().getValues();
  if (data.length <= 1) return ContentService.createTextOutput(JSON.stringify([])).setMimeType(ContentService.MimeType.JSON);
  
  var headers = data[0];
  var result = [];
  for (var i = 1; i < data.length; i++) {
    var obj = {};
    for (var j = 0; j < headers.length; j++) {
      obj[headers[j]] = data[i][j];
    }
    result.push(obj);
  }
  return ContentService.createTextOutput(JSON.stringify(result)).setMimeType(ContentService.MimeType.JSON);
}

function doPost(e) {
  try {
    var sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
    var payload = JSON.parse(e.postData.contents);
    
    // Create Header if table is empty
    if (sheet.getLastRow() === 0) {
      sheet.appendRow(["id", "date", "slot", "topic", "name", "department", "phone", "attendees", "equipment", "status", "note", "createdAt"]);
    }
    
    if (payload.action === 'CREATE') {
      sheet.appendRow([
        payload.id, payload.date, payload.slot, payload.topic, 
        payload.name, payload.department, payload.phone, payload.attendees, 
        payload.equipment, payload.status, payload.note || '', payload.createdAt || new Date().toISOString()
      ]);
    } else if (payload.action === 'UPDATE') {
      var data = sheet.getDataRange().getValues();
      for (var i = 1; i < data.length; i++) {
        if (data[i][0] == payload.id) {
          sheet.getRange(i + 1, 1, 1, 12).setValues([[
            payload.id, payload.date, payload.slot, payload.topic, 
            payload.name, payload.department, payload.phone, payload.attendees, 
            payload.equipment, payload.status, payload.note || '', data[i][11] || payload.createdAt || ''
          ]]);
          break;
        }
      }
    } else if (payload.action === 'DELETE') {
      var data = sheet.getDataRange().getValues();
      for (var i = 1; i < data.length; i++) {
        if (data[i][0] == payload.id) {
          sheet.deleteRow(i + 1);
          break;
        }
      }
    }
    return ContentService.createTextOutput(JSON.stringify({status: "success"})).setMimeType(ContentService.MimeType.JSON);
  } catch (err) {
    return ContentService.createTextOutput(JSON.stringify({status: "error", message: err.toString()})).setMimeType(ContentService.MimeType.JSON);
  }
}