implement basis docker network

module.nix

@@ -1,18 +1,47 @@
-{ config, lib, ... }:
+{ config, lib, pkgs, ... }:
 
 with lib;
 
 let
-  cfg = config.foo.bar;
+  cfg = config.docker-networks;
 
-in
-
-{
-  options.foo.bar = {
-    enable = mkEnableOption "foobar";
+  dockerNetwork = { ... }: {
+    options = {
+      usedBy = mkOption {
+        type = with types; listOf str;
+        default = [];
+      };
+    };
   };
 
-  config = mkIf cfg.enable {
-    # ...
+  mkService = name: network: let
+    mkBefore = map (x: "docker-${x}.service") network.usedBy;
+  in rec {
+    wantedBy = [ "multi-user.target" ];
+    after = [ "docker.service" "docker.socket" ];
+    before = mkBefore;
+    requires = after;
+
+    serviceConfig = {
+      ExecStart = ''
+        ${pkgs.docker}/bin/docker network create ${name}
+      '';
+      ExecStop = ''
+        ${pkgs.docker}/bin/docker network rm ${name}
+      '';
+      RemainAfterExit="true";
+      Type="oneshot";
+    };
+  };
+in
+{
+  options.docker-networks = mkOption {
+    default = {};
+    type = types.attrsOf (types.submodule dockerNetwork);
+    description = "docker networks";
+  };
+
+  config = mkIf (cfg != {}) {
+    systemd.services = mapAttrs' (n: v: nameValuePair "docker-network-${n}" (mkService n v)) cfg;
   };
 }