let
  allKeyDir = "/etc/nixos/ssh_keys";
  readKeyFile = filePath: 
    let
      content = builtins.readFile filePath;
      lines = builtins.filter (line: line != "") (
        builtins.filter builtins.isString (
          builtins.split "\n" content
        )
      );
    in lines;
  
  getUserKeys = username:
    let
      userDir = "${allKeyDir}/${username}";
    in
      if builtins.pathExists userDir then
        let
          files = builtins.attrNames (builtins.readDir userDir);
          allKeys = builtins.concatMap (file: 
            readKeyFile "${userDir}/${file}"
          ) files;
        in allKeys
      else [];
  users = builtins.attrNames (builtins.readDir allKeyDir);
in
rec {
  keys = builtins.listToAttrs (map (user: {
    name = user;
    value = getUserKeys user;
  }) users);
  ssh_users = users;
  getKeys = getUserKeys;
}