function appendHeaders(rawMail: string, headers: [key: string, value: string][]): string {
  // Use the last eol in mail. If no eol, use LF.
  const eol = rawMail.match(/\r\n|\n/g)?.at(-1) ?? '\n'
  const headerStr = headers.map(h => `${h[0]}: ${h[0]}`).join(eol);

  if (rawMail.length === 0) { return headerStr; }

  const endOfHeadersMatch = rawMail.match(/(\r\n|\n){2}/)
  if (endOfHeadersMatch == null) {
    const endWithEOL = rawMail.endsWith('\n')
    return rawMail
  }
}

class AppSate {
}

export function add(a: number, b: number): number {
  return a + b;
}

// Learn more at https://docs.deno.com/runtime/manual/examples/module_metadata#concepts
if (import.meta.main) {
  console.log("Add 2 + 3 =", add(2, 3));
}