import * as XLSX from "xlsx";

/**
 * Export an array of row objects to a .xlsx file and trigger download.
 * @param rows Array of objects (keys become column headers)
 * @param filename Download filename (without .xlsx)
 * @param sheetName Optional sheet name (default "Sheet1")
 */
export function exportChartToXlsx(
  rows: Record<string, unknown>[],
  filename: string,
  sheetName = "Sheet1"
): void {
  if (rows.length === 0) {
    const ws = XLSX.utils.aoa_to_sheet([[]]);
    const wb = XLSX.utils.book_new();
    XLSX.utils.book_append_sheet(wb, ws, sheetName);
    XLSX.writeFile(wb, `${filename}.xlsx`);
    return;
  }
  const ws = XLSX.utils.json_to_sheet(rows);

  // Auto-set column widths based on header length (simple heuristic).
  const header = Object.keys(rows[0] ?? {});
  if (header.length > 0) {
    ws["!cols"] = header.map((h) => ({
      // Basic width: header length + padding, minimum 12
      wch: Math.max(12, h.length + 4),
    }));

    // Make header row look like a header (bold).
    header.forEach((_, colIdx) => {
      const cellRef = XLSX.utils.encode_cell({ r: 0, c: colIdx });
      const cell = ws[cellRef];
      if (cell) {
        cell.s = {
          font: { bold: true },
        };
      }
    });
  }

  const wb = XLSX.utils.book_new();
  XLSX.utils.book_append_sheet(wb, ws, sheetName);
  XLSX.writeFile(wb, `${filename}.xlsx`);
}