{
  description = "A NixOS Configuration";

  inputs = {};

  outputs = {self, ...}: let
    sources = import ./unflake.nix;

    system = "x86_64-linux";

    packageSets = rec {
      stable = sources.nixpkgs-stable.legacyPackages.${system};
      unstable = sources.nixpkgs-unstable.legacyPackages.${system};

      in_tree = import ./pkgs {
        unstable_pkgs = unstable;
        stable_pkgs = stable;
        inherit extra_lib;
      };
    };
    lib = packageSets.unstable.lib;
    extra_lib = sources.library.extraLib {inherit lib;};

    extra_modules = {
      nixos = {
        agenix = sources.agenix.nixosModules.default;
        turtle = sources.turtle.nixosModules.nixos;
        disko = sources.disko.nixosModules.default;
        impermanence = sources.impermanence.nixosModules.impermanence;
        simple-nixos-mailserver = sources.simple-nixos-mailserver.nixosModule;
        rocie = sources.rocie.nixosModules.default;
        home-manager = sources.home-manager.nixosModules.home-manager;
        lanzaboote = sources.lanzaboote.nixosModules.lanzaboote;
      };
      home = {
        nix-index-database = sources.nix-index-database.homeModules.nix-index;
        nixvim = sources.nixvim.homeModules.nixvim;
        turtle = sources.turtle.nixosModules.home-manager;
      };
    };
    module_args = {
      inherit
        sources
        # extra package sources
        openPRsNixpkgs
        packageSets
        # extra information
        system
        ;
    };
    special_args = {
      inherit
        self
        # Needs to be a special argument, because it is used for determining the `imports`
        # value (via `mkByName`).
        extra_lib
        extra_modules
        ;
    };

    openPRsNixpkgs = {};

    treefmtEval = import ./treefmt.nix {
      inherit (sources) treefmt-nix;
      pkgs = packageSets.unstable;
    };

    hosts = import ./hosts {
      inherit
        self
        extra_lib
        module_args
        special_args
        system
        ;
      inherit
        (sources)
        nixpkgs-unstable
        nixpkgs-stable
        deploy-rs
        ;
    };

    deployChecks = builtins.mapAttrs (system: deployLib: deployLib.deployChecks self.deploy) sources.deploy-rs.lib;
    tests = lib.attrsets.filterAttrs (_: v: !(v ? meta && v.meta.broken)) (import ./tests
      {
        inherit sources packageSets module_args special_args extra_lib;
      });
    # myPkgsFlat =
    #   builtins.listToAttrs
    #   # Filter out the `override` and `overrideDerivation` functions
    #   (builtins.filter
    #     ({ name, value, }: lib.attrsets.isDerivation value)
    #     (lib.lists.flatten
    #       (lib.attrsets.mapAttrsToList
    #         (name: value:
    #           if lib.attrsets.isDerivation value then
    #             [ { inherit name value; } ]
    #           else
    #             lib.attrsets.mapAttrsToList
    #               (name: value: { inherit name value; })
    #             value
    #         )
    #         packageSets.in_tree
    #       )
    #     )
    #   );
  in {
    checks."${system}" =
      extra_lib.warnMerge
      deployChecks."${system}"
      (extra_lib.warnMerge
        tests
        {formatting = treefmtEval.config.build.check self;}
        "the flake checks and formatting")
      "the flake checks and deploy rs checks";

    legacyPackages."${system}" = packageSets.unstable;

    packages."${system}" = packageSets.in_tree;

    formatter."${system}" = treefmtEval.config.build.wrapper;

    devShells."${system}".default = packageSets.unstable.mkShell {
      packages = [
        packageSets.unstable.deploy-rs

        # Used to update the stalwart-mail spamfilter
        packageSets.unstable.nix-update

        packageSets.unstable.nvd

        (sources.agenix.packages."${system}".default.override {
          nix = packageSets.unstable.lixPackageSets.latest.lix;
        })
      ];
    };

    deploy.nodes = hosts.nodes;
    inherit (hosts) nixosConfigurations;
  };
}