ci: run nix flake check on ci (#583)

* ci: run nix flake check on ci

* ci: fix tests

.github/workflows/nix.yml

@@ -0,0 +1,35 @@
+# Copyright © 2025-26 l5yth & contributors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Nix
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  flake-check:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Install Nix
+        uses: cachix/install-nix-action@v30
+        with:
+          extra_nix_config: |
+            experimental-features = nix-command flakes
+      - name: Run flake checks
+        run: nix flake check

README.md

@@ -210,6 +210,45 @@ example `ALLOWED_CHANNELS="Chat,Ops"`); packets on other channels are discarded.
 Use `HIDDEN_CHANNELS` to block specific channels from the web UI even when they
 appear in the allowlist.
 
+## Nix
+
+For the dev shell, run:
+
+```bash
+nix develop
+```
+
+The shell provides Ruby plus the Python ingestor dependencies (including `meshtastic`
+and `protobuf`). To sanity-check that the ingestor starts, run `python -m data.mesh`
+with the usual environment variables (`INSTANCE_DOMAIN`, `API_TOKEN`, `CONNECTION`).
+
+To run the packaged apps directly:
+
+```bash
+nix run .#web
+nix run .#ingestor
+```
+
+Minimal NixOS module snippet:
+
+```nix
+services.potato-mesh = {
+  enable = true;
+  apiTokenFile = config.sops.secrets.potato-mesh-api-token.path;
+  dataDir = "/var/lib/potato-mesh";
+  port = 41447;
+  instanceDomain = "https://mesh.me";
+  siteName = "Nix Mesh";
+  contactLink = "homeserver.mx";
+  mapCenter = "28.96,-13.56";
+  frequency = "868MHz";
+  ingestor = {
+    enable = true;
+    connection = "192.168.X.Y:4403";
+  };
+};
+```
+
 ## Docker
 
 Docker images are published on Github for each release:

flake.nix

@@ -14,6 +14,7 @@
         # Python environment for the ingestor
         pythonEnv = pkgs.python3.withPackages (ps: with ps; [
           meshtastic
+          protobuf
           requests
         ]);
 
@@ -22,7 +23,11 @@
           name = "potato-mesh-web";
           runtimeInputs = [ pkgs.ruby pkgs.bundler pkgs.sqlite pkgs.git pkgs.gnumake pkgs.gcc ];
           text = ''
-            BASEDIR="''${XDG_DATA_HOME:-$HOME/.local/share}/potato-mesh"
+            if [ -n "''${XDG_DATA_HOME:-}" ]; then
+              BASEDIR="$XDG_DATA_HOME"
+            else
+              BASEDIR="$HOME/.local/share/potato-mesh"
+            fi
             WORKDIR="$BASEDIR/web"
             mkdir -p "$WORKDIR"
 
@@ -60,7 +65,11 @@
           runtimeInputs = [ pythonEnv ];
           text = ''
             # The ingestor needs to run from parent directory with data/ folder
-            BASEDIR="''${XDG_DATA_HOME:-$HOME/.local/share}/potato-mesh"
+            if [ -n "''${XDG_DATA_HOME:-}" ]; then
+              BASEDIR="$XDG_DATA_HOME"
+            else
+              BASEDIR="$HOME/.local/share/potato-mesh"
+            fi
             if [ ! -d "$BASEDIR/data" ]; then
               mkdir -p "$BASEDIR"
               cp -rT "${./data}" "$BASEDIR/data/"
@@ -107,6 +116,27 @@
             echo "To run the ingestor: cd data && python mesh.py"
           '';
         };
+
+        checks.potato-mesh-nixos = pkgs.testers.nixosTest {
+          name = "potato-mesh-data-dir";
+          nodes.machine = { lib, ... }: {
+            imports = [ self.nixosModules.default ];
+            services.potato-mesh = {
+              enable = true;
+              apiToken = "test-token";
+              dataDir = "/var/lib/potato-mesh";
+              ingestor.enable = true;
+            };
+            systemd.services.potato-mesh-ingestor.wantedBy = lib.mkForce [];
+          };
+          testScript = ''
+            machine.start
+            machine.succeed("grep -q 'XDG_DATA_HOME=/var/lib/potato-mesh' /etc/systemd/system/potato-mesh-web.service")
+            machine.succeed("grep -q 'XDG_DATA_HOME=/var/lib/potato-mesh' /etc/systemd/system/potato-mesh-ingestor.service")
+            machine.succeed("grep -q 'WorkingDirectory=/var/lib/potato-mesh' /etc/systemd/system/potato-mesh-web.service")
+            machine.succeed("grep -q 'WorkingDirectory=/var/lib/potato-mesh' /etc/systemd/system/potato-mesh-ingestor.service")
+          '';
+        };
       }
     ) // {
       # NixOS module
@@ -327,6 +357,7 @@
                 INSTANCE_DOMAIN = "http://127.0.0.1:${toString cfg.port}";
                 CONNECTION = cfg.ingestor.connection;
                 DEBUG = if cfg.debug then "1" else "0";
+                XDG_DATA_HOME = cfg.dataDir;
               } // lib.optionalAttrs (cfg.allowedChannels != null) {
                 ALLOWED_CHANNELS = cfg.allowedChannels;
               } // lib.optionalAttrs (cfg.hiddenChannels != null) {