modules/pipewireLowLatency: use modular config files

Fixes breakage caused by NixOS/nixpkgs#220332.

modules/pipewireLowLatency.nix

@@ -1,92 +1,86 @@
 {
   config,
   lib,
+  pkgs,
   ...
 }:
 # low-latency PipeWire configuration
 # extends the nixpkgs module
 let
   cfg = config.services.pipewire.lowLatency;
+  qr = "${toString cfg.quantum}/${toString cfg.rate}";
+  json = pkgs.formats.json {};
 in {
   options = {
     services.pipewire.lowLatency = {
-      enable = lib.mkEnableOption "Enable low latency";
+      enable = lib.mkEnableOption (lib.mdDoc "Enable low latency");
+
       quantum = lib.mkOption {
-        description = "Minimum quantum to set";
+        description = lib.mdDoc "Minimum quantum to set";
         type = lib.types.int;
         default = 64;
         example = 32;
       };
+
       rate = lib.mkOption {
-        description = "Rate to set";
+        description = lib.mdDoc "Rate to set";
         type = lib.types.int;
         default = 48000;
         example = 96000;
       };
     };
   };
 
-  config = let
-    qr = "${toString cfg.quantum}/${toString cfg.rate}";
-  in
-    lib.mkIf cfg.enable {
-      services.pipewire = {
-        config = {
-          # pipewire native config
-          pipewire = {
-            "context.properties" = {"default.clock.min-quantum" = cfg.quantum;};
-          };
-
-          # pulse clients config
-          pipewire-pulse = {
-            "context.properties" = {};
-            "context.modules" = [
-              {
-                name = "libpipewire-module-rtkit";
-                args = {
-                  "nice.level" = -15;
-                  "rt.prio" = 88;
-                  "rt.time.soft" = 200000;
-                  "rt.time.hard" = 200000;
-                };
-                flags = ["ifexists" "nofail"];
-              }
-              {name = "libpipewire-module-protocol-native";}
-              {name = "libpipewire-module-client-node";}
-              {name = "libpipewire-module-adapter";}
-              {name = "libpipewire-module-metadata";}
-              {
-                name = "libpipewire-module-protocol-pulse";
-                args = {
-                  "pulse.min.req" = qr;
-                  "pulse.min.quantum" = qr;
-                  "pulse.min.frag" = qr;
-                  "server.address" = ["unix:native"];
-                };
-              }
-            ];
+  config = lib.mkIf cfg.enable {
+    # pipewire native config
+    environment.etc."pipewire/pipewire.d/99-lowlatency.conf".source = json.generate "99-lowlatency.conf" {
+      context.properties.default.clock.min-quantum = cfg.quantum;
+    };
 
-            "stream.properties" = {
-              "node.latency" = qr;
-              "resample.quality" = 1;
-            };
+    # pulse clients config
+    environment.etc."pipewire/pipewire-pulse.d/99-lowlatency.conf".source = json.generate "99-lowlatency.conf" {
+      context.modules = [
+        {
+          name = "libpipewire-module-rtkit";
+          args = {
+            nice.level = -15;
+            rt.prio = 88;
+            rt.time.soft = 200000;
+            rt.time.hard = 200000;
           };
-        };
-        # lower latency alsa format
-        media-session.config.alsa-monitor = {
-          rules = [
-            {
-              matches = [{node.name = "alsa_output.*";}];
-              actions = {
-                update-props = {
-                  "audio.format" = "S32LE";
-                  "audio.rate" = cfg.rate * 2;
-                  "api.alsa.period-size" = 2;
-                };
-              };
-            }
-          ];
-        };
+          flags = ["ifexists" "nofail"];
+        }
+        {
+          name = "libpipewire-module-protocol-pulse";
+          args = {
+            pulse.min.req = qr;
+            pulse.min.quantum = qr;
+            pulse.min.frag = qr;
+            server.address = ["unix:native"];
+          };
+        }
+      ];
+
+      stream.properties = {
+        node.latency = qr;
+        resample.quality = 1;
       };
     };
+  };
 }
+# TODO: use wireplumber config
+# lower latency alsa format
+# media-session.config.alsa-monitor = {
+#   rules = [
+#     {
+#       matches = [{node.name = "alsa_output.*";}];
+#       actions = {
+#         update-props = {
+#           "audio.format" = "S32LE";
+#           "audio.rate" = cfg.rate * 2;
+#           "api.alsa.period-size" = 2;
+#         };
+#       };
+#     }
+#   ];
+