Add backup service to minecraft-server

modules/server/minecraft.nix

@@ -5,6 +5,9 @@
   ...
 }:
 with lib;
+let
+  serverStdinPath = config.systemd.sockets.minecraft-server.socketConfig.ListenFIFO;
+in
 {
   options.my.server.papermc.enable = mkOption {
     type = types.bool;
@@ -17,6 +20,42 @@ with lib;
       package = pkgs.papermc;
       dataDir = "/srv/minecraft";
       openFirewall = true;
+      eula = true;
+    };
+
+    systemd.services."minecraft-server-backup" = {
+      path = with pkgs; [
+        gnutar
+        gzip
+      ];
+
+      script = ''
+        echo 'say Une backup du serveur va commencer dans 1 minute.' > ${serverStdinPath}
+        sleep 1m
+
+        cat << EOF > ${serverStdinPath}
+        say Sauvegarde en cours...
+        save-off
+        save-all
+        EOF
+
+        tar -cpzf /srv/minecraft-backups/backup-$(date -u +%Y%m%d_%H%M%S).tar.gz ${config.services.minecraft-server.dataDir}
+
+        cat << EOF > ${serverStdinPath}
+        save-on
+        say Sauvegarde terminée !
+        EOF
+
+        # Deleting saves older than 2 weeks
+        find /srv/minecraft-backups/ -type f -mtime +14 -name 'backup-*.tar.gz' -delete
+      '';
+
+      serviceConfig = {
+        Type = "oneshot";
+        User = "root";
+      };
+
+      startAt = "*-*-* 00:00,12:00";
     };
   };
 }