{
  /*
    nixConfig = {
    extra-substituters = [
      "https://nix-community.cachix.org"
    ];
    extra-trusted-public-keys = [
      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
    ];
    };
  */

  inputs = {
    doom-emacs.flake = false;
    doom-emacs.url = "github:hlissner/doom-emacs";
    home-manager.inputs.nixpkgs.follows = "nixpkgs";
    home-manager.url = "github:nix-community/home-manager/release-23.11";
    nix-formatter-pack.inputs.nixpkgs.follows = "nixpkgs";
    nix-formatter-pack.url = "github:Gerschtli/nix-formatter-pack";
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
    pre-commit-hooks.inputs.nixpkgs.follows = "nixpkgs";
    pre-commit-hooks.inputs.nixpkgs-stable.follows = "nixpkgs";
    pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
  };

  outputs = inputs:
    let
      remoteNixpkgsPatches = import nixpkgs/patches.nix;
      localNixpkgsPatches = [
      ];
      originPkgs = inputs.nixpkgs.legacyPackages."x86_64-linux";
      nixpkgsPath = originPkgs.applyPatches {
        name = "nixpkgs-patched";
        src = inputs.nixpkgs.outPath;
        patches = map originPkgs.fetchpatch remoteNixpkgsPatches ++ localNixpkgsPatches;
        postPatch = ''
          patch=$(printf '%s\n' ${builtins.concatStringsSep " "
             (map (p: p.sha256) remoteNixpkgsPatches ++ localNixpkgsPatches)} |
            sort | sha256sum | cut -c -7)
          echo "-patch-$patch" >.version-suffix
        '';
      };
      profile = "/nix/var/nix/profiles/system";
      inherit (inputs.nixpkgs) lib;
      #nixosSystem = lib.nixosSystem;
      nixosSystem = import (nixpkgsPath + "/nixos/lib/eval-config.nix");
      forAllSystems = f: lib.genAttrs lib.systems.flakeExposed (system: f rec {
        inherit system;
        #pkgs = inputs.nixpkgs.legacyPackages.${system};
        pkgs = import nixpkgsPath {
          inherit system;
          overlays = import nixpkgs/overlays.nix;
        };
      });
      self = with lib.fileset; toSource {
        root = ./.;
        fileset =
          intersection
            (unions [
              ./home-manager
              ./homes
              ./hosts
              ./nixos
              ./nixpkgs
              ./share
              ./users
              ./shell.nix
            ])
            (fileFilter
              (file: lib.any file.hasExt [
                "clear"
                "conf"
                "cred"
                "crt"
                "css"
                "el"
                "hs"
                "json"
                "nix"
                "patch"
                "pem"
                "pub"
                "sh"
                "theme"
                "vim"
              ]) ./.);
      };
    in
    rec {
      # nix -L build .#hello
      packages = forAllSystems ({ pkgs, ... }: pkgs);

      # nix -L build .#nixosConfigurations.oignon.config.system.build.toplevel
      # nix -L build .#nixosConfigurations.oignon.config.boot.kernelPackages.kernel.configfile
      # nix -L build .#nixosConfigurations.oignon.pkgs.hello
      # nix eval --raw .#nixosConfigurations.oignon.config.networking.nftables.ruleset
      nixosConfigurations = lib.genAttrs
        (builtins.attrNames (lib.filterAttrs (_n: v: v == "directory") (builtins.readDir (self + "/hosts"))))
        (hostName: nixosSystem {
          system = null;
          specialArgs = {
            # Required to avoid infinite recursion
            # when `inputs` is used in `imports`.
            inherit inputs;
          };
          modules = [
            nixos/default.nix
            (import (self + "/hosts/${hostName}.nix"))
            {
              _module.args = {
                inherit hostName;
                hosts = nixosConfigurations;
                host = nixosConfigurations.${hostName}._module.args;
              };
              nixpkgs.overlays = import (self + "/nixpkgs/overlays.nix");
              nixpkgs.config.allowUnfreePredicate = pkg: builtins.elem (lib.getName pkg) [
                "anydesk"
                "cudatoolkit"
                "geogebra"
                "hplip"
                "memtest86-efi"
                "nvidia-settings"
                "nvidia-x11"
              ];
            }
            inputs.home-manager.nixosModules.home-manager
            {
              home-manager.useGlobalPkgs = true;
              home-manager.useUserPackages = true;
              home-manager.verbose = true;
              home-manager.backupFileExtension = null;
              home-manager.extraSpecialArgs = {
                inherit hostName inputs;
              };
            }
          ];
        });

