Add NixOS modules

nix/module.nix

@@ -0,0 +1,78 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.update-from-hydra;
+
+  repositoryOpts = { config, ... }@moduleAttrs: {
+    options = {
+
+      updatePath = mkOption {
+        type = types.path;
+        description = ''
+          Path to the symlink pointing to the hydra build output store path
+        '';
+      };
+
+      hydraUrl = mkOption {
+        type = types.str;
+        example = "https://hydra.clerie.de/job/clerie/chaosevents/packages.x86_64-linux.chaosevents/latest-finished";
+        description = ''
+          Url to Hydra
+        '';
+      };
+
+      storeUri = mkOption {
+        type = types.str;
+        description = ''
+          Uri to nix store from which the store path build in Hydra can be copied from
+        '';
+      };
+
+      startAt = mkOption {
+        type = with types; either str (listOf str);
+        default = "hourly";
+        description = ''
+          How often the directory should be updated.
+          Format specified by `systemd.time 7`.
+          This value can also be a list of `systemd.time 7` formatted
+          strings, in which case the service will be started on multiple
+          schedules.
+        '';
+      };
+    };
+  };
+
+in {
+  options = {
+    services.update-from-hydra = {
+
+      enable = mkEnableOption "Make a hydra build output availiable with a symlink and keep it up to date";
+
+      paths = mkOption {
+        type = with types; attrsOf (submodule repositoryOpts);
+        default = {};
+      };
+
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.services = (mapAttrs' (name: path: let
+      in nameValuePair "update-from-hydra-${name}" {
+        inherit (path) startAt;
+        wantedBy = [ "multi-user.target" ];
+        serviceConfig = {
+          Type = "oneshot";
+        };
+        path = [ pkgs.nix ];
+        script = ''
+          ${pkgs.update-from-hydra}/bin/update-from-hydra "${path.hydraUrl}" "${path.updatePath}" "${path.storeUri}"
+        '';
+      }
+    ) cfg.paths);
+  };
+}
+