chore: introduce central api key extraction service generator

nixarr/lib/api-keys.nix

@@ -0,0 +1,79 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+with lib; let
+  cfg = config.nixarr;
+
+  # Helper to create API key extraction for a service
+  mkApiKeyExtractor = serviceName: serviceConfig: {
+    description = "Extract ${serviceName} API key";
+    after = ["${serviceName}.service"];
+    requires = ["${serviceName}.service"];
+
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = true;
+      # Use DynamicUser if the parent service does
+      DynamicUser = serviceConfig.serviceConfig.DynamicUser or false;
+      # Only set User if not using DynamicUser
+      ${
+        if !(serviceConfig.serviceConfig.DynamicUser or false)
+        then "User"
+        else null
+      } =
+        serviceConfig.user or null;
+      Group = "api-keys";
+      UMask = "0027"; # Results in 0640 permissions
+
+      ExecStartPre = [
+        "${pkgs.coreutils}/bin/mkdir -p ${cfg.stateDir}/api-keys"
+        "${pkgs.coreutils}/bin/chown root:api-keys ${cfg.stateDir}/api-keys"
+        "${pkgs.coreutils}/bin/chmod 750 ${cfg.stateDir}/api-keys"
+        # Wait for config file to exist
+        "${pkgs.bash}/bin/bash -c 'while [ ! -f ${serviceConfig.stateDir}/config.xml ]; do sleep 1; done'"
+      ];
+
+      ExecStart = pkgs.writeShellScript "extract-${serviceName}-api-key" ''
+        ${pkgs.dasel}/bin/dasel -f "${serviceConfig.stateDir}/config.xml" \
+          -s ".Config.ApiKey" | tr -d '\n\r' > "${cfg.stateDir}/api-keys/${serviceName}.key"
+        chown $USER:api-keys "${cfg.stateDir}/api-keys/${serviceName}.key"
+      '';
+    };
+  };
+in {
+  config = mkIf cfg.enable {
+    users.groups.api-keys = {};
+
+    # Ensure all services that need API keys are in the group
+    users.users = mkMerge [
+      # Static users
+      (mkIf cfg.transmission.enable {torrenter.extraGroups = ["api-keys"];})
+      (mkIf cfg.transmission.privateTrackers.cross-seed.enable {cross-seed.extraGroups = ["api-keys"];})
+    ];
+
+    # Add api-keys group to services with DynamicUser
+    systemd.services = mkMerge [
+      (mkIf cfg.sonarr.enable {sonarr.serviceConfig.SupplementaryGroups = ["api-keys"];})
+      (mkIf cfg.radarr.enable {radarr.serviceConfig.SupplementaryGroups = ["api-keys"];})
+      (mkIf cfg.lidarr.enable {lidarr.serviceConfig.SupplementaryGroups = ["api-keys"];})
+      (mkIf cfg.readarr.enable {readarr.serviceConfig.SupplementaryGroups = ["api-keys"];})
+      (mkIf cfg.prowlarr.enable {prowlarr.serviceConfig.SupplementaryGroups = ["api-keys"];})
+      (mkIf cfg.recyclarr.enable {recyclarr.serviceConfig.SupplementaryGroups = ["api-keys"];})
+
+      # Create API key extractors for enabled services
+      (mkIf cfg.sonarr.enable {"sonarr-api-key" = mkApiKeyExtractor "sonarr" cfg.sonarr;})
+      (mkIf cfg.radarr.enable {"radarr-api-key" = mkApiKeyExtractor "radarr" cfg.radarr;})
+      (mkIf cfg.lidarr.enable {"lidarr-api-key" = mkApiKeyExtractor "lidarr" cfg.lidarr;})
+      (mkIf cfg.readarr.enable {"readarr-api-key" = mkApiKeyExtractor "readarr" cfg.readarr;})
+      (mkIf cfg.prowlarr.enable {"prowlarr-api-key" = mkApiKeyExtractor "prowlarr" cfg.prowlarr;})
+    ];
+
+    # Create the api-keys directory
+    systemd.tmpfiles.rules = [
+      "d ${cfg.stateDir}/api-keys 0750 root api-keys - -"
+    ];
+  };
+}