init nix-racer substituter proxy

modules/core/nix.nix

@@ -32,19 +32,94 @@ in
       nh
     ];
 
-    environment.etc = lib.mapAttrs' (name: value: {
-      name = "nix/path/${name}";
-      value.source = value.flake;
-    }) config.nix.registry;
+    environment.etc =
+      (lib.mapAttrs' (name: value: {
+        name = "nix/path/${name}";
+        value.source = value.flake;
+      }) config.nix.registry)
+      // {
+        "nix/nix-racer.toml".source = (pkgs.formats.toml { }).generate "nix-racer.toml" {
+          listen = "127.0.0.1:2048";
+          substituters = [
+            {
+              penalty = 0;
+              url = "https://mirror.sjtu.edu.cn/nix-channels/store";
+            }
+            {
+              penalty = 50;
+              url = "https://mirrors.ustc.edu.cn/nix-channels/store";
+            }
+            {
+              penalty = 0;
+              url = "https://nix-community.cachix.org";
+            }
+            {
+              penalty = 0;
+              url = "https://cache.garnix.io";
+            }
+            {
+              penalty = 100;
+              url = "https://cache.nixos.org";
+            }
+          ];
+        };
+      };
+
+    systemd.services.nix-racer = {
+      description = "Nix substituter proxy with parallel cache queries and latency-aware selection";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network-online.target" ];
+      wants = [ "network-online.target" ];
+
+      serviceConfig = {
+        Type = "simple";
+        ExecStart = "${lib.getExe (pkgs.callPackage ./nix-racer/_package.nix { })}";
+        Restart = "on-failure";
+        RestartSec = 5;
+
+        DynamicUser = true;
+        CapabilityBoundingSet = [ "" ];
+        DeviceAllow = "";
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        NoNewPrivileges = true;
+        PrivateDevices = true;
+        PrivateTmp = true;
+        ProtectClock = true;
+        ProtectControlGroups = true;
+        ProtectHome = true;
+        ProtectHostname = true;
+        ProtectKernelLogs = true;
+        ProtectKernelModules = true;
+        ProtectKernelTunables = true;
+        ProtectSystem = "strict";
+        RestrictAddressFamilies = [
+          "AF_INET"
+          "AF_INET6"
+        ];
+        RestrictNamespaces = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+        SystemCallArchitectures = "native";
+        SystemCallFilter = [
+          "@system-service"
+          "~@resources"
+          "~@privileged"
+        ];
+        UMask = "0077";
+      };
+    };
 
     nix.settings = {
       experimental-features = "nix-command flakes pipe-operators";
-      substituters = [
-        "https://mirrors.ustc.edu.cn/nix-channels/store"
-        "https://mirrors.sjtug.sjtu.edu.cn/nix-channels/store"
-        "https://mirror.sjtu.edu.cn/nix-channels/store"
-        "https://nix-community.cachix.org"
-        "https://cache.garnix.io"
+      substituters = lib.mkForce [
+        "http://127.0.0.1:2048"
+
+        # "https://mirrors.ustc.edu.cn/nix-channels/store"
+        # "https://mirrors.sjtug.sjtu.edu.cn/nix-channels/store"
+        # "https://mirror.sjtu.edu.cn/nix-channels/store"
+        # "https://nix-community.cachix.org"
+        # "https://cache.garnix.io"
       ];
       trusted-public-keys = [
         "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="