nixos: Add a quickpeepIndex service if an autoIndexUrl is specified

nixos_modules/quickpeepSearch.nix

@@ -48,6 +48,15 @@ with lib;
           Config path to use, in RON format.
         '';
       };
+
+      autoIndexUrl = mkOption {
+        default = null;
+        type = with types; nullOr str;
+        description = ''
+          HTTP(S) URL to an index (list) of rakepacks.
+          If specified, the indexer will periodically fetch new packs from that list and then add the pages within to the search index.
+        '';
+      };
     };
   };
 
@@ -73,5 +82,19 @@ with lib;
         ExecStart = ''${quickpeep}/bin/quickpeep ${cfg.bindHost}:${builtins.toString cfg.bindPort}'';
       };
     };
+
+    systemd.services.quickpeepIndex = mkIf (cfg.autoIndexUrl != null) {
+      after = [ "network.target" ];
+      description = "Fetches rakepacks from a feed and adds pages to the search index.";
+      serviceConfig = {
+        Type = "simple";
+        User = "${cfg.user}";
+        ExecStart = ''${quickpeep}/bin/qp-indexer --config ${lib.strings.escapeShellArg cfg.configPath} --feed ${lib.strings.escapeShellArg cfg.autoIndexUrl}'';
+      };
+    };
+
+#     TODO systemd.timers.quickpeepIndex = mkIf (cfg.autoIndexUrl != null) {
+#
+#     };
   };
 }