Add support for simple web server

module.nix

@@ -5,7 +5,7 @@ self: {
   system,
   ...
 }: let
-  cfg = config.programs.actual-importer;
+  cfg = config.services.actual-importer;
 
   appConfig = (pkgs.formats.yaml {}).generate "actual-importer.config.yaml" cfg.config;
 
@@ -13,14 +13,32 @@ self: {
     name = "actual-importer";
     runtimeInputs = [self.packages.${system}.default];
     text = ''
-      actual-importer -c "${appConfig}" "$@";
+      actual-importer "$@" -c "${appConfig}";
     '';
   };
 in
   with lib; {
-    options.programs.actual-importer = {
+    options.services.actual-importer = {
       enable = mkEnableOption "actual-importer";
 
+      server = {
+        enable = mkEnableOption "actual-importer server";
+
+        port = mkOption {
+          type = types.port;
+          description = "The port on which importer will be listening on";
+          default = 3000;
+          example = 8080;
+        };
+
+        openFirewall = mkOption {
+          type = types.bool;
+          description = "Whether the configured port should be opened on firewall";
+          default = false;
+          example = true;
+        };
+      };
+
       config = mkOption {
         type = types.attrs;
         description = "The actual-importer config which will be eventually converted to yaml";
@@ -49,5 +67,21 @@ in
 
     config = mkIf cfg.enable {
       environment.systemPackages = [app];
+
+      systemd.services.actual-importer-server = mkIf cfg.server.enable {
+        enable = true;
+
+        description = "ActualBudget importer server";
+
+        wants = ["network.target"];
+        after = ["network.target"];
+        wantedBy = ["multi-user.target"];
+
+        serviceConfig = {
+          ExecStart = "${self.packages.${system}.default}/bin/actual-importer serve ${toString cfg.server.port} -c ${appConfig}";
+        };
+      };
+
+      networking.firewall.allowedTCPPorts = mkIf cfg.server.openFirewall [cfg.server.port];
     };
   }