default.nix

with import <nixpkgs> { };
with builtins;

rec {
  yaml2nix = path:
    let
      jsonOutputDrv =
        runCommand "from-yaml" { nativeBuildInputs = [ remarshal ]; }
        ''remarshal -if yaml -i "${path}" -of json -o "$out"'';
    in fromJSON (readFile jsonOutputDrv);
  run = state: env:
    let
      folder = "helm/${state}";
      hf = import ../${folder}/helmfile.nix;
      var = {
        values = lib.mergeAttrs (yaml2nix ../${folder}/env/defaults.yaml)
          (yaml2nix ../${folder}/env/${env}.yaml);
        environment.name = env;
      };
      vals = val: "TODO: fetch ${val} using ${pkgs.vals}";
    in hf { inherit lib var vals; };
}

Running it with

nix eval --json --impure --expr '(import ../../nixhf/default.nix).run "atlantis" "prod"'