// User/source text stays a string cell, including leading '=' and embedded newlines.
export async function createTenderWorkbook(tenders) {
  if (!Array.isArray(tenders) || !tenders.length) throw new Error('Dışa aktarılacak ihale bulunamadı.');
  const {default:ExcelJS} = await import('exceljs');
  const book = new ExcelJS.Workbook();
  book.creator = 'İhaleist';
  const sheet = book.addWorksheet('İhale Listesi');
  sheet.columns = [
    ['İKN',20],['Başlık',65],['Kurum',45],['Şehir',20],['İhale tarihi',18],
    ['İhale saati',15],['Alım türü',25],['Sektör',30],['CPV',35],['Kaynak',55],
  ].map(([header,width])=>({header,width}));
  for (const t of tenders) {
    sheet.addRow([t.ikn,t.baslik,t.kurum,t.sehir,t.tarih,t.saat,t.alimTuru,t.sektor,
      t.cpvLabel || (Array.isArray(t.cpv) ? t.cpv.join(', ') : t.cpv),t.kaynakUrl].map(v=>String(v ?? '')));
  }
  sheet.views = [{state:'frozen',ySplit:1}];
  sheet.autoFilter = {from:'A1',to:`J${tenders.length+1}`};
  sheet.getRow(1).font = {bold:true};
  sheet.eachRow(row=>{row.alignment={vertical:'top',wrapText:true};});
  return book.xlsx.writeBuffer();
}