nixos-config/flake.nix

{
  description = "NixOS system configuration";

  inputs = {
    flake-utils.url = "github:numtide/flake-utils";

    nixpkgs.url = "github:nixos/nixpkgs/nixos-20.09";
    nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";

    home-manager.url = "github:nix-community/home-manager/release-20.09";
    home-manager.inputs.nixpkgs.follows = "nixpkgs";

    krops.url = "github:Mic92/krops";
    krops.inputs.flake-utils.follows = "flake-utils";
    krops.inputs.nixpkgs.follows = "nixpkgs";

    nixos-hardware.url = "github:nixos/nixos-hardware/master";

    nix-pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix/master";
    nix-pre-commit-hooks.inputs.flake-utils.follows = "flake-utils";
    nix-pre-commit-hooks.inputs.nixpkgs.follows = "nixpkgs";

    sops-nix.url = "github:Mic92/sops-nix";
    sops-nix.inputs.nixpkgs.follows = "nixpkgs";

    infinisilSystem.url = "github:Infinisil/system/91c5df20db68a995155218c5334db0e394185ca8";
    infinisilSystem.flake = false;

    bang-evaluator.url = "git+https://git.sbruder.de/simon/bangs";
    bang-evaluator.inputs.flake-utils.follows = "flake-utils";
    bang-evaluator.inputs.nixpkgs.follows = "nixpkgs";

    aria2_exporter.url = "github:sbruder/aria2_exporter";
    aria2_exporter.inputs.flake-utils.follows = "flake-utils";
    aria2_exporter.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs =
    { self
    , aria2_exporter
    , bang-evaluator
    , flake-utils
    , home-manager
    , infinisilSystem
    , krops
    , nix-pre-commit-hooks
    , nixos-hardware
    , nixpkgs
    , nixpkgs-unstable
    , sops-nix
    }: flake-utils.lib.eachDefaultSystem
      (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        inherit (pkgs) lib;
      in
      {
        checks = {
          pre-commit-check = nix-pre-commit-hooks.lib.${system}.run {
            src = ./.;
            hooks = {
              nixpkgs-fmt.enable = true;
            };
          };
        };

        apps = {
          deploy = lib.mapAttrs
            (hostname: machine:
              let
                inherit (krops.packages.${system}) writeCommand;
                inherit (krops) lib;
              in
              writeCommand "/bin/deploy-${hostname}" {
                target = lib.mkTarget "root@${machine.config.deployment.targetHost}" // {
                  extraOptions = [
                    # force allocation of tty to allow aborting with ^C and to show build progress
                    "-t"
                  ];
                };
                source = lib.evalSource (lib.singleton {
                  config.file = {
                    path = toString ./.;
                    useChecksum = true;
                    filters = [
                      {
                        type = "include";
                        pattern = "/machines/${hostname}/";
                      }
                      {
                        type = "exclude";
                        pattern = "/machines/*/";
                      }
                    ];
                  };
                });
                command = targetPath: ''
                  nixos-rebuild switch --flake ${targetPath}/config -L --keep-going
                '';
              })
            self.nixosConfigurations;

          unlock = lib.mapAttrs
            (hostname: machine:
              let
                inherit (machine.config.deployment)
                  targetHost
                  unlockOverV4;
              in
              pkgs.writeShellScriptBin hostname ''
                set -exo pipefail
                # opening luks fails if gpg-agent is not unlocked yet
                pass "devices/${hostname}/luks" >/dev/null
                ssh \
                    ${lib.optionalString unlockOverV4 "-4"} \
                    -p 2222 \
                    "root@${targetHost}" \
                    "cat > /crypt-ramfs/passphrase" < <(pass "devices/${hostname}/luks")
              '')
            self.nixosConfigurations;

          updateInputs = pkgs.writeShellScriptBin "updateInputs" ''
            set -e
            git diff --exit-code -s flake.lock || (echo "Lockfile has unstaged changes, refusing to update." >&2 && exit 1)
            git diff --cached --exit-code -s flake.lock || (echo "Lockfile has staged changes, refusing to update." >&2 && exit 1)
            nix flake update
            git diff --exit-code -s flake.lock && echo "Already up to date." && exit 0
            git commit -m "Update flake inputs" flake.lock
          '';

          showKeyFingerprint = pkgs.writeShellScriptBin "showKeyFingerprint" ''
            gpg --with-fingerprint --with-colons --show-key "keys/''${1}.asc" | awk -F: '$1 == "fpr" { print $10; exit }'
          '';
        };

        devShell = pkgs.mkShell {
          buildInputs = (with pkgs; [
            nixpkgs-fmt
            sops
            ssh-to-pgp
          ]);

          shellHook = ''
            find ${./keys} -type f -print0 | xargs -0 ${pkgs.gnupg}/bin/gpg --quiet --import
          '' + self.checks.${system}.pre-commit-check.shellHook;
        };
      }) // {
      overlay = import ./pkgs;

      nixosConfigurations = nixpkgs.lib.mapAttrs
        (hostname: { system
                   , extraModules ? [ ]
                   , targetHost ? hostname
                   , unlockOverV4 ? true
                   }: nixpkgs.lib.nixosSystem rec {
          inherit system;

          modules = [
            (./machines + "/${hostname}/configuration.nix")

            home-manager.nixosModules.home-manager
            sops-nix.nixosModules.sops

            aria2_exporter.nixosModules.aria2_exporter
            bang-evaluator.nixosModules.bang-evaluator

            # NIX_PATH for legacy tooling and flake registry pinning
            {
              nix = {
                nixPath = [
                  "nixpkgs=${nixpkgs}"
                ];
                registry = {
                  nixpkgs.flake = nixpkgs;
                };
              };
            }

            # overlays
            ({ config, ... }: {
              nixpkgs.overlays = [
                self.overlay
                (final: prev: {
                  unstable = import nixpkgs-unstable {
                    inherit system;
                    config = config.nixpkgs.config;
                    overlays = config.nixpkgs.overlays;
                  };
                })
              ];
            })

            # deployment settings
            ({ lib, ... }: {
              options.deployment = {
                targetHost = lib.mkOption {
                  type = lib.types.str;
                  readOnly = true;
                  internal = true;
                };
                unlockOverV4 = lib.mkOption {
                  type = lib.types.bool;
                  readOnly = true;
                  internal = true;
                  description = "Whether to unlock the host over IPv4 (only)";
                };
              };
              config.deployment = {
                inherit
                  targetHost
                  unlockOverV4;
              };
            })
          ] ++ extraModules;
        })
        (import ./machines {
          inherit
            infinisilSystem
            nixos-hardware;
        });
    };
}