dotfiles/bin/gpg-key-to-datamatrix

#! /usr/bin/env nix-shell
#! nix-shell -p typst dmtx-utils nushell -i nu

def get-chunked-key [keyid?: string] {
  let flags = [
    "--export-secret-key", "--export-options", "export-minimal"
  ] | do { if keyid == null { $in } else { $in | append $keyid}}
  let key = (gpg ...$flags)
  let length = ($key | bytes length)
  # 1555 is the maximum length in bytes split data evenly
  let n = ($length / (($length / 1555)| math ceil)) | math ceil
  0..$n..$length
    | each {|i| $key | bytes at $i..<($i + $n)}
}

def generate-typst-doc [tmp: string, length: int] {
  0..<$length
    | each { |i|
      let path = $tmp
        | path join $"dmtx-($i).svg"
        | path relative-to $env.PWD

        ['#image("', $path, '")'] | str join
      }
    | str join "\n"
}

def main [keyid?: string, outfile = "dmtxdata.pdf"] {
  let tmpdir = mktemp -d -p . -t tmp.key-2-matrix-XXX
  let byte_chunks = get-chunked-key $keyid

  $byte_chunks | enumerate | each {|it|
    $it.item | dmtxwrite -e 8 -o ($tmpdir | path join $"dmtx-($it.index).svg")
  }

  let doc = generate-typst-doc $tmpdir ($byte_chunks | length) 
  $doc | typst compile - $outfile

  rm -r $tmpdir
}