type Cell = string | number | null | undefined

/**
 * RFC 4180 CSV with a BOM so Excel opens UTF-8 correctly. Cells that a spreadsheet would treat as a
 * formula are prefixed with an apostrophe (CSV injection).
 */
export function toCsv(header: string[], rows: Cell[][]): string {
  const cell = (value: Cell) => {
    let text = value === null || value === undefined ? '' : String(value)
    if (/^[=+\-@\t\r]/.test(text)) text = `'${text}`
    return /[",\r\n]/.test(text) ? `"${text.replace(/"/g, '""')}"` : text
  }
  return '' + [header, ...rows].map((row) => row.map(cell).join(',')).join('\r\n') + '\r\n'
}