{
  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";
    nix-formatter-pack.inputs.nixpkgs.follows = "nixpkgs";
    nix-formatter-pack.url = "github:Gerschtli/nix-formatter-pack";
    nixpkgs.url = "github:NixOS/nixpkgs/fdebb81f45a1ba2c4afca5fd9f526e1653ad0949";
    pre-commit-hooks.inputs.nixpkgs.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
        '';
      };
      inherit (inputs.nixpkgs) lib;
      profile = "/nix/var/nix/profiles/system";
      forAllSystems = f: lib.genAttrs lib.systems.flakeExposed (system: f rec {
        inherit system;
        #pkgs = inputs.nixpkgs.legacyPackages.${system};
        pkgs = pkgsForSystem system;
      });
      pkgsForSystem = system: import nixpkgsPath {
        inherit system;
        config = {
          allowUnfree = true; # For hplip
        };
        overlays = import nixpkgs/overlays.nix;
      };
      nixosSystem = import (nixpkgsPath + "/nixos/lib/eval-config.nix");
      #nixosSystem = inputs.nixpkgs.lib.nixosSystem;
    in
    {
      nixosConfigurations = lib.genAttrs
        (builtins.attrNames (lib.filterAttrs (_n: v: v == "directory") (builtins.readDir ./hosts)))
        (hostName: nixosSystem {
          system = "x86_64-linux";
          pkgs = pkgsForSystem "x86_64-linux";
          specialArgs = {
            inherit hostName inputs;
          };
          modules = [
            {
              config._module.args = {
                inherit hostName inputs;
                hosts = inputs.self.nixosConfigurations;
              };
            }
            (import nixos/modules.nix)
            (import nixos/options.nix)
            (import (./hosts + "/${hostName}.nix"))
            inputs.nixpkgs.nixosModules.notDetected
            inputs.home-manager.nixosModules.home-manager
            ({ pkgs, ... }: {
              nix.registry.nixpkgs = lib.mkDefault { flake = inputs.nixpkgs; };
              nix.package = pkgs.nixFlakes;
              nix.extraOptions = "experimental-features = nix-command flakes";
              #nixpkgs.overlays = import nixpkgs/overlays.nix;
              /*
            system.nixos.versionSuffix = ".${
              lib.substring 0 8 (inputs.self.lastModifiedDate or inputs.self.lastModified)}.${
              inputs.self.shortRev or "dirty"}";
            system.nixos.revision = lib.mkIf (inputs.self ? rev) inputs.self.rev;
              */
              # Let 'nixos-version --json' know about the Git revision of this flake.
              system.configurationRevision = lib.mkIf (inputs.self ? rev) inputs.self.rev;
              /*
            system.configurationRevision =
              if inputs.self ? rev
              then inputs.self.rev
              else throw "Refusing to build from a dirty Git tree!";
              */
            })
            {
              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
      devShell = forAllSystems ({ pkgs, system, ... }: pkgs.callPackage ./shell.nix
        {
          inherit pkgs inputs system nixpkgsPath;
          inherit (inputs.self.checks.${system}.pre-commit-check) shellHook;
        });
      # nix -L run .#oignon.switch
      apps = forAllSystems ({ pkgs, system, ... }:
        with builtins;
        mapAttrs
          (hostName: { config, ... }:
            let
              inherit (config.system) build;
              target = "\"\${TARGET:-root@${config.networking.hostName}.${config.networking.domain}}\"";
              scriptApp = scriptName: ps: script: {
                type = "app";
                program = (pkgs.writeShellScript "${hostName}-${scriptName}" ''
                  export PATH="${lib.makeBinPath ([ pkgs.coreutils ] ++ ps)}:$PATH"
                  set -eux
                  ${script}
                '').outPath;
              };
            in
            rec {
              # 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://${target}${lib.optionalString config.install.substituteOnDestination " --substitute-on-destination"} ${build.toplevel}

                ssh ${target} set -x ';' \
                  systemctl reset-failed nixos-fallback '2>/dev/null' ';' \
                  systemd-run -u nixos-fallback --description=nixos-fallback /bin/sh -xc '''\'''
                    PATH=${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

                ssh ${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 ${profile}
              '';
            })
          inputs.self.nixosConfigurations);
      # nix flake check
      checks = forAllSystems (args: with args; {
        pre-commit-check = inputs.pre-commit-hooks.lib.${system}.run {
          src = inputs.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;
            };
          };
        }
      );
    };
}