l: add bindfs module

lass/3modules/bindfs.nix

@@ -0,0 +1,51 @@
+with import <stockholm/lib>;
+{ config, pkgs, ... }:
+let
+  cfg = config.lass.bindfs;
+in {
+  options.lass.bindfs = mkOption {
+    type = types.attrsOf (types.submodule ({ config, ... }: {
+      options = {
+        target = mkOption {
+          description = ''
+            destination where bindfs mounts to.
+            second positional argument to bindfs.
+          '';
+          default = config._module.args.name;
+          type = types.absolute-pathname;
+        };
+        source = mkOption {
+          description = ''
+            source folder where the mounted directory is originally.
+            first positional argument to bindfs.
+          '';
+          type = types.absolute-pathname;
+        };
+        options = mkOption {
+          description = ''
+            additional arguments to bindfs
+          '';
+          type = types.listOf types.str;
+          default = [];
+        };
+      };
+    }));
+    default = {};
+  };
+
+  config = mkIf (cfg != {}) {
+    systemd.services = mapAttrs' (n: mount: let
+      name = replaceStrings [ "/" ] [ "_" ] n;
+    in nameValuePair "bindfs-${name}" {
+      wantedBy = [ "local-fs.target" ];
+      path = [ pkgs.coreutils ];
+      serviceConfig = {
+        ExecStartPre = pkgs.writeDash "bindfs-init-${name}" ''
+          mkdir -p '${mount.source}'
+          mkdir -p '${mount.target}'
+        '';
+        ExecStart = "${pkgs.bindfs}/bin/bindfs -f ${concatStringsSep " " mount.options} ${mount.source} ${mount.target}";
+      };
+    }) cfg;
+  };
+}

lass/3modules/default.nix

@@ -1,6 +1,7 @@
 _:
 {
   imports = [
+    ./bindfs.nix
     ./dnsmasq.nix
     ./ejabberd
     ./folderPerms.nix