nix: seralize TOML config in the NixOS module

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: Ia6171de7832659075918879c31420e376a6a6964

nix/modules/nixos.nix

@@ -6,33 +6,117 @@ self: {
 }: let
   inherit (lib.modules) mkIf;
   inherit (lib.options) mkOption mkEnableOption;
-  inherit (lib.types) package;
+  inherit (lib.types) package bool str listOf attrsOf submodule int nullOr anything;
 
   cfg = config.services.pscand;
+
+  settingsFormat = pkgs.formats.toml {};
+
+  configFile = settingsFormat.generate "pscand.toml" {
+    scanner_dirs = cfg.scannerDirs;
+    log_dir = cfg.logDir;
+    ring_buffer_size = cfg.ringBufferSize;
+    journal_enabled = cfg.journalEnabled;
+    file_enabled = cfg.fileEnabled;
+    scanners =
+      lib.mapAttrs (_: scanner: {
+        enabled = scanner.enabled;
+        interval_secs = scanner.interval;
+        extra = scanner.extra;
+      })
+      cfg.scanners;
+  };
 in {
   options.services.pscand = {
     enable = mkEnableOption "Pluggable System Condition Monitoring Daemon";
+
     package = mkOption {
       type = package;
       default = self.packages.${pkgs.hostPlatform.system.pscand};
       defaultText = "self.packages.$${pkgs.hostPlatform.system}.pscand";
       description = "The pscand package to use";
     };
+
+    scannerDirs = mkOption {
+      type = listOf str;
+      default = ["${cfg.package}/lib/pscand/scanners"];
+      description = "Directories to load scanner plugins from";
+    };
+
+    logDir = mkOption {
+      type = str;
+      default = "/var/log/pscand";
+      description = "Directory for log files and heartbeat";
+    };
+
+    ringBufferSize = mkOption {
+      type = int;
+      default = 1000;
+      description = "Number of log entries to keep in memory for crash recovery";
+    };
+
+    journal.enable = mkEnableOption "logging to Systemd journal";
+    file.enable = mkEnableOption "logging to file";
+
+    scanners = mkOption {
+      type = attrsOf (submodule {
+        options = {
+          enabled = mkOption {
+            type = bool;
+            default = true;
+            description = "Whether this scanner is enabled";
+          };
+
+          interval = mkOption {
+            type = nullOr int;
+            default = null;
+            description = "Collection interval in seconds (null = use scanner default)";
+          };
+
+          extra = mkOption {
+            type = attrsOf anything;
+            default = {};
+            description = "Scanner-specific configuration options";
+          };
+        };
+      });
+      default = {};
+      description = "Per-scanner configuration settings";
+      example = {
+        system = {
+          enabled = true;
+          interval = 5;
+        };
+        sensor = {
+          enabled = true;
+          interval = 10;
+          extra = {sensors = ["coretemp" "nvme"];};
+        };
+        power = {
+          enabled = true;
+          interval = 30;
+        };
+      };
+    };
   };
 
   config = mkIf cfg.enable {
-    systemd.packages = [cfg.package];
+    environment.etc."pscand/pscand.toml".source = configFile;
 
     systemd.services.pscand = {
       wantedBy = ["multi-user.target"];
       after = ["network.target"];
       serviceConfig = {
         Type = "simple";
-        ExecStart = "${cfg.package}/bin/pscand";
+        ExecStart = "${cfg.package}/bin/pscand run --config /etc/pscand/pscand.toml";
         Restart = "on-failure";
         RestartSec = "5s";
-        Environment = ["${cfg.package}/lib/pscand/scanners"]; # FIXME: make this configurable
+        Environment = "PSCAND_SCANNER_DIRS=${lib.concatStringsSep ":" cfg.scannerDirs}";
       };
     };
+
+    systemd.tmpfiles.rules = [
+      "d ${cfg.logDir} 0755 root root -"
+    ];
   };
 }