      # nix -L develop  or  direnv allow
      devShells = forAllSystems ({ pkgs, system, ... }:
        {
          default = pkgs.callPackage (self + "/shell.nix")
            {
              inherit pkgs inputs system nixpkgsPath;
              inherit (checks.${system}.pre-commit-check) shellHook;
            };
        }
      );

      # nix -L run .#oignon.switch
      apps = forAllSystems ({ pkgs, system, ... }:
        with builtins;
        mapAttrs
          (hostName: { config, ... }:
            let
              inherit (config.system) build;
              scriptApp = scriptName: ps: script: {
                type = "app";
                program = (pkgs.writeShellScript "${hostName}-${scriptName}" ''
                  export PATH="${lib.makeBinPath ([ pkgs.coreutils ] ++ ps)}:$PATH"
                  set -eux
                  ${script}
                '').outPath;
              };
            in
            {
              # Example: nix run .#aubergine.switch
              "switch" = scriptApp "switch" [ ] ''
                shopt -s globstar

                chmod -R g-rwx,o-rwx **/*.gpg
                trap 'git reset **/*.gpg' EXIT
                git rm -rf --cached --ignore-unmatch **/*.gpg # prevent copying to /nix/store

                nix-store --add-root hosts/${hostName}.nixpkgs --indirect --realise ${nixpkgsPath}
                nix-store --add-root hosts/${hostName}.root --indirect --realise ${build.toplevel}

                nix copy --to "ssh://${config.install.target}?''${targetStore-}"${lib.optionalString config.install.substituteOnDestination " --substitute-on-destination"} ${build.toplevel}

                if ssh ${config.install.target} set -x ';' \
                  systemctl reset-failed nixos-fallback '2>/dev/null' ';' \
                  test "''${NO_NIXOS_FALLBACK:+set}" '||' \
                  systemd-run -u nixos-fallback --description=nixos-fallback /bin/sh -xc '''\'''
                    PATH=${with pkgs; lib.makeBinPath [ coreutils nix systemd ]}
                    sleep $((10 * 60))
                    ${profile}/bin/switch-to-configuration switch
                    systemctl reboot
                  '\'''' '&&' \
                  ${build.toplevel}/bin/switch-to-configuration test
                then
                  ssh ${config.install.target} -o ControlPath=none set -x ';' \
                    systemctl stop nixos-fallback.service ';' \
                    nix-env --profile ${profile} --set '${build.toplevel}' ';' \
                    ${build.toplevel}/bin/switch-to-configuration boot '&&' \
                    nix-env --delete-generations 7d --profile ${profile}
                else
                  tput rev
                  echo WARNING: switch-to-configuration was not registered at boot
                  tput sgr0
                  ssh ${config.install.target} -o ControlPath=none set -x ';' \
                    systemctl stop nixos-fallback.service
                  false
                fi
              '';
            })
          nixosConfigurations);

      # nix flake check
      checks = forAllSystems (args: with args; {
        pre-commit-check = inputs.pre-commit-hooks.lib.${system}.run {
          src = self;
          hooks = {
            nixpkgs-fmt.enable = true;
          };
        };
      });

      # nix fmt
      formatter = forAllSystems ({ pkgs, ... }:
        inputs.nix-formatter-pack.lib.mkFormatter {
          inherit pkgs;
          config = {
            tools = {
              deadnix.enable = true;
              nixpkgs-fmt.enable = true;
              statix.enable = true;
            };
          };
        }
      );
    };
}