{
  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";

  outputs =
    { self, nixpkgs }:
    let
      forAllSystems =
        f:
        nixpkgs.lib.genAttrs [ "x86_64-linux" "aarch64-linux" ] (
          system: f (import nixpkgs { inherit system; })
        );
    in
    {
      devShells = forAllSystems (pkgs: {
        default = pkgs.mkShell {
          packages = with pkgs.ocamlPackages; [
            dune_3
            ocaml
            angstrom
            angstrom-unix
            camlzip
            ppx_inline_test
            ocaml-lsp
            ocamlformat
            ocamlformat-rpc-lib
            utop
          ];
        };
      });

      packages = forAllSystems (pkgs: {
        default = pkgs.ocamlPackages.buildDunePackage {
          pname = "inshellah";
          version = "0.1";
          src = ./.;
          nativeBuildInputs = [ pkgs.git ];
          buildInputs = with pkgs.ocamlPackages; [
            dune_3
            ocaml
            angstrom
            angstrom-unix
            camlzip
          ];

          meta.mainProgram = "inshellah";
        };
      });

      nixosModules.default =
        {
          pkgs,
          lib,
          config,
          ...
        }:
        {
          imports = [ ./nix/module.nix ];
          programs.inshellah.package = self.packages.${pkgs.stdenv.hostPlatform.system}.default;
          programs.inshellah.snippet = ''
            let inshellah_complete = { |spans| 
                let completions = (^inshellah complete ...$spans) | from json
                # dynamic completions
                let additional = if ($completions == null and
                  ($spans | length) > 0) {
                  match $spans.0 {
                    "nix" => {
                        $env.NIX_GET_COMPLETIONS = ($spans | length) - 1
                        let nix_output = $spans | run-external $in | split row -r '\n' | str trim | skip 1
                        let entries = if (($nix_output | length) < 6 and
                          ($spans | last) =~ "[a-zA-Z][a-zA-Z0-9_-]*#[a-zA-Z][a-zA-Z0-9_-]*") { 
                            hide-env NIX_GET_COMPLETIONS
                            $env.NIX_ALLOW_UNFREE = 1
                            $env.NIX_ALLOW_BROKEN = 1
                            $nix_output | par-each { |e|
                                  try {
                                     { value: $e, description: (^nix eval --impure $e --apply "f: f.meta.description" err> /dev/null) }
                                  } catch {} finally {
                                    { value: $e, description: "" }
                                  }
                                }
                         } else {
                           $nix_output | each { |e| { value: $e, description: "" } }
                         }
                        $entries
                    }
                    "systemctl" => {
                      let units = systemctl list-units | split row -r '\n' | drop 7 | split column -r '\s[A-Za-z\.\-\_\\0-9]*\s*' | headers | select UNIT
                      let kw = $spans | last
                      let entries = $units | filter { |e| e =~ $kw }
                      $entries
                    }
                    _ => { null }
                  }
                } else { null }
                $completions | append $additional
            }
            $env.config.completions.external = {enable: true, max_results: 200, completer: $inshellah_complete}
          '';
        };
    };
}