programs/arqbackup: init module (#1474)

modules/module-list.nix

@@ -103,6 +103,7 @@
   ./services/jankyborders
   ./programs/_1password.nix
   ./programs/_1password-gui.nix
+  ./programs/arqbackup.nix
   ./programs/bash
   ./programs/direnv.nix
   ./programs/fish.nix

modules/programs/arqbackup.nix

@@ -0,0 +1,41 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}:
+
+let
+  cfg = config.programs.arqbackup;
+in
+{
+  options = {
+    programs.arqbackup = {
+      enable = lib.mkEnableOption "Arq backup";
+
+      # If `arq` is not available then we set `default` to `null` to prevent
+      # eval from breaking while `arq` hasn't been merged yet. Only if a user
+      # enables the module will they be required to set this option.
+      package = lib.mkPackageOption pkgs "arq" (lib.optionalAttrs (!pkgs ? arq) { default = null; });
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    environment.systemPackages = [ cfg.package ];
+
+    launchd.daemons.arqagent = {
+      command = "${cfg.package}/Applications/Arq.app/Contents/Resources/ArqAgent.app/Contents/MacOS/ArqAgent";
+      serviceConfig.Label = "com.haystacksoftware.arqagent";
+      serviceConfig.RunAtLoad = true;
+      serviceConfig.KeepAlive = true;
+    };
+
+    launchd.user.agents.ArqMonitor = {
+      command = "${cfg.package}/Applications/Arq.app/Contents/Resources/ArqMonitor.app/Contents/MacOS/ArqMonitor";
+      serviceConfig.Label = "com.haystacksoftware.ArqMonitor";
+      serviceConfig.RunAtLoad = true;
+      serviceConfig.KeepAlive = true;
+      managedBy = "programs.arqbackup.enable";
+    };
+  };
+}