feat: Add swayidle as a systemd service

fix #29

config/programs/sway.nix

@@ -2,6 +2,7 @@
   imports = [
     ./wl-clipboard.nix
     ./mako.nix
+    ./swayidle.nix
   ];
   wayland.windowManager.sway = {
     enable = true;

config/programs/swayidle.nix

@@ -0,0 +1,34 @@
+{ pkgs, ... }:
+let
+  lock-script = pkgs.writeScript "suspend" ''
+    ${pkgs.swaylock}/bin/swaylock -f -c 000000
+    ${pkgs.mpc-cli}/bin/mpc pause
+  '';
+  screen-off-script = pkgs.writeScript "screenOff" ''
+    ${pkgs.sway}/bin/swaymsg "output * dpms off"
+  '';
+  suspend-script = pkgs.writeScript "suspend" ''
+    ${pkgs.systemctl}/bin/systemctl suspend
+  '';
+  resume-script = pkgs.writeScript "resume" ''
+    ${pkgs.sway}/bin/swaymsg "output * dpms on"
+  '';
+  unlock-script = pkgs.writeScript "unlock" ''
+    ${pkgs.procps}/bin/pkill swaylock
+    ${pkgs.mpc-cli}/bin/mpc play
+  '';
+in
+{
+  systemd.user.services.swayidle = {
+    Unit = {
+      Description = "swayidle";
+      PartOf = [ "graphical-session.target" ];
+    };
+    Install = {
+      WantedBy = [ "graphical-session.target" ];
+    };
+    Service = {
+      ExecStart = "${pkgs.swayidle}/bin/swayidle -w timeout 300 ${lock-script} timeout 305 ${screen-off-script} timeout 900 ${suspend-script} resume ${resume-script} lock ${lock-script} unlock ${unlock-script}";
+    };
+  };
+}